Polly-fill and active subs... (1 Viewer)

[Jeff_LIII]

I currently have two JBL S120Pii subs and while i'm pretty satisfied with their performance, i can't help but want to tweak a bit. I'm not big on DIY with regards to speakers so bear with me if this is a stupid question: Can i stuff polly-fill into the enclosure of an active subwoofer? The frequency reponse on these goes to 22hz and i want to squeeze out a few more (mmmmmm...sub harmonic bass...) If i can't fill it, is there anything else i can do? Any advice would be wonderful.

 

[Dustin B]

There's not a lot you can do to tweak a commercial sub like that. When you stuff an enclosure with polyfill you are making it look bigger to the driver and port. When the enclosure looks bigger the frequency the port is tuned to will go down a bit and the sub will sound a little tighter. So if you want go ahead and try it.

Figure out the internal volume of the enclosure and then add 1-1.5 lbs of polyfill for every cubic foot. This will make the enclosure seem 20-30 percent larger to the driver and port. Just make sure you don't let the polyfill get to compact anywhere, and try and keep the opening of the port inside the enclosure as clear as possible. Gonna be difficult as 1.5lbs per cubic foot is a lot of polyfill.

 

[Jeff Hoak]

Jeff_LIII

I have the same JBL sub (only 1 though). As an experiment I picked up a 20 oz. bag of polyfill from the local Wal-Mart and stuffed the whole bag in the sub.

A very noticeable improvement in the overall "tightness" of the bass. Seems to be a lot less "ringing" on some notes. I alwasy felt like the decay of some tones wasn't quite right with that sub. The polyfill fixed it.

Probably the best $2.69 I've ever spent.

 

[Jeff_LIII]

I'm glad to hear that someone else has done this with the same sub. My main complaint is that yeah it does seem to be kinda loose sometimes-plenty of ooomph, just needs some cleaning up. My only concern is with it overheating-did you or do you have any problems? Also, did you just stuff it through the port or did you remove the woofer to fill the enclosure?

 

[Dustin B]

You'll have to remove the driver or amp. I don't think you could do a proper job trying to jam it in through the port.

 

[Geoff L]

I would remove the driver (very carefully) and stuff it.
Fluff the polyfill up a bit. Going threw the driver opening will allow you to see the transformer on the amp and the end of the port.
Those are the 2 areas you want to try and keep the fill away from. The port can suck the fill up and blow it out at higher spl levels. And fill laying on the transformer is just not a good idea.
If you have a spl meter and test disc, measure your freq response before stuffing and after. Just don't change anything between the tests. Receiver volume knob, bass level in the receiver, sub crossover or sub amps volume pot, etc. Will allow you to see what kinda of changes are happening. Not a perfect test but will give you a good idea of what happened. Your ears are most important, but validation of what you think you hear is always fun.
Best of luck
Geoff
Edit:
Dustin beat me to it as usual

 

[Brian Bunge]

I wouldn't worry too much about the polyfil coming into contact with the transformer. Polyfil is not flammable. I've built several subs with plate amps that are open to the inside of the enclosure and stuffed them with plenty of polyfil. Definitely keep it away from the port opening though.

Brian

 

[Dan Pawlowski]

ahhhhhh stuff it

 

[Jeff Hoak]

I was concerned about heat too. When I got the driver out all of my worries ended. The amp is totally enclosed inside the cabinet. It has a plastic cover over it the keeps the polyfill from coming in contact with any of the electronic components.

I also figured that the connecting wires to the drive would be very light. I was right. I had planned to replace them with some heavier wire during the stuffing project. As it turned out, with the amp cover in place I couldn't change the wires without tearing the amp out as well. At the moment I didn't have the time to dig THAT deeply into the sub so the re-wire project got abandoned. Not that I expect it to have any real effect at all but it certainly can't hurt.

Yet another project for another time...