I am building a few custom sub boxes for myself and some friends. I am using mdf board and plan on making a few different sizes. My question is, what is polyfill? i have heard some people talk about having the inside lined with polyfill but i have no idea what it is. is it a spray on insulation of some type. Can somebody please tell me what it is, if it helps and where i could get it in canada.

 

Its kinda like what pillows are made of. If i am not mistaken it makes the box seem bigger than it is. For the sub at least.

 

it changes the acoustics of the box to make the box "seem" bigger, you can play around with it to see how much you want for your sound.

Using Polyfill in a Custom Subwoofer Box | Klaus Audio

 

polyfill should be able to be found at any walmart or hobby store

but its uses are up in the air to be honest. it really only makes a difference if ur box is way too small. if u build a custom box the right size then no polyfill should be necessary