In regards to polyfill; I was told if you are trying to add volume (virtual volume I suppose) then you should fill the enclosure with it. The driver should be sitting on a pillow of polyfill. This sounds correct as you are attempting to increase the time the sound wave take to travel from the driver to the rear wall and back again.

Would any experts like to chime in on this one?

Thanks

 

polyfill = insulator

you don't want any motor to be insulated so keep polyfill from contacting the back of the woofer !!!!

the fill transfers mechanical energy into heat through motion and friction.... relativly low Q subs will be affected to a greater extent then high Q woofers... a pound per foot is the general rule of thumb... keep in mind that we are actually making the box smaller and there is a point of diminishing if not negative return... also high freq energy is attenuated the most so while with subs playing <100hz you may have minimal affect; but the box resonance caused by distortion may be reduced !!!

 

go to this link and read it. lots of information there.

http://web.archive.org/web/20020808224043/integra.cyberglobe.net/caraudio/resources/fiberfill/