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post #781 of 794 Old 12-07-2014, 12:47 PM - Thread Starter
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Originally Posted by BasementBob View Post
As you pass two layers and green glue, you start to get to the point where other things are dominant like doors and flanking.
Yeah, that's the dominant rule of thumb that most people who care about such things go by. I've heard many times that anything more than than two layers very quickly gets into the law of diminishing returns. Indeed, if you look at all of the tests done of wall assemblies for STC, that appears to be very true.

BUT I haven't seen any evidence that this advice takes into account bass! Where are the tests that show the same steep drop-off of increased efficacy after two layers when a sweep of 10Hz to 100Hz is run?

The problem, I think, is that it costs a lot of money to run a controlled test on a wall assembly and there likely won't be enough payback if your target market is only theaters and studios. Organizations like the NRC and companies like Green Glue need to really focus on shared living areas like apartments since that's where the money (and regulations) are -- and in those cases, STC is a very good measurement since it's unlikely that you'll be encountering low frequencies on a regular basis.

Maybe some ad-hoc tests could be done by people building their theaters in real time. For instance, if you're building a theater with three or more layers of drywall, then run some tests after each layer and compare the differences. It won't be completely accurate since Green Glue takes some weeks to really do its thing, but it'll be a start...
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post #782 of 794 Old 12-07-2014, 04:17 PM
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I am in the preliminary planning stages of a theater build. I will have three foundation walls for the theater, but the ceiling is my largest concern. I too have been trying to research and figure out what the best way is to contain the bass in that room.

Just thinking out loud, what about building a box around a sub with a mic and measuring gear at a fixed position and measuring the level with each layer built around the box? I have a uxl18 sitting around right now that I would be willing to try this on if others thought this would yield anything worthy or meaningful.


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post #783 of 794 Old 12-07-2014, 05:52 PM
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Quote:
Originally Posted by granroth View Post
BUT I haven't seen any evidence that this advice takes into account bass! Where are the tests that show the same steep drop-off of increased efficacy after two layers when a sweep of 10Hz to 100Hz is run?

The problem, I think, is that it costs a lot of money to run a controlled test on a wall assembly and there likely won't be enough payback if your target market is only theaters and studios. Organizations like the NRC and companies like Green Glue need to really focus on shared living areas like apartments since that's where the money (and regulations) are -- and in those cases, STC is a very good measurement since it's unlikely that you'll be encountering low frequencies on a regular basis.
I think it's more accurate to say:
- they (NRC, GreenGlue) publish tests for which there is good science. The NRC and Orfield and Riverbank facilities are only certified down to a certain frequency, and beyond that the facility itself has flanking issues so large that they make test results below that frequency progressively awful. That said, they do publish unofficial results down under 80hz. For example, here's one down to 31.5 hz: here (scroll down to Appendix B, and note the possible resonance frequency near 40 hz).
- or to say the same thing another way, even with a multi million dollar government funding, it's hard to stop bass.
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post #784 of 794 Old 12-07-2014, 07:03 PM - Thread Starter
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Originally Posted by btinindy View Post
I am in the preliminary planning stages of a theater build. I will have three foundation walls for the theater, but the ceiling is my largest concern. I too have been trying to research and figure out what the best way is to contain the bass in that room.

Just thinking out loud, what about building a box around a sub with a mic and measuring gear at a fixed position and measuring the level with each layer built around the box? I have a uxl18 sitting around right now that I would be willing to try this on if others thought this would yield anything worthy or meaningful.
I asked a very similar question near the beginning of this thread:

Quote:
Originally Posted by granroth View Post
Question: What are the prevailing opinions on the validity of small scale soundproofing tests?

I'm wondering if it's possible to perform some small scale tests to compare various soundproofing methods. I'm not even remotely suggesting that any small scale tests would even start to approach the reliability of a full lab test... but would they be at least a little useful?

The biggest reason I'm thinking that maybe they wouldn't be at all valid is because I'm 99% certain that small scale tests absolutely won't work for comparing acoustical treatment plans. Acoustical treatments are designed to work with specific wave lengths and so the actual size of a room matters a lot.

But is that true for soundproofing? If all I'm going to test is an overall DB drop, then would a small scale test at least approximate a result?
And Bob's answer at the time:

Quote:
Originally Posted by BasementBob View Post
Quote:Originally Posted by granroth 

I'm wondering if it's possible to perform some small scale tests to compare various soundproofing methods. I'm not even remotely suggesting that any small scale tests would even start to approach the reliability of a full lab test... but would they be at least a little useful?


Yes.
Brian once did an experiment like this:
Most of the noise through a wall is at resonance, and resonance can be tested with a small 1'x1' piece of material and an accelerometer.
As I recall, he used it to give him a better idea of what to build full scale and test in a real testing facility.

But resonance in a 2 leaf wall, is because of the leaf-air-leaf system, I'm not sure how to test that small scale off hand.

I think he even mused how to, although I don't know if he ever got around to it, make his own testing facility with thin concrete walls to test gypsum walls approximately.
Quote:Originally Posted by granroth 

But is that true for soundproofing? If all I'm going to test is an overall DB drop, then would a small scale test at least approximate a result?

No.
Just good quick hints of what to really test; of what might give good results.
Now I was specifically thinking about testing such things as gaps between walls and how much insulation to use and such. Apparently that won't work small scale.

Would testing layers of drywall to combat bass work in small scale? Is it different enough that it might make sense? Bob, any opinion here?

Thinking out loud... a big problem would definitely be flanking unless the box was constructed to completely enclose the subwoofer. That is, the floor would need to be build identically to the walls and ceiling of the box.

Since mass is what nominally matters, that makes me wonder if it refers to mass as a "per square inch" perspective or as a whole. Would a wall that is 10'x10' have less bass absorption capability than one that is 20'x10' since the latter has far more overall mass? If the total mass matters, then a small scale test can't work at all since it has so much less total mass than a true wall. If it's per square inch, then the size doesn't matter.

But here's my actual thought -- do it!! Sometimes you don't know how something will work until you try it. Maybe the learned opinion would be that, indeed, small scale would do nothing. But maybe you run some tests and you see a huge difference with each layer of drywall. That'd be a useful bit of data, regardless.
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post #785 of 794 Old 12-07-2014, 08:42 PM
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That is what I am thinking. My thought was just to install the sub on the floor as I plan to install it (pad and carpet on top of plywood). Build a box (5 sided) to sit over the sub and then add layers to the box. While the absolute data may not be overly useful because of scale the relative data of each layer should give me some indication of how to proceed.


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post #786 of 794 Old 12-08-2014, 07:47 PM - Thread Starter
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Moving this quote to this thread, since it'll likely be a more searched thread in the long term and this info is golden.

Quote:
Originally Posted by TMcG View Post
Granroth - You are dead-on with your statements with the exception that three damped layers has been tested. In fact, it is addressed in the IB-3 clips installation manual. Extensive testing has also been done by Saint Gobain and the Canadian building code organizations on the matter (primarily for noise transmission from foot fall traffic in multi-family dwellings), none of the results I could find in a pinch (translation - I don't ever use web bookmarks )

Two layers is effective for the upper bass frequencies. The third layer gives you significant damping down to 40Hz, especially in the critical 40Hz-80Hz range that shakes upstairs coffee tables.
If you do find those results, let me know and I'll add them to the index.

BasementBob earlier linked to a WhisperClips test that had non-certified measurements down to 31.5Hz. What is notable to me is that with two layers of drywall (no Green Glue) it only has a transmission loss of 28dB at 80hz and it gets notably worse as the frequency goes down. 28dB doesn't seem very good at all. If you're playing a movie with your subwoofer pumping 90dB (not uncommon, I believe) than everybody outside of the theater is hearing your sub at 60dB and higher. That's pretty noticeable.

I found this Green Glue paper where they compare using Green Glue vs extra drywall: http://www.greengluecompany.com/site...%20Drywall.pdf. They muddy the waters a little by not always comparing apples to apples, but what really stands out to me is how little of a difference more layers is making. Even three layers of DW on each side of the wall plus GG in between each is only marginally better than two layers, even without Green Glue (when it comes to bass).

Based on these results, I'm starting to think that while two layers of DW+GG won't cut it for bass, then neither will three layers. Or four.

Those results that show significant damping down to 40Hz would be very appreciated right about now

Quote:
Originally Posted by TMcG View Post
But I also think there is a limitation to the design of the IB-3 clips which Fatshaft (and many others) used on his ceiling. Although *somewhat* decoupled, the connection to the structure is being overwhelmed by the low frequency energy it is trying to limit getting through. In other words, the LFE in his system just kicks too much a$$ and he would have had to use better decoupling products that can dissipate more vibration energy. The PAC RSIC-1 would have been a better clip to start with because of the Neoprene, but even then I think the LFE energy would be too much. Kinetics Noise Control makes a really sweet IsoMax Resilient clip that has a ton of neoprene to absorb the energy, but even then I would have cause for pause. I believe there's also some fault to the recommended construction technique of ceiling / wall / ceiling / wall for the layers.

I prefer a different method in both construction and product. I will install all three wall layers with offsetting seams and with 5/8" OSB (or ply) as the first layer. So it's 5/8" OSB / GG / 5/8" drywall / GG / 5/8" drywall. All of this is tied directly into a decoupled wall structure, so something like Serenity Mat (rubber underlayment) on the floor under the sill plate and decoupled at the top by building the wall short and using either the IB-3 bracket, or I prefer the Kinetics Noise Control CWCA Wall decoupling bracket which has significantly more decoupling and vibration isolation through 1.5" of Neoprene. Pictures of my previous install HERE.

I will use the same three layers for the ceiling construction, but prefer a spring loaded or suspension approach (product) to absorb the energy. It's one thing for the LFE energy to find its way through a handful of hard connection points as in Fatshaft's install, but it's another thing entirely when you are asking for LFE energy to lift hundreds of pounds of damped mass as part of a isolated and suspended ceiling structure. In my last theater I used Kinetics Noise Control ICW Wood Frame Ceiling hangers. They were great, but a bit of a pain to install because of the Cold Rolled Steel "C" channel you have to use before attaching the resilient channel. If you wanted the best performance, then these are your brackets, but they were pricey (about $20-$30 each if I recall correctly).

This time around I am using the Kinetics Noise Control WAVE Hanger. Significantly less expensive and a much easier installation with less materials while still maintaining a very low profile and giving you a true suspension ceiling that is fully deflected under load. Considering the main 2-story foyer of our home is right above the theater and it is covered with hardwoods, it will be important to me to get the best possible isolation for my ceiling.

Hope this helps.
Yeah, I point to Fatshaft's video mostly as an extreme example of what can happen. The total amount of energy there definitely eclipses most theaters and the walls physically attached to the ceiling joists also creates notable flanking paths, which also make the affect of just the drywall less clear.

Focusing more on more robust decoupling in the form of suspension is a very interesting idea! The standard advice says that only more mass will really combat bass, but your explanations on the spring effect is very compelling.

When it comes time to build your new theater, do you think you could run some tests in between each layer of drywall? It wouldn't be directly applicable to anybody not using similar suspension techniques as you BUT as long as those remain a constant, you'd at least see what kind of difference just the increases in mass make.
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post #787 of 794 Old 12-08-2014, 08:42 PM
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Quote:
Originally Posted by granroth View Post
If you're playing a movie with your subwoofer pumping 90dB (not uncommon, I believe) than everybody outside of the theater is hearing your sub at 60dB and higher. ... Even three layers of DW on each side of the wall plus GG in between each is only marginally better than two layers
Two things to look into:
1. Sound loudness curves. So they might not hear it; but they might feel it, or hear the dishes rattle.
2. The rule-of-thumb is a doubling of mass gives an increase of 6dB of soundproofing. So moving from 2 layers of drywall to 3 layers, could be as much as a 3dB(?) increase, but not more.

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post #788 of 794 Old 12-10-2014, 07:02 AM
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Quote:
Originally Posted by granroth View Post
When it comes time to build your new theater, do you think you could run some tests in between each layer of drywall? It wouldn't be directly applicable to anybody not using similar suspension techniques as you BUT as long as those remain a constant, you'd at least see what kind of difference just the increases in mass make.
Glad you found the info helpful. I posted a follow-up with links in Beast's thread, FYI.

I've never made measurements before, but I would be willing to do it....I just need you to tell me what hardware I need and software. I assume you are talking about some sort of calibrated USB mic and REW software, but let me know if you are thinking of something different.

I've already passed getting a good base line, though, because I've added two layers of 5/8" with Green Glue in between the ceiling joists of the theater. Moving forward I can measure the impact of insulation then all three layers progressively. Heck, I'll even perform the test 30 days later after the Green Glue has reached its fully-cured potential!
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post #789 of 794 Old Yesterday, 02:55 AM
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Advice on hardwood floor laying technique

Hi,
I would like some advice on what the best way to lay my black oak hardwood floor in my dedicated Home Theater.

I have sound proofed the room as described in this post.

Quoting from the post, "Finally, I had another contractor lay a double 5/8"OSB floor with green glue, on top of a 10 mm rubber matt I bought from an Italian company called Isogomma. Underneath the the rubber matt were the original wooden pine boards.
Underneath the pine boards is a large cavity - 8" high - and then the house's original flat roof made out of roofing felt.
Update December 5, 2014: I just accepted an offer from a contractor to fill out the 8" cavity with paper wool
"

So, the question is how to lay the 15 mm oak floor. It is a multi-layer/laminated parquet floor with two plywood layers and a 3.6 mm oak layer on top, and with tongue and groove.
Charcoal Oak from Soldidfloor



I see three options:
1) Glue it directly to the double OSB w/ GG underfloor with specialized glue. The parquets/panels are also glued to each other in the tongue and groove.


2) Green glue it directly to the double OSB w/ GG underfloor. The parquets/panels will be glued to each other in the tongue and groove with standard tongue and groove glue.



3) Lay it floating on a 1/8 to 1/4" subfloor, on the double OSB w/ GG.

6 mm soft board


or (3 mm)


or 2 mm kork:


My goal is to optimize sound proofing, as well as the acoustical character of the floor.

Thanks :-)

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Need advice on soundproofing a narrow basement home theater room

Hello folks,

I need help making the right compromises for a narrow basement room for a home theater.

Attached is a picture and a layout of the room. The room itself is

11'6" wide without any framing on the exterior walls
23'6" long with electrical panel on one end
7'6" from the concrete floor to the ceiling joists

The basement is 70% below grade with cinderblock walls from the thirties.

My biggest concern is the narrowness of the room. If I add conventional soundproofing/soundtreatment on all sides, then it gets even narrower.

What compromises can I make to keep the room width to the max?
- Sound proof just the wall along the staircase
- Sound proof the ceiling with hat channel + DD + GG

Any suggestions and pointers greatly appreciated. Also, please feel free to point me to other posts and builds on this forum that tackled a similar situation.

Thanks a ton!
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post #791 of 794 Old Yesterday, 05:11 PM
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Quote:
Originally Posted by flyfishingnitin View Post
Need advice on soundproofing a narrow basement home theater room

Hello folks,

I need help making the right compromises for a narrow basement room for a home theater.

Attached is a picture and a layout of the room. The room itself is

11'6" wide without any framing on the exterior walls
23'6" long with electrical panel on one end
7'6" from the concrete floor to the ceiling joists

The basement is 70% below grade with cinderblock walls from the thirties.

My biggest concern is the narrowness of the room. If I add conventional soundproofing/soundtreatment on all sides, then it gets even narrower.

What compromises can I make to keep the room width to the max?
- Sound proof just the wall along the staircase
- Sound proof the ceiling with hat channel + DD + GG

Any suggestions and pointers greatly appreciated. Also, please feel free to point me to other posts and builds on this forum that tackled a similar situation.

Thanks a ton!
Although my room is not as narrow as yours I am dealing with a 12' wide room after talking with ted from the sound proofing co we came to the ideal. That clips and channel on the ceiling with DD and GG would be my best option followed by DD and GG on the walls as not to narrow the room anymore then necessary. After weighing all options for me the width of the room was a big concern. it out weighed the complete sound proof options I can deal with some sound loss as the family mostly watches together.
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post #792 of 794 Old Yesterday, 09:50 PM - Thread Starter
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Quote:
Originally Posted by flyfishingnitin View Post
Need advice on soundproofing a narrow basement home theater room

Hello folks,

I need help making the right compromises for a narrow basement room for a home theater.
[SNIP]
It's very important for anybody looking to soundproof their room to first establish what their requirements are, but it's doubly important if you have "non standard" rooms or needs. That is, the generic advice tends to focus on a specific type and size of home theater with an assumption on what kind of soundproofing you'd expect. If you have such a theater and you follow the advice, then you're golden.

But if your theater has hard limits in certain areas (in your case, both width and height), then the generic advice no longer works. Now it's extremely important to learn what your specific needs are, in order to try and come up with a solution that might fit those needs.

So... off the top of my head:

1. Are there noisy external sources clearly audible in the basement (e.g., loud neighbors, trains, trucks, etc)?
2. What is the ambient noise level in the basement now? What do you want it to be in the theater when you're done?
3. Do you plan on watching movies where sound escaping would be a big problem (e.g., baby trying to sleep, etc)?
4. Are you a bass fanatic? Plan on having eight 18" subwoofers? More?
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post #793 of 794 Old Today, 04:22 AM
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Ok so for me:

1) no
2) 38db. It's higher when the hvac is on. I would like it to remain at 38db
3) yes. But for a sleeping wife. The babies sleep through anything
4) yes. But I will only ever have my dual xs30's

My room will be 13'x16'x8' but that's before framing and dd
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Quote:
Originally Posted by flyfishingnitin View Post
Need advice on soundproofing a narrow basement home theater room

Hello folks,

I need help making the right compromises for a narrow basement room for a home theater.

Attached is a picture and a layout of the room. The room itself is

11'6" wide without any framing on the exterior walls
23'6" long with electrical panel on one end
7'6" from the concrete floor to the ceiling joists

The basement is 70% below grade with cinderblock walls from the thirties.

My biggest concern is the narrowness of the room. If I add conventional soundproofing/soundtreatment on all sides, then it gets even narrower.

What compromises can I make to keep the room width to the max?
- Sound proof just the wall along the staircase
- Sound proof the ceiling with hat channel + DD + GG

Any suggestions and pointers greatly appreciated. Also, please feel free to point me to other posts and builds on this forum that tackled a similar situation.

Thanks a ton!
I think Granroth's questions are critical, to know what to do - need to know the objectives.

Another question I would have, is what your Speaker plans are... generically meaning, in-wall, in-ceiling, or 'on-wall'. If In-Wall, that then narrows down your options for what to do with the framing.

As posted in your thread by BigmouthininDC... I would consider metal studs. You might need to look at weight capability (i.e., can you hang two sheets of drywall on it)...

But if I think about the narrows


Air Gap + Stud + 1st Layer DW+ 2nd Layer DW
1" +3.5" + .625" + .625" = 5.75" x 2 side walls = 11.5" Traditional Stud
0.5" +1.625" + 0.5" + .625" =3.25" x 2 side walls = 6.5"

The air gap is usually the space between the studs & exterior walls... I think you could minimize this with limited impact.

The narrowest steel stud I think is 1 5/8", a fair bit smaller than a 2x4". Again, worth checking if it can handle the weight of two layers of sheeting (OSB or Drywall).

I chose to use my 1st layer on my wall as 1/2" OSB vs 5/8" Drywall. I am doing fabric panels, so, the ability to attach those anywhere into 'wood' vs worrying about find an attachment point was important. I then did Green Glue, and a 5/8" layer of Drywall.

Of course, if you want 'in wall' speakers, the above won't achieve that for you. I think I saw 2.5" steel studs... so, 2.5" steel stud + 0.5" air gap + 0.5" drywall + .625" drywall might get you deep enough for in-walls.

I used clips & channels, which I ran perpendicular to my joists, but if you want to save ~1", you add blocking and run them parallel to the joists. My main ceiling height was 8'8", so, I wasn't supper concerned about that 1".
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