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Folks,

Does anyone use an isolation platform for their sub, like an Auralex Great Gramma? Pros and cons?

Thanks,

deadhead
 

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I'm using the Great Gramma with an SVS PB12-Plus/2 which was sitting on a wooden floor. IMO it sounds better with the platform but it's not something that I can measure.

Bob
 

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Items such as these decouple the subwoofer from the floor minimizing resonance that occurs. These items are even useful on carpet as carpet is not effective in decoupling a subwoofer from the floor due to wavelength size in the bandpass.

If ones goal is achieving maximum fidelity it is essential that the subwoofer be decoupled from the floor. At the same time many people seem to prefer the perceived greater bass, primarily in movies, created by having a subwoofer coupled to the wall, as in IB, or floor, as is more typical, due to the resonances created and felt in the form of excess vibration.
 

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so-decoupling, but how? on a box? concrete blocks? how high? your insights are appreciated.
walt / yacht422
The easiest way to decouple a subwoofer would be using a product such as the one asked about in the original post, the Auralex Gramma pad. The pad is essentially a piece of carpeted hardboard with a few inches of stiff latex foam that will not compress greatly with weight. While this foam is stiff, it is not stiff enough to actually transmit energy from the subwoofer to the surface it is placed on so it is decoupled.
 

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andrew: thx for the advice. most of the sound "stuff" is still smoke and mirrors to me - some good info, some advertising hype, some truly essential items. as this is my 1st h/t, i'm reading and asking everywhere/one!
again, my appreciation
walt
 

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andrew: thx for the advice. most of the sound "stuff" is still smoke and mirrors to me - some good info, some advertising hype, some truly essential items. as this is my 1st h/t, i'm reading and asking everywhere/one!
again, my appreciation
walt
Start with concrete blocks and a carpet sample ($4 investment). If you hear a difference, then you can plan on spending more on the real thing down the road.
 

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walt here: i am in fl., nd the floor is 6" poured concrete, padding, carpeting.
so - - - what are the advantages of decoupling? is it sonic, or viseral?
thx
walt
 

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Start with concrete blocks and a carpet sample ($4 investment). If you hear a difference, then you can plan on spending more on the real thing down the road.
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.

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. Then either place these feet on the bottom of the subwoofer or for a more stable approach glue the foam feet to a piece of hardwood and place the subwoofer on it. Alternatively, one could purchase foam online and build a decoupling unit fairly easily that could look far more professional and nicer than the Auralex offerings.
 

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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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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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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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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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... 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 :yes:
 

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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 :yes:
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.

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 :bigsmile:
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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... 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 :dontknow:

Or is just when using a 30lb sub that doesn't work??? :scratchhead:
 

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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 :dontknow:

Or is just when using a 30lb sub that doesn't work??? :scratchhead:
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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Discussion Starter #20
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.

deadhead
 
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