How Did You Acoustically Treat Your Dedicated HT? (1 Viewer)

[Scott-C]

The more I research acoustic treatments, the more confused I get. Would you care to comment on what I write below and perhaps try to answer some of the questions I ask along the way? It is a summation/generalization of what I've learned about the subject that may or may not be completely correct. Thanks for reading and assisting.
Room Soundproofing
I understand that the first step is to soundproof the room as much as possible, and that this is generally done using insulation, soundboard, and a "room-within-a-room" which I believe is two layers of drywall with space in between them. I'm really having trouble understanding how to build the "room-within-a-room". Can someone please explain exactly how this is built?
Acoustic Treatments
Once the room is adequately soundproofed, then it appears important to put absorptive materials on the front (screen) wall, as well as below ear level on all other walls. Reflective or diffusive materials should be placed above ear level on all walls (except the screen wall). Would someone please tell me what materials they used to accomplish this and is there a way to do it so that it looks "professional"? (i.e. I don't want egg crates exposed in a finished dedicated HT). I'm not averse to DIY sound panels to accomplish this but I am in need of more info on how it's done. Some of the sights I've been to are not instructional enough for this "wanna-be" carpenter.
What did you do to treat your room, and how satisfied are you with the results?
Thanks!

 

[Rob Lloyd]

I canhelp with the 1st part. The room-within-a-room is not quite what you said. Lets say you have your dedicated HT in the basement.

Your HT room would be built inside all other housing surfaces - the walls would be seperate from other adjoining walls leaving a gap between the walls. Those walls would then support the new ceiling joists. These new ceiling joists would have no contact with the floor above.

This helps reduce the vibration transferred from the HT to the floor above and the walls next to it.

Now for the double dry-wall - it's 2 sheets attached together (with different seams though). This helps increase the soundproofing of the walls in the HT. There are other ways of soundproofing that others will be able to explain much better than I can.

 

[Scott-C]

Rob,
Thanks. So I assume to make that work, you'd nail the floor boards to the cement floor in a basement just a few inches away from the concrete wall, thus leaving a space in between the original concrete wall and the new drywall? Then you'd put up the vertical studs (screw them into the floor studs), and then just attach new ceiling joists to the top or top/side (using metal stud hangers) of the new vertical studs, leaving a few inches of space between the new ceiling joists and the original ones (that are also the floor joists for the room above)? In that scenario, none of the new studs/joists touch any of the old ones, and the only contact with the original construction is through the floor. To get around that, you could build a sub-floor of some type and decouple it from the cement with some type of acoustic material, yes?
I hope that explanation is reasonably clear. I'm not a carpenter so I'm just trying to envision how this works.
If my understanding of this is correct, is this a sturdy construction? It sure sounds like it would "sway" to me, unless I'm missing something.

 

[MikePon]

Scott,
There is a commercially available way to achive the room-within-a-room idea.
See www.asc-soundproof.com
They have alot of information and pictures to explain what there system consists of and how it is installed. Not cheap though. It will cost me about $2000US before insulation & drywall for a 12' x 23' room.
I still plan on doing it though since my theater will be directly below a future babies room. I will be getting to that stage within a month or so!!

 

[Scott-C]

Thanks for the link Mike. I'm hoping to do the work myself and avoid the cost of a system like this, if possible. But it's good to know options like this exist!

 

[Chad Anson]

Scott,

Your second post is essentially correct. I've read several posts that mention that structural integrity is not a problem. For one thing, the "inside" room isn't load bearing - it doesn't have to support the floor above, etc. Using accepted carpentry practices (16" studs OC, etc.), you should have no problem with swaying. The side walls and ceiling keep everything square. The weight of the drywall and framing material, along with being bolted to the floor, would keep the room in place. Do a web search for "floating ceiling" or "floating walls" (avsforum.com has some good archived messages in their theater construction forum -- though they sometimes get a little too hypertechnical).

Good luck!

 

[Greg_R]

The treatments don't need to be egg-crate foam. Usually it is some form of panel with acoustically transparent cloth (and the treatment underneath). Hopefully someone will come along with more experience and give you the details...

 

[Scott-C]

Chad,
Thanks for verifying that my visualization of the room-within-a-room concept is correct. I've been lurking around AVS Forum for more info and will continue to do so, but you're right - sometimes it gets a little too technical for a construction novice like myself. That's kind of why I started this thread, as a means for getting straightforward explanations to some of this and ironing out some questions I've had in my mind. I really appreciate the help and being able to piggyback on the experiences of others who have been through this.
Greg_R,
Yes, I was thinking of some type of panels but to date, I haevn't been able to find an explanation for how to build them that I can follow. And, the concept gets very confusing to me because I often don't know the intended benefits of a "sound panel" - i.e. is it for absorption, reflection, or diffusion?
What would be great is if someone can give me clear instructions on how to make the panels so that below ear level they are absorptive, and above they are reflective (if that is the way they're supposed to be done), and tell me exactly where to put them. I've heard of using the "mirror" trick, where you move a mirror around the walls of a room, and put diffusive (I think) treatments wherever you can see the speakers in the mirrors. But this is just one of many strategies I've heard and I'm worried that if I took this approach I might make the room too "dead" or otherwise not acoustically good.
There's a lot of ideas out there - I'm just trying to latch onto some sturdy basic principles and get instruction on how to build what I need to build to adhere to these principles.
Thanks for the help - keep it coming please!

 

[Pat]

Scott-C,
I think this might help with your DIY needs.
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I haven't done them myself yet but they are on my list of things to do

 

[Ben L C]

Scott,
Here is a link that might be helpful in making some acoustical panneling.
www.avscience.com/acousticpannel.htm
Ben

 

[Chip_Slattery]

Scott,
A couple of links to sites that may help you visualize what the others have been talking about:
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Eric Reed's HT
Both of these sites have excellent construction photos detailing what went into their DIY theaters.

 

[Chad Anson]

Scott, as I understand stand it, you generally want sound below ear level to be absorbed and not diffused. Most of the theater construction threads I've followed use a product made by Johns Mansville called "TheaterShield Plus." It comes in a big roll and is tacked to the drywall and usually covered in acoustically transparent fabric (for aesthetics only). The downside is that TheaterShield Plus can be difficult to get and is somewhat expensive -- maybe on the order of ~$1000 to treat a decent size room (ear level and below on the back, and side walls in addition to the entire screen wall). I've read where others have used a much less expensive product called "soundboard" (from Home Depot or Lowes) covered in acoustically transparent fabric. I believe that soundboard comes in 4'x8' sheets.

 

[Chris S]

where you move a mirror around the walls of a room, and put diffusive (I think) treatments wherever you can see the speakers in the mirrors

Is this statement correct? I thought it was suppose to be absorptive treatments.
I also found this set panels at Audio Advisor, which come 4 to a set. Not to bad if you really don't have the time to build your own. And for those who are new to this sort of stuff (like me) check out Goodwins High End - Room Design. On this page there is a nice section about room soundproofing and acoustic treatment. It gives a nice higher level overview of a bunch of these topics.
Chris S.

 

[Scott-C]

Guys, thanks for all the great info and links. I'm going to check out all of them over the next day or two. It seems like there's some great info in here and I'll need a few days to take it all in!

Quote:

Chad, Now I'm really confused - I thought soundboard was for soundproofing the room (i.e. use it all over the room, on ceilings, floor, etc. under drywall to keep HT sounds in the room and other sounds out). Am I mistaken here? Incidentally, I was at Home Depot today and saw a product called "Insulation Sheathing" that came in 4' x 8' sheets and looked like compressed cardboard; R value of 3.5 or something close to that. Is this "soundboard"? If soundboard is covered in acoustic fabric and used for absorption, I guess I would just put it on the walls below ear level, and then use some other product above ear level.

 

[Chad Anson]

Scott, the soundproofing (or isolation) mostly comes from the floating ceiling/walls and double drywall. I did some research and learned that soundboard really isn't what you want on the inside for absorption.
http://www.avsforum.com/avs-vb/showt...ght=soundboard
http://www.avsforum.com/avs-vb/showt...ght=soundboard
I think I'm going to bite the bullet and go with the TheaterShield+ (or its successor, as TheaterShield+ may have been discontinued) rather than making DIY acoustic panels. Although there is mention in one of the above threads of an alternative. Another alternative that looks pretty promising is Knauf 1" 3.0PCF-FSK Insulation Board http://www.knauffiberglass.com/index...dDetail&ID=12. Also check out their Acoustic Board http://www.knauffiberglass.com/index...dDetail&ID=21. You may have luck finding a supplier under industrial insulation in the yellow pages.
Also, I'm pretty certain you want reflective surfaces on the walls above ear level. In fact, the THX standard encoding assumes some reflectivity of the upper walls and certainly the ceiling. It is with this assumption that the soundfield is built.
Diffusion is a different beast altogether... it is intended to prevent direct reflections back to your ear(hence the mirror test). From what I've been able to gather, you need some level of diffusion (columns, soffits, diffusors in corners... anything to break up the 'boxiness' of the room) but the precise amount that you need depends on several things including the exposed surface area in the room.
Great summary thread- (Look for posts by Dennis Erskin, he is a very knowledgeable source; and Ted White on the second page of the thread)
http://www.avsforum.com/avs-vb/showt...ight=diffusion
Thread on diffusion-
http://www.avsforum.com/avs-vb/showt...ight=diffusion
Thread calculating amounts of diffusion and absorption-
http://www.avsforum.com/avs-vb/showt...ight=diffusion
Good construction pics including wall treatments-
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I hope this was helpful-
Chad

 

[Scott-C]

Chad,
Though I haven't looked at all of the links you sent me, all I can say is thanks. That's lot of info you provided and I really appreciate it.
I'll be looking at all of this and will post any comments or questions I have.

 

[Greg_R]

One other thing to mentioned is that there is a huge difference (acoustically) between a HT room (multi-channel only) and a Media room (stereo and multi-channel). You also need to identify what problems your room has (too reflective? too much absorbtion?). Just don't start slapping down treatments... find out what needs to be corrected first. Everest's "Handbook of Acoustics" is a good starting point to understanding the main issues.

 

[Ben L C]

Greg,

Excellent threads. Very helpfull and informative. Thanks for your research. The mass of information that is out there is unimaginable. Now to only discern what is the best and to put them into practice.

Ben

 

[Chad Anson]

FYI, Scott Vonhof used a product called Soundboard as a substitute for Theatershield+ and seems to be pretty happy with his theater. Check out http://www.avsforum.com/avs-vb/showt...hreadid=120050 and look for his comments and a link to his theater in his signature.

 

[Scott-C]

Chad, Funny you should mention his site. I've been there a lot the past few days reading up on his site. He did use Soundboard, but he recommends a product called Insul-Shield from Johns Mansville. Although a little more expensive than soundboard, he claims the increased cost is somewhat negated by the ease of use of this product. He recommends putting it (or the soundboard) on the wall only below ear level.
His site is pretty good for learning about HT construction and even has some diagrams of the layers of materials to be used in an HT.
For me, my initial thinking is to use 2 x 6 studs for the floor joists, and stagger-stud 2 x 4's to them (I'm not sure of the distance between studs yet. Anyone have any suggestions? 8" OC?). A layer of drywall on the outside of the studs, then a layer of drywall on the inside of the studs, with insulation between the two layers of drywall. Floating ceiling with joists attached to the top of the vertical studs. How does this sound?