Polyfill.....proper usage?????
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Joined: Aug 2009
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From: IL
Polyfill.....proper usage?????
Here is a general question on the use of polyfill.
What's the best usage....when airspace is tight?....or is it more of shape of the box itself? If it's for small airspace boxes, what does it exactly do, or what is the theory behind it.
My Alpine TypeR that's in my mustang gave general box dimesions that would work good for the sub, and it also said to use a small layer of polyfill on the back wall of the enclosure. That it would reduce resonance if I remember corectly.
I'm building a box for two 8" in my Screw and the air space is going to be right on the low side for the recomended sealed enclosure. I was wondering if or how much fill I should use, and what the sound differences would be with and without?
What's the best usage....when airspace is tight?....or is it more of shape of the box itself? If it's for small airspace boxes, what does it exactly do, or what is the theory behind it.
My Alpine TypeR that's in my mustang gave general box dimesions that would work good for the sub, and it also said to use a small layer of polyfill on the back wall of the enclosure. That it would reduce resonance if I remember corectly.
I'm building a box for two 8" in my Screw and the air space is going to be right on the low side for the recomended sealed enclosure. I was wondering if or how much fill I should use, and what the sound differences would be with and without?
Senior Member
Joined: Oct 2010
Posts: 327
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From: Austin, Tx
When I did research on using polyfill it said to use 1 lb of poly for every 1 cube of airspace.
I should make the subs thing the box is bigger. Has to do with the fibers of the polyfill and how they react and change the thermodynamics in the box.
I should make the subs thing the box is bigger. Has to do with the fibers of the polyfill and how they react and change the thermodynamics in the box.
Technical Article Contributor
Joined: Aug 2006
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From: Northern California
Thermodynamics? lol Lang thermodynamics is heat related.
What polyfill does is slow the sound wave coming off the back of the speaker. Slower sound waves means more time for them to hit the inside edge of the box and come back to the speaker (in a sealed enclosure). This makes the box perform like a slightly larger box which results in better low frequency extension.
When should you use it? IMO anytime you use a sealed enclosure you should use poly fill, it can't hurt. And yes about 1 pound of fill per cubic foot. Hell when i popped open the stock Ford sub enclosure it had poly fill in it.
What polyfill does is slow the sound wave coming off the back of the speaker. Slower sound waves means more time for them to hit the inside edge of the box and come back to the speaker (in a sealed enclosure). This makes the box perform like a slightly larger box which results in better low frequency extension.
When should you use it? IMO anytime you use a sealed enclosure you should use poly fill, it can't hurt. And yes about 1 pound of fill per cubic foot. Hell when i popped open the stock Ford sub enclosure it had poly fill in it.
Senior Member
Joined: Oct 2010
Posts: 327
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From: Austin, Tx
Hey now, I was being serious about the thermodynamic part. 
This is all a product of having a mind with way to much empty space to fill up.
http://www.soundsolutionsaudio.com/f...g-of-polyfill/
Stuffing a box with polyfill makes it seem larger and it all relates to thermodynamics. When polyfill is added to an enclosure, it changes the behaviour of the airspring in the enclosure from "adiabatic" to "isothermal". The term "adiabatic" implies that there is no heat transfer occurring. An isothermal process occurs once the polyfill has been added. As the air passes through the polyfill, the fibers wiggle and cause some of the energy created by the airspring to be dissipated as heat. This heats the surrounding air molecules warmer, causing the air to become less dense. Being that sound passes easier through a denser medium, the speaker interacts with your enclosure as if it is larger than it actually is. The effective increase in enclosure size can be as much as 40%!
This is all a product of having a mind with way to much empty space to fill up.
http://www.soundsolutionsaudio.com/f...g-of-polyfill/
Stuffing a box with polyfill makes it seem larger and it all relates to thermodynamics. When polyfill is added to an enclosure, it changes the behaviour of the airspring in the enclosure from "adiabatic" to "isothermal". The term "adiabatic" implies that there is no heat transfer occurring. An isothermal process occurs once the polyfill has been added. As the air passes through the polyfill, the fibers wiggle and cause some of the energy created by the airspring to be dissipated as heat. This heats the surrounding air molecules warmer, causing the air to become less dense. Being that sound passes easier through a denser medium, the speaker interacts with your enclosure as if it is larger than it actually is. The effective increase in enclosure size can be as much as 40%!