Aesthetically pleasing acoustic improvements?

Discussion in 'Home Theater Projects' started by Josh~H, Jul 28, 2003.

  1. Josh~H

    Josh~H Stunt Coordinator

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    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?
     
  2. DaleBesh

    DaleBesh Stunt Coordinator

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    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
     
  3. Terry Montlick

    Terry Montlick Stunt Coordinator

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    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
     
  4. Derek*k

    Derek*k Auditioning

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    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.
     
  5. Josh~H

    Josh~H Stunt Coordinator

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  6. Josh~H

    Josh~H Stunt Coordinator

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  7. Derek*k

    Derek*k Auditioning

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

    [​IMG]
     
  8. Josh~H

    Josh~H Stunt Coordinator

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  9. Torgny Nilsson

    Torgny Nilsson Second Unit

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    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.
     
  10. Terry Montlick

    Terry Montlick Stunt Coordinator

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    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. [​IMG]

    Regards,
    Terry
     
  11. TimForman

    TimForman Supporting Actor

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    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..
     
  12. Josh~H

    Josh~H Stunt Coordinator

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    Terry - thanks for the capsule report. [​IMG]

    Tim - I'm definitely going to try the DIY panel approach. I think I basically follow what you did to create your ceiling panels, but do you have it written up more explicitly somewhere? Or even a picture of what you did might be helpful.
     
  13. Josh~H

    Josh~H Stunt Coordinator

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    Well, I found various online instructions on how to create these DIY panels. I have a whole bunch of 1x5 planks already, so I'll rip those a bit narrower. I picked up a 4x8 pegboard at the Home Depot yesterday, along with a roll of R13 insulation. I think I made a mistake with the insulation though. At the store, it appeared that the 'R' value was correlated with the depth. So the R13 that I got was only 3.5 inches deep -- everyone else seems to be using 6" deep stuff. But at my Home Depot 6" corresponded to R25 or something like that.

    Is it OK to use two layers of kraft-backed 3.5" R13? I guess the main problem is that there would be two layers of the kraft paper, and that could cause an extra layer of reflection in the higher frequencies. Should I bother seeking out 6" insulation then, or make do with what I already have?
     
  14. John Karpiscak

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    Hi! Where did you find the instructions for the DIY panels? I'm getting closer to purchasing the acoustic wall fabrics and want to creat my own panels. I just want to take advantage of others experiences.

    Thanks!

    jk3
     
  15. TimForman

    TimForman Supporting Actor

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    I'm sorry my web page is hosed. I'll have to rebuild. I saw other people using heavy material (plywood) on their panels. Since I wanted to hang them from the ceiling I didn't want to go that heavy. Plus, someone will have to explain to me the advantage of adding a reflective material like plywood to something intended to absorb sound 'cuz i doan gitit. I built a rectangular frame with a single perpedicular crossbrace with 1x4 pine. I fastened 1" chicken wire on one side of the frame then used the cheapest R-13 paper-backed insulation I could find. I layed it in paper facing the chicken wire, then applied polyester batting on the exposed fiberglass. This was done to contain the fibers. I found some nice colored burlap for $3.99/yd and fastened that over the batting. Rather than attaching the panels flush to the ceiling I used swag hooks with hollow wall anchors, attached hangers to the frame and hung them up. Not only is this easier, it provides and additional airspace above the panels for even more sound absorbing effect.
     
  16. Josh~H

    Josh~H Stunt Coordinator

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    John K -- I just did a search on "absorbtion" on this forum, and found several interesting links. Here's a good page that has a few different options for (and pictures of) DIY absorbtion and diffusion panels, and bass traps.

    http://t-3.cc/users/audioworx/page2DIYpanels.html

    Tim - Thanks for the description. Your method is very similar to that of the ones in the link I provided. I might skip the chicken wire step, though I haven't decided. I'm also contemplating a design where the frame members are interleaved to provide a gap around the perimeter; a gap where I can stuff more insulation, and allow that to absorb rather than the wood frame which would reflect. I'll put up pics later...it should be quite easy to construct.

    Tim, I see you also used R13. Did it come in 6" depth? I'm still trying to determine whether my 3.5" deep R13 can be stacked, or if I should get a different 'R' rating that corresponds to a 6" depth.
     
  17. TimForman

    TimForman Supporting Actor

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    Technically speaking, paper is less effective than insulation but I doubt it would hurt anything. Yes, the R-13 is 3.5 inches thick but it works well. With the batting I have over 4 inches of depth. Also, the poly batting extends around the frames as does the burlap. There is no exposed wood on my panels.
     
  18. John Karpiscak

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    Thanks guys, that's some great ideas!

    The reason I asked this is I've got 2 walls in my home theater to finish, both are home exterior walls.

    Starting with a bare concrete block wall, my original idea was to:
    1. cover it with insulation (heat loss considerations),
    2. frame it out (standard 2x4 stud wall for cables electrical things),
    3. Add fiberglass insulation (heat loss and acoustic considerations),
    4. Cover with 2 layers of acoustic ceiling tiles.
    5. Cover that with acoustic fabric.

    all floor to ceiling.

    Too much? Waddaya think?

    jk3
     
  19. TimForman

    TimForman Supporting Actor

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    Insulation and acoustic tiles are great for the higher frequencies. The reasoning behind wall framing with drywall is that this arrangement will help absorb the lower frequencies by actually moving rather than being a rigid reflective surface.
     
  20. Frank joe

    Frank joe Stunt Coordinator

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    what about texture paint , its cheaper then the wall paper.
    u can creat many effects on the walls.
     

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