Polyfill in subwoofer enclosures


hoodlegend
02-21-2006, 04:30 AM
Can anyone please tell me how much polyfill should be used per cubic feet. Ive been lookin all over for an answer for that. can u please help me out.

thank you

bumpinstang77
02-21-2006, 08:37 AM
Any amount from fully stuffed to just lined. The more you add the SLIGHTLY larger the enclosure will seem.

Jet-Lee
02-21-2006, 10:08 AM
If you add 1lb of poly fill for every cubic foot of space, your subwoofer will act like the box is 1/3 bigger.

1ft^3 + 1lb polyfill = 1.33ft^3 that the speaker "see's"
3ft^3 + 3lbs polyfill = 4ft^3 that the speaker "see's"

Make sense?

OffRoadSonoma
02-21-2006, 02:07 PM
So if I put 3 lbs of poly fill into a 1ft^3 box would the speaker act like it was in a 2ft^3 box? or even if I went big and used a 4ft^3box with 8 lbs of poly fill. Would the speaker think it was in a 6.66ft^3 box? Or can you only put 1 lb of poly fill per ^3??

Jet-Lee
02-21-2006, 04:37 PM
So if I put 3 lbs of poly fill into a 1ft^3 box would the speaker act like it was in a 2ft^3 box? or even if I went big and used a 4ft^3box with 8 lbs of poly fill. Would the speaker think it was in a 6.66ft^3 box? Or can you only put 1 lb of poly fill per ^3??
In theory, that's how it works. But IIRC, I read somewhere that putting 2lb/ft is more like 100% gain, instead of 66%.

If you were to graph the effectiveness vs. amount it would look more like a geometric curve than a linear line, if that makes any sense.

I think that's right.

I know the 1lb/ft = 33%+ is correct though.

skyice
09-29-2009, 11:21 PM
1 lb. of pollyfil to 1 cu. ft. box size.
Pollyfil tricks your sub into thinking it's in a bigger box by about 30%.
What this process really does is highers your Q.

Qtc - value for the damping provided for a driver in a sealed enclosure. Denotes the enclosures ability to
control the driver response at resonance. Qtc = 0.707 is the optimum value for sealed enclosures, providing
flattest response and highest SPL for deep bass extension. Enclosures for this value are often rather large.
Lower Qtc can give even better transient response, down to a Qtc of 0.577 for the best damping and
transients, but the enclosure is usually huge and SPL's are down. A Qtc of 1.0 is a compromise between deep
bass and transient response vs. smaller sized enclosure. Larger subs can go with an even higher Qtc, as their
resonant frequency is often very low, but Qtc's above 1.5 can begin to sound very muddled and boomy, and
sacrifice deep bass extension and transient response for enhanced mid-bass peaks (louder).

I have a 3 cu. ft. sealed box with 12 in. subs in it. The inner volume of the box is slightly smaller because of the space the magnet of the subs take up. I added about 2.7 lbs. of pollyfil on all sides of the box. I notice a tighter bass sound. I don't know why, but this process caused my subs to hit way harder at a much lower amp gain. Before the polyfil my amp gain was turned up 3/4's the way, almost full power from the amp. Now that the polyfil is in I have to put my gain at less than half. I guess the positive side of this, is my amp only pushes half the wattage to slam the same bass as it did before. I may have gained a db. or 2 louder. It gave me more of a tight mid bass sound that is clean, rather than boomy.

PaulD
09-30-2009, 05:18 PM
this thread is 3 years old, the people no longert even post here

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