How much can pollyfill get me away with....... (1 Viewer)

[Chris Carswell]

I read a great post about it here;
Link Removed
but still have 2 main questions about pollyfill.
1.It is my understanding that you can make the box "seem" larger that it is by stuffing it. Lets say I have a PORTED box that is 5 cu ft. I need it to be 6.25 cu ft. for optium performance but don't I don't want to build a bigger box or have a bigger one in the corner of my house. I could fill it with 5lbs pollyfill (1 lb per cu ft) and will play / seem like a 6.25 cu ft. box correct?
2.Do I port the box according to the 5 cu ft. size or the new 6.25 cu ft size? For example a 4" port would need to be 12" long to be tuned to 21hz in a 5 cu ft. box , where as in a 6.25 cu ft box it would only need to be 9" long. It would seem more logical to use the 6.25 size and go with the 9" port but I though I would run it by the higher powers to be here on the forum
Thanks Guys!!!

 

[Ryan Schnacke]

Not one of the higher powers but my opinion on #2 is that you would calculate port length based on the larger effective box volume. For instance, I took some measurements on the SVS 25-31PC and I estimate its internal volume is about 80L. If I'm generous and use 85L, calculations say it would require a 15.1 inch straight port to hit 25Hz. But the port SVS uses is about 14 inches and flared, so figure 13 inches straight. The difference must be in the filling.

 

[Patrick Sun]

Yup. This happened to me when I stuffed the hell out of my Sunosub III, and dropped the tuning down to around 13Hz (when I was shooting for 16Hz with the existing port length and didn't factor in the extra polyfill).

 

[Chris Carswell]

Cool, Thanks guys