Im building a box for behind the seat of my standard cab, i cant quite get the reccomended volume my subs say they need, The box says they need 1.25 cubic feet to opperate at there prime, the biggest box i could design is only 1.00 cubic feet... so my question is if i fill the box with polyfill, does that stuff make the sub think that the box is bigger than it really is?? in otherwords will filling the box with polyfill make the box better than just leaving it empty (space wise).... its a sealed box. Thanks
yes polyfill works wunders ,i bag is usually 1 c.f it does work ,but remeber you need to take the wood thickness ,and speaker displacement into factor too, most subs have the specs on the papers ,boxes ,or the net hope it helps
To answer your question, polyfill does in fact make the box seem larger than it is by slowing down the air waves inside the box. General advise says 1lb per current cubic but to really gain an exact amount of volume you need to adjust how much you put in. The tables goes as:
Adding polyfill also helps dissipate heat and eliminates standing waves in some box shapes. Generally polyfill is regarded as a good thing, just don't overdo it. Too much can become a bad thing.
Most people don't use loose unbound polyfill due to the fact it comes out of the port. Some people do use carpet, really thin wall insulation, dynamat, almost anything that can be stapled to the back interior wall to reduce standing waves but (correct me if I'm wrong) usually isn't used to fool the sub into thinking it's a larger box.
You are basicly insulating the box. so it keeps more heat in, and imo wouldn't it also deaden the sound? And it would actually reduce the size of the box.
no it wouldnt make sense to use polyfill on ported enclosures ,because you have a port to tune the box ,thats what your trying to do with the polyfill in a sealed enclosure ,tune it .if not you wouldnt really be worried about air space
Yes, you are "technically" insulating the box, but it doesn't work that way. Loose polyfill doesn't muffle/deaden the sound because bass is non-directional unlike smaller speakers. Placing polyfill in front of a midrange or tweeter speaker would in fact deaden it because those smaller waves are affected by mass. Ever noticed how you can tell where a tweeter is placed but you have trouble locating a properly tuned sub? That's how people with cars put subs in the trunk and it sound like the sub is up front. Low frequencies are not affected by mass in front/behind.
It works to enlarge the volume by slowing down the sound waves. The mass of polyfill impedes the sound wave making it take longer to reach the wall of the box, just like a larger box would act.