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Thread: Room Acoustics.

  1. #1
    Suspended PeruvianSkies's Avatar
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    Oct 2006

    Room Acoustics.

    Hey gang....

    Gotta question. I have a good friend who I am just getting into the whole home theater/audio world and he is really enjoying it. I even gave him some of my older gear so he could have a quick jump at it. Here's the deal...

    Right now he is in a room that is 11x16X7. The ceiling is low, which I think is a good thing. The speakers are set up in his room lengthwise so that they are about 2-3 feet away from the one wall, which makes them about 13 feet from the opposite wall, and about 8-9 feet from the couch/listening position. The room is carpeted and he does have a few things hanging on the wall. He is NOT in a budgetary position though to really spend any money on room acoustics at this point, but I told him I would ask around about some recommendations on ways to help improve his room conditions.

    So the first question is...

    Should as much of the walls be covered with various things as possible? He mentioned putting a large blanket on the backwall that the speakers are facing. He also wanted to put some posters and various other things that could possible absord some sound as welll.

    What are some other possible items that might help him out? Also, should he try to leave some wall space near the actual speakers in order to help the bass response? If they are tucked towards the corner (3 feet from back wall and about 1/2 foot from the side walls).

    Any help would be appreciated as I already told him this is not my strong subject, especially with DIY stuff.

  2. #2
    Loving This kexodusc's Avatar
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    Nov 2003
    Department of Heuristics and Research on Material Applications
    Treating a room isn't something you can try to cheat on to get by - you've either got to do it, or not do it, IMO.

    Low ceilings aren't a good thing - leads to more reflections of increased intensity - but it's not the biggest culprit in his room, so he can worry about it later.

    Wall hangings and furniture throughout the room will help a bit - but not very much. What's more, they can hurt as much as they help. Especially if they don't stick out much from the wall and aren't made of absorptive material. There's some benefit to avoiding having all bare walls, but really you're just trading one muddying reflection for another.

    A blanket along the rear wall will only absorb higher frequencies (and not much of those), this could cause a tonal imbalance because the midrange and bass won't be absorbed by the blanket. You'll lose the liveliness to the sound - in some rooms it works, in others it's not needed. With carpet, I'm guessing it's not a problem.

    He could try to place "things" at the 1st and 2nd reflection points in the room, but success isn't guaranteed, you may not like the results - you can do a quick google search to find methods on doing this, but the 2 person mirror trick is usually the easiest. Run a mirror along the wall while he's sitting in the sweet spot - when he sees the speakers drivers in the mirror, he's found reflection points. Treat the 3 reflection points on both left and right wall, and ceiling if possible someday.

    The carpet makes a big difference, he's got that going for him.

    Ideally you want a lot of absorption throughout the room, with some diffusive material behind the listening position (to create a large spacious effect). Without buying room treatment, this is hard to accomplish but bookshelfs with randomly arranged books in each shelf work very well.

    Ideally, you'd want at least 50% absorption in a home theater room (and usually much higher), with some diffusion in strategic places, and bass corner traps to smooth out the bass response in the room. That's hard to do with just a typical room's contents.
    Room treatment doesn't have to be expensive, you can buy various acoustic foams for as cheap as under $1 a sq ft - if he's handy, the DIY approach can save a ton of money and allows you to build customized treatment to your room. I built about 200 sq ft of rigid fiberglass panels and bass traps covered in a neutral fabric to replace my Auralex and Sonotec acoustic foam panels - I did it cheaper than than I could buy 50 sq feet of coverage (though the foam was given to me). Not only do the panels work 2 to 4 times better below 500 Hz, they look a lot better too. $100 and some spare time on a weekend goes a long way.

    After years of trying to do something with nothing in my rooms, I finally gave in to the truth that plants and lamps and foot stools aren't room treatment and don't do much. Sooner or later you either have to live with your room's acoustic problems or spend a bit of money to address them - room acoustics are the most neglected area of most stereo/home theater systems, and a small investment there yields often the greatest returns in sound quality improvement. The people here who know me will tell you I'm not one who recommends throwing money at a system or a problem unless it's the last resort, and then I'm so cheap that I want to make sure it's the most effective use of my money (why I like DIYing everything), but this is one area you really have to spend a bit on if you're really serious about putting forth the effort.

    Here's some great reading in simple to read, plain english - I don't agree with everything in the article, but Mr. Winer is right about a lot of things :
    More info at his company's site: has a lot of good info on room treatments scattered throughout the site, and a description of what their products claim to do.

    Good place to start for now. If he's interested in pursuing room treatments there's a lot of excellent web resources available. He may decide it's just not worth his effort for whatever reason, and that's fine too.

  3. #3
    Suspended PeruvianSkies's Avatar
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    Oct 2006
    Thanks for the help. I know that this is not IDEAL for him, but it's better than nothing I suppose.

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