How many layers of DW = decoupling? - AVS Forum
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post #1 of 19 Old 01-01-2012, 10:11 AM - Thread Starter
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I have a sandwich of DW+GG on my basement HT ceiling. Only problem is that it is coupled (my ignorance ) .
Given that I can't take it down b/c
(a) my wife is very sensitive to dust, and would flip if I took down the ceiling causing tons of dust to go up to the now exposed 1st floor (exposed - other than the flooring)
(b) time/cost to take down the ceiling
(c) in addition, there's drywall compound spackle over the ENTIRE ceiling (again, my ignorance) and from what I've read this is dangerous to breath in , and takign down the ceiling may cause it to become airbourne.

That being the case (that the ceiling is coupled) - AND my only concern (other than safety) is keeping LFE from getting up to the joists, and then through the house.

My Q is - how many layers of 5/8" DW and how many GG applications would give the same LFE containment as I would have gotten had I done it "the right way" and decoupled the wall to start + DW/GG. i.e. how may layers would I need to keep the LFE contained in the HT?

btw - I'm sure you already know this, but I've got to say that Ted White is by far the biggest help and a Genuine help and not just out to make a sale. I've called him multiple times, practically begging him to buy more stuff from him - and he keeps on giving me other alternatives via standard materials. Through his help, I've shored up the rest of my mistakes, and now (I hope) remain with only the problem of the ceiling. I feel guilty calling him again (plus interested in consensus) so I'm posting the Q here, but Ted: thanks so much, I'm very grateful.
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post #2 of 19 Old 01-01-2012, 06:16 PM
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Adding more DW is not going to help as the current DW is coupled to the floor joists. If you added whisper clips and channel to the existing ceiling I believe you'll end up with a triple leaf effect (no good).

Bottomline, remove the DW and do it right or add some drywall to the existing for minimal assistance and live with the ceiling coupled. I'm not sure you have many other options unfortunately.
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post #3 of 19 Old 01-01-2012, 06:30 PM - Thread Starter
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Lets say that I added 3 additional layers of 5/8"dry wall (making a Total of nearly 3" of dry wall in total with the 3/4" that's already there.) I'd hope that's enough, but if nec. I can add 3 layers of green glue between the newly added DW) wouldn't the sheer mass and dampening keep the rumbling down?
Or is it truly decoup,e or nothing?
By the way can the 2x6 joists support the weight of 3"worth of dry wall (house is approx. 50 years old, and room is approx 10x20' - part of a full basement (I'll start a separate thread for this Q, so as to not confuse things)
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post #4 of 19 Old 01-02-2012, 05:58 AM
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I would worry that your ceiling would not hold all that weight! I'm not a really wiz on decoupling, but I assume that you can almost never eliminate all sound from getting through. Is your leakage so bad now that your willing to rip your ceiling down?

The lazy man finds the easiest way ... Ben Franklin
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post #5 of 19 Old 01-02-2012, 06:46 AM - Thread Starter
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Quote:
Originally Posted by vzphoneman View Post

I would worry that your ceiling would not hold all that weight! I'm not a really wiz on decoupling, but I assume that you can almost never eliminate all sound from getting through. Is your leakage so bad now that your willing to rip your ceiling down?

My Q is one of threshold - i.e. currently there's enough noise that I can't watch a movie with th sub on at night without some risk of waking the kids.

If adding DW will do the trick, then why go through the effort, expense, etc (listed above)
However, if adding 3 more layers of DW won't do it, then I might go ahead and rip down the current ceiling.

Though, even if I did rip down the ceiling, I have one side wall attached (coupled) to the ceiling beam anyway - and I don't think that I'd be able to take that down (it's 3" of drywall (it's REALLY heavy) in a 2x4 frame attached to the ceiling joists - it'd be a major job,
So the Q is- woudl the coupling of the walls, ruin the gain I'd achieve by decoupling the ceiling?

Again, I'm trying to reach that threshold (not necessarily reach perfect sound containment) - but on the other hand if I'm short of that, it's $ and effort wasted.
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post #6 of 19 Old 01-02-2012, 07:05 AM
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check out this thread...you may find some options to help you.

http://www.avsforum.com/avs-vb/showt...hreadid=452667

The lazy man finds the easiest way ... Ben Franklin
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post #7 of 19 Old 01-02-2012, 07:10 AM
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I would give Ted White a call.
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post #8 of 19 Old 01-02-2012, 07:37 AM
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Add some kind of transducer or bass shaker to the furniture. I rarely use my sub at night anymore after doing this. I can listen at fairly loud volume with the whole family sleeping (wife, 1 and 4 year old kids) and not wake them. My ceiling is one layer of 5/8" tongue and groove pine nailed to the floor joists. Might not be ideal from a audiophile perspective but I've been happy with the results.
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post #9 of 19 Old 01-02-2012, 11:30 PM - Thread Starter
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I see that if I'm going to do this (and be happy) I'm going to need to "do it over and do it right"
Lesson learned - many things in this hobby I've found that the many members have much more heightened senses and thus go for things / equipment - which for me I woudln't tell the difference (e.g. my ears would be happy with lesser equip and treatment and not even notice the difference at a certain point) - this has lead to the idea of not heeding some advice here thinking just like I don't need the highest end equip, I also don't need the highest end sound proofing.
Lesson learned - when it comes to sound proofing the above doesn't apply- - it's purely a matter of how loud you want to enjoy the movie, and if you like LFE / subwoofer. IF so, regardless of audio sensitivy - you need it done right.
On the other hand, I don't think I would have been able to "Do it right" the first time (lack of funds) - so my partial job - has allowed me to enjoy a HT (albeit without the sub) for a few years, and if not, I probably woudln't have started this hobby at all.

Now I see that I'll have to stay with what I have until I get up the time and $ (and approval) to take down what I have and "Do it right".
Oh well - I was planning to add a few layers of dry wall on the work day off today - and blast a movie tonight - Instead - I perhaps saved myself from collapsing my ceiling, and had a nice day out with my wife...
One Question - - I understand that to do it over, I'll need to take down the existing coupled DW GG sandwhich , though I want to know if I'll also need to take down the insulation filling the cavity :
(a) perhaps to put DW+GG on the top of the ceiing (underside of upper floor ) - since the noise is only from the basement (lower level) HT to prevent it from coming up?
(b) perhaps b/c my joists are 2x8 (actual measurement is 1.5 x7) and I filled the cavity competly with 2 layers of R-13 insulation - is that too much, will I need to take it down b/c there's no air space (all filled with insulation)?

thx!
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post #10 of 19 Old 01-03-2012, 05:53 AM
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Quote:
Originally Posted by cgott42 View Post

One Question - - I understand that to do it over, I'll need to take down the existing coupled DW GG sandwhich , though I want to know if I'll also need to take down the insulation filling the cavity :
(a) perhaps to put DW+GG on the top of the ceiing (underside of upper floor ) - since the noise is only from the basement (lower level) HT to prevent it from coming up?
(b) perhaps b/c my joists are 2x8 (actual measurement is 1.5 x7) and I filled the cavity competly with 2 layers of R-13 insulation - is that too much, will I need to take it down b/c there's no air space (all filled with insulation)?

thx!

I personally wouldn't go to the effort/cost of putting up dd/gg on the bottom of the flooring between the joists. I have read that it helps cut down footfall noise from above, but it's not really part and parcel of the "normal" isolation recommendations. I did without that extra step and bass levels are contained
quite nicely even with the WAF sleeping directly above in the MBR.

If you take down ceiling and then do clips/hat/channel/dd/gg you should be good. Ted recommends filling the joist cavity with R-19 and that anything more is diminishing returns...BUT since you already have two layers or R-13 which should be filling your 7" height without compression, I'd just leave it there as there's no harm in doing that.
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post #11 of 19 Old 01-03-2012, 06:17 AM
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+1

Fundamentally, the coupled construction will limit the LF bass isolation, as others have stated.

Also, adding more and more mass will only get you so far.

So if you wanted to add one more sheet (3 total) of 5/8" drywall, that would be OK. You'd have improvement, but likely not satisfaction. Adding a fourth layer of drywall would not yield much more than three so that's not the route to take.

Ultimately this would be best if decoupled.

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post #12 of 19 Old 01-03-2012, 07:01 AM - Thread Starter
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Quote:
Originally Posted by Ted White View Post

+1

Fundamentally, the coupled construction will limit the LF bass isolation, as others have stated.

Also, adding more and more mass will only get you so far.

So if you wanted to add one more sheet (3 total) of 5/8" drywall, that would be OK. You'd have improvement, but likely not satisfaction. Adding a fourth layer of drywall would not yield much more than three so that's not the route to take.

Ultimately this would be best if decoupled.

I have a sidewall (split in 2 parts 10' each (separated by doorway) which is a 2x4 frame and filled with 3" of dryway. Thus each wall segment is approx. 7-800 lbs ea. For each segment , the top 2x4 is drilled directly into the joists (actuallly through the ceiling DW and then into the joists (4" DW screws)). Each is attached in about 3 (maybe 4 locations/joists). i.e. they are coupled.
If I undergo this ceiling redo, will I need to redo the walls too? Also if the ceiling is removed, that will leave a gap (was wood (2x4) - 1" DW - joist and now would be wood (2x4) - 1" space - joist) - is this a problem (structurally speaking)
An idea: - perhaps with the layers of DW ceiling between the 2x4 and joists removed - would I be able to saw off the screws (perhaps leaving one if nec.) - i.e. can the wall stand on it's own (since it's soo heavy, that I doesn't need to be attached to the ceiling
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post #13 of 19 Old 01-04-2012, 12:07 PM - Thread Starter
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Quote:
Originally Posted by fotto View Post

...If you take down ceiling and then do clips/hat/channel/dd/gg you should be good. Ted recommends filling the joist cavity with R-19 and that anything more is diminishing returns...BUT since you already have two layers or R-13 which should be filling your 7" height without compression, I'd just leave it there as there's no harm in doing that.

This morning I measured R-13 insulation and it's approx. 5" when not compressed. So since I have 2 layers of it, squeezed into a 7" cavity - there must be some compression of it.
Will this be a problem that will require me to take out the insulation?
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post #14 of 19 Old 01-04-2012, 12:26 PM
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I can't imagine that will be a problem. R-13 is specified at 3.5" and made to fit into a standard 2x4 wall cavity (which is 3.5" deep BTW) (without undue compression) to maintain it's insulation value.

I'm making an educated guess that it's just a bit "uncompressed" at 5" in freespace and that "recompressing" it to 3.5" or 7" for two layers won't cause you any grief. The compression concern is more geared towards a tighter compression like crushing it together between your palms for example.
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post #15 of 19 Old 01-04-2012, 12:30 PM - Thread Starter
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Gotcha - thx
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post #16 of 19 Old 01-11-2012, 08:48 AM
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I would agree with Floyd.

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post #17 of 19 Old 01-11-2012, 05:46 PM
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In the high end car audio world we do sound blocking by adding Closed Cell foam and MLV over the area to be treated. The closed cell foam is the decoupling layer (Isolation clips and furring) and the MLV is the blocking layer (DW + GG). Might be worth investigating in this instance with the only problem being that you will need to rely solely on glue to hold the ceiling up.
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post #18 of 19 Old 01-11-2012, 06:06 PM
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Well, while analogous, they are not interchangeable. No need for foam backed MLV in floors, walls or ceilings.

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post #19 of 19 Old 01-11-2012, 06:50 PM
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Yes that would get horrendously expensive very quickly (using MLV) but I was suggesting that perhaps using a CCF layer to decouple another layer of DW might be effective if he can't use proper isolating clips.

Happy to be proven otherwise should this not be a functional alternative however. It is merely an avenue to investigate.
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