is it nessesary to use foam/insulation when building a subwoofer box?

i am building a bandpass subwoofer box for my car and i am wondering if it is nessesary to use foam/insulation to deaden the sound. i usually use it when i build speaker boxes but i dont know if subwoofer frequencies will resonate like mid and high ones do. in case your wondering i have 2 800 watt 12 in (generic brand) subwoofers im putting in it for now anyway.

insulation or polyfill is normally used in sealed boxes that are smaller than the manufacturer of the sub recommends. The reason we use it is to diffuse the backwaves so that the soundwaves don’t bounce back off the inside of the box and hit the back of the speaker cone. When this happens it causes the cone to vibrate and distorts or partially cancels out the sound.
If the sealed side of your bandpass box is smaller than the recommended size for the sub, filling the sealed side will help. I never use polyfill in ported boxes, it is not necessary.

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2 Responses to “ is it nessesary to use foam/insulation when building a subwoofer box? ”

1. granpajoel says:

   July 11, 2009 at 6:03 pm

   no you will be good
   References :
2. cplkittle says:

   July 11, 2009 at 6:21 pm

   insulation or polyfill is normally used in sealed boxes that are smaller than the manufacturer of the sub recommends. The reason we use it is to diffuse the backwaves so that the soundwaves don’t bounce back off the inside of the box and hit the back of the speaker cone. When this happens it causes the cone to vibrate and distorts or partially cancels out the sound.
   If the sealed side of your bandpass box is smaller than the recommended size for the sub, filling the sealed side will help. I never use polyfill in ported boxes, it is not necessary.
   References :