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post #1 of 34 Old 07-11-2008, 08:53 AM - Thread Starter
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What is the idea of filling the stage and riser with sand ?
Does the sand acts as a bass trap. Called gik acoustics and they told me sand does not have any acoustic properties.
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post #2 of 34 Old 07-11-2008, 09:07 AM
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No, I think it's designed to be a vibration damper. Makes the stage really heavy and unlikely to vibrate if/when you put a subwoofer on it.

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post #3 of 34 Old 07-11-2008, 09:27 AM - Thread Starter
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That is what I thought.
Thanks for confirming it.
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post #4 of 34 Old 07-11-2008, 10:00 AM
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Remember that all speakers have some vibration so using sand is recommended if you have any speakers attached to or sitting on your stage/screenwall.... so it's not only to dampen subwoofer vibrations.

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post #5 of 34 Old 07-11-2008, 10:17 AM
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Quote:
Originally Posted by HSINGH View Post

What is the idea of filling the stage and riser with sand?

I think you'd do better with a hollow wood platform with fluffy fiberglass stuffed inside the cavity. That will damp vibration and also add some bass trapping.

--Ethan
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post #6 of 34 Old 07-11-2008, 10:35 AM
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To properly anchor multiple subs and speakers, you need to couple the speakers to something with considerably more mass than that of the speakers. Once you do so, kinetic energy is transferred to that mass. If that mass happens to be your house, you'll find a wall somewhere in your house that is now a speaker.

The sand provides mass (the stage is NOT a bass trap). The sand provides excellent mechanical damping. Sand would not be used in the seating platform riser.

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post #7 of 34 Old 07-11-2008, 10:51 AM
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Quote:
Originally Posted by Dennis Erskine View Post

To properly anchor multiple subs and speakers, you need to couple the speakers to something with considerably more mass than that of the speakers. Once you do so, kinetic energy is transferred to that mass. If that mass happens to be your house, you'll find a wall somewhere in your house that is now a speaker.

The sand provides mass (the stage is NOT a bass trap). The sand provides excellent mechanical damping. Sand would not be used in the seating platform riser.

Hsingh, I'm not sure who you spoke with at GIK, but I have a feeling that what we have here is a simple miscommunication.

Totally agree with Dennis. Everything in nature has an acoustical property, just as everything in nature reacts to light or heat. It's simple physics. The fact that sand is typically used in the application that Dennis described above does not mean in any way that it is neutral acoustically.

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post #8 of 34 Old 07-11-2008, 12:00 PM
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In 1969 I bought some Warfdale speakers that used sand filled cavities in the cabinet construction. Suckers were heavy.
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post #9 of 34 Old 07-11-2008, 01:07 PM - Thread Starter
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Mr Frank, Read an article on diy network website where they are using sand filled column as base traps. http://www.diynetwork.com/diy/hi_fam..._13912_3471072

Talked to Mr Bryan @ gik acoustics. He did say that sand is used as a dampner rather than as a bass traps.
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post #10 of 34 Old 07-11-2008, 01:34 PM
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That article is not coming up. In any case, I wouldn't place a lot of stock in their knowledge of this topic. In any event, a sand filled column is not going to work as a bass trap at frequencies we humans would care much about.

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post #11 of 34 Old 07-11-2008, 01:47 PM
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Quote:
Originally Posted by Dennis Erskine View Post

That article is not coming up. In any case, I wouldn't place a lot of stock in their knowledge of this topic.



I remember the sand filled column business from that 4 part series they did on home theaters. Also in that show was placing speakers in large cabinets in the front of the room and using differing insulating materials in alternating stud bays to reduce resonances. All head scratchers.

from the article: "It's easy and inexpensive to build your own bass trap --
Take a concrete form and tape off the bottom of one end, fill the form with sand and then tape off the other end. It's that simple. You can place the bass traps next to the front left and right speakers (figure G), then eventually hide them behind a fabric panel (figure H)."






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post #12 of 34 Old 07-11-2008, 02:09 PM
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I seem to remember that series as well. I recall they re-capped a lot of old concepts that were held circa 1990

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post #13 of 34 Old 07-12-2008, 09:27 AM
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Quote:
Originally Posted by HSINGH View Post

Read an article on diy network website where they are using sand filled column as base traps.

That article is a joke, and whoever wrote that is clueless. As Dennis said, sand in a cardboard tube offers no useful absorption at bass frequencies (or any other audible frequencies).

--Ethan
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post #14 of 34 Old 07-14-2008, 04:41 AM
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Perhaps someone can clarify this for me, its been bugging me for a while.

You've got a concrete slab, you make a box and fill it with sand, which weighs more then your speaker. Sit the speaker on it and its de-coupled? I fail to see how this transfers energy into the room rather than into the slab and into the house?

Something else I have read is that you should put an acoustic mat under this box? and that de-couples it? where can I find a mat that wont flatten to the point that its worthless with ~150kg sitting on it?

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post #15 of 34 Old 07-14-2008, 05:08 AM
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Elill...
If you build your stage and fill it with sand (and the stage does not contact the walls), you have created a structure that, while not decoupled, does damp the kinetic energy transfer into the slab. As you suggest, a better method is to place a damping agent (such as a rubber mat) under the stage framing to further isolate the stage from the slab. Acoustik Mat is one such product that will work very nicely. (contact Ted at www.soundproofingcompany.com). The product will NOT flatten out (total pounds and pounds per square inch are different). Because the impedance of a concrete slab is entirely different than that of a wood framed floor, this technique is important when you're building a room over a framed floor. The downside, however, is unless you plan for the static weight of the stage, it is very likely your floor system will not handle the weight.

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You've got a concrete slab, you make a box and fill it with sand, which weighs more then your speaker. Sit the speaker on it and its de-coupled? I fail to see how this transfers energy into the room rather than into the slab and into the house?

Good question. The damping does not re-direct energy, it simply converts kinetic energy to heat reducing the transfer into the remainder of the home's structure. The high mass of the stage, and the positive attachment of the sub to that stage, is the mechanism which works to improve efficiency. When the driver moves forward, the cabinet wants to move backward. Preventing this backward motion is helpful. It takes mass to do that.

That doesn't mean we have overcome the equal but opposite reaction...it means we're doing a better job of managing what's going on.

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post #16 of 34 Old 07-15-2008, 05:45 AM
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No acoustic properties of sand? Nonsense! Just do a web search for "Singing Sand." This property has been studied as early as 1890.

As for more mundane properties of sand, it is definitely an effective damping material, with a relatively high loss factor. I thought I had some frequency info on this, but couldn't find it. The exact mechanisms for sand damping aren't well understood, but there are a few theories, including damping of standing waves in structures filled with sand.

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post #17 of 34 Old 07-15-2008, 06:22 AM
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Oh yeah Grand Haven Michigan has the singing sand...

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post #18 of 34 Old 07-15-2008, 09:15 AM
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Quote:
Originally Posted by Terry Montlick View Post

As for more mundane properties of sand, it is definitely an effective damping material, with a relatively high loss factor. I thought I had some frequency info on this, but couldn't find it. The exact mechanisms for sand damping aren't well understood, but there are a few theories, including damping of standing waves in structures filled with sand.

So I'm planning to fill my theater's walls with sand... Ok I'm just kidding, but might be an interesting experiment!
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post #19 of 34 Old 07-15-2008, 06:03 PM
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Quote:


The exact mechanisms for sand damping aren't well understood, but there are a few theories, including damping of standing waves in structures filled with sand.

Sounds like a good PhD thesis.

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post #20 of 34 Old 07-16-2008, 09:14 AM
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I'm building my stage now and I have two questions.
1- How do I decouple the stage from the wall? Do I just let it sit freely on the concrete floor or anchor it some how?
2- What do I fill it with??? Sand or Insulation???
Any help would be great.
Thanks
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post #21 of 34 Old 07-16-2008, 09:46 AM
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Going back to the column theory for acoustic damping.
1. If we use a concrete form and sand as a dumping agent. Would the -cardboard surface & somewhat solid sand be more of a reflective agent-hard surface.
2. Create a structural column, i.e. chicken wire frame and stuff it full of some high absorption fiberglass material (wrapped it with some nice cloth) create a better trap?
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post #22 of 34 Old 07-16-2008, 10:05 AM
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Quote:
Originally Posted by BILLSID29 View Post

I'm building my stage now and I have two questions.
1- How do I decouple the stage from the wall? Do I just let it sit freely on the concrete floor or anchor it some how?
2- What do I fill it with??? Sand or Insulation???

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!

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post #23 of 34 Old 07-16-2008, 10:51 AM
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Quote:
Originally Posted by DAB View Post

Going back to the column theory for acoustic damping.
1. If we use a concrete form and sand as a dumping agent. Would the –cardboard surface & somewhat solid sand be more of a reflective agent-hard surface.
2. Create a structural column, i.e. chicken wire frame and stuff it full of some high absorption fiberglass material (wrapped it with some nice cloth) create a better trap?

Arggghhh! There is no credible column theory, at least not with sand. You can try and copy ASC's tube traps. These are a variation on Harry Olson's old fiberglass cylinder absorbers (US patent #2502020, 1950. Look it up here). Here's a link to building one very simple version:

http://www.geocities.com/jonrisch/basstrap.htm

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post #24 of 34 Old 07-17-2008, 11:03 AM
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Quote:
Originally Posted by Terry Montlick View Post

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

Thanks for the info Terry!
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post #25 of 34 Old 04-11-2009, 06:38 PM
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Hi all,
I have read all of the posts and everyone is filling the stage with sand and the risers with insulation.
If the stage will not actually have the BASS speaker or mains sitting on it, could it not be used as a BASS TRAP by filling it with insulation instead of sand?

I dont have any risers in my theatre/billiards room. I wouldnt mind a bass trap though... and the stage would be the only way i can get one.

OR, i just get rid of the stage idea and thats the end of that,

if you have an opinion on this, i would LOVE to hear it! thanks very much.
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post #26 of 34 Old 04-12-2009, 12:30 AM
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I am planning to build a 4 X Shiva 12" LLT sub into the back of my riser ( internal volume of sub is 28 cu ft )

the total volume of the riser is 81 cu ft ( including the sub ) and balance of the riser will be filled with fiberglass insulation

The riser will be sitting on the Delta FL subfloor which is covered with 5/8 T&G OSB anchored every 2 feet ... riser does not come in contact with the exterior walls ( 1" gap on left and 2' on right )

There will be a Axiom 600 sub at the front of the room on a sand filled stage

Will this have a negative impact on my soundproofing efforts with the sub/riser directly on the subfloor ?

Here is a sketchup of the room minus the proposed stage for the Axiom and LR speakers to sit on

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post #27 of 34 Old 04-12-2009, 05:11 AM
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Quote:
Originally Posted by ScruffyHT View Post

There will be a Axiom 600 sub at the front of the room on a sand filled stage

Will this have a negative impact on my soundproofing efforts with the sub/riser directly on the subfloor ?

No.

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post #28 of 34 Old 04-12-2009, 07:48 AM
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So the riser with a sub inside will be fine directly on the subfloor? ... just checking
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post #29 of 34 Old 04-12-2009, 08:06 AM
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Quote:
Originally Posted by ScruffyHT View Post

So the riser with a sub inside will be fine directly on the subfloor? ... just checking

No. I would not recommend putting a sub inside the riser. But if you absolutely insist, build a cutout with solid walls in the riser for the sub, allowing space for adequate ventillation. fill the riser with sand as well.

If you want bass shakers, then buy bass shakers. Trying to add subs to the riser to fulfill this function will probably be disappointing.

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post #30 of 34 Old 04-12-2009, 08:30 AM
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Quote:
Originally Posted by Terry Montlick View Post

No. I would not recommend putting a sub inside the riser. But if you absolutely insist, build a cutout with solid walls in the riser for the sub, allowing space for adequate ventillation. fill the riser with sand as well.

If you want bass shakers, then buy bass shakers. Trying to add subs to the riser to fulfill this function will probably be disappointing.

Not sure what you mean by building a cutout and ventilation ?

this sub is not a substitute for bass shakers ... it is a stealth sub to eliminate me having to build another 13 cu ft sub for the front of the room
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