The New Room | The-audio-expert

soundofmind
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The New Room Feb 27, 2021 8:58:05 GMT

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Post by soundofmind on Feb 27, 2021 8:58:05 GMT

Our new home should be complete in September. We are downsizing, but the good thing is that there is an unfinished room in the basement that will hopefully meet minimal requirements for a decent listening room / home theater. At completion, the ceiling will have 5/8” sheetrock applied to the trusses giving a height of 8’ 1 ½”. When done, height from floor covering to ceiling is expected to be at 7’ 11 3/8”. The wall to the right in the first drawing will likely be moved to make the room less square. Hard closed cell spray foam insulation will be applied within the 2x4 stud walls, probably covered with 5/8” heavy sheetrock. The doorways shown will have solid core doors – two are 32 by 80 and one is 28 by 80. The smaller rack to the upper left is for equipment and the other two are general storage heavy duty steel with ½” wood shelves. The chairs are Stressless recliners, which don’t require power and are easy to move around. The positions of chairs and speakers are a starting point with the 2.0 layout taken from the cardas website.

I really like the Dali Helicon speakers (400 mains, C200 center, IW 200 in wall monopole for the sides) and Dali Mentor 2 rears that are carried over from the current home, along with the Gemstone 7 x 200W amplifier and 15” sealed Velodyne subwoofer. The sound processor will likely be the Monolith HTP-1, which can store six different Dirac correction profiles, possibly helpful when moving between the stereo and 7.1.4 positions shown in the drawings. The goal is to treat the room so little correction is required.

I am hoping that the adherence to the golden Sepmeyer 1 : 1.60 : 2.33 ratio will work well with generous usage of conventional bass traps and other thinner absorbers as required. I have some experience with REW and have plenty of time to experiment to make the room sound as good as possible. The drawings include both a 2.0 (2.1 if I move the subwoofer in front of the center or elsewhere) listening position for one person in addition to a home theater setup, which will include four Atmos speakers in the ceiling. The 2.0 or 2.1 position is the most important for tuning treatment, but I really want the 7.1.4 layout to work almost as well using 2.1, because the room is meant to share.

I know that soundproofing isn’t the first focus of this forum, but I also need to try and limit sound into the ceiling and the wall on the right.

I have questions and humbly ask for your input – please direct me to other relevant forum threads:
1. Does anyone have experience with a room with similar dimensions? What were the results? Could you provide a link and / or descriptions on what was done to improve the sound?
2. Would it be a bad idea to make the room wider than shown in the drawings? I wouldn’t be following the golden ratio, but would be gaining volume. The extra room would be nice, but it seems problems would be created by making the room more square.
3. How do you suggest I cover the concrete floor? Carpet is probably my first choice – perhaps the choice of pad would make a difference. It probably wouldn’t affect bass, but could absorb some mid to high frequencies, which may be a good thing. I’m trying to avoid reducing the usable vertical dimension.
4. You Tube has been my friend lately and one comment made was that adding a lot of treatment to a wall shrinks the room, which would certainly disrupt the golden ratio. He was referring to thick diaphragmatic bass traps, which certainly would make the room shorter where used, because the sound hits the fairly rigid surface of the diaphragm. If I use something more conventional like a series of 4” or 6” thick Rockboard 40 or 60 absorbers with sufficient gap to the wall, does that effectively shorten the room?
5. In addition to the corners, it seems that the back and front of the room need the most treatment for bass. The last drawing shows the permanently mounted screen right against the sheet rock. The screen needs to move away from the wall to allow for sound treatment. I am hoping to move it no more than 4”, perhaps fill that area with 2” Rockboard 40 or 60 with a 2” gap.
a. It is optimistic to think that will give me enough absorption?
b. Would a conventional screen block the sound treatment too much? Is an acoustically transparent screen really important here?
6. Dispersion seems to be suggested mainly for the back wall. Again this might mess with the golden ratio. Would it be a good thing to consider for this size room? The goal is not to make the room dead, but controlled and musical.
7. Would there be anything to gain by elevating the subwoofer by a foot or so?
8. Should something other than heavy 5/8” sheet rock be considered for the walls?
9. It seems the most often discussed method of isolating sound is the green glue approach. I was wondering if anyone tried anything like this or could suggest something better. The bottom of my ceiling trusses are about 8’2”, so there isn’t much room for something exotic. The carpet or whatever is used on the floor eats up some of that height.
a. For the ceiling, put something like 4” of Rockboard between trusses, use clips and hat channel to hang a double layer of sheet rock with green glue in between.
b. A similar approach could be taken to the wall on the right, or make a double wall.

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Last Edit: Feb 27, 2021 9:24:00 GMT by soundofmind

rock
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Posts: 893

The New Room Feb 27, 2021 13:39:17 GMT Hexspa likes this

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Post by rock on Feb 27, 2021 13:39:17 GMT

My first impression is since you're building, do the sound isolation first. See Rod Gervais on Gear Slutz or get his book. Since you're building, consider adding mass to your floor above the theater and possibly the entire 1st floor. If you need to increase structural load bearing, you can do that now...if it's not too late. Consider flanking paths and isolate them. Consider isolating A/C heat ducts.

For #4 porous acoustic treatment in the room does not subtract room dimensions. The rigid boundaries determine the dims.

Diffusion on the back wall is good, Real Traps make a combination bass trap diffusor.

That's all for now but hopefully other will add to this thread.

soundofmind
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Posts: 2

The New Room Feb 27, 2021 21:44:21 GMT

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Post by soundofmind on Feb 27, 2021 21:44:21 GMT

Thanks Rock! Rod's book is ordered. Agreed that the surfaces have to be addressed before the good stuff goes inside the room.

This builder creates cookie cutter homes, allowing no significant custom changes before construction. The ceiling in the theater will be ripped down, so perhaps some mass can be applied to the underside of the main floor between the trusses. It might also make sense to take up the carpet in the room above, lay some sort of dense pad and then reinstall the carpet.

When considering the ceiling, it's very important to prevent theater sound from traveling through those wide open trusses. When I started looking for conversations on such topics, there seems to be some consensus that you need mass (e.g. the isolated sheet rock sandwich) but with plenty of low density insulation versus something denser like RockBoard.

Since it's new construction, the venting is flexible foil with a spiral wire versus metal ducts. I don't know if it incorporates any insulation to provide a little dampening.

Thanks for the confirmation about the acoustic treatment dimension question and diffusion.

rock
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Posts: 893

The New Room Feb 27, 2021 23:23:08 GMT

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Post by rock on Feb 27, 2021 23:23:08 GMT

I think you're on the right track. Yes, about mass from the underside but it's much easier from the top. If you can add the mass from the top (MDF comes to mind) you can deal with the floor levels from room to room with custom thresholds. (I've done that when installing ceramic tile with underlayment) Check with your builder about the load the floor can handle. I'm not a builder or engineer so I have no point of reference about what the numbers should be so you'll need to get a handle on that somehow.

You also mentioned about clips (and RC channels) installing the ceiling, Rod has stuff on that in his book but get on Gear Slutz and see what his current ideas are.

Flexible ducts are way quieter so good you have them. I've seen them to have an inch of insulation around a plastic flexible duct. Home runs to the air handler for both supply and return will isolate the best if you can.

About your "Golden Ratio" of course it's best to go with the "best" modal spacing but if you need/like a wider room, see if you can fit it into an alternate acceptable ratio. In the end, your treatment will help smooth out the modes. But the point is, you really only have one chance the get the room dims the way you want them so there may be acceptable compromises???

Cheers, Rock

Hexspa
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Am I A Musician Or?

Posts: 2,176

The New Room Mar 1, 2021 22:23:09 GMT

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Post by Hexspa on Mar 1, 2021 22:23:09 GMT

Feb 27, 2021 8:58:05 GMT soundofmind said:

1. Does anyone have experience with a room with similar dimensions? What were the results? Could you provide a link and / or descriptions on what was done to improve the sound?

2. Would it be a bad idea to make the room wider than shown in the drawings? I wouldn’t be following the golden ratio, but would be gaining volume. The extra room would be nice, but it seems problems would be created by making the room more square.
3. How do you suggest I cover the concrete floor? Carpet is probably my first choice – perhaps the choice of pad would make a difference. It probably wouldn’t affect bass, but could absorb some mid to high frequencies, which may be a good thing. I’m trying to avoid reducing the usable vertical dimension.
4. You Tube has been my friend lately and one comment made was that adding a lot of treatment to a wall shrinks the room, which would certainly disrupt the golden ratio. He was referring to thick diaphragmatic bass traps, which certainly would make the room shorter where used, because the sound hits the fairly rigid surface of the diaphragm. If I use something more conventional like a series of 4” or 6” thick Rockboard 40 or 60 absorbers with sufficient gap to the wall, does that effectively shorten the room?
5. In addition to the corners, it seems that the back and front of the room need the most treatment for bass. The last drawing shows the permanently mounted screen right against the sheet rock. The screen needs to move away from the wall to allow for sound treatment. I am hoping to move it no more than 4”, perhaps fill that area with 2” Rockboard 40 or 60 with a 2” gap.
a. It is optimistic to think that will give me enough absorption?
b. Would a conventional screen block the sound treatment too much? Is an acoustically transparent screen really important here?
6. Dispersion seems to be suggested mainly for the back wall. Again this might mess with the golden ratio. Would it be a good thing to consider for this size room? The goal is not to make the room dead, but controlled and musical.
7. Would there be anything to gain by elevating the subwoofer by a foot or so?
8. Should something other than heavy 5/8” sheet rock be considered for the walls?
9. It seems the most often discussed method of isolating sound is the green glue approach. I was wondering if anyone tried anything like this or could suggest something better. The bottom of my ceiling trusses are about 8’2”, so there isn’t much room for something exotic. The carpet or whatever is used on the floor eats up some of that height.
a. For the ceiling, put something like 4” of Rockboard between trusses, use clips and hat channel to hang a double layer of sheet rock with green glue in between.
b. A similar approach could be taken to the wall on the right, or make a double wall.

1. It's nearly a 1:2.35:2.35 ratio. Two or more identical dimensions will emphasize their related modal influence. That means you can expect extra ringing and elevated SPL at that wavelength and maybe its doubles and halves.

2. Volume is good because it makes reflections weaker and pushes down the room's lowest fundamental resonance. Not sure if anyone's correlated its offsetting power to that of room ratios. Let's just say that bigger and less square is on one side of the rainbow and a small cube is the left hand path.

3. To me, it's a floor. It's not like you're going to walk on mesh as in an anechoic chamber. To live in the space, it needs practicality. Put on the floor what you find most enjoyable to walk on. This is small potatoes compared to positioning and thick absorbers.

4. YouTube is not really your friend. It's like someone who'll lead you to water only to let you fall in face first and sell tickets to your flailing. That said, in a square room, tuned absorbers might be something I'd consider. Depends on how far I could get with broadband. Since most rooms need more broadband than most are willing to install, we typically push that before resorting to pressure absorbers.

5. It's true that sound pressure builds in corners. However, that's true of any boundary. Corners simply have more boundaries. Beyond that, for bass, all large parallel surfaces will support resonances. The front and rear of the room will be treated more for reflections. Behind the speaker, absorbers minimize SBIR. Behind your head, later reflections are dampened. Side walls also support resonances. In my room, I got a better result from placing the panels I originally had on my rear wall on my side walls instead.

2" with 2" gap is on that left side of the continuum I just talked about. 8" rigid with FRK and an 8" gap or even 2' fluffy with FRK and a 2' gap is on the other side. You can golden ratio until you're blue in the face. Without damping the resonances and reflections, it'll merely be fool's gold. The thicker the panel, the more lower frequencies are dampened. Ratios are about bass. Thick panels are about bass. See the connection? If you care about ratios, you want thick treatment so you can clearly hear your well-supported bass range.

6. Not just dispersion but diffusion. Scattering is the more broad term whereas diffusion has more criteria applied to it. I don't have, nor have I used, diffusers. Even so, I consider them after broadband. I'd go so far as to say they're in the same category as resonant absorbers: fine but have enough broadband first.

There's no such thing as a 'musical room'. That's a subjective assessment. Your 'musical' might be another's 'washed out'. This small room, on its own, will do no favors to your sound. After you have at least 15% surface area covered with 4-8"-thick rigid absorbers, you can decide if it's too dead in the highs. From there, try adding FRK which improves bass absorption and reflects back above 1kHz. If even then you want more liveness, or less coherent reflections - which is totally fine - you can consider adding diffusion.

Edit: I just realized that I have about 15% coverage in my space. That's just enough to get one or two functional areas right. I actually would like to double it to use the rear of the room for sound recording. 15% is by no means too dead. There's plenty of space for diffusers.

7. Probably not. I've found that 1/4 the width of the room, near the front wall and on the floor (or ceiling) is the best place for one subwoofer. Try that first and if it doesn't work, try working from there.

8. Like you already know, making a fabric wall can expose existing insulation to higher frequencies. If you're using closed-cell insulation, you won't get that benefit.

9. I know very little about isolation.

Last Edit: Mar 1, 2021 22:41:49 GMT by Hexspa

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