Amount of Diffusion vs. Absorption - AVS Forum
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post #1 of 8 Old 12-12-1999, 08:04 AM - Thread Starter
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I converting an 11.5' x 24.25' x 8.15' room into a home theater room. Currently, it has hardwood floors, and 2 large windows. Plus, the room dimensions aren't exactly optimal. The clap test has very ugly results.

I'm willing to add the following absorption items to the room: a 6" drop ceiling with acoustical tiling and fiberglass above; seal the windows with plywood and silicon sealant; 6" of fiberglass on the side walls with some sort of cloth "wall" to hide it; how ever much fiberglass is needed on the front and real walls; and carpet with some sort of absorptive pad underneath.

My concern is that maybe I'm putting too much absorption in and I should add some diffusion panels around the room, I'm just not sure where or how much to add. Or maybe I just need to cut back on the absorption. Any suggestions? Thanks!

Todd

[This message has been edited by toddmclaughlin (edited December 12, 1999).]
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post #2 of 8 Old 12-12-1999, 12:48 PM
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Todd:

The total amount of absorption and diffusion requires some modelling of the room and knowledge of your speakers.

This model must take into account your furniture, the type and amount of fiberglass panel (each type has different absorption at different frequencies). The attempt is to get reverberation time flat and within tolerance. Once this is done, an intelligent stab can be taken with modes. The other consideration is where this absorption and diffusion must be placed for optimal effect.

With the correct reference materials in your library and some knowledge of Excel, you may be able to work out some of the data on your own (but, as with anything, book learning is 10% of the solution).



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post #3 of 8 Old 12-13-1999, 03:18 PM - Thread Starter
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That makes sense. Can you recommend any sources for this info? I've been reading the Home Theater Architect column in Stereophile's Guide to Home Theater but it seems like Russ keeps repeating himself month after month. I do have quite a bit of experience with Excel.

Unfortunately, I don't know what brand/model of speakers I will ultimately be using. I hope this doesn't cause to big of a problem for design.

Todd
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post #4 of 8 Old 12-13-1999, 09:44 PM
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The book I'd suggest is Sound Studio Construction on a Budget by Alton Everest.

The make/model of the speakers you select will have many impacts (of all the things that make a difference in the reproduction chain ... first is the room, second are the speakers).

The first impact is based upon the orientation and physical dimensions of the speakers where orientation means the direction of the drivers (DSP6000 have side firing woofers, for example). The physical dimensions will speak to the ease (or lack thereof) of installing the speakers in an asthetic way. Asthetic may mean fitting in with your room decor and furniture placement or it may mean hidding them out of site.

The second impact relates to the dispersion characteristics of the speaker itself. Center channel speakers (non-THX) are famous for lobing, or comb-filter effects. That aside, knowing the dispersion characteristics will begin to resolve the issue of what type of treatments may, or may not, be needed on the ceiling, floor, or that acoustically ugly glass coffee table in front of your primary seating position. For a THX speaker, you have a real clear picture of how the thing will behave. For other speakers (be they better, equal or worse), these characteristics either need be measured or gleened from reviews where these characteristics were measured.



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post #5 of 8 Old 12-14-1999, 12:51 PM - Thread Starter
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Thanks for your advice so far. I just ordered the book from Amazon.com. I also found Acoustical Techniques for Home and Studio and The Master Handbook of Acoustics in our library at work. Both are by Everest. I'll look through them until the other book arrives. Thanks!

Todd
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post #6 of 8 Old 12-15-1999, 08:14 PM
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Todd,

You can also get a program which will calculate a the type of absorption/diffusion/reflection of your HT. Its made by RPG and can be purchased for $99.95 at www.audioadvisor.com. You can also check out the RPG web site at www.rpginc.com. There is some excellent stuff there. But there is nothing like true professional advice, like Dennis Erksine, I understand he is very good.

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post #7 of 8 Old 12-16-1999, 04:15 PM
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Todd,

If you're planning on spending serious coin on your theater you should consider contracting with Dennis. I started out doing what you're doing and decided to get it right the first time. I hired Dennis. It's going perfectly.

Ted

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post #8 of 8 Old 12-18-1999, 01:45 PM - Thread Starter
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Ted,

So how's that work with you two being in different states?

Todd
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