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PostPosted: Tue Jun 25, 2019 5:17 am 
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By extending the line parallel to the baffle to the adjacent wall, that line cuts though my door. Even if I move the speakers more to the front wall, I won’t be fully clear from the door. So no can do. Unfortunately.
Two options: 1) Modify the typical soffit shape to fit your door. 2) Turn the room around to face the other wall (with the window). There's plenty of space to do soffits at that end of the room.

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PostPosted: Thu Jul 04, 2019 2:42 am 
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I can't use the wall with the window to build a soffit there, because there's a heater underneath the window. If I close up all of that, I no longer have heating in the room and I can not access the pipes and heater in case of a leak. With regards to the other option, what a bout yet another idea:

I've been playing with REW Room Simulator, while waiting for some wood work for my super chunks.
Attachment:
REW RoomSim Long Throw.jpg

I've noticed that when I turn everything 90 degrees counte clockwise (the long wall without the door becomes the fromt wall), the entire predicted spectrum becomes smoother, and the massive dip at 80 - 100Hz shifts up to just above 100Hz, which makes it easier to treat, though still difficult. Also, I have more surface on the front and back walls to place absortion (SBIR issues) and (I think) the door also becomes less of a problem.
Attachment:
REW RoomSim Short Throw.jpg

So this looks like a good compromise. I know: Stuart is allergic to compromise (and rightfully so!). However, this room was not purpose designed to be a mix studio. And, frankly, a soffit seems like too big and too expensive an endeavour for me at this time. There's so much work and materials involved, I'm afraid it's going to be out of my budget and outside of my skill set.

When I follow the proposed plan and the results are good, I will save up money and try the soffit route, after all. Because I definetely see the benefits. But at this time I have no idea what I'm doing when "designing" one. And, as stated, I want to try what happens when I turn everything 90 degrees counter clockwise. Might be worth my while, without breaking the bank (and my back).

Can somebody tell me what exactly the purpose is of a cloud in a small room? The way I see it, in my room the mode between floor and ceiling lies at 71Hz, which is outside the range of resistance based absorption. So, how I can counteract it? Helmholtz resonator on the ceiling?
And what causes the dip at around 80Hz - 100Hz in both scenario's? Simulated, the dip becomes significantly less deep, when I move closer to the front wall, keeping the speakers at the same location. But then I deviate significantly from the proposed 35%.
Attachment:
REW RoomSim Closer to front wall.jpg

In the Short Throw scenario the irregularity around 110Hz is about as good as it can get in this simulated, untreated room...

Things to ponder....


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Last edited by The Sound Guy on Thu Jul 04, 2019 4:13 pm, edited 2 times in total.

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PostPosted: Thu Jul 04, 2019 10:13 am 
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I can't use the wall with the window to build a soffit there, because there's a heater underneath the window. If I close up all of that, I no longer have heating in the room
Then don't close it up! :) Make a soffit that leaves the heater free. Or just don't use that heater, and set up a different heater elsewhere in the room...

Quote:
I've been playing with REW Room Simulator,
It's a useful tool, but all it tells you is the predicted frequency response based on modal response. That's not the entire picture of the room response! Not by any means. Very far from it.

Quote:
I've noticed that when I turn everything 90 degrees counte clockwise (the long wall without the door becomes the fromt wall), the entire predicted spectrum becomes smoother, and the massive dip at 80 - 100Hz shifts up to just above 100Hz,
... and you also move your head much closer to the rear wall, where you will be getting major reflections inside the Haas time, and thus messing with your psycho-acoustic perception of the sound... Early reflections from the back wall are a big "no-no" in studio design! You want your head as far as possible from the rear wall, in order to meet (or at least approach) the "20-20" criteria (hence my screen name: it has nothing to do with the year 2020... :) ). the "20-20" criteria says that you must avoid all reflections within the first 20ms of the direct sound, and even then they must be 20 dB down form the direct sound. This is a basic criteria for successful control room design. And you cannot achieve that with the rear wall just a short distance behind your head! Your room is only 3 m wide, and your head is about two thirds of that distance.... so your head is just 1 m from the rear wall. That's barely 6 ms for the reflections from the rear wall. With the lengthwise orientation, your room is 4.6m long and your head is about one third of that distance, so it's about 3 from the rear wall. That's about 19.6 ms for the reflection from the rear wall.... Very close to where it needs to be.

So what's the problem? Well, if your ears and brain hear the direct sound, and also a reflection of the direct sound both arriving within 20 ms of each other, then your brain is unable to figure out that it is actually two separate sounds. They have to further apart than 20 ms to do that. Over 30 ms is better, but 20 is decent. So, since your ears and brain don't realize that you are hearing a reflection, instead they assume that the combination of the two is just one single sound. And since that "combination" is very different from each of the individual sounds, your brain decides that it actually came from a different direction, and that the frequency curve was different from what it really was... :shock: :!: This is all about the field of psycho-acoustics: how your brain perceives the sound, rather than what a mic would measure. Mics and ears are very different: they do not work the same. Since you have a pair of ears, and since each ear picks up a slightly different version of any sound (because they are spaced apart, and have your head in between), your brain uses the subtle timing differences and level differences and phase differences, to figure which direction the sound came from. All those little curly folds and wrinkles of your ears are actually a key part to this, since they provide additional timing, phase and level differences that your amazing ears can use to figure things out. In fact, those folds and wrinkles create specific interference patterns inside your ear canal, which your ear then recognizes as indicating where the sound came from. The problem is, that when you get a sound plus its reflection in less that 20 ms, and less the 20 dB difference, the effect is exactly the same as what the wrinkles and folds would cause from just the direct sound! That totally confuses your poor old ears, and messes with your brain: there are now two sets of interference patterns in your ear canal: one from the "wrinkles and folds", and the other from the reflected sound that arrive in less than 20 ms. So your brain does what it normally does with all such interference patterns: it interprets that as meaning the sound came from ANOTHER direction, different from the one it really came from! As you can imagine this is not a good things for a control room... The room is lying to your brain, messing with it's ability to correctly decide where the sound came from (panning), and what the frequencies were (eq)....

So, do avoid a room layout where you get reflections within 20ms....

Quote:
So this looks like a good compromise. I know: Stuart is allergic to compromise (and rightfully so!).
8) :lol: Actually, studio design is all about compromises! That's what I do, all day every day when designing studios: play off one aspect against another, compromising some things in order to improve others... The trick is to continue juggling all those compromises, until each one is at it's lowest level, and the studio is optimized... :)

Quote:
However, this room was not purpose designed to be a mix studio.
To be very honest, very few of the studios I design are purpose-designed! More often than not, I just get a pre-existing room with fixed dimensions, shape, doors, windows, etc. Then I have to fiddle with all those compromises, to make it work.

Quote:
a soffit seems like too big and too expensice an endeavour for me at this time. There's so much work and materials involved, it's going to be out of my budget and outside of my skill set.
Can you use a hammer? Can you use a saw? Then you have the skill set. Can you buy 2x4 framing at your local hardware store? Can you buy sheets of MDF, and nails, and insulation? They there's no problems with materials either! :)

Quote:
When I follow the proposed plan and the results are good, I will save up money and try the soffit route, after all.
Which implies that you will then have to trash most of the treatment that you had built up to that point, because it won't be applicable any more... The treatment is different for a room with soffits, as compared to a room without soffits. Very different. If you want to build soffits later, that basically means you will need to re-do most of the room...

Quote:
But at this time I have no idea what I'm doing when "designing" one.
The basic concept is simple: A big plank of wood with a hole in it to poke the speaker through, and a frame to support it. That's all it is, basically.

Quote:
I want to try what happens when I turn everything 90 degrees counter clockwise.
Try it by all means! And post the REW data, so we can show you just how bad it is... :) Then you can turn it back again...

Quote:
Can somebody tell me what exactly the purpose is of a cloud in a small room?
A properly designed cloud accomplishes many things: One is modal smearing, second is RFZ, third is ceiling treatment, forth is eliminating the ceiling bounce, fifth is overall room decay response, sixth is that it looks cool, ...etc.

Quote:
The way I see it, in my room the mode between floor and ceiling lies at 71Hz, which is outside the range of resistance based absorption.
Ummmm... Your FIRST axial room mode in the vertical direction is at 71.8 Hz, yes, but the SECOND vertical axial mode is at 143.5 Hz, and the THIRD vertical axial is at 215.3. But you also have tangentials involving the ceiling at 80.8, 92.1, 103.4, 118.4, 132.7, 136, 141..... And you have obliques at 99.4, 118.4, 141.0..... All of those are treatable with 15cm of suitable porous insulation, with the possible exception of the first two (71.8, and 80.8 ) All the others are with the range. But that doesn't matter, since the lowest frequencies will also be hit by the back of the cloud, or by the membrane effect, or by the air gap above the cloud, or by other design features that can be built into a cloud.

Here's an example from a room that was recently completed by one of my clients. Here's the waterfall plot before the cloud went in:
Attachment:
FCR-REW-WF-10-500--before-cloud.png


And then again AFTER the cloud was in place:
Attachment:
FCR-REW-WF-10-500--after-cloud-first-test.png


I think you can see the massive difference, even down at 70 Hz, which you are worried about..

Here's the spectrograms from the same tests. Before:
Attachment:
FCR-REW-SP-10-500--before-cloud.png


And AFTER:
Attachment:
FCR-REW-SP-10-500--after-cloud-first-test.png


Once again, you can see the massive difference, even in the 70 Hz region.

Quote:
And what causes the dip at around 80Hz - 100Hz in both scenario's?
Probably floor bounce. I'm not sure if the algorithm in Room Sim takes that into account, but that's typical of all small rooms. There's always a dip somewhere in that region, which is set by the distance between the mix position and the speakers.

Quote:
Simulated, the dip becomes significantly less deep, when I move closer to the front wall
Yup. Because it will move to higher frequency as you get closer to the speaker (shorter path), and thus is partly compensated by modal issues in the same region.

Quote:
In the Short Throw scenario the irregularity around 110Hz is about as good as it can get in this simulated, untreated room...
so what? :) I would certainly not base my room layout and design on a very basic simulation of frequency response, and worse still, without any treatment in the room!

Here's what it looks like with minimal typical treatment:
Attachment:
Sound-Guy--room-sim-with-treatment.jpg


Quite a difference!

Besides, you are only looking at frequency response, which isn't even the most important aspect of a room's acoustics! You should be looking at the time-domain response. That's what really matters. You should never base major layout or treatment decisions on frequency response alone. Without the context of time-domain response and phase response, the frequency response graph is not much use... especially when it is merely a simulation... You would also want to know about reflections, diffusion, the ITDG, the shape of the impulse response, and many other things. FR is just one small aspect of overall acoustic response: don't focus on that too much: it really isn't that important, until you get to the final stage of tuning.

Quote:
Things to ponder....
Or calculate... :)


- Stuart -


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PostPosted: Thu Jul 04, 2019 5:19 pm 
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Stuart, thank you for your lengthy reply.
Soundman2020 wrote:
Besides, you are only looking at frequency response, which isn't even the most important aspect of a room's acoustics! You should be looking at the time-domain response. That's what really matters. You should never base major layout or treatment decisions on frequency response alone. Without the context of time-domain response and phase response, the frequency response graph is not much use... especially when it is merely a simulation... You would also want to know about reflections, diffusion, the ITDG, the shape of the impulse response, and many other things. FR is just one small aspect of overall acoustic response: don't focus on that too much: it really isn't that important, until you get to the final stage of tuning.

Point taken. I realize that simulation is only an approximation of what could happen in a room.
Soundman2020 wrote:
The Sound Guy wrote:
a soffit seems like too big and too expensive an endeavour for me at this time. There's so much work and materials involved, it's going to be out of my budget and outside of my skill set.
Can you use a hammer? Can you use a saw? Then you have the skill set. Can you buy 2x4 framing at your local hardware store? Can you buy sheets of MDF, and nails, and insulation? Then there's no problems with materials either! :)

Materials are available. I don't have a table saw, nor even a circular saw, though. I'm actually terrified of circular saws. I've seen too many accidents involving circular saws (I work in health care, radiology). So I will have to have everything made to order. Wich costs €€€. I do have and can operate a drill and electrical screw driver.

However hypothetical it is, I question the logic of going "all out" with this room, when it's not generating any money (yet) to pay for itself. Currently, I have a normal full-time day job. It pays my bills, but there's not a lot left to spend on the side. I'm afraid I'm also looking at replacing my Mac, since it's been developing some problems. These may be software related, which could hopefully be solved by upgrading (or just re-installing) OSX. But, I may have to upgrade Protools too, if I upgrade OSX. But I digress. Bottom line: I'm very concious about investment versus generated income.

I will further investigate soffits with regards to materials needed and their cost.
Alternatively, how about this:
Attachment:
0ca77e7f-b3b5-4526-9cac-b132fa4496d2.JPG

The S2X fit inside the Super Chunks, but the baffle will stick out a few cm's. I can move them a little more to the side wall so as to make them flush with the face of the super chunks, which places the mix position farther back in the room ( >35%).
Soundman2020 wrote:
The Sound Guy wrote:
I want to try what happens when I turn everything 90 degrees counter clockwise.
Try it by all means! And post the REW data, so we can show you just how bad it is... :) Then you can turn it back again...

Another point taken. I might acutally just do that, if only to provide some evidence that could be of use for others with a similar room.

Soundman2020 wrote:
The Sound Guy wrote:
Things to ponder....
Or calculate... :)

How?! :| I'm still learning about acoustics. It seems the more I learn, the more I know I don't know. When is one "ready" to start, or at least develop a good plan? With every step I take, it seems there are more things to concider, so I need to rework the plan. Still motivated, but I'm starting to get impatient. I want to get started. But only if the plan is good.
I've received a price quote for the woodwork needed for the super chunks. I'd like to move forward with that. But concidering the above, I'd better wait a while..?


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PostPosted: Thu Jul 04, 2019 10:28 pm 
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By reading this and this I get the stong feeling that there is quite a lot more to soffits than just having speakers poking through holes in a wooden face, bolted to a wooden frame...
Where can I find in depth information on how to do soffits properly?
I get that they need to be very sturdy, stiff and with a stiff and heavy baffle. Also, there seems to be some math involved in properly floating a speaker inside a soffit. Putting the monitor on a heavy, sturdy stand and building a baffle around it won't cut it, I guess..?


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PostPosted: Wed Oct 23, 2019 2:02 pm 
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I get the stong feeling that there is quite a lot more to soffits than just having speakers poking through holes in a wooden face, bolted to a wooden frame...

It all depends on how intense you want to get with your design and build. Basically the hard material around your speaker is just attempting to extend the size of your speaker baffle. Actually, in a well designed room, the side walls (maybe going all the way to your rear wall) are extensions of the baffle. This is ultimately attempting to be an "infinite baffle".

Quote:
Where can I find in depth information on how to do soffits properly?

Digging more into this forum you will find countless examples of this. It seems each person tackles it their own way (floating the speaker, floating the speaker in a floating speaker enclosure, firmly mounting the speaker). I wouldn't say there is a right or wrong way per say.

Quote:
I get that they need to be very sturdy, stiff and with a stiff and heavy baffle.

Yes.

Quote:
Also, there seems to be some math involved in properly floating a speaker inside a soffit.

The Sorbothane calculator apparently is flawed but close to correct. Basically, the difficult math would be figuring out what to use under the speaker as there is more force pushing down on the speaker once the top Sorbothane material is applied (with ~20% deflection).

Quote:
Putting the monitor on a heavy, sturdy stand and building a baffle around it won't cut it, I guess..?

This has worked for many people. However, there are disadvantages to this method vs floating. One major one would be that the speaker stand would have to basically be straight down the floor and eat up valuable bass trapping space.

Greg

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PostPosted: Mon Nov 18, 2019 3:08 am 
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Hi Folks,

High time for an overdue update.

For several reasons I've ditched the Soffit route. At least for now. I simply can't get my head around how to do it properly in the space I have avialable. So I went with super chunks and broadband absorber panels.
Currently I have three and a half super chunk. The last one, in the right rear corner has, to be constructed around heating pipes, which is a bit of a pain. But it's a matter of putting the materials that I already have together, and super chunk 4 will also be ready.

I have six broadband absorber panels. Two on the front wall and two on either side of the mix position.

This room is far from finished, but my ears tell me that the sound has vastly improved compared to what it was when I did the first measurements. I still think there is a massive dip from somwhere around 75Hz all the way up to about 110Hz. I'm pretty sure there are more inconsistencies, but they are difficult to quantify by ear.

Even though there is still a lot of work to be done, I thought it would be interesting to see the effect of this basic (and incomplete) treatment.

This is the link to the base line measurements (no treatment);
https://www.dropbox.com/s/mgz2f78zwawb4 ... .mdat?dl=0

This is the link to the measurements made today.
https://www.dropbox.com/s/ojslbvtck05gh ... .mdat?dl=0

The measurements confirm that there is still a lot to be done. But frankly, I can't make very much of these results, aside from the fact that I still need a lot more treatment in the really low bass range. But what type? What could cause the massive dip around 100Hz? And how can I reduce it?
I'm sure there are also some problems concerning the rear wall, which currently is untreated. Can anyone help me further interpret these measurements, so that I (we, hopefully) can determine how to move on?

Awesome!! Thanks!!


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PostPosted: Mon Nov 18, 2019 5:50 pm 
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The improvement is staggering! Congratulations so far!

Your mid and high frequencies are getting to dead. The opposite can be said for your low frequencies. If I were you, I would find some more corners to bass trap (floor and ceiling corners). Get as much bass trapping as you can. As you can see in your MDAT, the more you bass trap, the better the frequency response gets around that dip. Re-measure after that and we can try to bring some life back into the room.

Greg

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PostPosted: Mon Nov 25, 2019 6:31 pm 
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Thanks, Gregwor.

So far I had no idea what to expect. But having built these treatments and having heard what they do, I'm astounded myself. And it's encouriging to see their positive effect in the measurements, too!

Based on those measurements, I figured I would need a lot more bass trapping. I have space for that on the front wall, ceiling (cloud), rear wall and all wall/ceiling corners. There is also space available on the side walls in the rear of the room.
However, I wonder what type of bass trapping would be best. It needs to be effective below about 200Hz, as far as I can tell from the measurements, but I need a lot of absorbtion below 100Hz (if it's safe to say so, based on RT-60). I doubt I will get that done efficiently with only GFR-based absorbtion. And besides that, the 90Hz dip still is a major issue when mixing, even though it's a lot less apparent than it used to be while casually listening.

I could treat the entire hight and width of the front wall between the superchunks with rockwool or glassfiber sheets, as well as a good part of the rear wall. But I'm wondering if it would be a better idea to construct membrane absorbers of the limp mass type? Rubber sheets, optionally loaded with sheet metal, like the ones built in this studio.

Any other, hopefully better, suggestions?


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PostPosted: Mon Nov 25, 2019 6:58 pm 
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"However, I wonder what type of bass trapping would be best. It needs to be effective below about 200Hz,"

Try vertical slot resonators using 6" x 2" vertical beams separated by 1/4" spaces across your room corners.

Here's the math

Attachment:
excel_1.JPG


Here's the corner use:

Attachment:
Corner_1.JPG


And here how it can be integrated into you design.

Attachment:
control_1.jpg


Cheers
john


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PostPosted: Mon Nov 25, 2019 7:21 pm 
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Thanks, John!

It looks like I could build this right on the front face of my existing superchunks!
It would mean, however, that my monitors would be placed a little farther from the front wall, lowering the first SBIR-related problem frequency...


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PostPosted: Wed Dec 04, 2019 11:56 pm 
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There's one thing that I don't quite get while looking at John's suggestion:
the calculator he posted takes the distance to the wall into account.
When I would mount a "slat face" onto my superchunks, the distance to the wall is variable, depending on the horizontal position on the face. Additionally, the space between the wall and slats is almost completely filled with glassfiber sheets. How can I incorporate that into calculations? Do I need to?

Also, as it is, the sheets of glassfiber in my superchunks are not all exactly the same size. This means that the distance from the slats to the glassfibre sheets will differ from glassfibre sheet to glassfibre sheet, but just a little. I've attached fabric over it, so it doesn't show. Since the difference is more or less random, do I need to account for it in the calculations?


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PostPosted: Thu Dec 05, 2019 8:37 am 
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Adding vertical slats in front of your superchunks will make the area behind them a sealed cavity apart from the air access via the gaps between the vertical slats.
It's the cavity that offers the resonant chamber for the slots.

cheers
john

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