# stuffing or lining?



## apilon (May 18, 2006)

Good morning all ,

I noticed that most of the time when you look at project DIY speakers, thre are instructions for the xover, some for cabinet assembly , sometmes they specify if the speaker need to be recessed or not but rearely there is indication about either stuffing or lining the interior or both. 

So in the absence of indication how t you determine if you need to stuff the cabinet with polyfill or just lining the walls with foam? And how do you determine the thickness of the foam to be applied or the amount of stuffing required?

Alain 
DIY NEWBIE


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## Guest (Feb 19, 2011)

Good foam products like sonic barrier are suppose to help with standing waves from behind the cone and keep them from bouncing back and hitting the back of the speaker cone. I've used sonic barrier and thick carpet padding. In general, it can only help for mid range and maybe mid bass. I've read fiberglass is better for a sub.

Polly-fill might help out just a tad with standing waves, but really, it's used to improve bass and simulate a larger box. Not sure on the exact amount, but it should be loose and never packed and not blocking ports.


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## Zeitgeist (Apr 4, 2009)

I think that the subwoofer logic of lined (acoustical fiberglass or foam) for a ported speaker and filling for a sealed speaker is probably a fair rule of thumb. I used 1lb/cuft of polyfil for the last sealed speaker I built.

Any of the manufactured speakers that I've seen are normally lined... I imagine that most aren't filled because of the cost..

The lining/stuffing is probably less important for speaker builds though.


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## markbakk (Feb 27, 2011)

A subwoofer enclosure that is used for low frequency reproduction only (and has according filtering applied) doesn't require any sort of filling really. You only need to dampen standing waves when they can exist in an enclosure. The lowest frequency is given by the biggest internal cabinet size: that equals half the wavelength of the lowest frequency that can cause you any problems.


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