Stage with or without sand for best audio performance

azhtnut · « **on:** 24 May 2010, 09:19 pm »

My media room was built in a former 2-car garage with a wood stage 9" or so above a concrete floor where my FL, FR, C, and 2 subwoofers sit. Dimensions are 5' deep x 16' across with a 6' arc in the middle that's about 9' deep from back to front. The stage was stained dark cherry and stapled and nailed together solidly, but am sure it still has a great deal of vibration / reverb.

I'm thinking there should be a way to pull apart a few of the stage slats and blow sand into the cavity without tearing most of the stage apart.

First question, is a sand filled stage a must in for this situation or is there another method that can be used to deal with vibrations other than spikes on the speaker feet than I already use?

Second question, has anyone else retrofitted a stage like this and are their machines for rental / purchase that would allow for blowing the sand or other material into the cavities under the stage?

Thanks,
Marty

bpape · « **Reply #1 on:** 24 May 2010, 09:23 pm »

The idea of sand is to fill it completely to stop it from acting like a big drum - especially with subs on top of it. In a retrofit, you'll not be able to fill it fully so you won't get the benefit. You'll only succeed in raising the resonant frequency where it's more offensive more often as the sand doesn't absorb, it just shrinks the cavity.

I'd recommend blowing in insulation instead as it will at least damp the resonant cavity somewhat.

Bryan

zybar · « **Reply #2 on:** 24 May 2010, 11:09 pm »

I didn't do a retrofit, but for the last stage/platform I built for my HT, I used insulation, not sand.

It is easier to install, easier to maintain, and easier to dispose of.

I did before and after listening tests, and adding the insulation definitely made a noticeable difference.

For insulation, I just used regular paper backed attic material. I can't recall the exact R value.

Bryan, any recommendations on specific insulation that should be used?

George

azhtnut · « **Reply #3 on:** 27 May 2010, 05:49 pm »

Thanks for your responses. Insulation sounds like a better way to go than the sand. Any help with the best type of blown-in insulation for this would be much appreciated.

Also, I have a pair of SVS PB12 Plus bottom firing subs in the middle of the stage, if that makes a difference. I tried them in the corners intially, but had way too much echo in the playback. Both are about 6' from the side wall and 5' from each other. They sound much better where they are now.

Marty

bpape · « **Reply #4 on:** 27 May 2010, 05:52 pm »

Just a generic cellulose type of blown in will work fine. Get as much in there as you can as it will settle a bit over time.

Bryan

jtwrace · « **Reply #5 on:** 27 May 2010, 05:54 pm »

If you use the approved "green" blown in stuff you can get a tax credit.

Big Red Machine · « **Reply #6 on:** 27 May 2010, 06:06 pm »

Is your sub sitting on the stage? If so, then I can see the sand. If not, then it would seem a waste of energy. My room does not work with the sub up front so my stage is only filled with batt. My seat riser is 12" tall and is filled with bags of blow-in insul and has 2 layers of 3/4 ply covering the 2x12 frame. The blow-in is (was) much cheaper.

No rattles or detrimental effects front or back of room as built. Pipes on the other hand......

azhtnut · « **Reply #7 on:** 28 May 2010, 04:56 pm »

I am back home where I can load a pic for reference. This is the old setup with the subs in the corner. They are now moved to inside of the FL and FR about 3' or 4' inside where they are in the picture. The FL and FR were moved about 1' toward the side wall from where they are in the picture.

Sorry, RP got a little washed out on the PJ screen from the camera flash.

Marty