Josh~H

I posted a similar message a couple days ago, but I was asking specifically about theater curtains at that time. Now, I'm just trying to figure out what's the best way to improve the acoustic properties of my "live"-sounding room (intended for home theater). Here's a diagram of my home theater.

My floors are concrete, and all the walls/ceiling are drywall. In the figure I put 2 possible locations for curtains, but I'm open to other suggestions as well. Someone mentioned previously that I could have bookshelves with randomly-sized books on them, for example.

He also mentioned installing an area rug. My wife's not keen on the rug idea, because we have a "designer" concrete floor...acid-stained with a funky orange/white swirl. I think I could sell her on a rug that doesn't cover the entire floor area -- for example, a rug that started in front of the TV, ended at the sofa, and left a foot or two of concrete on the sides. Such a rug would cover about 60-70% of the area of the concrete. Would this level of cover likely provide a noticable reduction in reflection?

I'm also interested in what -- if anything -- I can put on the walls to deaden the sound. The requirement is that it can't just be patches of material placed in a few odd, anti-symmetrical locations. My wife wouldn't go for that. Are there any attractive wall-coverings available that has reasonable sound-deadening properties?

DaleBesh

Acoustic wallpaper does not come cheap. I know of only one brand myself, Levsound, but I'm sure there are others. You would need to find out who carries it in your area.


http://levwall.com/levsound_samples.htm

Terry Montlick

Hi Josh,

Any area that you can cover with acoustic treatment is beneficial. It's pretty much proportional to the percentage of the room surface area covered. You don't have to give up your concrete floor. An area rug which covers the "mirror points" on the floor between you and front speakers will help.

Track-based stretch fabric is unsurpassed aesthetically. You can use it over any of your existing drywall with an inch or so of absorption behind it. It covers any portions of wall, floor to ceiling, and comes in a large variety of colors and patterns. You can't tell it from solid wall except by feel.

Of course, it's nowhere as cheap as a do-it-yourself treatment. But much of the aesthetic quality comes from the workmanship in the installation. Go to Google and do a search on "home theater fabric treatment".

Regards,
Terry

Terry Montlick Laboratories
Alpha Certification
The Standard for Home Theater Acoustics
www.tmlaboratories.com

Derek*k

Have you considered hanging paintings at the strategic reflection points? I got the idea from a Crutchfield article on prepping a living space for sound. Basically, if you live in any larger area with a college, student art comes cheap, and it's all original. The space behind the canvas can be lined with batting or fiberglass, and it'll do a decent job. It's not on par with a full acoustic trap or anything, but anything non-reflective will make a HUGE difference (posters with glass over them are EVIL).

The other thing I highly recommend is shelving. Stuff a couple full of books and knick-nacks. They help amazingly (all of the shelves and stuff on them act as very effective traps).


EDITed for an accidental incomplete thought.

Josh~H

Terry -

Not much to my surprise, my google searching quickly led me to soundwall.net There's your name right on their page.

Well, I'll treat your suggestions with even more respect, as you obviously know what you're talking about. At my current budget level, I'm looking more towards DIY types of treatments. I've already exhuasted most of my HT budget on a HDTV, DVD player, A/V amp, speakers, etc. I don't doubt that I'd be far more pleased with the types of products you mentioned, but unfortunately it's not in the cards at the moment.

I'm curious, what does "track-based" mean exactly?

Josh~H

Derek -

Paintings I had not really considered, but I will now. I'd be far more likely to convince my wife to buy paintings than a more utilitarian DIY item. I'm very intrigued by what you said about posters with glass over them. Intuitively, glass seems like it would be a very hard, very reflective surface for sound to bounce off of. The reason I'm keenly interested in this is that I already have a small number of old LP's that are framed in glass-covered enclosures. Are you suggesting that these may actually be useful acoustic treatments? I'd love to buy more, as I have a large stash of un-framed LP's that would be nice to display.

I also have a floor-to-ceiling shelf (in-wall) unit at the rear of the room that is filled with hundreds of video games and related VG hardware. I never suspected that it would be an acoustic asset, but it sounds like it might actually help out in this area.

Derek*k

No no no no. Sorry I was unclear. Glass (or anything visually reflective) is EVIL and should be avoided.

Josh~H

Yeah, that makes more intuitive sense. I guess I'll have to find another home for my glass-framed LP's.

Torgny Nilsson

I have a similar problem. I am putting together a home theater in a 10 by 19 foot room with concrete floors (also acid stained) and drywall on the walls. I am installing bookshelves down one of the side walls and will hang art here and there on the other side wall (though the art will be framed under glass). I am also putting a rug over the central area on the floor, leaving the concrete exposed only on the edges. I am inclined to leave the drywall and to not install any other sound treatment.

I did, however, hear from one guy who installed sound board over his drywall and then put carpet or fabric over the sound board. He claims it works well. I would be inclined to try it, but I need a surface that can be painted and on which I can hang picture hooks. I don't know if sound board qualifies as it is paper based.

I have always liked the idea of putting together some fabric covered frames, or simply getting some blank art canvases and painting them, but you can't hang anything on them, so they are out of the running.

All of this is very confusing. I have heard that you should dampen all of the walls, that you should leave the top 3 or 4 feet without any covering, that you should and should not dampen the wall behind your speakers and tv, etc. I think I will just have to wing it and see. I can always go back and change it later.

Terry Montlick

Hi Torgny,

Yes, acoustical treatment can be confusing. I'll try to give a capsule report.

The most needed acoustical treatment is absorption, because home theaters are almost always too "live" -- too much reverberation. Multi-channel surround soundtracks have the reverb mixed into them. If the room adds too much of its own, there is poor fidelity to the soundtrack, plus low dialog intelligibility.

To reduce reverberation, you can put absorbers up anywhere, on any wall or ceiling surfaces. The more square feet of absorber you use, the less reverberation you have.

As for specific spots, there's an addition acoustical problem which HT rooms have -- early reflections. These come from the "mirror points" on reflective walls anywhere between you and your speakers. Early reflections cause poor localization of sounds coming from your front speakers.

So as long as you are putting up absorbers, you might as well make them do double duty, and place them at least at the mirror points on the front wall, side wall, and possibly ceiling. An area rug or carpeting will generally handle the floor.

What kind of absorbers? Thick and porous to air is best. Rigid fiberglass covered in acoustically transparent fabric is excellent, as is fire-safe acoustical foam. The thicker it is, the lower down its frequency range extends.

Is it possible to over-treat a HT? Yes in theory, but in practice it's pretty hard to do. What some folks think of as overtreating is actually uneven treating. If you just use 1-inch thick fiberglass on each and every room surface, you may have nice low reverberation above about 500 Hz, but high reverberation below 500 Hz. Some treatment using thicker material - 3 inches or more - is recommended.

Diffusion is good to even out the sound field. Bookshelves with uneven-depth books make good diffusers, and they contribute some absorption as well.

I hope this scratches the surface, and provides at least some guidance. Acoustics is definitely a complicated subject. That's why there are home theater acousticians like me.

Regards,
Terry

Terry Montlick Laboratories
Alpha Certification
The Standard for Home Theater Acoustics
www.tmlaboratories.com

TimForman

Start with the ceiling. I'm surprised that this seems to be a common oversight. Many modern HT speakers are designed to utilize wall reflections. It's very easy, inexpensive and unobtrusive to hang a couple of DIY acoustic panels on the ceiling. I made mine with 1x4 frames, 1" poultry wire, R-13 fiberglass insulation, poly batting and colored burlap. It made an incredible difference. My room is similar to yours, concrete floor, wood frame and drywall walls and ceiling. I have wall to wall carpeting and the usual sofa, etc..

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