John Sayers' Design Forum

John Sayers' Recording Studio Design Forum

A World of Experience
Click Here for Information on John's Services
It is currently Sun Nov 17, 2019 9:31 am

All times are UTC + 10 hours




Post new topic Reply to topic  [ 47 posts ]  Go to page 1, 2, 3, 4  Next
Author Message
PostPosted: Mon Feb 25, 2019 11:26 am 
Offline

Joined: Sat Jan 31, 2015 8:28 am
Posts: 20
Location: Delta, BC Canada
Hey Everyone,

I've been reading on this site for some years, dreaming about the opportunity to put what I have learned into action, and now I am in the middle of a massive house renovation with eyes on putting in a room for mixing and recording vocals/guitar/bass. Given that I'm doing this while the house is already under renovation, I would love a little bit of guidance, course correction and positive encouragement as I try to figure out the design before my contractor needs to actually do the job. Or, if it appears I am that far off, a good dose of hard truth from someone to tell me I should hire a designer to get it over the line.

So let me start with some pictures.

This is the state of the building as it currently stands...
Attachment:
BackyardReno.jpg

Attachment:
TV_Studio_PoolHouse_Wing.jpg

roughly 2/3rds of the way down on the wing on the right hand side of the first photo is where I will be putting this room. Second photo is a close up of the wing taken from another angle.

So, I've got a small 10'1" wide by 15' deep by 9'6" high rectangular space set aside, that will be in between my TV room and a room that will be housing some pool equipment, of which the pump can be fairly noisy (about 60db). I spent some time with this tool from Bob Golds, and while I know it's small, it's as big as I can get it without impeding too much on the TV room space (which is a priority for my whole family, not just me...) while still giving me a decent starting room ratio.

I've started to model the space (mostly framing) in sketchup too, attached below for another perspective.
Attachment:
FullWingCapture.jpg


I'm planning a room within a room design, with 2x4 stud construction with 2 layers of 5/8" drywall + Green Glue on the inner leaf walls, and the outer leaf will be 2x4 studs on the side walls with 1 layer of 5/8" drywall, and 2x6 on the front and back walls with 1/2" plywood and stucco (front and back walls are exterior walls). Inner leaf ceiling will be likely 2x6 (thinking 2x4 would be too small to support the double drywall). The outer leaf ceiling is 2x12 I believe... I will have to fact check that next time I am at the site. All air gaps stuffed with fiberglass insulation.

In a perfect world I would hope for 80dbs of isolation, but I think in all reality I'd be happy with 60... Using the TL calculator that I found in a thread on this site, I think I should be between 60 and 70 dbs of isolation with this plan save for frequencies below about 50hz, but I am also understanding of the fact that real world doesn't happen in a spreadsheet. So if it sounds like I am setting myself up for failure please let me know.

The room will be built on a slab, so no need for anything special there, but in the slab already will be some hot water radiant heating. And I am thinking that I'll be finishing the floor with hardwood.

I am going to be using track lighting to prevent me punching holes into my leaves for pot lights, and plan on putty pads and acoustic sealant for all the boxes and switches. I've also already spoken with my contractor about a star ground for the 5 outlets that are planned in the room. The electrical panel is in the pool house right next door, so I believe running home runs for all the ground wires shouldn't be too much of a stretch, and will work out the details with the electrician before he starts.

So I find myself in a spot now where I need to get to a place where I can direct my contractor on what to do so we can get as far as we need to pass an inspection so I don't hold up the whole house renovation schedule. If I can get to that then I don't mind taking my time to finish the rest... meaning acoustic treatment and any finishes.

So with that I feel like I need to figure out 2 things to continue progressing. 1) Where to place my walls for flushmount speakers so I can finalize where the lights and the outlets will go, and 2) What's the minimum I need to do for HVAC to not kill myself... (This studio is for some mostly solo sessions after kids go to bed, and won't be used for marathon sessions mon-fri.) My main concern is fresh air, as I already have the heated floors, and I live in a fairly cold climate that probably won't need much AC.

And of course... if anyone thinks that I'm grossly neglecting something else that I should be considering...

So for the soffit mounted speakers, I am trying to figure out the position of the infinte baffle, and am struggling to find an orientation that works. I started by measuring 38% of the room (the dotted line in blue below), and creating an equilateral triangle and placing the baffles perpendicular to the line from my listening position, but the distance I used for the sides of my equilateral triangle were arbitrary... I quickly found out that what I designed would not leave enough room inside the baffle for my speakers.
Attachment:
38PercentListeningPosNoRoomForSpeaker.jpg


I then moved the baffles away from the wall to create room for the speaker, and found that my listening position was then in the middle of the room, which isn't good.
Attachment:
MovedListeningPosToMiddle.jpg


I then moved the walls and left the listening position where it was, and I think I found a decent compromise, but the 2 infinite baffles meet in the middle of the wall straight in front of me. I don't know if this is a problem or not, I just can't recall seeing it in any images or build threads that I've read. I could flatten that spot in between the baffles, but then the speakers would be quite close to the front most edge of the baffle, and I'm sure that would affect the baffle performance.
Attachment:
38PercentListeningPosWallsJoinAtFront.jpg

So, having said all of that here are my questions:

1) Is it a problem if my left and right infinite baffles meet in the front centre of my room at a point? Or also, is there a tried and true method to figuring out where to put the baffles that I am missing in my searches?

2) For HVAC, I have looked at mini-splits and my contractor was talking about a heat pump, but before I go off trying to figure out the ducting and silencer boxes for those implementations, can anyone suggest the simplest way to get fresh air into the room given that I don't have a heating requirement, and likely won't have much of a cooling requirement? Or alternatively point me to why my way of thinking about this is naive.

Oh, and

3) My outer leaf walls in the front and back are just plywood and then stucco (full disclosure I need to figure out the details of what all is added on top of the plywood before the stucco application as I don't yet know), but should I be thinking about adding drywall to the inside of the plywood or is that overkill because the exterior wall mass with Stucco applied will be more than the side walls?


Thank you in advance for any advice that you can provide, and thank you all retroactively for providing this resource and community for people like me.

-Aaron

PS. I think I covered off everything in the before you post sticky, but apologies if there's something that I missed...


You do not have the required permissions to view the files attached to this post.


Report this post
Top
 Profile  
 
PostPosted: Mon Feb 25, 2019 1:37 pm 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11984
Location: Santiago, Chile
Hi Aaron, and Welcome to the Forum! :)

Congrats on your renovation/studio build! Looks like it's going to be a really nice place.

Quote:
So, I've got a small 10'1" wide by 15' deep by 9'6" high rectangular space set aside,
Roughly 150 square feet, with a nice high ceiling? Excellent.

Quote:
of which the pump can be fairly noisy (about 60db).
IT would be good to measure the frequency spectrum of that pump. Also, is it hard-bolted to the same slab as your room will be on? IF so, you might want to consider putting in some isolation mounts for that pump, so that it does not transmit vibration directly into the slab.

Quote:
I'm planning a room within a room design, with 2x4 stud construction with 2 layers of 5/8" drywall + Green Glue on the inner leaf walls,
:thu:

Quote:
and the outer leaf will be 2x4 studs on the side walls with 1 layer of 5/8" drywall,
Depending on how much isolation you need, it might be an idea to do that leaf the same as the inner: 2 x 5/8" drywall + GG.

Quote:
Inner leaf ceiling will be likely 2x6 (thinking 2x4 would be too small to support the double drywall).
Don't guess here! Get your structural engineer to calculate that for you. I will need to support the dead load (I'm assuming 2 x 5/8" drywall + GG here too?) as well as any additional load inside the room, such as lights, acoustic treatment, decorations, electrical wiring, HVAC ducts/registers, possibly HVAC silencer boxes (which are large and heavy!), etc. So let your engineer know about all that, and he can tell you what size joists your ceiling will need to safely handle the load.

Quote:
In a perfect world I would hope for 80dbs of isolation,
That's unlikely in a home studio. The flanking limit of a concrete slab on grade is around 70 dB usually, so to get more than that you'd need to float the floor (and the entire room, actually). It can be done, but the cost rises drastically once you get into that type of build.

Quote:
but I think in all reality I'd be happy with 60..
So is ore reasonable, and do-able. But you'd definitely need the extra drywall and GG on the outer.leaf in that case.

Quote:
Using the TL calculator that I found in a thread on this site, I think I should be between 60 and 70 dbs of isolation with this plan save for frequencies below about 50hz,
TL is for the entire spectrum and takes into account the way you measure it. You won't be getting 70 dB at 50 Hz, for example: you will be getting "70 dB", total. You also don't even need 70 dB at 50 Hz, due to the way human hearing works. As long as your MSM resonant frequency is at least an octave below the lowest frequency you need to isolate, and your total TL is 60 or more, you should be good.

Quote:
The room will be built on a slab, so no need for anything special there, but in the slab already will be some hot water radiant heating.
That's fine, but a word of warning: You will be building your inner-leaf walls on top of that slab, and you will need to bolt them down. So do mark the locations of the pipes very carefully: you don't want to put a bolt through the pipes! Alternatively, you can use thermal imaging after the heating system is working, to see where the pipes are.

Quote:
And I am thinking that I'll be finishing the floor with hardwood.
Careful there! Some types of hardwood flooring have an air gap between the wood and the slab: you can't do that for a studio. Just some type of underlay is fine, but no air gap.

Quote:
I am going to be using track lighting to prevent me punching holes into my leaves for pot lights,
:thu:

Quote:
and plan on putty pads and acoustic sealant for all the boxes and switches.
You could do it that way, but given that you need high isolation, it would be better to do everything surface-mount. There are some quite neat systems for that:
Attachment:
surface-mount-electrics-01.jpg


Try to minimize the number of penetrations of your walls: Ideal is to have only one single penetration where the power feed comes in, then do everything from there within the room, surface-mount.

Quote:
1) Where to place my walls for flushmount speakers so I can finalize where the lights and the outlets will go,
Cool! So you plan to soffit-mount / flush mount your speakers! Excellent! That opens a whole PLEASE DELETE ME I AM A PANDY6 SPAMMER's box for the design, though.... Designing a soffit-mount system take a while...

Quote:
2) What's the minimum I need to do for HVAC to not kill myself
That's also a big can of worms! The basic concept is that you need to circulate the entire volume of air in the room at least 6 times per hour, you need to replace about 20% to 30% of that with fresh air, dumping the same volume of stale air to the outside, you need to do all that while keeping the air velocity at the registers under 300 fpm (200 would be better), and also retaining the isolation that you spent so much to create, and also removing the right amount of latent heat and sensible heat form the room for the two extreme situations (max occupation by hot sweaty musicians on the hottest, most humid day in mid summer, vs. one single person sitting quietly on the coldest, driest day in mid-winter)... That's all! Simple! 8)

Quote:
My main concern is fresh air, as I already have the heated floors, and I live in a fairly cold climate that probably won't need much AC.
Not so sure about that! Your room will be extremely will insulated: double air-tight seals, very thick, massive walls, double insulation, very thick, plus treatment in the room... Put a few musicians in there with gear, instruments, hot pizza, hot coffee, lights, computers, etc. and you'll be producing quite a bit of heat and humidity. HVAC is needed.

Quote:
So for the soffit mounted speakers, I am trying to figure out the position of the infinte baffle, and am struggling to find an orientation that works.
Start by forgetting about the equilateral triangle myth... :) More about that below...

Quote:
I started by measuring 38% of the room (the dotted line in blue below),
38% is not written in stone: it's just a good starting point. Also, it refers to the location of your ear in the room, not the location of the apex of the triangle.... Two very different things...

Quote:
and placing the baffles perpendicular to the line from my listening position
That doesn't look perpendicular on your diagram! What needs to be perpendicular is the acoustic axis of the speaker, not the line to the listening position. The speakers don't point at the listening position anyway... :) (more on that later too...)

Quote:
I quickly found out that what I designed would not leave enough room inside the baffle for my speakers.
Then move your baffles further in to the room.

Quote:
but the distance I used for the sides of my equilateral triangle were arbitrary...
Then don't start with arbitrary distances and arbitrary triangles! :)

Quote:
but the 2 infinite baffles meet in the middle of the wall straight in front of me. I don't know if this is a problem or not, I just can't recall seeing it in any images or build threads that I've read.
There's a reason why you haven't see that: because it's not a good idea, acoustically.

Quote:
I could flatten that spot in between the baffles, but then the speakers would be quite close to the front most edge of the baffle, and I'm sure that would affect the baffle performance.
Sort of, but not really...

Quote:
1) Is it a problem if my left and right infinite baffles meet in the front centre of my room at a point?
Yes.

Quote:
is there a tried and true method to figuring out where to put the baffles that I am missing in my searches?
Yes! Start by forgetting the stuff you see all over the place, such as the mythical triangle, and they mythical 38%, and the mythical 30° angle...

I'm being rather cryptic here so far, so let me explain: I'm copying-and-pasting some of this from posts I've written in the past on the subject, then modifying it to fit your case too:

First, Forget the famous equilateral triangle! It's a myth....

Well, OK, it's a myth that this is the only possible way to set up your speakers: it isn't. It's merely a good starting point, and works for most rooms, but is NOT necessarily the best for any room at all! It is nothing more than a simplified misrepresentation of how it should actually be. That "equilateral triangle" thing is all over the internet, in all types of books, all over YouTube, and every place else you look. But that does not make it correct. It would only be correct under two very specific conditions:

1) If the speakers and your head were set up some place where there is no room around them: out in the open, where the speakers are not "acoustically loaded" by the room, and there are no reflections or reverberant field. And:

2) For all listeners who have had their ears surgically transplanted onto their eyeballs! :shock:

Think about it. Every speaker manufacturer will tell you that the absolute flattest, cleanest sound from their speakers is "on axis": when your ear is lined up perfectly with the acoustic axis of the speaker. Yet those "equilateral triangle" diagrams usually show the acoustic axes from the two speakers interesting in the middle of the engineer's head, which means that the ears are NOT on axis! The EYES are on axis... :roll: So if your ears are in your eyeballs, the equilateral triangle is the correct way to set up your speakers. For the rest of us, the speakers need to be set up so that the acoustic axes are aimed at the ears, not the eyes.

In fact, there are some indications that show the axes should actually be aimed a bit outboard of the ears, not directly at them, since the head itself affects the sound as it approaches the ears, and also to create a wider sweet spot around the mix position. Thus, the acoustic axes from your speakers should intersect at some point several inches behind your head, not in the middle of your head. Usually it turns out that the speakers are usually aimed at a point about 12 to 18 inches behind your head.

There are good locations for the speakers in the room, and there are bad locations. There are also good locations for the mix position (engineer's ears) in the room, and bad locations. In most rooms, creating the "equilateral triangle" puts the speakers in a bad location, or the head in a bad location, or both. And if you put them both in good locations, then you no longer have an "equilateral triangle". My answer to that is: "So what?" There's no logical or acoustic reason why the distance between the speaker cones must be identical to the distance between the cone and your ears. Yes, the distance from the left speaker to your left ear must be the same as the distance form the right speaker to your right ear, in order to ensure that the two sounds arrive in phase and at the same intensity: Absolutely. But that has nothing at all to do with the distance between the speakers! In what way does that distance cause the sound to be better or worse? Answer: In no way!

In fact, if you look at the polar response of the human ear, maximum sensitivity is at about 50° off to the side, not 30°. So spreading the speakers further apart and angling them in a bit more would actually be a good idea.

The ONLY reason why everyone shows the "equilateral triangle", is supposedly because of standardization. The theory is that if all control rooms have the speakers 30° off then they should all sound the same: all the sound stages should be identical, and all the stereo images should be perfect copies of each other, and all the sweet spots should be the same size and shape.... and of course, that is pure garbage! Even for rooms where the speakers are set up spot on for the "equilateral triangle", it is very evident that they don't sound alike, the sweet spot is not the same, the stereo imaging can be different, and the sound-stage too. So this is not a valid reason.

In other words: the triangle is a myth.

The truth is that the speakers should be set up at the best point in the room for YOUR speakers in YOUR room, and your head should be set up at the best location for YOUR head in YOUR room, then the speakers should be angled correctly such that the acoustic axes of the speakers intersect several inches behind your head, usually around 12" to 18" back.

But that means they won't be angled at 30° any more! :shock: Yup. So what? There is nothing magical about 30°. It just happens to be the angle you need to create an equilateral triangle, but once you abandon that myth, then you are automatically abandoning the need for a 30° angle: Yes, both speakers must be angled exactly the same, so the angles on each side are identical, but it does not have to be 30°. Anywhere from 25° to 35° is just fine, and under certain circumstance you could even go as far as 20° and 45°. Not more than that, though, for other reasons that I don't have time to go into here.

But you don't have to take my word for it: try it out for yourself! In your house, set up your speakers in the classic text-book "equilateral triangle", 2 feet away from the front wall, 1/3 and 2/3 of the room width, angled exactly 30°, with your chair set up so that the axes pierce your eyeballs and intersect in the middle of your head, then carefully listen to your favorite music like that (flat EQ: don't adjust!). Listen to a few songs that you know really well, and pay attention to the bass tightness, accurate definition in the mids, clarity in the highs, as well as the width of the sound-stage, and clarity in the stereo imaging. Move your head side to side, and forwards / backwards, to see how that changes, and how big your "sweet spot" is. Then quickly and silently (all sounds turned off, so as not to lose the mental reference of what you just heard) move everything around to set it up the way I outlined above: Speakers against front wall, set further apart, angled the same but to point behind your head, not at your eyes... and now and listen to the same songs again, at the same volume, once again paying careful attention to all of the above.

Then tell me which setup works best... Which one gives you the best stereo imaging, clearest sound-stage, and broadest sweet-spot, as well as the tightest bass, best definition in the mid range, and clearest, detailed high end? :)

Don't believe all of the "one size fits all" hype about how so set up your room. All rooms are different. All need different setups. Very seldom does the best setup work out to be a 30° equilateral triangle.

Unless your ears are in your eyes! :)

Now for the 38% myth:

First, the famous "38% rule" is not a rule at all. Wes is sorry he ever even put that out in public, as so many have misunderstood it completely, and don't even understand what he was saying anyway! Simply put: all rooms have "modes", which are the frequencies where standing waves form, due to the dimensions of the room. You can't get rid of them, and even if you could, doing so would be a BAD idea. The problem is that there are not enough of them in the low end. Plenty in the mid range, and abundantly plenty in the high end, but few and far between in the low end. Wes did some math, noting where room modes always form in rooms as percentage of the length, and came to the conclusion that the location in the room where modes are theoretically at the least noticeable, is 38%. That's all. The modes are still there! They don't go away at 38%. They are still very active all over the room, just a little less so at 38%. The problem is, some people don't get it at all, and go nuts trying to get things to work out so their ear holes will be exactly 38.00000% of the room depth, accurate to the nearest nanometer... without realizing that if they happen to lean forward just a bit in their chair, they will already be waaaayyyy of from 38%. Lean forward 6 inches in a room 10 feet long, and you went from 38% to 33%! :shock: :roll: Lean back 6 inches, and you went from 38% to 43%! Oh no! It's the end of the world! (not.) So unless those misguided folks have their heads clamped in a steel vice, they will NEVER be at 38% of the room depth. And would never even notice, in any case! When was the last time you were mixing, leaned forward a bit in your chair, and said "Damn! I can hear that darned 91.38 Hz modal peak here! I better lean back a quarter inch again".... :)

So no, you don't need to be at 38%. 33 to 42 is fine, and even outside of that a bit can still be acceptable. In fact, most engineers feel that the room sounds better when they are a bit in front of that supposedly perfect 38% location closer to 34% seems to be preferred... So 38% is a good starting point, but that's all. There are many reasons why it might be a good idea to be several % points away from there, as long as you avoid being close to 25% or 50%. Those really are bad spots.

Next, the "30° angle" myth:

In reality, it is fine to have your speakers slightly out of that range: 28° to 40° is good, but you can go down to 25° or up to 45° if you need to. 29° to 38° works very well in most rooms. Don't get stuck on nailing that exact 30° angle!

Yes, there are consequences: changing the angle does, indeed, change the stereo imaging and sound stage, and having the speakers at a higher angle will, indeed, increase the width of the sound stage and exaggerate the stereo imaging. But that's actually a GOOD thing, as it improves your ability to resolve directions and positions on the sound stage! So if you are into panning things here and there in your mixes to make them more interesting, the you can do so much more precisely if your speaker angle is greater than 30° azimuth. It also extends the sweet spot in the front-to-back direction, which is good if you do a lot of leaning forward and backward as you mix, but it does "squish up" the sweet spot from side to side... however, that usually isn't a problem unless you have a very large console and need to lean (or roll your chair) a lot to the left or right as you mix. But in most small rooms with DAWs or compact consoles, that isn't an issue. You tend to sit on the center line, and lean forwards/backwards, but not side-to-side. So once again, having the speakers further apart and more angled, is a good thing.

However, you DO need to keep the speakers the same distance from your ears: so if the left speaker is 118 cm from your left ear, then the right speaker also needs to be 118cm from your right ear. That's important for symmetry of the stereo image and sound-stage. BUT!!!! They do not also need to be 118 cm apart! You can spread them further apart, or closer together, as needed. Once again, the world will not come to an end, and you won't be arrested for not having that speaker-to-speaker distance the same as the speaker-to-ear distance.

So how do you use all the above to find the right places for everything?

Start with the specifications for a critical listening room. There's a few documents that lay that out in great detail, and one of them is ITU BS.1116-3. Chapters 7 and 8 have a lot to say about the acoustic specifications for the room and speakers. ITU BS.1116-3 recommends the best distance for speaker separation as being 2 to 3 m, and up to 4m is acceptable under some conditions. It also recommends that the distance from each speaker to the listening positions can be as much as 1.7 times the distance between them, and even up to 2 times that distance in special cases. Closest distance is half the speaker separation. (So much for the equilateral triangle! Based on these specs, that triangle can be greatly squished or stretched...) So for example if your speakers are exactly 2m apart, then the distance from each speaker to the corresponding ear could be anywhere between 1m and 4m. That blows the equilateral triangle thing completely out of the water! That's all in chapter 8 of the document, if you are interested. It also recommends that the sweet spot does not need to be wider than a a radius of about 0.7m around the nominal mix position. There's no point in trying to listen outside that circle, no matter how the speakers are arranged, or how good the room is.

So how do you start laying out the room then:

Start with you, then your speakers. Start with your head (ears) located about 35% from the front wall: anywhere from 30% to 45% is acceptable, but 33 to 38% is best, and 35% is sort of in the middle of that, and allows some room for adjustment. In any case, most engineers seem to prefer a location a little closer to the front wall that 38%.

Measure that distance: how far is your head from the front wall? Try setting up your speakers that distance apart, and see where they turn out. Hopefully, it will be within the limits recommended by BS.1116-3, and also your speakers will not be too close to the side walls of the room. By "too close", I mean less than about 20% of room width. When you do this setup, allow plenty of room between your speakers and the front wall: the speakers will be mounted inside the soffit, in a very rigid, massive enclosure box that takes up space on all sides inside the soffit, and you still need room for cooling air behind it, and room to get your hands in to adjust things: allow at least four or five inches from the rear corner of the speaker, up the wall surface. When you measure the distance between the speakers, and the distance from speaker to ear, you use the acoustic center of the speaker, not the top, bottom, left, or right side of the cabinet, and not the geometric center either. It's the acoustic axis you want: that's the reference point for all measurements relate to your speakers. Check your speaker manual to find out where that is, or ask the manufacturer. It will be a point on the front face of the speaker, somewhere between the center of the woofer and the center of the tweeter, and much closer to the tweeter. That's the spot that you use for setting the height of the speaker, and the distance from the side walls, and the distance between them, and the distance from speaker-to-ear.

So nudge things around a bit until it makes more sense: the angles and distances start working out nicely, within the ranges I mentioned. If you find you can't do that, then adjust the location of the mix position, until you can. You should end up with a good compromise between speaker separation, speaker-ear distance, mix position location, and speaker angle (don't forget that the speaker points at a spot behind your head, not in your head!). With all that in place, draw the lines perpendicular to the speaker axis (in other words, parallel to the speaker face) to represent the front baffle of the soffits. The width of the soffit baffle should be at least three times the diameter of your woofer, preferably 4 or even 5 times, if the room is big enough. The speaker should not be in the center of the baffle: I try to offset it to about 3/5 of the width if possible. So when you draw the line that represents your baffle, take those into account. Let's say your speaker has an 8" driver, so 3*8 = 24" minimum width, but let's shoot for more: 5*8= 40" wide. Set the speaker at 3/5 of that, so 24" from one edge, and 16" from the other edge. It doesn't really matter which edge. So draw your baffle like that: 40" wide, with 3/5 of that centered on the speaker axis. Now you can add "wings" that extend out to the side walls at other angles, if necessary, and a center baffle to join the two soffits if necessary.

That's the basis. That's roughly the procedure I use when designing soffits. Here's an example, currently under construction, nearing completion: thread about Steve's high-end control room in New Orleans Take a close look at those soffits, to get ideas about how to do yours.

Quote:
2) For HVAC, I have looked at mini-splits and my contractor was talking about a heat pump,
Tomaeetos... tomahhhtoes. Same thing, different name. Mini-split systems have an indoor unit (sometimes called the "evaporator") and an outdoor unit (sometimes called the compressor, or condenser.... or the heat pump!) The compressor (outdoors) is usually the same as the "heat pump". In systems that can do both heating and cooling (most can), the compressor is correctly called a "heat pump", but even for systems that only do cooling, it is sometimes still called the "heat pump".

Quote:
can anyone suggest the simplest way to get fresh air into the room given that I don't have a heating requirement,
As I mentioned, the majority of mini-split systems have both functions: they can heat, and they can cool. And when they are heating, they are massively more efficient than your under-floor heating system! A good, modern mini-split can easily draw just 2000 watts of electrical power, and deliver the equivalent of 6000 watts, 7000 watts, or more of actual heating. Highly efficient. A point to ponder when considering your heating bill...

But even if you never use it to heat, it will most likely still have that capability: most mini-split systems do. It's also a good back-up, in the event that your underfloor heating system develops a problem...

And in any case, there fresh-air / stale-air issue is not related to the type of mini-split you get, nor to whether or not you use it to heat the room.

Quote:
and likely won't have much of a cooling requirement?
Are you SURE about that? Half a dozen musicians in there, along with gear, instruments, pizza, etc. can be producing the equivalent of several thousand watts of sensible heat load, plus a few more of latent heat load on a humid day...

Quote:
can anyone suggest the simplest way to get fresh air into the room
Through a duct system, with silencer boxes, and a fan, all of which are sized to provide about 30% of the 6-changes-per-hour circulation rate, while producing no more than 300 fpm at the registers, and not exceeding the static pressure rating of your fan, and keeping the same acoustic isolation as the rest of the studio...

Quote:
3) My outer leaf walls in the front and back are just plywood and then stucco (full disclosure I need to figure out the details of what all is added on top of the plywood before the stucco application as I don't yet know), but should I be thinking about adding drywall to the inside of the plywood or is that overkill because the exterior wall mass with Stucco applied will be more than the side walls
Stucco is basically mortar, so assume a density of roughly 1900 kg/m3. It's heavy, and in a decent thickness, you should have enough mass there to not need to worry about beefing it up. But do the math to be sure: the goal is that your MSM frequency is about the same for all walls, the ceiling, all windows, and all doors, and that the total isolation of all of those parts is roughly the same. One easy way to ensure that, is to keep the surface density of each leaf consistent throughout. So the glass in the window has the same surface density as the door, and the same surface density as the leaf itself, and the sane surface density as the HVAC silencer box, etc. If you can't do that for some reason, then compensate in the regions where the surface density is lower, by increasing the air gap by the right amount.

Quote:
PS. I think I covered off everything in the before you post sticky,
You did great! Excellent first post: everything is in there, in suffient detail.


- Stuart -


You do not have the required permissions to view the files attached to this post.

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Wed Feb 27, 2019 8:41 am 
Offline

Joined: Sat Jan 31, 2015 8:28 am
Posts: 20
Location: Delta, BC Canada
First of all, Stuart, you are the man! Thanks so much for the very quick reply, and the wealth of knowledge, I really appreciate the help. There's a lot to cover, and a lot for me to go over here, and I was going to wait to go through the process before I reply, but figured I owed you some sort of response sooner than that given the time and effort that you gave to your response to me (which is greatly appreciated :D ). So some thoughts below:

Quote:
IF so, you might want to consider putting in some isolation mounts for that pump, so that it does not transmit vibration directly into the slab.

Good call, I will definitely do this.

Quote:
Depending on how much isolation you need, it might be an idea to do that leaf the same as the inner: 2 x 5/8" drywall + GG.

I'm thinking I will do this as well, as your other comment about getting to 60 db suggests I should.

Quote:
Don't guess here! Get your structural engineer to calculate that for you.

Check. Will get the Engineer to validate.

Quote:
You will be building your inner-leaf walls on top of that slab, and you will need to bolt them down. So do mark the locations of the pipes very carefully

Another great call. Will discuss this with my contractor to make sure we account for that too.

On this same note, though, my understanding is that the soffit structure is not part of the inner leaf, but does need to be firmly attached to the room to help anchor it and prevent virbation (not sure if my understanding is correct on this one)... do you suggest that this should be bolted through the floor as well?

I am also considering doing the rough soffit design now to enable me to finalize the placement of lights/outlets, but leaving the actual building of the soffit until after the reno so I can take my time with the finer details of the design and build it myself. I ask the question for 2 reasons, the first one is the need to know if I need to mark the floor for the pipes for the soffit, and the second one is because I'm trying to wrap my head around if I have to put the flooring down before or after the soffit structure or if it matters. If the soffit structure just needs to be affixed to the walls firmly, but doesn't need to be bolted to the floor, then I can lay the floor now underneath and build the soffit on top post reno.

Quote:
Careful there! Some types of hardwood flooring have an air gap between the wood and the slab: you can't do that for a studio. Just some type of underlay is fine, but no air gap.

Further to the above, I am planning a glue down application directly to the concrete, are you suggesting the potential for an air gap is with the Hardwood floor itself or the underlay? If it's the latter, with the glue down directly to the concrete, I believe I will be ok. If it's the former, maybe I need to rethink.

Quote:
You could do it that way, but given that you need high isolation, it would be better to do everything surface-mount.

Great call. I wasn't aware that was an option.

Quote:
Ideal is to have only one single penetration where the power feed comes in

I am picturing some metal conduit into a junction box attached on the inside wall, with the surface mount outlets branching out from there. Do you know of any good threads or materials to read up on this way of doing things? I will also discuss with my contractor/electrician as they may just know how to do this, and how to do it with the star ground.

Quote:
Designing a soffit-mount system take a while...

Yeah, that's why I asked the questions above on if it's something I can delay until after the reno when I can take my time with it.

Quote:
Not so sure about that! Your room will be extremely will insulated: double air-tight seals, very thick, massive walls, double insulation, very thick, plus treatment in the room... Put a few musicians in there with gear, instruments, hot pizza, hot coffee, lights, computers, etc. and you'll be producing quite a bit of heat and humidity. HVAC is needed.

Roger that. I'm starting to think about this now... thinking about potentially using the unused portion of the pool equipment room for some silencer boxes, and then running them outside to the compressor/heat pump. The thing I'm worried about with this though, is that it weakens my isolation on the wall next to that noisy pool pump... I still need to do some more reading and design to figure out how big my silencers would need to be to see if I can get them in between studs or not... Sorry, just thinking out loud.

Quote:
it refers to the location of your ear in the room, not the location of the apex of the triangle.... Two very different things...

The amount of times I have read that on this site only to say... "of course, that makes total sense", and then for me to actually not consider it in my own design is embarrassing... but duly noted. Thanks.

Quote:
Quote:
but the 2 infinite baffles meet in the middle of the wall straight in front of me. I don't know if this is a problem or not, I just can't recall seeing it in any images or build threads that I've read.
There's a reason why you haven't see that: because it's not a good idea, acoustically.

Is there a way to calculate an acceptable minimum separation of the baffles, or a generally accepted size for the flat front wall?

Quote:
Yes! Start by forgetting the stuff you see all over the place, such as the mythical triangle, and they mythical 38%, and the mythical 30° angle...

I'm being rather cryptic here so far, so let me explain: ...

Wow, this is awesome... Thanks for taking the time to lay this out for me in this big section. Going through the process now, and will follow up when I think I have something.

Quote:
Stucco is basically mortar, so assume a density of roughly 1900 kg/m3. It's heavy, and in a decent thickness, you should have enough mass there to not need to worry about beefing it up. But do the math to be sure

I will do the calculations here.

Quote:
the goal is that your MSM frequency is about the same for all walls, the ceiling, all windows, and all doors, and that the total isolation of all of those parts is roughly the same.

Is this just for efficiency so you're not wasting money/time over isolating some parts of the room that aren't the weakest link? Or is there an acoustic reason for this as well?


That's probably enough for now. Stuart, thanks again for your help here.

-Aaron


Report this post
Top
 Profile  
 
PostPosted: Wed Feb 27, 2019 9:53 am 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11984
Location: Santiago, Chile
Quote:
First of all, Stuart, you are the man! Thanks so much for the very quick reply, and the wealth of knowledge, I really appreciate the help
:thu: You are welcome! That's what the forum is all about. Helping out others, giving back some of what you learned, etc.

Quote:
On this same note, though, my understanding is that the soffit structure is not part of the inner leaf, but does need to be firmly attached to the room to help anchor it and prevent virbation (not sure if my understanding is correct on this one)... do you suggest that this should be bolted through the floor as well?
You probably don't need to bolt down your soffit sole plates, no: They will rest on the slab, though, and they will probably be nailed/screwed into the wall sole framing. You could bolt them down if you want, but it's probably not necessary... unless you have massively huge speaker, pumping out huge amounts of power!

Worst case: if it turn out that you do need to bolt it down (unhappy inspector, for example), and you didn't mark the locations of the pipes, there's a "plan B" for finding them later: Thermal imaging:
Attachment:
thermal-camera-radiant-floor-IR image2.jpg

Rent or borrow a thermal camera, and take a few pics with the heating system on: the locations of the pipes will be very evident, and you can mark them "after the fact".

Quote:
I am also considering doing the rough soffit design now to enable me to finalize the placement of lights/outlets, but leaving the actual building of the soffit until after the reno so I can take my time with the finer details of the design and build it myself.
Smart move! :thu: Makes sense. Leave yourself plenty of "wiggle room" to figure out the soffit later, and move things around as needed. That's why I usually try to leave the finish flooring until last, right at the end, when the rest of the room is completely finished, only then do the flooring. It also has practical benefits: no floor damage from dropped hammers and spilled paint! Let that happen to the slab, then put the flooring in after all possibel hammers have already been dropped, and also possibly paint cans have already been knocked over... ( Yup: speaks the voice of experience... :P :roll: Been there, done that.... )

Quote:
I'm trying to wrap my head around if I have to put the flooring down before or after the soffit structure or if it matters.
See above...

Quote:
If the soffit structure just needs to be affixed to the walls firmly, but doesn't need to be bolted to the floor, then I can lay the floor now underneath and build the soffit on top post reno.
It depends on how you design it, but I normally have a sole plate that rests on the slab across the front of the soffit, and the floor butts up against that. Then there's trim on the soffit that covers the floor/soffit junction.

Quote:
Further to the above, I am planning a glue down application directly to the concrete, are you suggesting the potential for an air gap is with the Hardwood floor itself or the underlay? If it's the latter, with the glue down directly to the concrete,
Careful with glued floors and under-floor heating! They'll tell you that it is fine, no problems, all will be well, one size fits all, everybody wins, blah, blah, but heat causes things to expand, and cold causes them to contract: over time, that can lead to things coming un-stuck, warping, bending, squeaking, etc. Personally, I usually recommend laminate flooring for my clients, since it is a great surface acoustically, looks great, wears well, goes in fast, can be fixed / replaced fairly fast, and isn't too expensive. Plus, it is not mechanically attached to your slab. You put down underlay, and it just sits on top of that. You leave small gaps around the edges to deal with expansion/contraction, and life is wonderful! For this reason of not being attached, it is sometimes called "floating flooring", which should NOT be confused with the concept of an acoustically floated floor.... same name, very different animal.

Quote:
I am picturing some metal conduit into a junction box attached on the inside wall, with the surface mount outlets branching out from there.
This is the way I do it for high isolation studios: Top view, looking down inside the wall at the two pieces of conduit, that are gently curved, one going through each leaf, with an empty gap in the middle between them:

Attachment:
Conduit-isolation-0-SML-ENH.png


Wrap a rubber sleeve of some type around that gap:
Attachment:
Conduit-isolation-1b-SML-ENH.png


That ensures that the two sides of the conduit are not mechanically connected. More views:
Attachment:
Conduit-isolation-2-SML-ENH.png


Attachment:
Conduit-isolation-3-SML-ENH.png


Keep the curves gentle, use over-size conduit ( to allow for future repairs / expansion ), offset the penetration points by at least one stud bay, so they are not facing each other, make the holes a little larger than the conduit, and pack the gap with truckloads of caulk! Use putty packs if you want for extra mass. After the cables are through, stuff insulation down both ends of the conduit as far as you can push it in, then seal the end with more truckloads of caulk.

The one on the inner leaf should, as you guessed, end up inside a junction box, and from there spreads out to where it is needed. If your electrical code insists on having a proper distribution panel with breakers inside the room, then the feed goes to that, and it spreads out around the room from there.

Quote:
thinking about potentially using the unused portion of the pool equipment room for some silencer boxes,
Silencer boxes are BIG. And heavy. For high isolation scenarios, you need two boxes per duct: one where the duct goes through the inner-leaf, the other where it goes through the outer leaf. You need two ducts: one for fresh air, one for stale air. So two ducts, two leaves = 4 silencer boxes. Big ones. Heavy ones. Think about places you can put those that won't take up space inside the room, if possible. For example, between ceiling joists, partially inside soffits, partially inside bass traps, etc.

Quote:
Is there a way to calculate an acceptable minimum separation of the baffles, or a generally accepted size for the flat front wall?
The idea is to maximize the speaker baffles, along the lines I mentioned, but not so much that it looks ugly! Studio design is mostly about acoustics, but also about aesthetics. If you design your soffits with a certain sized center section, and it looks out of proportion, then try changing it! Make it bigger, or smaller until it looks good. Consider different materials, adding trim, different color scheme... Lot's of things to think of when designing a studio!

Quote:
Is this just for efficiency so you're not wasting money/time over isolating some parts of the room that aren't the weakest link? Or is there an acoustic reason for this as well?
Yes to all of the above! :) It's basically to ensure that all sides of your room are acting pretty much the same, with no major differences, and one of the reasons for that is to be efficient and effective: no wasted time/materials on overkill, but also keeping the entire room up to the minimum level. The other is acoustics: If one wall happens to not isolate very well, then some frequencies will "escape" through that wall, partially, while the opposite wall will reflect those same frequencies back into the room. So you won't have symmetry....

- Stuart -


You do not have the required permissions to view the files attached to this post.

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 02, 2019 7:49 am 
Offline

Joined: Sat Jan 31, 2015 8:28 am
Posts: 20
Location: Delta, BC Canada
Hey Stuart,

Thanks again for your response. Super helpful. And I am now confident on delaying the final design of my soffits :). However, I am now sure that I can not delay the HVAC design any further... so I am getting deeper into my HVAC reading, and was hoping for a bit of direction.

I'm currently trying to figure out how big the box will need to be so I will know where I can put it, and this is what I know so far...

My room volume = 9'9 1/4" x 14'1 1/2" x 8'11 7/8" = roughly 1240 cf
(I know this is less than I originally said, but I made the rookie mistake of quoting the outer leaf dimensions of the room, not the inner leaf... so I lost some cubic feet there :( )

According to your comment earlier in the thread, I need around a 6 times per hour refresh rate.

Which means my cubic feet per minute should = Refresh rate * Volume / 60 = 6*1240/60 = 124 cfm

Then from this:

Quote:
The basic concept is that you need to circulate the entire volume of air in the room at least 6 times per hour, you need to replace about 20% to 30% of that with fresh air, dumping the same volume of stale air to the outside, you need to do all that while keeping the air velocity at the registers under 300 fpm (200 would be better), and also retaining the isolation that you spent so much to create, and also removing the right amount of latent heat and sensible heat form the room for the two extreme situations (max occupation by hot sweaty musicians on the hottest, most humid day in mid summer, vs. one single person sitting quietly on the coldest, driest day in mid-winter)... That's all! Simple! 8)

I took that I need to try to get to sub 300fpm at the register, so I used a calculator I found on this site.
And it suggested I need a 9" diameter opening at the register.

This is where I am getting a bit confused as I try to understand the internal cross sectional area of the silencer box, which I need to do to figure out how big it needs to be to figure out where I can put it... So here is my new set of questions:


1) Does anything seem wrong with my process so far?

2) With a 9" diameter at the register does that mean that I need double that cross sectional area inside the silencer box? i.e. the cross sectional area of 9" diameter register is = 3.14*4.5^2 = 63.585 square inches, so the cross sectional area of my silencer box needs to be 127 ish square inches? Or is the double the cross sectional area only for the silencer box with respect to the ducting between silencer boxes? i.e. if I use a 6" duct then my cross sectional area in my silencer is 3.14*3^2 = 28.26 so my cross sectional area in my silencer would need to be 56.5 square inches?
I guess in the end, I believe understand the principle of and requirement for the impedance mismatch and the importance of the cross sectional area change, but am confused as to where it needs to happen.

3) If the answer to the above is the latter, then does the air velocity in the ducting matter elsewhere in the system, or only as it hits the register? I ask because if I used a 4" diameter duct vs a 6" diameter duct then it would require a smaller silencer box, right? Or maybe the better question is what is the calculation I need to do to determine duct sizing?

4) OK, posing this question makes me feel like I really don't understand the concept here... But here goes. I've read that I should be aiming for a straight run of ducting that is 5x the diameter of the opening of the silencer box to ensure that turbulence is gone before the air hits the register. However, I'm also under the impression from reading that the silencer box needs to be directly attached to the opening at the leaf that it is penetrating (I took this to mean not connected with flex duct, but effectively built to open into the penetration). How do these 2 things jive together given the required cross sectional area at the register. If it's 9", the run would need to be 45" long to get to the silencer box. I get that this could work if you extended the vent inside the inner leaf, but how would you ever flush mount a vent to the inner leaf if both of these things needed to be true?


OK... I am getting dizzy here, and I still haven't got a clue where I am going to put these things... But I'll leave it to that for now.

Thanks again in advance for your help.

-Aaron


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 02, 2019 9:04 am 
Offline

Joined: Sat Jan 31, 2015 8:28 am
Posts: 20
Location: Delta, BC Canada
OK, while the HVAC question is sitting, I switched back my focus to the speaker locations... and have one more question for you Stuart.

I started down following your process for coming up with a location, and immediately found a problem.

Quote:
Start with the specifications for a critical listening room. There's a few documents that lay that out in great detail, and one of them is ITU BS.1116-3. Chapters 7 and 8 have a lot to say about the acoustic specifications for the room and speakers. ITU BS.1116-3 recommends the best distance for speaker separation as being 2 to 3 m, and up to 4m is acceptable under some conditions.

Quote:
Hopefully, it will be within the limits recommended by BS.1116-3, and also your speakers will not be too close to the side walls of the room. By "too close", I mean less than about 20% of room width.


With my room width at 9'9 1/4", 20% from my side wall is about 23 and a half inches. If I subtract that from my room width, I get about 5'10". 5'10" is less than the ITU BS.1116-3 recommendation of a 2m minimum speaker width (roughly 6'7 1/2").

Next question is:

1) If a compromise has to be made, where is it better to compromise. Speaker width or proximity to the side walls? Or a halfway house between both?

Thanks again!

-Aaron


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 02, 2019 9:43 am 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11984
Location: Santiago, Chile
Quote:
However, I am now sure that I can not delay the HVAC design any further... so I am getting deeper into my HVAC reading, and was hoping for a bit of direction.
HVAC is big. A very big deal! It's never too soon to get into that, for a studio.

Quote:
Which means my cubic feet per minute should = Refresh rate * Volume / 60 = 6*1240/60 = 124 cfm
:thu:

Quote:
I took that I need to try to get to sub 300fpm at the register, so I used a calculator I found on this site. ... And it suggested I need a 9" diameter opening at the register.
That gives you about 63 in2 cross sectional area, which is about 0.44 ft2, so do the math: 124 F3/M / 0.44 ft2 = 281 FPM. Close enough to 300.

However, don't get confuse here: the 300 FPM figure is for the air velocity at the registers: it an go faster in the ducts that link the silencer boxes to each other, and to the AHU. You only really need to worry about the velocity at the register. So you could probably use 8" duct to link your boxes.

Quote:
This is where I am getting a bit confused as I try to understand the internal cross sectional area of the silencer box, which I need to do to figure out how big it needs to be to figure out where I can put it...
You already have part of your answer: the minimum cross sectional area you can allow at the registers, is 63 in2 (or 0.44 ft2, if you prefer). That's the MINIMUM! If you go less than that, then the flow velocity will be higher, so it is better to go with more area Also, that refers to the OPEN area of the register: Registers usually have vanes and sometimes mechanisms that partially block the air flow, and if yours have movable vanes, then they could block the flow considerably. So you need to figure that out too: if the open area od your register is, for example, 80%, then you divide the minimum cross-sectional area by that percentage, to get the area of the typical registers. Eg, 63 in2 / 80% = aprox 79 in2. So that's what you'd look for in a registers: an 8" by 10" would be about right for that hypothetical scenario.

Quote:
So here is my new set of questions:
1) Does anything seem wrong with my process so far?
So far, so good! Taking into account the above caveats...

Quote:
2) With a 9" diameter at the register does that mean that I need double that cross sectional area inside the silencer box?
Correct. So you would need at least 126 in2 cross sectional area.... However, I usually try to design silencers such that there are TWO abrupt changes: One going in, and one going out. I like to increase the area at the register end, to ensure even slower flow.

Quote:
i.e. the cross sectional area of 9" diameter register is = 3.14*4.5^2 = 63.585 square inches, so the cross sectional area of my silencer box needs to be 127 ish square inches?
Right. Roughly. But do take into account that if you use smaller diameter ducts between boxes, the percentage change will be larger, which is better. So for example, if you used 6" duct, the area would be 28in2, the speed in the duct would about 675 FPM, and the change in area from 28 (duct) to 127 (silencer) is a factor of 4.5. That's great! Much better than the factor of 2, which is the MINIMUM. Of course, you don't want to go too small on the duct diameter, as then you'd be getting very high velocities in the ducts, which implies more turbulence, more flow resistance, more noise, more problems.... But 675 FPM is OK.


Then, if you can get another increase t, say, 250 in2 on the actual registers, that's yet another factor of 2, so even more isolation. To do this, I often design silencers boxes to split the air flow into two paths, with each one having its own register on the end, so you can get large reductions in flow like that.

Quote:
Or is the double the cross sectional area only for the silencer box with respect to the ducting between silencer boxes? i.e. if I use a 6" duct then my cross sectional area in my silencer is 3.14*3^2 = 28.26 so my cross sectional area in my silencer would need to be 56.5 square inches?
Try to keep the changes in cross section large: AT LEAST a factor of two. If you can get a higher factor, as I mentioned above, then that's better, as it implies greater isolation. And work backwards from the registers, starting with the area you need there, plus the factor for open area, plus a safety margin, then go back through the silencer box, then the ducts. However, to also take into account the AHU itself! If it puts out a flow of, say 400 CFM at 800 FPM, then take a look at the cross section of that, and work forward from there too: if the cross section is, for example, 80in2, then you don't want to try forcing that into a 6" duct, which only has 28in2! The pressure drop and velocity increase would be just too much. You could only use a 6" duct for that if you were planning to also have another, larger, duct taking the rest of the flow somewhere else. An 8" duct would probably be OK for such an AHU, but 10" would be better.

Quote:
I guess in the end, I believe understand the principle of and requirement for the impedance mismatch and the importance of the cross sectional area change, but am confused as to where it needs to happen.
Make it happen as often as you can, and at least four times: once at the entry and once at the exit for each box.

Quote:
3) If the answer to the above is the latter, then does the air velocity in the ducting matter elsewhere in the system,
It matters to a certain extent (see above discussion), but it's not critical, as long as the flow velocity is reasonable. But if you find yourself with velocities of 4000 FPM in a 2" duct, then something is wildly wrong! :)

Quote:
I ask because if I used a 4" diameter duct vs a 6" diameter duct then it would require a smaller silencer box, right?
Nope! The silencer box still need to be the same size, since you do need to get the flow velocity down below 300 FPM at the register, which is right on the end of the sleeve that comes out of the silencer box... Do the changes from small area to large area early in the flow path, then from large area to even larger area right before the register.

Quote:
I've read that I should be aiming for a straight run of ducting that is 5x the diameter of the opening of the silencer box to ensure that turbulence is gone before the air hits the register.
If possible yes. Sometimes that isn't possible, but at least three times.

Quote:
However, I'm also under the impression from reading that the silencer box needs to be directly attached to the opening at the leaf that it is penetrating
Right.

Quote:
How do these 2 things jive together given the required cross sectional area at the register.
Like this:

Attachment:
SOUNDMAN2020--HVAC-split-flow-silencer--rev--S0134.jpg


Attachment:
SOUNDMAN2020--HVAC-split-flow-silencer--bot--S0134.jpg


That's my proprietary design, by the way, that I developed years ago, and have used in many studios. Feel free to copy the concept, as long as you don't try to pass it off as your own, or try to sell it for commercial purposes!! :)

So, you have your duct coming in, smallish diameter, and immediately it enters the box, that widens out to about double, then the flow path splits in two, with each path being at least twice the cross sectional area, preferably more (4 times is good, so you get a factor of eight change). Then you have another change at the register sleeve where it leaves the box itself and goes through the leaf. The final sleeve is long enough that the turbulence is reduced before the flow hits the register.

Quote:
If it's 9", the run would need to be 45" long to get to the silencer box.
So don't make it 9" then! :)

- Stuart -


You do not have the required permissions to view the files attached to this post.

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Sat Mar 02, 2019 10:08 am 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11984
Location: Santiago, Chile
You started out in negative territory, before you got to the speaker locations! Check out 8.2.2.1....

You said your floor area is "10'1" wide by 15' deep": That's about 150 ft2, which is only about 70% of the minimum area.... Therefore, you won't be able to set things up exactly as they say, since your room does not fit the dimensions that they based their recommendations on.

However, don't get too worried here: just because their minimum is 215, that does not mean that a room with 216 is perfect and a room with 214 is terrible! Not at all. 215 is the minimum recommended, because that's the size that allows you to meet all the specs fairly easily: you can go smaller than that, if you have no choice, but it will be harder to meet the specs. That's all. It will need more acoustic treatment, and more careful design, but it won't be disgustingly bad in there. The smaller it is, the harder it gets. I have designed rooms similar in size to yours, and they worked out just fine. The smallest room I've done so far is 97 ft2, and the customer is rather happy with the results. His unsolicited comment: "All I can say is HOLY CRAP, this thing is insane. I’ve never heard imaging so clear and such full low end like this! Its pretty incredible! There were points in time particularly over the summer while i was working 17 hour shifts and then building this thing in my time off, that I questioned if I had made the right choice; But this really exceeds anything I could have expected. Bravo on your design Stuart, it’s truly impressive.". So yeah, with careful design, your 150 ft2 can be quite decent, I think! :) That's 50% larger than the tiny room above...

So, back to the problem: Your room is smaller than the recommended size, so you'll have to reduce the dimensions correspondingly. If you can't get 2m between the speakers, then reduce that to something reasonable.

Another way of approaching the layout is from the listening position: start with your head at about 1/3 of the room depth (front-wall-to-back-wall) or maybe a tad more: try 36%, then set your speakers around that distance apart. Your room is 15 feet long, so based on this, your head will be .36*15 = 5.4 feet from the front wall. Your speakers can then be around 5.4 feet apart. ...

Quote:
1) If a compromise has to be made, where is it better to compromise. Speaker width or proximity to the side walls? Or a halfway house between both?
It's a juggling game, and there are many factors to take into account! For example, might it be BENEFICIAL to have your speakers at the exact 25% width points, to automatically avoid exciting the associated mode? What frequency is that mode? Would your speakers even trigger it? Would it be hard to treat otherwise? Would it be a problem at the mix position? If there's a benefit, then evaluate that location. Otherwise, avoid that spot like the plague, and try other spots, a little closer in or out...

Juggle, jugggle... juggle... Welcome to the wonderful world of studio design! When you can keep 47,428 tennis balls in the air all at once, then you are ready to design your studio... it certainly seems like that's how many parameters you have to juggle to achieve success! :)


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Sun Mar 17, 2019 2:30 pm 
Offline

Joined: Sat Jan 31, 2015 8:28 am
Posts: 20
Location: Delta, BC Canada
Hey Stuart,

Again, thank you so much for all your help. You should write a book or teach a class if you don't already...

I've really been struggling with figuring out the placement of the silencer boxes. And I'm hoping you can clarify a few more things for me...

1) Trying to figure out if there is a way to fit the boxes inside the gaps between the joists in my outer leaf ceiling. I have a 16x12 inch gap in the outer leaf ceiling joists to work with... and those are going to be running perpendicular to the 2x6 joists in my inner leaf. see image below:
Attachment:
OuterLeafJoists.jpg

so am trying to figure out if I can construct a box that can fit in that space. If the box is 2x1/2" MDF and has a 1" duct liner, I'm losing 2" per side, so the effective room I have to use is 12" x 8" which would give me a cross sectional area of 96 square inches. Which already isn't enough... but even if it was enough, I am unclear if I'm doing that right. Is the cross sectional area of the box what matters, or the path around the baffles? i.e. do I need to maintain the cross sectional area around the baffles too, meaning if 96 square inches was enough, would I actually need a much larger box so that the path around the baffles is 12" x 8" like in the image below, meaning that the box actually needs to be around twice as wide?
Attachment:
CrossSectionAreaQuestion.jpg


2) OK, even if the answer to 1 is that the area doesn't need to be maintained around the baffles, I have a problem in that I only get 96 square inches... which brings me to my second question around air exchanges. Is 6 changes per hour mandatory if 80-90 percent of the time it's just going to be me in there and for the rest of the time it would likely be just me and 1 other person? Can I get away with 4 changes per hour? I ask because if it's only 4 changes per hour I have 4*1240/60=82.67 cfm. And when I punch that into the calculator I get a diameter of 7.5" for a duct velocity of roughly 270 f/m. This would give me a cross sectional area of 44.18 square inches, meaning I'd only need 89ish square inch cross section in the silencer box.

3) In the event that the answer to #1 is that it's just the cross section of the interior of the box ignoring the baffles (which as I type, I'm would bet that it isn't), and that 4 exchanges per hour is acceptable, the next question I would have is if all 4 boxes could be attached to my outer leaf joists? I ask because my inner leaf joists are only 2x6, so I definitely wouldn't be able to fit the box in those. If that's the case, could I connect the 2 silencers that connect to my inner leaf and the registers inside my room such that they are decoupled from the inner leaf and just use acoustic caulk around a small gap between the register and the inner leaf drywall? (feel free to ignore this one if the answers to #1 and #2 make this question moot.)

4) OK, as I said, I fear that the answer to #1 is that I need to maintain the cross section around the baffles in the silencer box... and if this is the case, I can't see how I could fit the silencers in the joists between my leaves. In the event that this is the case, I am wondering if it's acceptable to only have 2 large silencers and utilize the pool equipment room for those. I believe that I saw a thread on this site where you helped someone design a silencer that penetrated both leaves, with some 2x4 constructed registers that were connected to the silencer with some heavy rubber or something to maintain the decoupling of the leaves. I can't for the life of me find the thread again though... If you do know what I'm talking about, would a system like this work in my situation if I could use the pool equipment room for the 2 large silencer boxes?

I worry that in this case both my registers would be on the side wall, and wouldn't be very effective, but I'm wondering if that might be enough to keep me alive and relatively comfortable considering I don't have that harsh conditions for most of the year, and still maintain enough of my isolation to get the job done.

Again, thanks for your help here Stuart. Trying to keep the faith, but these silencer boxes are making me feel a bit defeated...

-Aaron


You do not have the required permissions to view the files attached to this post.


Report this post
Top
 Profile  
 
PostPosted: Sun Mar 17, 2019 5:01 pm 
Offline

Joined: Sat Jan 31, 2015 8:28 am
Posts: 20
Location: Delta, BC Canada
And while I'm at it, I wanted to run my baffle design by you to see if I have something workable.

I played around with some of the distances and I think I have a reasonable compromise here. But I wanted to walk you through my thinking to see if I went astray anywhere, and I also have a few questions that I was hoping you could answer.

I started by placing the listening position at ~35% like you suggested, then placing the speakers at a distance 20% of the room width from the side walls to try to maximize the width of my sound stage. I nudged around the speakers to try to do the best I could to maximize listening distance, and make sure I was within the specs of .5 to 2 times the width for the listening distance, while aiming the speakers about 12" behind my head.

Where I netted out was a width of ~5'9 1/2" and listening distance of about ~5'8". And the speakers are angled about 31.6 degrees.

I then started on the actual baffle... The speaker I am looking at using in the baffle is a 3 way speaker with the largest driver being 7", so 5x that is a 35" wide baffle at least. I am not working with a ton of space, so I just made it 35" wide. using the 2/5ths and 3/5ths guideline that you gave me, I made it 14" to one edge, and 21" to the other.

Which leads to my first couple of questions...

1) Should I be measuring that 14 and subsequent 21 inches from the acoustic axis of the speaker, or from the edge of the speaker cabinet? (I did it from the acoustic axis, and am hoping that's ok because I don't have much more room to work with.)

2) In joining the two baffles with a flat wall right in front of me, I can't help but think that I've moved the yard stick on where the position that is 35% of my room length is. So my question is after all is said and done, do I measure that point from the front of the baffle to the rear of the room, or from the inner leaf front wall to the rear of the room? (I'm really hoping you say baffle. Currently my listening position is about 37% of the room length if I should measure from the baffle front wall, and not the inner leaf front wall. Probably ok at 42% if it is measured the other way, but getting closer to 50% which I don't like.)

Next thing I noticed was with a 47" high ear height when sitting, the speakers would be firing right into the back of my computer monitors and my secondary set of speakers that I would check mixes on... So I wanted to raise them up. I noticed in another thread that you suggested a maximum of 10 degrees that I could angle the speaker, so I basically maxed it out, raised them up 10 degrees from the listening axis point behind my head, then tilted the speakers down 10 degrees, and that got them up over the desk/monitors/second speakers. I'm not sure if I did this right or if this is acceptable in my circumstances and would love your thoughts on this methodology.

So I ended up with something like this:
Attachment:
SpeakerDistanceAndListeningDistance.jpg

Attachment:
AngledBaffle.jpg

(Note: that is not my actual desk, I will likely build a bespoke desk when I'm finished the room, but It felt like a good representation of what I would have.)

In any case this is currently where I sit with it. As I said before, I would love to hear your thoughts on where I am. Whether I am barking up the right tree or not, I have a few other questions I was hoping you could guide me on...

3) Now that I have angled part of the front wall of the baffle, I was thinking about what point to start that angle from, as I still want to use the space behind the baffle for hangers. Thinking about the 5x the diameter of the biggest driver guideline, I started to angle the wall 14" below the acoustic axis of the speaker. This however doesn't really jive with the 2/5ths 3/5ths guideline, though, as I just continued that angle up to the ceiling of the inner leaf. Also, this speaker height is 53% of height of the room, which seems dangerously close to 50% too, and I'm not sure if that is acceptable.

4) What should I do with the space from the outer edge of my baffle to the sidewalls? Should I just extend that wall past the listening position to create some angles that reflect sound to the back of the room instead of to my ears? Or should I think about some kind of absorption or diffusion for that piece of wall?

5) Answer to #4 notwithstanding, I'm a little fuzzy on what's a good way to actually attach the baffle wall to the side walls given the bottom plate won't be anchored to the floor? Do I just screw through the drywall into the nearest stud? Or is there some other generally accepted method to do this? Also, should I be attaching the structure to the ceiling? Or am I trying to keep the structure mostly decoupled?

Thanks again in advance for your time.

-Aaron


You do not have the required permissions to view the files attached to this post.


Report this post
Top
 Profile  
 
PostPosted: Mon Mar 18, 2019 3:36 pm 
Offline
Moderator
User avatar

Joined: Wed Feb 01, 2017 6:03 pm
Posts: 1034
Location: St. Albert, Alberta, Canada
Quote:
If the box is 2x1/2" MDF

Find a place that sells 1" MDF. You won't be able to find it at Home Depot, but there are specialty places that sell it around your area I'm sure. Try Formations in Langley. There really is no point in screwing around putting two layers of 1/2" together for silencer boxes.

Quote:
I'm losing 2" per side, so the effective room I have to use is 12" x 8" which would give me a cross sectional area of 96 square inches.

You'll need to lose at least another inch off of that in order to decouple the silencer from the joists using something like insulation or rubber or some sort. Also, that is NOT your cross sectional area flowing through your box. Using your largest dimension of 11" and my little algorithm of x = (width available - 8)/2, your x dimension of your cross sectional area is 1.5". That's scary. Okay, then the other dimension making up your cross sectional area can be up to your 7" minus the 4" of MDF and ductliner. Therefore, it will be 3". So, your total cross sectional area if you try to fit a silencer box into your joist cavities would be 1.5" x 3" = 4.5 square inches. Not 96.

Quote:
Trying to keep the faith, but these silencer boxes are making me feel a bit defeated...

That is why we always bring up HVAC and stress the importance of the design. So many people write things like, "Well I'm just going to see how hot it gets and I'll add some HVAC later if I need it". As you can see, the HVAC determines everything. Don't feel defeated. There are ways around it. You just need to get creative and find the space for it elsewhere. The front, or back, or sides of the room. Or maybe make tall skinny boxes that still utilize your joist cavities that hang down into your cloud area or something like that. It's easy to mess around in SketchUp!

Quote:
1) Should I be measuring that 14 and subsequent 21 inches from the acoustic axis of the speaker, or from the edge of the speaker cabinet? (I did it from the acoustic axis, and am hoping that's ok because I don't have much more room to work with.)

Stuart can clarify, but my guess is that the center of the speaker is what makes sense.

Quote:
2) In joining the two baffles with a flat wall right in front of me, I can't help but think that I've moved the yard stick on where the position that is 35% of my room length is. So my question is after all is said and done, do I measure that point from the front of the baffle to the rear of the room, or from the inner leaf front wall to the rear of the room? (I'm really hoping you say baffle. Currently my listening position is about 37% of the room length if I should measure from the baffle front wall, and not the inner leaf front wall. Probably ok at 42% if it is measured the other way, but getting closer to 50% which I don't like.)

The baffles are going to change the perceived length of the room acoustically for different frequencies, but modal distribution is ultimately going to be affected by the boundaries of your room --> your inner leaf. That's why the hangers live behind your baffle/soffit/soffit wings. So unless Stuart says differently, I'd keep your head at the 35% room length based off of your inner leaf sheathing.

Quote:
Next thing I noticed was with a 47" high ear height when sitting, the speakers would be firing right into the back of my computer monitors and my secondary set of speakers that I would check mixes on... So I wanted to raise them up. I noticed in another thread that you suggested a maximum of 10 degrees that I could angle the speaker, so I basically maxed it out, raised them up 10 degrees from the listening axis point behind my head, then tilted the speakers down 10 degrees, and that got them up over the desk/monitors/second speakers. I'm not sure if I did this right or if this is acceptable in my circumstances and would love your thoughts on this methodology.

10 degrees is the MAX you should ever go. You should aim for less than 5 degrees if possible. The ultimate solution you should come up with is building a custom desk where your screens are down inside of it or low enough to alleviate the issue. Also, I understand your desire for a second set of speakers, and sure, maybe check on some, but with a properly designed control room, I personally don't understand why you think you should make mix decisions based off of a second set of speakers that are going to suffer from things like SBIR. If you really want to check on a second set of speakers on stands, maybe set them on stands that crank up or something so that they are out of your way until you want them. I just think it's crazy to make your entire soffit design suffer due to a set of speakers that are going to sound like crap compared to your soffit mounted ones.

Quote:
4) What should I do with the space from the outer edge of my baffle to the sidewalls? Should I just extend that wall past the listening position to create some angles that reflect sound to the back of the room instead of to my ears? Or should I think about some kind of absorption or diffusion for that piece of wall?

That is where your soffit wings go. They are an extension of your "infinite baffle" and like the baffles that your speakers are mounted in, they must be angled to provide a reflection free sphere around your head.

Quote:
I'm a little fuzzy on what's a good way to actually attach the baffle wall to the side walls given the bottom plate won't be anchored to the floor? Do I just screw through the drywall into the nearest stud? Or is there some other generally accepted method to do this? Also, should I be attaching the structure to the ceiling? Or am I trying to keep the structure mostly decoupled?

Sorry, why won't the side wall bottom plates be anchored to the floor? They need to be very very strong and rigid in design.

You're making great progress, keep it up!

Greg

_________________
It appears that you've made the mistake most people do. You started building without consulting this forum.


Report this post
Top
 Profile  
 
PostPosted: Wed Mar 20, 2019 3:49 am 
Offline

Joined: Sat Jan 31, 2015 8:28 am
Posts: 20
Location: Delta, BC Canada
Thanks for the reply Greg,

Some further thoughts/questions from me below:

Quote:
Find a place that sells 1" MDF.

Good call. Will definitely do that.

Quote:
Also, that is NOT your cross sectional area flowing through your box. Using your largest dimension of 11" and my little algorithm of x = (width available - 8 )/2, your x dimension of your cross sectional area is 1.5".

I'm a bit confused now. I don't follow your algorithm, can you expand on the thinking behind it? Why would you subtract 8" off the width available?

I'm wondering if I wasn't clear enough in my previous Post. In my situation, I have 16x12" available, I already removed 4 inches from each side for the mdf and duct liner to get to 12x8... I now know from your comment about decoupling that I should subtract another 2 inches from the width, which would get me to 10x8" of usable air space...

I am inferring from the divide by 2 in your algorithm that in fact I do need to maintain the cross sectional area around the baffles and I can't just use 10x8" as my cross sectional area... So I am guessing I'm at around 40 square inches... which really doesn't help me... Let me know if I am now thinking about this correctly.

If I am now thinking about this correctly, then I'm hoping Stuart can chime in about the design I was referring to in question #4 of my previous post ... as I worry that might be my next best option.

Quote:
Quote:
1) Should I be measuring that 14 and subsequent 21 inches from the acoustic axis of the speaker, or from the edge of the speaker cabinet? (I did it from the acoustic axis, and am hoping that's ok because I don't have much more room to work with.)

Stuart can clarify, but my guess is that the center of the speaker is what makes sense.

Would love some clarity on this one if you are reading Stuart.

Quote:
The baffles are going to change the perceived length of the room acoustically for different frequencies, but modal distribution is ultimately going to be affected by the boundaries of your room --> your inner leaf. That's why the hangers live behind your baffle/soffit/soffit wings. So unless Stuart says differently, I'd keep your head at the 35% room length based off of your inner leaf sheathing.

Got it. Thanks.

Quote:
10 degrees is the MAX you should ever go. You should aim for less than 5 degrees if possible. The ultimate solution you should come up with is building a custom desk where your screens are down inside of it or low enough to alleviate the issue. Also, I understand your desire for a second set of speakers, and sure, maybe check on some, but with a properly designed control room, I personally don't understand why you think you should make mix decisions based off of a second set of speakers that are going to suffer from things like SBIR.

The secondary speakers aren't a big deal, and to your point I probably won't need them, so I am pretty sure I can get them out of the way on stands but it's the monitors that I was mostly worried about. But what you say makes sense so I might rethink this one. To be honest though, aesthetically it just felt that the speakers should be higher on the wall too when I was looking at it in Sketchup. However, point taken, and while aesthetics are still very important to me getting a great sounding room is paramount. After all it would be easier to not have to angle the structure anyway.

Quote:
That is where your soffit wings go. They are an extension of your "infinite baffle" and like the baffles that your speakers are mounted in, they must be angled to provide a reflection free sphere around your head.

Is this as simple as just extending them past my listening position, or using the mirror test to make sure that I am not getting any first reflections off those walls? Or is there some other method I should be considering when deciding where to extend the wings to?

Quote:
Sorry, why won't the side wall bottom plates be anchored to the floor? They need to be very very strong and rigid in design.

Sorry for the confusion... The side wall bottom plate will be anchored to the floor. Earlier in the thread we concluded that the bottom plate of my baffle structure doesn't need to be anchored to the floor. However, my question about good methods to attach the baffle structure to the room is still outstanding unless you are suggesting that the baffle bottom plate does need to be anchored to the floor.

One more question for Stuart. Earlier in the thread you posted a picture to some good looking surface mount electrical outlets...
Attachment:
SurfaceMountElectrics.PNG

Any chance you know what product is in this pic? In my searches everything I see looks hideous in comparison.

Thanks again everyone for your help.

-Aaron


You do not have the required permissions to view the files attached to this post.


Report this post
Top
 Profile  
 
PostPosted: Wed Mar 20, 2019 2:22 pm 
Offline
Moderator
User avatar

Joined: Wed Feb 01, 2017 6:03 pm
Posts: 1034
Location: St. Albert, Alberta, Canada
Quote:
I'm a bit confused now. I don't follow your algorithm, can you expand on the thinking behind it? Why would you subtract 8" off the width available?

In my design I added length to the baffles to ensure that the sound would have to go around them, not just around the 1" duct liner. It might be an inch or so too much, but it's a fail safe. I'll revisit it to make sure. But, you can simply draw it up in SketchUp and see for yourself.

Quote:
To be honest though, aesthetically it just felt that the speakers should be higher on the wall too when I was looking at it in Sketchup.

You're probably used to seeing the massive speakers soffit mounted in big studios. Those speakers are shooting towards the back of the room for the band/producers to hear. The speakers acoustic axis should be at the same height as your ears when you're sitting in your chair. For tall 3 way speakers, people will often flip the speaker up side down (so the woofer is at the top) so that the acoustic axis is where it needs to be and prevent the woofer from being obstructed by the desk.

Quote:
Is this as simple as just extending them past my listening position, or using the mirror test to make sure that I am not getting any first reflections off those walls? Or is there some other method I should be considering when deciding where to extend the wings to?

Use the search feature on the forum to look up ray tracing. It's very very important that you do ray tracing in SketchUp to ensure your design works perfectly. Also, you need to ray trace not only your horizontal plane, but trace your vertical plane as well so that you know how to build your ceiling cloud. The cloud can make things very tricky if you don't have a nice tall ceiling!

Quote:
Sorry for the confusion... The side wall bottom plate will be anchored to the floor. Earlier in the thread we concluded that the bottom plate of my baffle structure doesn't need to be anchored to the floor. However, my question about good methods to attach the baffle structure to the room is still outstanding unless you are suggesting that the baffle bottom plate does need to be anchored to the floor.

I'd at least glue the bottom plates of everything to the floor. Sure, they will be anchored to the wall and massively heavy structures, but why not glue them?

Greg

_________________
It appears that you've made the mistake most people do. You started building without consulting this forum.


Report this post
Top
 Profile  
 
PostPosted: Wed Mar 20, 2019 3:46 pm 
Offline
Moderator
User avatar

Joined: Wed Feb 01, 2017 6:03 pm
Posts: 1034
Location: St. Albert, Alberta, Canada
Quote:
I'm a bit confused now. I don't follow your algorithm, can you expand on the thinking behind it? Why would you subtract 8" off the width available?

Okay, I checked out my notes here. I messed with it and leaving a total of 1" of MDF on the baffles overlapping one another through the path (1/2" on the end of each baffle) here is it:

x = (y-7)/2

x being a dimension of your cross sectional area
y being the total width of your silencer box

Remember, you SHOULD leave at least 1/2" around the outside of your silencer box for some dampening material like insulation.

I'll maybe draw this up in SketchUp.

Greg

_________________
It appears that you've made the mistake most people do. You started building without consulting this forum.


Report this post
Top
 Profile  
 
PostPosted: Wed Mar 20, 2019 4:06 pm 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11984
Location: Santiago, Chile
Quote:
And while I'm at it, I wanted to run my baffle design by you to see if I have something workable.
First, your speakers are too high up, and they are angled down. There's several problems with that. Firstly, that sends reflections from the desk surface into your ears, which is a Bad Thing. And secondly, having the speakers significantly above the horizon means that the sound is coming down at your ears from above, and that messes with the ability of your ears and brain to accurately determine directionality and frequency response. Your brain is "tuned" to expecting most sounds to come from in front of you, and that's why your ear pinna are shaped the way they are: all those fleshy folds and curves are not there to make your ears look pretty; they are key acoustic parts of your ear system. Those fleshy folds and curves direct sound into your ear canal in certain ways, that cause complex interference patterns inside your ear canal... and your brain, amazingly, can figure out from those patterns, what angle the sound came from, and what the frequency response was. If the sound comes from too high above, instead of straight ahead, that causes you brain to misinterpret the patterns. Ok, so it's a small effect, but still very real, and since you want the room to be the best it can be, just put your speakers where they belong: With the acoustic axis of the speakers at the same height above the floor as your ears. The "standard" height is 120cm, or about 47 1/4", because that's the average height of the the ears of most people, when seated. Personally, I prefer to put the axis just a little higher than that, to help with other issues, but not more than an inch or two, max.... and not tilted down.

Second, you seem to have the acoustic axis of your speakers drawn in the wrong place: it looks like you have it centered on the tweeter, but that isn't correct. Check with your speaker manufacturer to find out where the real acoustic axis is for your specific speaker.

Third, you have your speakers laying on their sides, which is not such a good idea (unless the specific speaker you are using is designed to ONLY be used like that). Here's why:
Attachment:
Speakers-mounted-vertically-and-horizontally-standing-up-laying-down-on-side.jpg


It is preferable to keep them upright, with the woofer and tweeter arranged vertically, not horizontally.

Quote:
Where I netted out was a width of ~5'9 1/2" and listening distance of about ~5'8". And the speakers are angled about 31.6 degrees.
All of those sound reasonable.

Quote:
The speaker I am looking at using in the baffle is a 3 way speaker with the largest driver being 7", so 5x that is a 35" wide baffle at least.
Except that you have the speaker laying on its side, so you should use that dimension. It's always better to make the baffle as wide as the room permits.

Quote:
1) Should I be measuring that 14 and subsequent 21 inches from the acoustic axis of the speaker, or from the edge of the speaker cabinet?
Acoustic axis... but first you need to make sure you have it in the right place on the speaker! It won't be at the tweeter...

Quote:
2) In joining the two baffles with a flat wall right in front of me, I can't help but think that I've moved the yard stick on where the position that is 35% of my room length is.
Welll... yes and no... sort of... maybe! :)

It depends on how you make the entire front faces of the soffit sections: If you were to make them solid surfaces, from ceiling to floor and wall to floor, then yes, you would have moved the entire wall towards you, effectively. But that's not normally how soffits are built. Only the speaker area itself has the solid, rigid, massive baffle, while the parts above and below have bass traps in them, and are exposed to the room. So the full length of the room is still there, acoustically. Yes, you will sort of "smear" that a bit, since the soffits do stick out into the room, but the effect won't be huge... The 38%, or 35%, or 1/3 or whatever "rule" is for modal reasons, and the modal response is related to the solid, rigid, massive boundaries of the room itself. So you still measure you mix position location from the front wall, as though there were no soffit there. The baffle and speaker section of the soffit are small compared to the wavelengths of the lowest modes, so those waves won't really see the soffits.

Quote:
Next thing I noticed was with a 47" high ear height when sitting, the speakers would be firing right into the back of my computer monitors and my secondary set of speakers
Then you have your computer monitors and secondary speakers in the wrong place! Move them.

Quote:
I noticed in another thread that you suggested a maximum of 10 degrees that I could angle the speaker
Not me! Some reference sources say 10°, others go to the ridiculously high 15°, but there's good psycho-acoustic reasons to never go higher than about 7°, absolute max, and personally I have never gone higher than 4.7°. That was for a specific case in a fairly large room, with speakers and a mix position that allowed me to do that. In a small room, I would not tilt the speakers at all. It's only feasible if the room is decently large. Even then, I prefer to avoid it where possible, due to the reasons I mentioned above.

Quote:
I'm not sure if I did this right or if this is acceptable in my circumstances and would love your thoughts on this methodology.
I would not do it like that, no. I would get the video screens off the desk and onto the front wall, completely out of the line to the speakers. Make them screens bigger, if necessary to see them clearly. Or move them down lower and tilt them backwards. And get your secondary speakers off the desk too! Put them on stands behind the desk, and move them to locations where they do not interfere with the direct line from the main speakers.

Also, get rid of that desk with the shelf on it: go for a low profile desk, that has nothing sticking up to cause acoustic problems. Keep everything as low as possible, out of the line of fire between the speakers and your ears. Don't forget that the basic goal here is that the sound from the speakers travels directly and unimpeded to your ears, unaffected by anything in the way. That's why it is called "direct" sound: it takes the short, straight line, and is not interred with by anything else. Keep everything away from that path.

Quote:
(Note: that is not my actual desk,
Good! Because it's not a good choice. If you look at some mastering studios, there is no desk at all, since the smartest mastering engineers do not want ANYTHING in the way of the sound. If there is a desk, it is small, and low profile. Mostly, they just have small "pods" on the floor arranged around their chair, with their gear in those. Within easy reach, of course, but low down, well away from the path from speaker to ear.

Desks have a very negative effect on room acoustics. I have developed a design you could use if you want, for a low impact desk that doesn't have too much negative effect on room acoustics.

Quote:
Thinking about the 5x the diameter of the biggest driver guideline,
Glad you used that word! It is, indeed, a "guideline". Bigger is better...

Quote:
4) What should I do with the space from the outer edge of my baffle to the sidewalls? Should I just extend that wall past the listening position to create some angles that reflect sound to the back of the room instead of to my ears?
Yes, absolutely! That's what RFZ is all about. Use whatever surfaces you can at the front of the room to force the early reflections away from the mix position, towards the rear of the room where they can be attenuated. Angle those wings accordingly, with hard, solid, rigid, massive surfaces in the center regions, and do the top and bottom regions similar to the soffits themselves, with bass trapping.

Quote:
5) Answer to #4 notwithstanding, I'm a little fuzzy on what's a good way to actually attach the baffle wall to the side walls given the bottom plate won't be anchored to the floor?
Ummmm.... why won't the sole plate be anchored to the floor? I'm not following that. How come you don't want to anchor it properly?

Quote:
I'd keep your head at the 35% room length based off of your inner leaf sheathing.
Right! The actual boundaries of the room, as if there was no soffit.

Quote:
You should aim for less than 5 degrees if possible.
:thu: And even then, only in rooms that are big enough to keep reflections off the desk, and not mess up the psycho-acoustic response in other ways.

Quote:
I personally don't understand why you think you should make mix decisions based off of a second set of speakers that are going to suffer from things like SBIR.
:thu: The reason I've heard for that, is that the engineer wants lousy speakers with lousy response (eg, NS10... :roll: ) in lousy locations in the room, to see how the mix will sound on typical lousy bookshelf speakers in a typical living room with a lousy shape and lousy layout. I guess they have a point, sort of, but from that point of view, just fiddle with the final EQ knobs randomly, then lie down on the floor under the desk with a newspaper over your head, just in case that's how the average person will listen to your mixes... :)
:shot:
More seriously, that might have been true once, 30 years ago, that most people would listen to your music on a "hi-fi" system in their living room, but today it's fare more likely that they will listen on ear buds hooked up to their iPhone, or in their cars, so that's how you should be checking our mixes: Stick in a set of ear buds right there in the studio, with the speakers off. Then listen again on your way home, in the car. You wont even be able to make the control room have the same acoustic response as the interior of a car, or a pair of ear buds, so just use the REAL thing to check that. Personally, I don't see much need for lousy monitors on the meter bridge these days.

Quote:
I just think it's crazy to make your entire soffit design suffer due to a set of speakers that are going to sound like crap compared to your soffit mounted ones.
:thu: :thu: :thu: :thu:

Quote:
Any chance you know what product is in this pic? In my searches everything I see looks hideous in comparison.
Legrand is what I use. It ain't cheap, but it looks good and works well.

http://www.export.legrand.com/EN/dlp-wa ... ng_95.html

Cal-centron also has some stuff like that.
http://www.calcentron.com/Pages/fram-tr ... aceway.htm

Electricduct is another.
https://www.electriduct.com/Cable-Raceways.html

Where I live, I can also get this imitation of Legrand, from an Argentinean company called Kalop:
http://www.kalop-productos.com/#!/-cable-canal/

Might not be available where you live though.

Try to find legrand: it's the best.... just not cheap.


- Stuart -


You do not have the required permissions to view the files attached to this post.

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 47 posts ]  Go to page 1, 2, 3, 4  Next

All times are UTC + 10 hours


Who is online

Users browsing this forum: Google [Bot] and 18 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group