will this help?

[TWF 10+ year member]

I have 2 15s hitting 145.6 legal and i was told that i can put polyfill in the box and it would improve it. Is this true? the boxes are sealed ~2 cubes

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[Immacomputer 10+ year member]

Polyfil almost never makes an enclosure louder. It will usually flatten and smooth out the response.

If you want louder, make the sealed enclosures smaller and throw more power at them. That is, if you don't have room for a ported enclosure. The smaller sealed enclosure will be louder at a peak but will not have the same low end as the larger sealed.