[sotwell]

My theater is on a concrete slab in the basement. How much value is there in filling with sand instead of insulation? I am running out of budget on the basement project and do now want to shell out the $200 for sand or the effort.


What if I put sand just in the stage sections of framing where the sub will sit and insulation in the others? What about just using a SubDude under the sub? I will be using the SVS PC-13 cylinder sub.

 

[SondekLP12]

I know of a theater in Michigan in 1976 that used sand bags behind their Altec Lansing "Voice of the Theater" speakers to help absorb a lot of the bass vibration coming from the cabinets where they were sitting on a shelf up front. It appeared they were testing the at that time "new" sound equipment to see if it could really strut it's stuff, and one of the side walls drywall came crumbling down. That's when they decided to use the sand bags behind each speaker's rear baffle. I don't think insulation would provide enough vibration control as sand.

 

[Mr.Poindexter]

At a minimum I would recommend sand beneath the sub but $200 for sand? It has been a long time since I built my stage but I don't recall spending that kind of money on sand and my stage wasn't exactly smallish.

 

[badata2d]

Carrying all that sand is like a rite of passage! Mine took 15 bags, which came to about $45. Make sure you get it inside though at Lowe's and not the stuff they keep outside. Its the same, but the inside bags were all completely dry.

 

[dc_pilgrim]

Here is what I pulled together in another thread:

Quote:

Quote:
Originally Posted by Jet Captain /forum/post/16567280


Thanks Dave..I am in a basement with a concrete floor. I can use sand however I am just having heartburn about bringing 100's of lbs. of sand down there. I have read on the forum that people have used insulation on concrete but I can't find the post and would love to know what their outcome/results are.

Well, dragging the sand down is a rite of passage. I seem to remember one guy took out a window and created a slide to transfer the bags down (it was WOOlly http://www.avsforum.com/avs-vb/showt...=869753&page=2 )


Dennis Erskine, uses insulation in upper floor builds and I am sure it doesn't hurt your room, just doesn't help as much. I was just reading his posts on the topic yesterday, and this is his discussion of what you are giving up. Makes me almost want to put one in my next build, even though I am not sure I have the room. Here is the quote:

Quote:
Originally Posted by Dennis Erskine /forum/post/9456283


The sand filled stage is a functional portion of a good home theater which, fortunately, can be disguised as something architectural and belonging in the room (such as stage, for example). First, the stage must be constructed AFTER the drywall is installed. Second, when it is built, it should not come into contact with any of the walls (and idealy be isolated from the floor or that great sound conductor called a concrete slab). Here's what it does:

1. the subs are anchored to the stage. For optimal subwoofer performance, the sub must be anchored to something of considerably more mass than the sub itself.

2. The dry play sand provides the mass; but, it is not a solid mass that would allow vibrations from the sub (and the other main speakers) to pass through on their merry way to the rest of the house...the sand is an absorber reducing (rather dramatically) the amount of kinetic energy entering the structure.

3. Because the kinetic energy is not being transferred to the structure, your walls do not become occasional speakers injecting distortion artifacts into the room.


[At the lower frequencies, the vibration enters the structure...within the home their a lots of walls of different sizes, shapes and mass. Each of this has a resonance frequency. When that resonance frequency is equal to or a harmonic of the frequency being produced by your sub, that wall becomes a speaker...and, a surprisingly loud one at that.]


Here's another POV. You're spending a bunch of money on your gear (and many times a few grand on your subwoofer). For $300 to $500 are you willing to bet it (the stage) won't help.


Until you've heard truly smooth bass response and the sound in a well calibrated room, you cannot imagine what you're giving up...and, I've a demo room for just that purpose.

EDIT - and check out this thread for some good build diagrams.

http://archive2.avsforum.com/avs-vb/...&post8162230

 

[sotwell]

Ok, so I may be leaning towards sand under the first few sections where the sub will sit, and insulation for the rest. Has anyone else done this?

 

[BritInVA]

I did but as understand it more mass is better.


Details in my thread (see index in first post)

 

[dk-customs]

Originally Posted by Dennis Erskine "First, the stage must be constructed AFTER the drywall is installed. Second, when it is built, it should not come into contact with any of the walls (and idealy be isolated from the floor or that great sound conductor called a concrete slab). "


DC, what does Dennis mean when he writes "idealy be isolated from the floor"? Is this with felt paper?


Thanks

 

[dc_pilgrim]



Quote:
Originally Posted by dk-customs /forum/post/16934161


Originally Posted by Dennis Erskine "First, the stage must be constructed AFTER the drywall is installed. Second, when it is built, it should not come into contact with any of the walls (and idealy be isolated from the floor or that great sound conductor called a concrete slab). "


DC, what does Dennis mean when he writes "idealy be isolated from the floor"? Is this with felt paper?


Thanks

Felt paper is one way. Acoustikmat is his preferred method. See BasementBob's grafic:

 

[Anthony A.]

is it adviseable to stuff the 1/4" gap around the perimeter of the riser with insulation? i always thought it should be left free and untouched to avoid sound transmission. from what i hear, compressed insulation will do this. if dennis or someone else could chime in that would be great.

 

[dk-customs]

DC, thanks for posting the picture! That helps alot. I will read that thread.

 

[dc_pilgrim]



Quote:
Originally Posted by Anthony A. /forum/post/16934456


is it adviseable to stuff the 1/4" gap around the perimeter of the riser with insulation? i always thought it should be left free and untouched to avoid sound transmission. from what i hear, compressed insulation will do this. if dennis or someone else could chime in that would be great.

I always thought free standing was the better method. Bob is pretty methodical though, so he must have read something once. I am not sure either approach will kill the install.


EDIT - here is Terry on point suggestion with or without the insulation:

Quote:
Originally Posted by Terry Montlick /forum/post/14302744


Don't let the stage touch the walls. Make sure it is free-standing, with a gap to the walls which can be filled with fiberglass insulation.


As for the stage, fill it with sand. You don't need to anchor it. It won't be going anywhere!

Regards,

Terry

Quote:
Originally Posted by dk-customs /forum/post/16934614


DC, thanks for posting the picture! That helps alot. I will read that thread.

Glad it helps. I also pulled up some helpful links in this post if you want to read even more:

http://www.avsforum.com/avs-vb/showt...4#post16933784


Not sure why I drag myself into these debates. Ironically I might skip the stage in my next build since the room is so small.

 

[Dennis Erskine]



Quote:
is it adviseable to stuff the 1/4" gap around the perimeter of the riser with insulation?

...but not tightly.