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I've searched and lurked around these forums off and on over the last 6 months, and have finally decided to post. I'm self-contracting a house, and hope to be pouring a slab in the next six weeks. The main floor of the house consists of 3 bedrooms, dining, living, kitchen and study, in a bit over 2500 sq ft. The second floor will likely remain unfinished initially, and will eventually consist of a 4th bedroom (and 3rd full bath), an open playroom/loft area, and of course, a dedicated home theater, in a bit over 1200 sq ft.


Previous homes have always contained a "living room" home theater, but this time I'm going all the way. I plan to keep my current equipment initially, and concentrate on "the room," as equipment is easy to upgrade later on. I have a Rotel RSX-1055 Receiver, with a crappy Sony DVD player, a couple of upgraded DirecTiVos, and a PS2 for sources. My speakers are B&W 602 S2 up front, 601 S2 in the rear, LCR60 center and a Velodyne 12" SW. In the past, video was provided be an analog 45" RPTV by Mitsubishi, which will continue to pull living room duty. In the theater, I plan on adding a Mitsubishi XD300U projector and a Stewart screen (90-100" depending upon the final configuration). An upgraded DVD player (by Rotel) would make me happy for a while. I know I've selected a native 4:3 projector - I prefer to have maximum width and mask for HD/"flat"/"scope" - I'm an old "real theater" projectionist.


My room will be 13'2" wide by 17'8" with 8' ceilings (except for a slope to 7' in the front and rear due to the roof). These measurements assume standard 2x4 wall construction and single 1/2" sheetrock. I plan on having 10 hi-back rockers installed, with at least one row on a riser (maybe both). I might like to have BassShakers/Sonic Transducers under the riser(s). Both my wife and I have worked for a major motion picture exhibitor in the past (she most recently) in and we have connections there to assist with seat procurement for cheap. I hoped to go "traditional" with the interior; carpet baseboards, carpet on the lower wall, maybe pleated curtains on the upper wall, sconces, etc. I will build my equipment into a rack set in the rear wall of the theater, with ventilation. The ceiling will be drywall.


I feel okay with most of my choices so far, but am a bit confused when it comes to sound suppression. Like most, I am more concerned about using the theater with others in the house, in a non-disruptive manner. My house is in a rural area, on 1/2 acre, and there is plenty of separation between houses. My exterior theater wall will be a minimum of 30' from my neighbor's nearest exterior wall.


With respect to sound suppression in the walls and floor, I feel the QuietSolution products may be cost prohibitive for me, though I have not fully investigated it. This is HT on a budget, as this new house follows the birth of my first child in May, which accompanied a "loss of income" as my wife is now a stay at home Mom, something that is valuable to both of us. I plan on doing as much of the HT as possible myself, so I'm really only looking at parts and tool rental with respect to costs. Green Glue looks interesting, and affordable, particularly in it's 50% application. Recently, at a home show I picked up a flyer from a company doing damp cellulose insulation - CelBar - that advertised as high as 58 STC. In addition, I am considering staggered 2x4s on a 2x6 plate, though I am afraid I cannot float my floor for lack of ceiling height.


I have considered contacting the honorable DE, but I'm imagining that's out of my budget, even for a consultation. I'm a consultant myself, I appreciate the value of hard-earned knowledge, so it's not a value consideration, as much as an absolute $$$ consideration.


Given my story above (I apologize for the length, for those of you still with me), these are my questions:


Do you see anything that looks or sounds seriously out of whack with what I plan to do? Do you see anything that looks of sounds like I'm doing the right thing? I've tried to include everything, honest!


Do you have any thoughts on GreenGlue/QuietRock/CelBar, with or without staggered studs, exclusively or in some combination? Please stop short of recommending that I GreenGlue two QuietRock sheets together on each side of a staggered stud wall filled with CelBar - I'm pretty sure that's not gonna happen ;)


Also, I see many references to GOM, and have figured out that it's some type of wall covering/fabric, available from Guilford of Maine, though I'm afraid I don't understand the collective appreciation of it yet. Anyone care to enlighten me?


Should I contact DE for a consultation? I really like to do things right...


I also have questions about BassShakers/SonicTransducers, and A/V distribution, but I'll post those in the appropriate forums.


Thanks for your time,


Dave
 

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Welcome to the forum.


Just a couple quick initial thoughts.


First, if you are going to have a slope on the front wall anyway, why not build the ceiling as 1 flat surface from 7' in front to 8' in back? This will eliminate 1 set of parallel surfaces in the room while keeping the room symmetric left to right throughout. Stuffing the cavity behind them with insulation will also create a variable depth cavity bass trap to help with internal acoustics.


Second, Green Glue looks like an awesome product from the test plots on the Audio Alloy site. I'll let other speak to it specifically as they have actual experience with the product.


Third, if the plan allows, don't put the HT right over the bedrooms. I assume that is obvious but thought I'd throw it out anyway.


When looking for isolation, remember that STC is an average rating over a wide variety of frequencies. Looking at various products, you'll see that most of them have MUCH lower ratings at low frequencies than at high ones. The most difficult thing to isolate is the low frequencies. This is not going to be made any easier by the fact that you are planning on 'shaking' the entire riser which will be coupled to the floor.


I looked at the CelBar docs and they don't show anything regarding specific ratings at specific frequencies - only the overall STC rating. It sounds like more of a dampening agent - showing to be approx 1" thick. I have no idea how it would work to stop structure born bass vibrations. My guess is not very well.


2 things stop bass - mass and physical decoupling. Adding a 2nd layer of drywall will stiffen things up nicely and also help block more bass due to the extra mass (not to mention another great place for Green Glue or some other sort of CLD). This is the only thing that seems contradictory in what you are looking to do vs. how you plan to build it. If you want isolation, double drywall is almost a must (and not a lot of extra cost, just extra labor).


I wouldn't discount floating the floor just for height reasons. Floating the floor with something like Acousti-Mat or Green Glue will not take away significantly from your room height (way less than 1") and will help reduce the structure born transmission. Using RSIC and Hat Channel still only costs you about 1" in height. Making sure the cavities between the floor joists are stuffed with plain old insulation will also help damp resonances in the cavity.


To keep the shakers from adding to the floor problem, you might want to consider decoupling the risers from the room floor by putting them on something like Auralex U-Boats. They are about $2 each. Your risers won't be that big so the cost is really not a lot. They only add about 1/2" to the height. Assuming you have a 13x6 riser, you'd need about 60 of them. They go under every joist approx every 16".


Just a few thoughts to start out with. There are a lot of great, experienced people on this forum who are always willing to help out. I'm sure there will be others offering additional solutions/suggestions.


Again, welcome.
 

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Discussion Starter · #3 ·
Thanks for the thoughtful reply. Though much can be learned by reading responses to other's questions, sometimes asking your own is necessary.


You mentioned building a sloping ceiling and filling it with insulation to create a bass trap. I've read a bit about bass traps, but I assumed they always came in the form of membrane panels or funky shaped foam blocks. Are you saying that the presence of a sloped drywall ceiling with fiberglass behind it will perform similarly? Should the "original" ceiling be drywalled too, or could it just be rafters?


I agree - I can't wait to hear reports from actual GreenGlue users...


Unfortunately, the HT is where it is. I don't think I mentioned that it's over the master bedroom. So, until my kids are old enough to use it by themselves, I'll always be in there. My wife, well, she can sleep in a theater, why not underneath one ;)


Regarding the floor, I do intend to GreenGlue an additional layer of plywood to the existing subfloor, at the very least (unless it turns out to be snake oil, which doesn't seem likely). I guess I just meant I didn't plan on something like isolated 2x4s as well. I suppose a 2x4 grid sitting on u-boats with two sheets of GreenGlued plywood would be pretty spiffy, though.


As far as the riser, I definitely planned on "u-boats" or something similar, if I do go the BassShaker/SonicTransducer route. I also considered doing the same to the stage/proscenium where my speakers and sub would sit, but wondered if "de-coupling" would help or hurt there?


I feel I should clarify that I am definitely entertaining double drywall, though only if I use something like GreenGlue to dampen the whole affair. The QuietSolution people seem to believe that two sheets alone is not worth the effort, and the Home Theater Mag people seem to think two sheets only makes the wall ring more (albeit without something link GreenGlue).


The comment about 2x4 walls with 1/2 sheet were only in reference to the dimensions, which are taken from the floor plans, which are the only place my theater exists now.
 

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GOM is a commonly used cloth due to it's 'acoustic invisibility'. If one wants a covered look over differening materials or just over plain drywall and does not want absorbtion, this is a good choice. It is NOT cheap though.


EVERY drywall wall over wood studs is a 'bass trap' to a certain extent. The entire wall becomes the diaphragm. Most construction by default has the cavity behind it the same depth, leading to more absorbtion at a certain frequency range. Making the cavity variable simply widens the range of absorbtion. While the diaphragm has the same resonance, the cavity behind it reflects at different times (due to spacing difference) and damps more and reinforces less.


You can insulate the stud cavities in the rafters and drywall over it - then insulate the variable cavity in between that and the theater ceiling. Nothing fancy, just good old pink stuff. I would probably recommend this route. Doing double drywall makes the walls and ceiling a LOT stiffer. This lets the diaphram vibrate less - ie less efficient trapping. If you seal off the top of the room totally from the wall cavities, then you just put a single layer on the ceiling. Check out the Auralex site and "acoustics 101". They have a couple drawings of using attics as bass traps and how to construct it.


If nothing else, you can use the cavity as a place to 'build in' absorbers, diffusion (if required) Helmholz absorbers (if you have speciific bass issues), etc. I've seen some people make the entire ceiling 1 big broad Helmholz absorber. With the kind of depth you'll have available, you could do some very effective trapping down pretty low.


As for the walls, 2 layers is definitely the way to go if you need isolation. Not sure where HTM is coming from. Yes, the additional stiffness will push the resonance up higher (which is what you want). The idea is to get it up to the point that it is not shaking the whole rest of the structure, is reflecting most sound to assist in isolation and in-room predictability, etc.


As far as the floor, that's really up to you. I really hate to give up headroom. Also, the RSIC route I was talking about is actually going to be about 2" (forgot the hat channel - doh!)


As you are going to be doing this a bit at a time, I think I'd:


1. Do the 2 layer floor separated by Green Glue for now.

2. Build the walls for the theater (separate them from the structure if you can.)

3. Drywall everything using the existing ceiling (roofline) - only 1 layer on ceiling.

4. Play with it and see how the isolation works. Measure the room and see what it needs in terms of bass trapping and other absorbtion. Use rugs to simulate the carpet for now.

5. If you find that you need more isolation, build the 2x grid with u-boats to float the floor. If you don't need it, that's just money saved. Now you can do the carpet route.


The beauty of this is that you can just move the risers out of the way if you need to float the floor and then drop them back in place. Yeah, you'll need some good friends to help as those won't weigh 10 lbs! Also, you are now floating only the flooring inside the room (more isolation and less $$$)


Before you put in the carpet, you should have a good idea of the low frequency properties of the room. You can go ahead and do whatever to the ceiling before you install the carpet to avoid the mess.


Welcome to the disease...
 

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Should I contact DE for a consultation? I really like to do things right...
Yes!!
 
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