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View Full Version : Polyfill still a good idea?



maylar
02-11-2012, 06:00 PM
It seems that conventional wisdom and standard practices have changed over the years, and I'm wondering if adding some polyfill to a sub enclosure is still common practice, or if it's been deemed a waste of time.

So, for you box builders... use polyfill all the time, never, special occasions? What say you?

Thanks

wenn_du_weinst
02-11-2012, 06:06 PM
Good luck getting a definite answer on this on. The best answer for it is, "sometimes"

I do feel it is useful, but not for the reason most people think it's used for.

SikFly
02-11-2012, 06:25 PM
i still use it, as i typically go with the smallest box i can get away with, don't really care what others do.

bubbagumper6
02-11-2012, 07:38 PM
Probably more of a personal preference then anything. I used it in my HT sub build just because it was a pretty small enclosure and I wanted to try and get some better low end. I say just try it both ways and go with the way that sounds the best to you. It's not like it's costly or difficult to install/remove.

neonblack
02-11-2012, 07:48 PM
For sealed enclosure (especially leaning towards < nominal size) use loose fill (not packed) and experiment with the amount until you get the sub response you want. Fill absorbs some of standing waves inside box dampening/reducing some air pressure so it will disturb the motion of the subwoofer less than if no fill was used. Some manufacturers say to use fill in vented enclosures, as well. I've seen lots of ported home audio speakers (B&W, JBL, Polk) that are stuffed with fill.

bubbagumper6
02-11-2012, 07:54 PM
For sealed enclosure (especially leaning towards < nominal size) use loose fill (not packed) and experiment with the amount until you get the sub response you want. Fill absorbs some of standing waves inside box dampening/reducing some air pressure so it will disturb the motion of the subwoofer less than if no fill was used. Some manufacturers say to use fill in vented enclosures, as well. I've seen lots of ported home audio speakers (B&W, JBL, Polk) that are stuffed with fill.

It tricks the subwoofer into seeing a larger enclosure volume and can lower tuning in a ported enclosure.

neonblack
02-12-2012, 12:28 PM
There's more Physics than Tricks involved. The sub doesn't "see" a larger enclosure. The idea is to absorb air pressure so the subwoofer is not disturbed and can then move correctly (the way it was designed to move) when signals are sent to it. That's why audio drivers are tested in acoustic chambers - so standing/reflecting waves interrupt the movement of the driver as little as possible.