Do Sub Stands make a difference?

I also have a pair of jl f113 subs. I've considered getting these Primacoustic recoil stabilizers.
Primacoustic Acoustic Solutions

the rx20 is rated to 140lbs. The JL is 115lbs.
http://www.primacoustic.com/recoil-specs.htm

These look like they are engineered well. They have a thick steal plate on top and some kind of thick soft material below the plate. They are also not that high off the ground.

I do think it should be easy to measure the sub's impulse with and without in REW. Even though it's a big hump, there should be some kind of difference. Whether it's an improvement, I dunno.
 
dallasjustice said:
The sub should be closer to the floor. The further off the floor it gets, the more likely you will get a "floor bounce"; SBIR cancellation from floor. Of course, it all depends on how far the sub is from seated position. But as a general rule, bass drivers should be closer to the floor.
Click to expand...
Aka, the Allison Effect.
 
Face said:
Aka, the Allison Effect.
Click to expand...

I would argue that it would depend on the room boundary type and volume level. There is no Allison Effect on a raised timber floor but there is on a concrete slab. Nothwithstanding, the F113 has room equalisation and phase control which would go along way to negate any significant Allison cancellation.
 
I need a better handle on what this Allison Effect is. I'm on a concrete slab.
QUOTE=Steve;134906]I would argue that it would depend on the room boundary type and volume level. There is no Allison Effect on a raised timber floor but there is on a concrete slab. Nothwithstanding, the F113 has room equalisation and phase control which would go along way to negate any significant Allison cancellation.[/QUOTE]
 
Allison Effect is not affected by stands?
The Allison Effect will take place with or without stands?
I'm on a concrete slab.
 
OK I'll have a stab... It will still take place regardless but I believe that raising the sub off a concrete slab would help especially at lower volume levels.

There is less of an Allison Effect with a sub on stands on a raised timber floor given an air space underneath.

It depends on the amplitude of the low frequency sound wave. Lower frequency travels further and through objects more easily, the amount of reflection depends on the modulated frequency and the density of the object in the path.

The degree of diffraction and reflection will depend on the empty (air) space (including underneath) eg. a raised timber floor before the next (denser) object is hit.

You will definitely get more reflection/diffraction on a concrete slab because of the concrete's greater damping coefficient. Although sound can still travel through it and the earth and annoy your neighbours next door if your sub is pushing huge waveforms.
 
The formula is explained here:
What is Speaker Boundary Interference? - Acoustic Frontiers

Generally, the closer the speaker is to the boundary, the higher the cancellation frequency. In the case of a sub, when its on the floor, the cancellation frequency is a non-issue. Of course, one needs to know seated position too. But in almost all setups this is true.

IOW, the further off the floor the sub gets, the lower the cancellation frequency. The only way to know for sure is to use the above formula.

Wood, Concrete and Sheetrock all reflect low frequencies. Of course, concrete is the most effective. But any solid barrier will reflect low frequencies.
 
dallasjustice said:
The formula is explained here:
What is Speaker Boundary Interference? - Acoustic Frontie

Generally, the closer the speaker is to the boundary, the higher the cancellation frequency. In the case of a sub, when its on the floor, the cancellation frequency is a non-issue. Of course, one needs to know seated position too. But in almost all setups this is true.

IOW, the further off the floor the sub gets, the lower the cancellation frequency. The only way to know for sure is to use the above formula.

Wood, Concrete and Sheetrock all reflect low frequencies. Of course, concrete is the most effective. But any solid barrier will reflect low frequencies.
Click to expand...


Sorry to like such a layman.
further off the floor the sub gets, the lower the cancellation frequency
I would have thought you want the cancellation frequency. IOW does that mean if the sub is off floor you get more cancellation? Or earlier cancellation?
 
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