Isolation platform for subwoofer? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 32 Old 06-20-08, 04:07 PM
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Re: Isolation platform for subwoofer?

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This method will not actually decouple the sub from the floor or the concrete blocks. The thickness and density of the carpet as it relates the wavelength produced by the subwoofer is not sufficient to remove transfered resonances.
No, but the concrete blocks themselves should be non-resonant. The carpet was just to keep from scuffing your sub.
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post #12 of 32 Old 06-20-08, 04:23 PM
 
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Re: Isolation platform for subwoofer?

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No, but the concrete blocks themselves should be non-resonant. The carpet was just to keep from scuffing your sub.
The concrete blocks actually do have the potential to transfer the resonances. This is so because it is unlikely that the concrete blocks, alone, have enough mass to completely dissipate the energy transfered from the subwoofer. Also, it is important to note that concrete itself is actually a relatively resonant material.

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post #13 of 32 Old 06-20-08, 06:32 PM
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Re: Isolation platform for subwoofer?

I've actually been looking for some sort of study or numbers on the resonant properties of concrete (Google let me down, for the most part). Anyone here got any leads?

From my amateur testing, I put a butt-kicker on one end of a concrete block (nylon webbing holding it on) put my hand onthe other side, and ran 20-200 HZ sweeps to see if I could feel/hear anything. Could hear some rattling (nature of the butt-kicker), feel nothing. Acknowledging the uneven response of those butt-kicker devices, this simple experiment seemed to indicate to me that concrete blocks would make good speakers stands (surely better than metal or wood), and should also make a decent isolation stand for a sub woofer. Yeah, my hand and ears aren't a very accurate test device, but for the purpose of determining material for speaker stand, they sure seemed adequate and practical.
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post #14 of 32 Old 06-20-08, 06:45 PM
 
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Re: Isolation platform for subwoofer?

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eugovector wrote: View Post
I've actually been looking for some sort of study or numbers on the resonant properties of concrete (Google let me down, for the most part). Anyone here got any leads?

From my amateur testing, I put a butt-kicker on one end of a concrete block (nylon webbing holding it on) put my hand onthe other side, and ran 20-200 HZ sweeps to see if I could feel/hear anything. Could hear some rattling (nature of the butt-kicker), feel nothing. Acknowledging the uneven response of those butt-kicker devices, this simple experiment seemed to indicate to me that concrete blocks would make good speakers stands (surely better than metal or wood), and should also make a decent isolation stand for a sub woofer. Yeah, my hand and ears aren't a very accurate test device, but for the purpose of determining material for speaker stand, they sure seemed adequate and practical.
The most accurate measurement would be taken with an accelerometer, but such a tool with an appropriate pre-amp would cost about $100-150. You could perhaps see if your local university library has any material engineering books that would contain the information.

Any material would make a suitable speaker stand if the speaker is decoupled from it presuming it is of sufficient strength to hold the speaker, of course. The comfort mats I previously mentioned are inexpensive, simple, way to decouple a standard bookshelf speaker from a stand. Using the foam online source one could easily, inexpensively, create a professional looking decoupling unit for heavier speakers or subwoofers as well.

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post #15 of 32 Old 06-21-08, 01:21 PM
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Re: Isolation platform for subwoofer?

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... A possible solution one could use for testing would be buying the foam comfort pads that are sold at Walmart for about $10. Cut it into 4"x4" squares and glue a 3 or 4 of these squares together...
Are you talking about this??? ... http://www.softtiles.com/content/view/28/39/ ... I think they will be easy to use; just cut the same size as the sub base, glue it and use it under sub
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post #16 of 32 Old 06-21-08, 01:26 PM
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Re: Isolation platform for subwoofer?

I you don't want to guess what to use to isolate your sub from floor .... just use this https://www.smarthome.com/8257fi.html ... this is used to isolate furniture
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post #17 of 32 Old 06-21-08, 01:49 PM
 
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Re: Isolation platform for subwoofer?

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Are you talking about this??? ... http://www.softtiles.com/content/view/28/39/ ... I think they will be easy to use; just cut the same size as the sub base, glue it and use it under sub
No, I am referring to a comfort mat such as this. The material you linked seems to be too dense to properly decouple a subwoofer.

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I you don't want to guess what to use to isolate your sub from floor .... just use this https://www.smarthome.com/8257fi.html ... this is used to isolate furniture
Typical rubber compounds such as this are also too dense to properly decouple a subwoofer. This density along side a low mass will allow for easy transmission of energy.

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post #18 of 32 Old 06-21-08, 02:08 PM
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Re: Isolation platform for subwoofer?

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... Typical rubber compounds such as this are also too dense to properly decouple a subwoofer. This density along side a low mass will allow for easy transmission of energy.
So, you mean that when using this under the furniture legs to isolate from the floor when using a buttkicker ... it will still transfer the energy (effect) to the floors??? ... I thought that this help to keep the shake in the seat and don't transfer to floor

Or is just when using a 30lb sub that doesn't work???
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post #19 of 32 Old 06-21-08, 02:22 PM
 
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Re: Isolation platform for subwoofer?

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salvasol wrote: View Post
So, you mean that when using this under the furniture legs to isolate from the floor when using a buttkicker ... it will still transfer the energy (effect) to the floors??? ... I thought that this help to keep the shake in the seat and don't transfer to floor

Or is just when using a 30lb sub that doesn't work???
Yes, this is the same as saying little rubber feet on the bottom of a subwoofer will effectively decouple it from the surface it sits on. This is simply untrue as physics does not allow for it.

I guess it is important to remind everyone that just because a product is advertised to do something does not mean it will.

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post #20 of 32 Old 06-21-08, 10:39 PM
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Re: Isolation platform for subwoofer?

I lost the chance at an Auralex Gramma on ebay, and decided to buy one online. It's great. I hear the explosions rather than the room rattling. It has almost exactly the same length and width as my Hsu sub. You almost don't even know it's there.

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