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Acoustic treatment question/advice


MercedesBerater

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MercedesBerater,

 

I haven't read the whole thread, but have you considered some diffusers, as well?  Having absorbers at ALL of the first reflection points (including the ceiling), but diffusers in the other areas, as well as some bare wall space may help preserve some "good" reverberation.  There are few things worse sounding than an over-damped room.  One of the best sounding rooms I have ever had had a huge fireplace at one end (rough hewn stone and brick, with surfaces aiming in many directions, a wood floor with a Persian rug covering most of it, and a plaster & lath ceiling interrupted by large ceiling beams.  The two speakers were on either side of the fireplace, out from the wall (not my Khorns; JBL), and toed-in.  There was an overstuffed couch and an overstuffed chair.

Edited by garyrc
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I have considered a rear wall with diffusion and absorption that's much thicker than the remainder of the room... Say 6-8" thick... And then doing a big.. Say two 4x6' diffusers.. Made up of 2x2" blocks cut at random lengths from 1"-8" so the overall depth equals the thickness of the absorbers 8"

And I think I'll be forgoing any ceiling treatments.. Hoping that the "live" ceiling will give a sense of height spaciousness

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Followed up with AcousticalSolutions on their product compared to AcoustiMac.

He said they use roxul & theirs performs much better - as almost all NRC ratings are computer models and not actually tested.

I hope me sending the quote from AcoustiMac his way gets him to drop price considerably...

From first email:

You can send me the other quotes and I will see what I can do for you no problem. Just keep in mind that if you are going with a 2” thick fiberglass panel, you won’t get a better NRC. They all say “1.15, 1.30…etc” But what that means is 100% absorption of speech frequencies. Anything over “1” is just a result of lab testing of a 3D item when the lab computer can only test a 2D surface. It adds in the thickness of the panel to compensate. If you need clarification on this, just let me know.

From second email:

Basically what I was going to talk about is that we are using a higher quality product than AcoustiMac. They are using a Roxul fill which is a very inexpensive, and frankly, cheap alternative to Johns Mansville Whispertone Wallboard.

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Here is a good site on how to build your own acoustic panels:

 

http://acousticsfreq.com/how-to-build-your-own-acoustic-panels/

 

 

These are a lot of work but there is a good guide on 3d diffuses:

 

http://www.pmerecords.com/Diffusor.cfm

 

I would make sure all the primary reflection points are absorbed but then alternate 50% diffuses and absorbers for the rest of the room.

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Followed up with AcousticalSolutions on their product compared to AcoustiMac.

He said they use roxul & theirs performs much better - as almost all NRC ratings are computer models and not actually tested.

I think you're over thinking this for first reflection points. It just doesn't matter. Any of these products are more than enough. All these tests are with the sound hitting straight on and in the frequencies that it matters all the 2" materials are about at a 1.0 or higher. First reflection points will have the sound hitting at an angle though and will automatically be higher.

Even if you did hit them straight on, read the text on Bob Gold's site:

http://www.bobgolds.com/AbsorptionCoefficients.htm

"Differences in coefficients of less than 0.15 are not significant."

Just seems like you're considering paying a fortune to split hairs on something that just doesn't matter. In terms of results, you'd be much better off putting that time, energy, and money into buying a calibrated microphone and learning REW. I especially wouldn't spend that kind of money until you know what you're doing. If you can prove that you need it for some reason with REW then go for it. Spending that kind of money based on a few cool pictures and marketing jargon doesn't make any sense though.

Edited by MetropolisLakeOutfitters
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I have considered a rear wall with diffusion and absorption that's much thicker than the remainder of the room... Say 6-8" thick... And then doing a big.. Say two 4x6' diffusers.. Made up of 2x2" blocks cut at random lengths from 1"-8" so the overall depth equals the thickness of the absorbers 8"

You can measure the need for this though. Doesn't make any sense to do all this without measuring. You may even do more harm than good when you just throw random solutions at your room.

Edited by MetropolisLakeOutfitters
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I have a client that owns a recording studio and has all the really cool mic's amd measurement devices... He has offered to come measure my room for free.

I just am trying to get a grasp on everything.. And waiting on carpet before I have him come over. I want to be prepared, and sound educated.

And know what product to go with as soon as I have data.

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-- if you want a good laugh.... I've obsessed over every other detail in the room just like this.

I probably stared at the side walls for hours trying to guess where I wanted lights & columns... Then I picked the location of lights and columns. Now... Lights 4" off walls, or 8" off walls... Column 4" deep, 6" deep.. Hmm how wide? 10" 12" 14" 8"?

What amount of curve to the front stage.. Flat sides with a center curve, while curve, whole flat? Etc etc...

This project has been an experiment in what it'll take to drive myself insane.

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I'm kind of curious about that bevel, I almost bet you could just run the thing through a table saw. The 6 pound material should be pretty danged stiff. Could almost do it with the 3 pound but 6 pound you could probably just saw the stuff.

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My 3 pound Knauf is stiff enough that if you press on it hard it will crush and won't bounce back. I think scrappy has Owens Corning, possibly the 6 pound 705 but I'm not sure, you can press on it and it feels kind of like styrofoam, almost like that green foam they put fake flowers in. That's why you can hang the stuff with no frame. It's basically just hard duct board.

Edited by MetropolisLakeOutfitters
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Here's a brilliant idea... I'll see if they can sell me a roll of the fabric I'm so fixated on having.

Problem solved!

When you get your material, I would go with a material that is acoustically transparent, as some materials might reflect vs allow the sound through (to allow the panels to work). 

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The rock board is stiff enough to cut a bevel in?? I've only ever seen / touched rockwool, which is pretty floppy and shreds quite easily.

I think you might be able to bevel cut if you use a saw that has no blades... I believe they are special blades for cutting foam (been years since I used one). The blades look like a meat cutter blade.

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