stuffing a sealed box

[suparunna2000 10+ year member]

what is the purpose of putting stuffing in a sealed box?

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[Excalibur0428 10+ year member]

i think to get rid of standing waves inside the box.

 

[newusername 10+ year member]

Something I posted on SSA:

Adding polyfill changes the box interior from a condition called adiabatic to isothermal; the energy that is normally stored in the air spring in the box is converted into heat and disappears from the system. The air pushes less on the speaker, the speaker "thinks" the box must be larger, and lowers the 'Q' of the enclosure. This will extend low end frequency response, as well as increase excursion and efficiency as well.
The debatable area always comes in when discussing standing waves. Firstly, the fundamental frequency typical of sub bass is so large in length that it is impossible to create a standing wave in 99.9% enclosures (over 28 feet long at 40hz). However, there is distortion present in all speakers (from a variety of causes: BL, Cms, and Inductance non-linearities are big ones) which presents higher harmonics in your frequency response. These harmonics could be small enough that standing waves would be diminished, but the effect would be extremely small and only appreciable with a driver that is absolutely terrible (ie. 5th order harmonic distortion or higher). As such, it is most appropriate and most noticeable in a midrange or full range enclosure.

All in all, polyfill can certainly be helpful. The worst thing you can do is not give it a chance.

 

[suparunna2000 10+ year member]

so then why not just buy a bigger box? the speakers "optimal" box size is .65 ft^3. My boxes are closer to 1.25. any suggestions?

 

[GrnEydDvl 10+ year member]

so then why not just buy a bigger box? the speakers "optimal" box size is .65 ft^3. My boxes are closer to 1.25. any suggestions?

Displace volume in your oversized box with wood blocks until you get down close to .65 cu ft. Or build a smaller box.

 

[JimJ 5,000+ posts]

Sometimes it's impractical to make a bigger enclosure to fit the space, other times you just want to experiment with a slightly lower Qtc alignment...

 

[ultimate157 5,000+ posts]

so then why not just buy a bigger box? the speakers "optimal" box size is .65 ft^3. My boxes are closer to 1.25. any suggestions?

For one case, Polyfill is great for people with limited space. Adding polyfill can improve the low end of a driver with an undersized box.

 

[suparunna2000 10+ year member]

eh, i will prolly just leave that sh1t. its only temporary anyway, it's not gonna make that much difference to my ears im sure.