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PostPosted: Thu Aug 11, 2011 12:30 pm 
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Location: São Paulo, Brazil
Hi there,

I've been spending so much time trying to find my way into building my own (tiny) studio, but I think I've reached my limit, it seems I simply cannot absorb any more information without asking some questions. First of all, let's go to the overview of what I'm intended to get, right?

Goal: I'm looking for a DAW based control room dedicated for stereo mixing and mastering, but also capable of recording some keys or electric guitars (with Eleven Rack or the alike). The initial DAW setup would be: Mac Pro + interface + MC Mix (2 or 3 units) + UAD2 + pair of HS80's and a HS10W (maybe a pair?). Hopefully things will work out well and I'll be able to expand a little on the gear side and go to 5.1 or even building a vocal/guitar booth in the next room. Fingers crossed!
At the moment I only have part of the gear and the room, nothing's been built so far.

Loudness: I rarely go over 85dB SPL (A weight) while mixing/mastering. There won't be any drums or loud guitars. The street's fairly noisy, but as you'll see on the Sketchup file the window in the room I'm (initially) planning on using faces the middle/back of the building (there are 2 apartments on each floor separated by a long elevator hall), so I'd "guess" it's around 50dB SPL (A weight). Unfortunately, I haven't even been able to take noise measurements and all because my brother just had triplets and they're all living there, huge mess (I've never seen so many baby bottle in my life!)... I'll get on to that asap.

The room: W x L x H = 2,65m x 4,34m x 2,46m. Window facing the back of the building is W x H = 1.62m x 1,41m, bottom edge at 0,87m. There's a wooden wardrobe that splits this bedroom (in the Sketchup file named as "Bedroom C") and the next one (named "Bedroom B") with an attached door leading to the corridor. Next to it is the access to the bathroom.

Budget: Not sure yet. I once thought of buying some nice stereo converters and monitors, but then an SOS article on converters made me change my mind into spending that money on acoustics first. I was looking at spending about US$3000-US$4000, but since the currency here will differ a lot and the building costs are not eligible to importing taxes (which are WAY too high for audio gear) I was hoping to skip this step for now. And let's face it, I don't think I'd be able to spend all that cash on the gear I was planning anyway, so let's try to keep a US$2000-US$3000 mark.

Before going to the next step, I just would like to say that even though I do not have record of a few of things I've read here or in other forums my questions still persist because there's just so much information and I get pretty confused sometimes. So if I say "oh, I remember reading this in that forum", just trust me that I did read it and, most importantly, that's how I understood it and that's why I'm asking it here cause I'm sure someone will be able to explain it to me. I know, I must improve my self-discipline while researching... Ok, so shall I place my questions now? =)

1) Mode calculators. Cool, you put the dimensions, the calculators show me peaks and valleys in my room's response, right? Or is it just peaks? I've once read in another forum that you must calculate all three types of room mode in order to actually treat a room, is that so? From what I've seen so far, it looks like these calculators on the web are usually only for axial modes, aren't they?

2) My biggest concern of all the treating room practice: how can I know (beforehand) how much absorption I need for my room? How many Helmholtz resonators do I need? How many and which type of diffusers? How much fiberglass? I mean, I'm sure it's a bit (a lot?) of a trial and error thing, but how can you minimize the margin for errors in order to avoid wasting time and money?

3) Flush mounting speakers seems to be the consensus around here, am I wrong? I saw a discussion in the forum about doing that with the ADAM AX Series and most replies agreed with the solution given by John. I actually asked ADAM and their reply was: "It is not good to flush mount speakers of small size. this only makes sense for big speakers. If you flush mount speakers from the AX range the early reflections will affect the frequency response - especially of the high frequencies - and stereo image will suffer.". So this brings me to: should I flush mount the Yamaha HS80M's right from the start of the project or leave them on a stand and when the time comes I flush mount something like a JBL LSR6332? Btw, I hope 1,5m between the speakers isn't too far apart in my room.

4) I'm starting to feel a bit more into free standing speakers for one reason: it's easy to perform future monitor upgrades, the worst I'd have to do would be resizing the speaker stands. But, let's consider 2 options for a room, one with a flush mount design, one with free stand, both equally treated to their needs. Would I still be benefited the most by flush mounting the speakers? What do I need to be careful with if I go for the stands option?

5) I haven't seen any HS80M flush mounted in any of the threads, aren't they recommended for that? Are there any monitors know to be NOT recommended?

6) Bob Katz recommends using two subs instead of one, but I usually see people using only one. I understand the purpose of the LFE in 5.1, but what about for music? I'm thinking of using subwoofer(s) in my monitoring to reinforce or supplement the HS80's performance, so shouldn't I use 2 subs (one reinforcing each speaker)? Or in such small rooms that doesn't really matter?

I guess those are my questions for now. I've attached a couple files I hope will be useful information. The SSL on the Sketchup file is just for reference. And to keep me motivated. =)

I almost forgot to say thanks in advance for any help! How rude...

http://www.tiagolorena.com/mixingroomde ... g_room.skp
Attachment:
Tiago Mixing Room.jpg

Attachment:
Apartment Floor Plan.jpg


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PostPosted: Thu Aug 11, 2011 2:26 pm 
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Hi Tiago, and welcome! Very nice first post, too!

Quote:
1) Mode calculators. Cool, you put the dimensions, the calculators show me peaks and valleys in my room's response, right? Or is it just peaks?
They show you the room "modes", which is the frequencies at which the room will resonate naturally, since the waves fit in perfectly between two or more surfaces. It isn't showing peaks or valleys : just the frequencies. The position of the peaks and valleys in the room depends on which mode and/or harmonic you are talking about: they will all have different locations in the room.

Quote:
I've once read in another forum that you must calculate all three types of room mode in order to actually treat a room, is that so?
Correct. Axial, tangential and oblique modes all matter. Some folks suggest that tangentials are not as important as axials, and that obliques are the least important, but others say that all are equally important.

Quote:
From what I've seen so far, it looks like these calculators on the web are usually only for axial modes, aren't they?
Most of them also do tangentials and obliques. Some don't. Here are the first 20 modes for your room:

39.7 Hz 1,0,0 Axial
65.0 Hz 0,1,0 Axial
70.0 hz 0,0,1 Axial
76.1 Hz 1,1,0 Tangential
79.4 Hz 2,0,0 Axial
80.5 Hz 1,0,1 Tangential
95.5 Hz 0,1,1 Tangential
102.6 Hz 2,1,0 Tangential
103.4 Hz 1,1,1 Oblique
105.8 Hz 2,0,1 Tangential
119.0 Hz 3,0,0 Axial
124.2 Hz 2,1,1 Oblique
130.0 Hz 0,2,0 Axial
135.6 Hz 3,1,0 Tangential
135.9 Hz 1,2,0 Tangential
138.1 Hz 3,0,1 Tangential
140.0 Hz 0,0,2 Axial
145.5 Hz 1,0,2 Tangential
147.6 Hz 0,2,1 Tangential

Quote:
My biggest concern of all the treating room practice: how can I know (beforehand) how much absorption I need for my room?
There are methods for figuring that, and on-line calculators as well, but they might or might not give you the correct answer. The best way is to do the "standard" basic treatment for the room, the measure the response acoustically and see what sill needs to be done.

It is a small room, so you will need a lot of bass trapping. A BIG lot of bass trapping. I would suggest putting large superchunk-style traps in as many corners as you can (there are twelve corners in a room). You will also need absorption on your first reflection points and on the rear wall, and some on the ceiling (clouds, maybe). Do that, measure the result, and see what still needs to be done. Much better than trying to predict.

But in any case, theoretically you would need 299 Sabins of absorption in that room, which implies covering roughly half of the entire surface area with perfect absorption.

Quote:
How many Helmholtz resonators do I need?
How long is a piece of string? What car should I buy? The answer to all of those is: it depends on the situation! Helmholtz resonators may or may not be the answer. You would only resort to tightly tuned (high Q) resonators if nothing else worked, and in general the broad-band approach is a much better way to go.

Quote:
How many and which type of diffusers?
For that room? None! It is too small for diffusers to be usable. Diffusers are good for larger rooms, not so for smaller rooms. Your problems will be in the low frequency end of the spectrum anyway, and diffusers are not feasible for that.

Quote:
but how can you minimize the margin for errors in order to avoid wasting time and money?
Simple! Don't try to predict too much! Go with the normal method: Lots of large bass traps (always needed in small rooms), absorption on first reflection points, clouds on the ceiling, maybe broadband slot walls on the sides, then measure the response. Based on the measurement, add additional treatment as needed.

Quote:
3) Flush mounting speakers seems to be the consensus around here, am I wrong?
Yes!!! No doubt about it. It makes so much sense, for so many reasons.

Quote:
"It is not good to flush mount speakers of small size. this only makes sense for big speakers. If you flush mount speakers from the AX range the early reflections will affect the frequency response - especially of the high frequencies - and stereo image will suffer.".
That's why you also treat the room for early reflections! :)

Quote:
So this brings me to: should I flush mount the Yamaha HS80M's right from the start of the project or leave them on a stand and when the time comes I flush mount something like a JBL LSR6332?
Those are rather different speakers! What you could do is to use Barefoot's method of soffit mounting, that makes it easier to replace the speakers with something different in the future.

Quote:
Btw, I hope 1,5m between the speakers isn't too far apart in my room.
Get them as far apart as you can while still having as much soffit area around them as possible, and also getting the geometry correct for your listening position. It looks like you should have enough room to do that.

Quote:
But, let's consider 2 options for a room, one with a flush mount design, one with free stand, both equally treated to their needs. Would I still be benefited the most by flush mounting the speakers?
Yes, without any doubt. No bass wrapping around the back of the speakers, no comb filtering off the front wall, no reflections off the front wall, very tight bass, very clean stereo imaging, etc.

Quote:
What do I need to be careful with if I go for the stands option?
Finding the right position for the speaker in the room. That is a compromise: you have to find the place in the room where the speakers are giving the least amount of problems, while still retaining symmetry and geometry. If you want to do that right, you have to spend a lot of time moving the speakers around, an inch or two at at time, and making measurements, until you find the best compromise location. The speakers should be far away from walls and corners if they are free standing, but in a small room that is impossible, so anything you do will be a trade-off.

None of that is necessary with soffit mounting, because the speakers are already in the best possible location.

Quote:
6) Bob Katz recommends using two subs instead of one, but I usually see people using only one. I understand the purpose of the LFE in 5.1, but what about for music? I'm thinking of using subwoofer(s) in my monitoring to reinforce or supplement the HS80's performance, so shouldn't I use 2 subs (one reinforcing each speaker)? Or in such small rooms that doesn't really matter?
It depends on the sub and the room! Once again, if you want to do it right you need to take the time to move the sub around until you get the best balance and response, while also not messing up the timing/phasing. And most likely a small room like that will be fine with just one sub.

Some comments on your layout: your mix position (listening position) is exactly in the center of the room: bad. You need to fix that by moving the chair closer to the front wall. That will mean changing the angle of the speakers a bit. Also, that closet (wardrobe) on the back wall is going to be a problem: large resonant cavity! You might want to think about ways of dealing with that.


- Stuart -

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PostPosted: Sat Sep 03, 2011 4:47 pm 
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Hi Stuart,

Thank you so much for the reply. Sorry for taking so long, but I've been very busy lately, still trying to raise the money to build my little studio! Anyways, although I've got some questions about your comments, I'd like to understand one thing before moving on with the design. Especially because I'll have to tweak my Sketchup project to post pictures and all. So, let's get to the question:

Correct me if I'm wrong, but what I've seen so far in this forum regarding bass traps is usually one those superchunks in the corners or a layer of insulation (fiberglass, rockwool) in a frame covered by fabric. That actually surprises me a lot because I've always thought that just insulation in a frame wouldn't do anything to low frequencies unless it was inside a sealed box, sort of like a membrane basstrap. In fact, many commercial basstraps are like that, aren't they? It's a big box filled with insulation, all sealed, with a membrane. So I'm still struggling to understand how these DIY basstraps actually work. And how well (or bad) do they perform compared to the membrane basstraps (like the commercial ones)? I remember seeing a book ages ago which showed the formulas to calculate all these different absorbers, including the distance between hangers, but I just can't remember the title, so if you have any recommendations I'd greatly appreciate it! =)

Cheers


Tiago


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PostPosted: Sun Sep 04, 2011 2:31 am 
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Quote:
That actually surprises me a lot because I've always thought that just insulation in a frame wouldn't do anything to low frequencies unless it was inside a sealed box, sort of like a membrane basstrap. In fact, many commercial basstraps are like that, aren't they? It's a big box filled with insulation, all sealed, with a membrane.
Two different principles of operation.

A membrane absorber (or "membrane trap") is a tuned pressure-based device. That means it is tuned to a specific frequency which is determined by the surface density of the membrane and the depth of the cavity behind it, and it is based on the pressure component of the sound waves, rather than the velocity component. Therefore it should be placed against the wall in the zone of the room where the pressure component is highest for the specific mode that is being treated.

A porous absorber (such as a superchunk) is a broadband velocity based device: That means that is isn't tuned to any specific frequency, but rather covers a broad range of frequencies, related in general to the thickness of the absorber, the distance from the wall behind it, and the gas flow resistivity of the absorber. Since they work on the velocity component of the wave, they should be spaced away from the wall, where the velocity is highest.

So each device has its place for treating room acoustics. Membrane traps are good when you have a specific mode that is giving you problems, and you want to treat just that exact frequency, without treating other adjacent frequencies. Porous absorbers are better when you have a bunch of several modes in the same general part of the spectrum, and you need to treat them all.

Now, since small rooms will always have numerous modal issues in the low end of the spectrum (simply because the room is small, regardless of exact shape, volume, dimensions or ratios), it is easier to just treat the entire low end of the spectrum, rather than trying to target dozens of specific frequencies. And since all room modes terminate in room corners, the best place to treat them all at once, is in the corners. Hence, superchunks go in corners.

Now, even though I said that they should be spaced away from the wall for maximum effect, you'll see that the actually go right up against the wall. That's because the "spaced away" is with reference to the path followed by the sound wave. If the sound wave is approaching the wall head-on (at 90°) then the "space away" is important, but if the sound wave is approaching at a lesser angle, then it travels through the absorber for a longer distance, and thus "thinks" that the absorber is further away from the wall that it really is. So for the edge of a 24" deep superchunk that is right up against the left wall (for example), a wave that is running at a very shallow angle, nearly parallel to that wall, will have to move through the entire 24" of absorber before it hits the back wall, then it will bounce and come back through all of those same 24" of absorber, so that wave "sees" an absorber that starts 24" away from the wall. Of course, a wave that comes head on to that edge will see practically no depth at all right there, but it will see the full depth of 24" on the other edge of the absorber (the edge against the rear wall).

So superchunks are very effective in treating low frequencies, provided that they are large and deep, and they cover a broad range of frequencies without needing to be tuned. Thus, that's generally the first approach to treating a room: large superchunks in many room corners. The treat all room modes whose wavelength is shorter than 4 times the depth of the superchunk. So a 24" deep superchunk treats all wavelengths of 96" or shorter very well (140 Hz and higher), and also treats even longer waves to a certain extent. even at 70 Hz that superchunk is still doing a reasonable job. And a 36" deep superchunk works great down to 94 Hz, and pretty well down to about 45 Hz.

So generally, you first put large, deep superchunks in many corners, then you measure the room to see where your remaining modal issues are, and you treat those specific frequencies with tuned traps.

Quote:
And how well (or bad) do they perform compared to the membrane basstraps (like the commercial ones)?
Each type works very well for the job it must do. Membrane traps, being tuned, work very well at the frequency they are tuned to, but do nothing at all for other frequencies. Absorbers don't absorb individual frequencies as well membranes do, but they absorb a whole range of frequencies, which is usually what you want to do in a small room.

Quote:
I remember seeing a book ages ago which showed the formulas to calculate all these different absorbers, including the distance between hangers, but I just can't remember the title, so if you have any recommendations I'd greatly appreciate it! =)


The best book I know of for that is "Master Handbook of Acoustics", by F. Alton Everest.


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PostPosted: Thu Oct 20, 2011 1:38 pm 
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Hi there,

Back from the dead with a few questions.

Stuart, you were talking about the depth of superchunks and how they work, but "depth" in what direction? Check out the image below, is it A or B to be considered "depth"?

Attachment:
Superchunk Depth.jpg


Like you said, I'll need lots of bass trapping in this room. From what I've been reading so far, for general purpose there are 3 main types I should look for: superchunks in the corners, broadband absorbers along the walls/ceiling and hangers. Did I miss any? Are there international standards for each insulation needed for these? I mean, how can I find the right ones here in Brazil?

I see in some cases people place hangers in their soffits, others just place rockwool loosely, what's the difference between them?

In regards to that closet, I thought of filling it with insulation or hangers (not cloth hangers!), is that a good start? What do you suggest? I can't get rid of the whole thing, that's a fact, but I can remove take away the doors in both rooms, fill it with insulation, exchange the doors with a perforated/slot panel, etc.

I'm facing a huge problem here (maybe someone smarter will have a solution). There are two doors really close to each other, one giving access to the room, another to the bathroom. I can't see a way of putting a superchunk there without compromising the bathroom door! I really need help to figure this one out!

You can see in the image below some details on the walls angles. The side walls have been angled to 8º as (usually) recommended, but it doesn't give me an RFZ, I reckon that's because the walls are too close together. Not too bad I guess, just put some high-mid absorber to fix it, right? What about the other 2 angles? Is there a problem they're not the same?

Attachment:
Bedroom C Soffit Angles.jpg


Do the speakers need to be right in the middle of the walls they're mounted in? You see there are 2 axes connecting the listening point to the speakers. Out from the center of the speakers is just passing by my ears (represented by the horizontal edges on that cross). Btw, that's right on the 38% mark (not 50% as you thought from the first drawing). All good so far?

I'll be able to take measurements in a couple weeks and then I promise to stop trying to predict too much (am I still doing that? :oops: ). Also, some pics could help. But I guess that's it for now.

Cheers


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PostPosted: Fri Oct 21, 2011 12:16 pm 
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Quote:
Stuart, you were talking about the depth of superchunks and how they work, but "depth" in what direction?
In whatever direction the sound waves are going! :)

In the example I gave, I was talking about "A", since I was discussing the two extreme cases of sound waves moving almost parallel to walls. Normally people talk about the distance across the front face (diagonal) of the superchunk, which means that if someone says a superchunk is 24", they mean the face is 24" wide, in which case "A" on your diagram would be about 17". If you wanted "A" to be 24", then the front face would be about 34" across, which is a good size for a superchunk.


Quote:
From what I've been reading so far, for general purpose there are 3 main types I should look for: superchunks in the corners, broadband absorbers along the walls/ceiling and hangers. Did I miss any?
Membrane traps, maybe? Helmhotlz resonators? :) Don't want to add confusion, and you probably don't need those, but you DID ask! :)

Quote:
Are there international standards for each insulation needed for these? I mean, how can I find the right ones here in Brazil?
You mean for the type of insulation to use inside the devices? Most types of mineral wool or fiberglass insulation will work, and also some other types of insulation, as log as it is open-cell and has similar gas flow resistivity characteristics. If you use fiberglass, then look for something with density of around 32 kg/m3, roughly. If you use mineral wool then look for stuff with a density of around 48 kg/m3, roughly. If you can't find those, then use something a but LESS dense (lighter) for bass traps, and a bit MORE dense (heavier) for the broadband devices.

Quote:
I see in some cases people place hangers in their soffits, others just place rockwool loosely, what's the difference between them?
Depends on what you want to do! :) There are usually two parts to the soffit: the section that has the speaker in it (normally all of the top half and some of the bottom half), and the section below that, which can be used for trapping, like John does in many of his designs. The top section needs some insulation, for damping, just like inside a normal speaker cabinet. If you use the bottom section for trapping, then you could put hangers in there if you want (John does, usually), or absorption, or maybe make it into some type of tuned device, if you happen to need one there. Plenty of options.

As far as I'm aware, there isn't much research available on hangers, how they work, design specs, dimensions, etc. Most of what I've seen written about them is empirical, figured out by people like John over many years of experience in many different studios. They just "know" how to do it, and their designs work really well, but they don't really do calculations on angles, sizes, spacing, etc., so there isn't much published material available on how to do that. But if you take a look at their designs, you'll start to see the basic concepts of how to do it, and if you do a design and ask John, he'll probably be happy to take a look at your design and tell you iff it will work or not, and suggest how you can improve it.

Quote:
In regards to that closet, I thought of filling it with insulation or hangers (not cloth hangers!), is that a good start?
Hard to say which is better. I'm just guessing here, but I reckon I would go with hangers if that were my room. Maybe you could line the back and sides with insulation, then put some hangers in the open space in the middle.

Quote:
I can't see a way of putting a superchunk there without compromising the bathroom door! I really need help to figure this one out!
Build a superchunk module on wheels, so you can push it out the way when you need to go through the door, and just wheel it into position when you need to do critical listening.

Quote:
You can see in the image below some details on the walls angles. The side walls have been angled to 8º as (usually) recommended, but it doesn't give me an RFZ, I reckon that's because the walls are too close together.
Yeah, you'd need a really steep angle to get an RFZ with side walls that close. Not do-able, I think. So just put heavy absorption on your first reflection points. You could even relax the side wall angles a bit, down to 6° maybe, so you still get a decent effect for flutter echo, but that would give you a bit more space on the front for enlarging your soffit panels.

Quote:
What about the other 2 angles? Is there a problem they're not the same?
Nope! Ideally it would be nice, but it's just not going to happen in a room with that shape/size. It's not a huge issue, so I wouldn't sweat it too much.

Quote:
Do the speakers need to be right in the middle of the walls they're mounted in?
Ideally, yes. Theoretically, you want the same amount of space on the left and on the right, as well as above and below. They should all be the same. But the room itself normally wont allow that, and there are practical issues with trying to implement such a plan anyway, but at least try to keep the left-right spaces the same.

Quote:
You see there are 2 axes connecting the listening point to the speakers. Out from the center of the speakers is just passing by my ears (represented by the horizontal edges on that cross). Btw, that's right on the 38% mark (not 50% as you thought from the first drawing). All good so far?
Looks good to me! But Eric is the speaker expert around here, so maybe he can chip in a bit with his comments.


- Stuart -

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PostPosted: Wed Jan 25, 2012 5:19 pm 
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Hi there,

So, it's been a very long time, I know... life's been pretty busy in the last months, didn't find the time to work on the design and read the threads. But I think there's been some good progress with the little time I got to put my hands on the design. As you'll notice, I decided to use another bedroom for the studio. If someone could take a look at the Sketchup file to follow up would be nice. I basically got stuck in a few questions:

1) What should I do with the closet doors? They're ~1.5cm thick. I'm not sure if I should just leave them there and seal the doors, or replace them with some sort of pegboard or perforated panel (sealed or not?), or simply remove them and cover with fabric... What do you guys suggest?

2) I see many designs with slat resonators on the splayed side walls, but how can I figure out what it's tuned for? I was thinking of putting a perforated panel such as the ones below, but not seal them. The holes would only be there to balance absorption and reflection in high frequencies (I seriously don't wanna end up with a room too dead). The same would be applied to the ceiling cloud. Any suggestions about this?
Attachment:
Control-Room-Scrambler.jpg

Attachment:
home studio.jpg


3) Stuart, you mentioned putting basstraps in as many corners as possible. I put 2 superchunks in the back, 2 square-ish on the ceiling and another between the speakers and the ceiling cloud. I tried putting 2 superchunks on the ceiling instead of the square-ish ones, but it felt a bit claustrophobic (it still does actually, but I can't see a better solution). Should those on the ceiling be "solid" like the corner superchunks in the back or they'd better be filled with mini hangers? Also, covering those with fabric only would do?

4) In the soffits, the upper portion will be filled with loose insulation (just like John's suggestions), the lower portion filled with hangers. It's a bit tricky to do that if I flush mount the subwoofer though. And some people (yourself included Stuart) recommend not mounting the subwoofer. Even so, I still tried doing it cause I've once heard a sub outside the walls in another studio, and then flush mounted... the latter sounded much better. Although I read and argument makes sense: considering ear height as the reference, the distance between my ears and the monitors won't be the same as the sub and my ears, therefore there would be a phase issue. Also letting it loose in the room gives me more freedom to find the best spot for it (I don't agree with that completely though, I'm not sure if in such a small room that would actually be as easy as it sounds). Anyway, is there anything wrong with what I did in the soffits so far?

5) The HS80M's are rear-ported. Yeah. That's just killing me... I really like these monitors, but I fear how they'll sound after soffit mounting them. I plugged the ports and they sounded like they lost their... mmm... "manhood". Is that sorta how they'd sound soffited? Don't know if the sub and the bass buildup could restore that low end... Anyways, what if instead of a solid MDF sheet on the soffits I used a perforated panel, would the rear ports still be able to fire back into the room somehow? What about redirecting the air coming from the back to the front?

That's pretty much it so far. Hope someone could take some time to help me out here! Here goes the Sketchup file:
http://www.tiagolorena.com/mixingroomdesign/tiago_mixing_room_v2.skp

Cheers


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PostPosted: Fri Feb 03, 2012 6:58 am 
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Hi Thaigo! Welcome back! :)

Quote:
1) What should I do with the closet doors?
They are probably fine as they are, unless you specifically think they are causing some type of issue. Just put the absorption on the front, but not as in your SKP: you have angled reflective panels on there, but you really need absorption. If they are causing issues (resonating), then maybe take off the doors and fill the closet with insulation. Make a nice bass trap!

Quote:
2) I see many designs with slat resonators on the splayed side walls, but how can I figure out what it's tuned for?
Use the equation for Helmholtz resonators! :) But actually you don't need to calculate much: just build them using John's design and dimensions, and you'll have a good general purpose broadband slot wall.

Quote:
I was thinking of putting a perforated panel such as the ones below, but not seal them.
Perf panel is another form of resonator, similar to slot walls. But if you don't seal it, it won't work! The Helmholtz effect requires a sealed air-tight chamber.

Quote:
(I seriously don't wanna end up with a room too dead)
Put 6 mil plastic in front of your bass trap absorption. That will keep the highs in the room while still letting the lows through.

Quote:
The same would be applied to the ceiling cloud. Any suggestions about this?
Right now your SKP shows a cloud with a wooden panel below: that's a reflective surface, the exact opposite of what the purpose of the cloud is! That should be just absorption there, with plastic below. You can put plywood on the TOP of the cloud, to make it a "hard backed cloud", if you suspect that you have vertical modal issues in the room.

Quote:
I tried putting 2 superchunks on the ceiling instead of the square-ish ones, but it felt a bit claustrophobic (it still does actually, but I can't see a better solution).
Do you mean "claustrophobic" in the visual sense, or the acoustic sense? In other words, toes it LOOK claustrophobic in there, or does it SOUND claustrophobic?

Quote:
Should those on the ceiling be "solid" like the corner superchunks in the back or they'd better be filled with mini hangers? Also, covering those with fabric only would do?
Either way will work. You could even just use flat panels angled across the corners, with an air gap behind. That will also work, just not quite as effectively.

Quote:
It's a bit tricky to do that if I flush mount the subwoofer though. And some people (yourself included Stuart) recommend not mounting the subwoofer. Even so, I still tried doing it cause I've once heard a sub outside the walls in another studio, and then flush mounted... the latter sounded much better. ... Anyway, is there anything wrong with what I did in the soffits so far?/quote]I prefer to not mount them, but there's no law against it! You can do it if you want, and it can be made to work out. But I'm not sure if the corner is the best place to do that. You'd probably be better of mounting it in the center panel (between the two soffits), and offset to one side or the other. Another option is to leave the lower section under that center panel open, and just put the sub down there, perhaps even facing sideways, instead of facing the room.

Quote:
The HS80M's are rear-ported. Yeah. That's just killing me... I really like these monitors, but I fear how they'll sound after soffit mounting them.
Yet strangely enough they have a bass roll-off "room control"! That's normally on speakers meant for flush mounting... Go figure!

I have heard that it is possible to soffit mount rear-ported speakers, but not easy. Eric would probably be the guy to comment on that: he's the speaker guy around here right now, and understands these things better than I do. As far as I know, part of it is to make sure to not obstruct the rear port, and that there is plenty of volume inside the soffit, but you might also need to do other stuff. Speakers are complicated things, even though they look simple. Small changes can have big effects...

Quote:
I plugged the ports and they sounded like they lost their... mmm... "manhood". Is that sorta how they'd sound soffited?
:lol: I don't think they' sound like that when soffit mounted! :)

If you are concerned about this, and really want to try with those speakers, the why not give it a go? Buy a piece of thick wood, cut a hole in it, and set it up across a room corner somehow to just to get an idea of how it might sound. But don't plug up the port! That will mess up the acoustics of the speaker, internally. If it sounds reasonable, then buy some more bits of wood and seal the box around the back, throw some old pillows and blankets inside for damping, and see how that sounds. There's no harm in experimenting, and you might be surprised.

Quote:
what if instead of a solid MDF sheet on the soffits I used a perforated panel, would the rear ports still be able to fire back into the room somehow? What about redirecting the air coming from the back to the front?
That would sort of defeat the entire point of soffit mounting! The concept is to extend the front face ("baffle") of the speaker box to a very large size, to prevent low frequencies from "wrapping around" behind. Cutting holes in the baffle would destroy the effect.

Quote:
That's pretty much it so far. Hope someone could take some time to help me out here!
What have you done to the room so far, and has it helped? How does it sound? How about some pictures? Also, try using REW to run an analysis on that room, and see what it is doing right now, so we can figure out what else you need to do to fix it.


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PostPosted: Fri May 18, 2012 5:31 pm 
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Hi Stuart, long time no see, eh?
So, I finished building the studio... sort of. I'm posting some (lame) pics for you to help me out here. I also wanted to post the Sketchup file, but it's about 2MB... not doable.
Attachment:
DSCF3924.jpg


I ran some sweep tones with Fuzzmeasure. The first graph is the left (red line) and right (green line) speakers, both with the subwoofer (which btw is not flushed, I put it in the center between the speaker, flipped the polarity and it just sounded great, never heard this set so tight!). Anyways, from my reading of the graphs, there's a peak at around 300Hz, 550Hz and 700Hz, a huge dip around 900Hz-1kHz and a really weird response from about 2kHz up to 10kHz! I tried putting a sheet of rockwool on the desk to see if that huge dip was a reflection caused by it, but it didn't help. So what do you think?
Attachment:
Freq Response Both.png


Here's also the waterfalls for each speaker.
Attachment:
Left Speaker Waterfall.png

Attachment:
Right Speaker Waterfall.png


To my ears, I just miss brightness and "air", but I guess that's the HS80's sound. Also, before building it the drawing looked claustrophobic, but now that that visual feeling is gone, I can say it sounds a bit claustrophobic. Not too much though, it could be just that I'm not used to those speakers in this room, and I may sound in contradiction, but this feeling could actually be due to a tighter sound in general. Anyways, the top end is bugging me a little.

I took the closet doors out, it's just the hangers and insulation inside (the doors caused some flutter echo).

The superchunk's front is covered with pegboard (I was afraid that without it it would absorb too much highs), but I'll give it a try without it later. It is not sealed, so shouldn't be working as a resonator (that is intentional). In the upper corners (stretching from the superchunks), there should be another type of "superchunk". This yellow "box" wasn't supposed to be an enclosed box, the damn carpenter did it that way... it was supposed to be just the framing, leaving the insulation exposed, but instead it's all plain MDF, only exposing insulation through the darker area seen on the picture (I told him to leave it like that until he makes the right one, unless you guys say "NO, take that out!!").
Attachment:
DSCF3929.jpg


The splayed panels on the sides... they're sorta half absorptive and half reflective. Since splaying the panel only by 7º wouldn't give me an RFZ, the idea was to make them just plain insulation up to the last reflection point to create an RFZ, then the other half with pegboard would avoid flutter echo and keep some brightness in the room (throwing the reflections behind the sweet spot). But now I'm afraid that's causing that weird response from 2kHz-10kHz.
Attachment:
DSCF3930.jpg


About the mid-low peaks (300Hz, 550Hz, 700Hz), I'm pretty sure it's gotta be a resonator to fix, but how do I calculate it when the panel is angled (after all, the distance to the wall varies and the formulas seem to be based on continuous depths)?

I have 2 million dollar questions (yeah, 2 questions, 1 million each!):
1) it's been almost a month that we did the front side of the studio (the soffit filled with insulation), and there's been a VERY strong smell in the room, I can't stay there for more than an hour!! My eyes sorta burn, so does my nose, and the headache... don't even know how to say it in English... The carpenter said it's not the window caulking, neither the wood, it must be the rockwool. Everyone else says otherwise, and I agree with them in one point: there's been 8-9 packs of insulation waiting in my living room for more than two weeks and there's NEVER been the slightest smell of anything. So, 1 million: is that "normal"? Is there anything I could do to get that out? Been leaving the entire apartment ventilating, but the studio itself has no windows. And winter just arrived here, I don't want to get cold anymore!
2) as you can see on the last picture, the fabric on the side panels are more transparent than expected. Is it a bad thing to cover insulation (or anything else) with two layers of fabric?

Cheers everyone


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PostPosted: Sat May 19, 2012 2:30 pm 
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Hi again Tiago! Glad to see that things are progressing well with your build. It's looking nice!

Do you have any place where you can upload the SketchUp file, so I can download it? I'd really like to see it, so I can get a better feel for how the room is now, measure things, and do some calculations.

OK, a couple of questions:

1) What did you use for the front panel of the soffits? In one photo I can see how you built the inside, but there's no photo that shows the front panel before you put the cloth on it. What type of wood did you use for that panel, and how thick is it?

2) Did you correctlyset the bass roll-off control and other controls on the speakers? There are four control switches on the back of the HS80M: How do you have those set up right now? Make a note of that, so you can get back to it again, but then try setting them like this: Mid EQ: +2dB. Room Control: -4dB. High Trim: -2 dB. Low Cut: 80 Hz (or 100 Hz, depending on what your subwoofer needs). Test the room again with the speakers set like that, and see if there is a difference. It is very important that you get the mic in exactly the same place you used for the first tests: It must be in the identical position, to within a few mm, or the comparison won't be valid.

3) Have you tried covering the mineral wool in your absorbers with thin plastic? (except the ones at your first reflection points, of course!) I suspect that the mineral wool is sucking out too much high frequency energy.

4) Can you repeat the same tests with REW instead of Fuzzmeasure? I don't have any way of running Fuzzmeasure, and I'm not familiar with it, but if you could sen me a REW data file I'd be able to look at the acoustic response in much more detail.

5) Does the cloud have a hard back on it (plywood, MDF, OSB, etc.)?

6) Have you tried angling the cloud? I would angle it about 10° (lower at the front and higher over your head), and especially if it has a hard back.

OK, on to your questions:

Quote:
I have 2 million dollar questions (yeah, 2 questions, 1 million each!):
Cool! Please deposit those millions in my account, and I'll answer your questions... :) ! :shot:

Quote:
there's been a VERY strong smell in the room, ... is that "normal"?
No, that's NOT normal, and I agree with you that it is most likely not the insulation. What does is smell like? What products did the carpenter us in there? Maybe you can get his empty containers and see if any of them smell like the problem odor in the room.

Quote:
My eyes sorta burn, so does my nose, and the headache...
That's definitely not normal! And not good either! It must be something pretty powerful if it is affecting you like that. Tell him to make a list of the products he used (brand and type), and maybe we can figure out what is causing it. Did he use any type of glue? Paint? Varnish? What type of caulking did he use?

But you do have to find out what it is, and get rid of it: it's dangerous to your health like it is now.

Quote:
2) as you can see on the last picture, the fabric on the side panels are more transparent than expected. Is it a bad thing to cover insulation (or anything else) with two layers of fabric?
No problem. Make the first layer black (the layer that goes directly over the insulation), then you can make the second layer whatever color you want, and that should fix the visual problem of different colors.

Quote:
then the other half with pegboard
What size are the holes in the pegboard, how far apart are they, and how thick is the pegboard? I'm wondering if that might be the problem with the 900 Hz. dip... maybe the pegboard hole pattern is tuned to 900 Hz...

Quote:
a really weird response from about 2kHz up to 10kHz!
That is a bit strange, but that might be reflections from somewhere, or comb filtering, or something like that.

Quote:
To my ears, I just miss brightness and "air",
That's evident in the graphs: There's a steep roll-off above about 8 k, and that is NOT what the HS80 should do. Here's how it should look:

Attachment:
Yamaha-HS-80M-frequency-response-graph-2.jpg


So there is something in your room that is taking out energy in the high end, or boosting the high mids, or something. I bet that covering all your superchunks with plastic instead of pegboard would make a difference there...

Quote:
It is not sealed, so shouldn't be working as a resonator (that is intentional).
That's good, but there still might be some effect there, especially at higher frequencies.

I love a challenge, and this is one! Gonna be fun to try to track down all of those problems and fix them... :)


- Stuart -


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PostPosted: Sat May 19, 2012 5:47 pm 
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Hey Stuart, thanks for the attention.
I'm not able to reply right now, but I got the Sketchup file online (I guess). See if it's working please.

http://www.tiagolorena.com/mixingroomde ... oom_v9.skp

That's it for now, I'll get back to your questions asap, I promise. =)

Cheers mate


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PostPosted: Sun May 20, 2012 2:03 am 
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Quote:
See if it's working please.
Yes, I got it OK. No problem. But I did notice that it only shows the actual acoustic treatment, not the inner-leaf or outer-leaf. Do you have a version with those in it? I think I might have seen some issues with the soffits and side panels, but I can only tell for sure if I can also see at least the inner-leaf.

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PostPosted: Sun May 20, 2012 7:53 am 
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Hey Stuart,

You asked about the outer/inner leaf... I'm not too sure what you're talking about, but I guess it's regarding the walls and isolation, am I wrong? Don't know if made it clear, but I am really just looking for the acoustic treatment, I wouldn't be able to work on isolation at this point. Or maybe I misunderstood your request.

Now, to your questions:

1) the front panels on the soffits are MDF covered with fabric. I left a 30cm opening at the bottom (taking almost the entire width of the panel) and a 10x25 cm at the top for ventilation. The MDF is 15mm thick.

2) I've set up the speakers like this: Low Cut @ 80Hz; Room Control @ -4dB; Mid EQ @ 0dB, High Trim @ 0dB. Subwoofer was set up: High Cut @ 80Hz; Low Cut OFF; Polarity Inversion IN. I gotta be honest your suggestion doesn't make sense to me (Mid EQ +2dB, High Trim -2dB), but there's no harm in trying, so I'll give it a shot later on and post the results.

3) No, haven't tried plastic, will give it a shot. Any specification on the type of plastic?

4) Sure, I'll try setting up REW and learning how to use it, if it goes well I'll send you the data.

5) and 6) None of the clouds have a hard back, only their "sides" (or "framing"). The cloud above the desk has a hard surface at about 20º and I placed it at a point where reflections from the ceiling would be blocked so they wouldn't hit the sweet spot (you can see that in the last picture). The second cloud isn't angled, but I'll give it a shot and let you know if anything changed. Also there are two layers of 50mm rockwool in both clouds.

The pegboard I've used is this:
Attachment:
Pegboard.JPG

The holes are about 4mm, around 8mm spaced and about 3mm thick.

Looking at the results so far, would you say using an EQ to fix the top end would be too "unwise"? Cause, to be honest, what's really bugging me is that weird curve above the 900Hz and that smell (been trying to reach the carpenter, but he just won't take my calls... this has been a real pain, I'm really pissed off with this dude). I don't want to diminish the present problems, I'm just trying to see if in general I'm on the right track. I'm sure the response will never be "ruler flat", but I'm wondering up to what point I could introduce an EQ in this scenario to improve the results?

Cheers!

And congrats for the Chelsea fans! (although, I was supporting Bayern...)


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PostPosted: Mon May 28, 2012 3:54 pm 
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Quote:
You asked about the outer/inner leaf... I'm not too sure what you're talking about, but I guess it's regarding the walls and isolation, am I wrong? Don't know if made it clear, but I am really just looking for the acoustic treatment, I wouldn't be able to work on isolation at this point. Or maybe I misunderstood your request.
Yes, that's right: the walls of your room are part of the acoustics, so they are important. For example, the distance between the acoustic panels and the wall surface can have a huge effect on frequency response. If you don't show where the walls are, then it's really hard to say what things are doing.

Quote:
1) the front panels on the soffits are MDF covered with fabric. I left a 30cm opening at the bottom (taking almost the entire width of the panel) and a 10x25 cm at the top for ventilation. The MDF is 15mm thick.
OK, that should be reasonable. Thicker MDF would have been better.

Quote:
I gotta be honest your suggestion doesn't make sense to me (Mid EQ +2dB, High Trim -2dB), but there's no harm in trying, so I'll give it a shot later on and post the results.
That's the idea! I want to see what difference it makes with those settings. I have a hunch...

Quote:
3) No, haven't tried plastic, will give it a shot. Any specification on the type of plastic?
6 mil polyethylene is probably a good start.

Quote:
The pegboard I've used is this:
I strongly suspect that the pegboard is the problem. For the dimensions you show, if there is any place where depth of the cavity is about 3 inches (around 75 mm) and the insulation behind the pegboard is about an inch thick (25mm), then the absorption graph for that is almost a perfect match for the issues that you are seeing on that response plot, including huge peak absorption at around 900 Hz, with additional peaks at around 2.5 k, 3.8k, and 5k... look at the red curve. If you have another place where the cavity is a bit less, just under three inches, then that matches your green curve perfectly, with peak absorption at 950 Hz, 3.1k, 4.2k. 5.3k, etc.

It looks very suspicious!

Can you take out that pegboard easily? If so, then take it out and repeat the test.


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PostPosted: Tue May 29, 2012 6:36 pm 
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Hey Stuart,

Quote:
Yes, that's right: the walls of your room are part of the acoustics, so they are important.

Sorry if the drawing didn't show the walls, I'm not much of an expert in SU, don't know a good workflow nor how to keep things organized. I'm pretty sure though that there's a hidden component called "Walls", so maybe you could search for it in the Outliner window. If it's not there I'll upload it again. Also, you mentioned you've seen something wrong with the soffits and side panels, what was it?

Quote:
Thicker MDF would have been better.

What thickness would suit best? What difference would it make being just 15mm?

The pegboard is still there on the superchunks, but I've loosened it on the screws, so it's even less tight on the edges now (avoiding even more a helmholtz effect). Been working a lot theses days, so couldn't get to purchase the plastic to cover it, but as soon as I get it I'll run the testes again replacing pegboard with plastic and with nothing over the insulation too, then post the results.

I have rerun the tests with REW as you requested, here's the file:
http://tiagolorena.com/mixingroomdesign ... -2012.mdat

I actually went a little bit further. First of all, I've taken the desk out of the equation for now, which has proven to fix that response at 2kHz-10kHz, so I decided to keep it out until I get the flattest response, THEN as I add object in the room I know well what's causing what. Also, I'm deeply sorry to inform that the first response I posted here (with Fuzzmeasure) was not with the Room Control set to -4dB, but -2dB! My bad! :oops:
As you'll see I ran sweeps with a default setting with no sub and the graphs show considerable energy at 40-50Hz, then a big dip at 70Hz, followed by the "usual" (and undesirable) peaks and dips up to 1k-ish. I never thought the HS80M's would talk down to 40Hz like that, but then my 70Hz just fall into a swirling black hole! What could be causing that? (see pic below)
Attachment:
default no sub.jpg


I followed your (still weird :D ) setup suggestion, it's in the REW file too. Here's a graph:
Attachment:
stuart setting.jpg


Here's two alternatives I thought to be a bit more logical:
Attachment:
low cut 100hz mid -2db high +2db with sub high cut 120hz.jpg

Attachment:
low cut 100hz mid -2db with sub high cut 120hz.jpg


Although... I still don't find it very confident with the last setting (Mid EQ -2dB, High Trim 0dB), everything seems to be a bit far away with that setting... BUT is an acceptable alternative. The one before that (Mid EQ @ -2dB, High Trim @ +2dB) was interesting at first, seemed to be filling that high end roll-off, but then it just turned out to be too much. The last 3 graphs were run with the sub.

Btw, I guess that top end roll-off COULD be the mic response. The Behringer ECM8000 isn't as reliable as one would like, so I'm trying to find someone I could hire at least an Earthworks M23 or M30 around here to run a few definitive tests, but no luck so far. Gotta keep it rolling with the ECM8000 for now.

Cheers


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