polyfill

Hi again,

I have 2 12" Infinity Reference subs, and I'm going with the ported enclosure built to the dimensions that Infinity specifies.  It asks for one-inch polyfill lining on all walls except the one with the subs... Anyways, I was wondering where I can get this lining, how much I should expect to pay for it, and whether or not it's really worth it?  All opinions and suggestions welcome! Thanks guys.

--mindctrl

I suggest you NEVER use fiberglass, if what you mean is the sort of fiberglass used as house insulation.  This stuff will shed fibers which can get caught in your drivers between the voice coil and the magnet assembly and can FRY your speakers.  Don't use it. 

I am, by the way, an "old school" guy! 

1 lb of good quality polyfill adds about 10% to the apparent volume of an enclosure.  So a 1 cuft sealed enclosure with 1 lb polyfill acts like 1.1 cuft of air space.  I have always used 1 lb per 1 cuft as my standard, but some people (and some loudspeaker manufacturers) recomend different standards.  It all depends on what you're trying to accomplish.

DYohn] wrote:

---

p>I suggest you NEVER use fiberglass, if what you mean is the sort of fiberglass used as house insulation.  This stuff will shed fibers which can get caught in your drivers between the voice coil and the magnet assembly and can FRY your speakers.  Don't use it. 

I am, by the way, an "old school" guy! 

---

Just so you know fiberglass is not a conductive material.  I have never heard of it frying a sub.  If you look in some of the older commercially built enclosures they did used to use fiberglass.  A good example is sound equipment used for concerts and such which is built by the same company that makes infinity and Jbl.

You are right, it will not fry a sub due to electrical conduction.  It will fry it because of mechanical interference with VC movement.  I have seen it happen, more than once.  Professional sound reinforcement cabinets did use fiberglass for a time in the 70's, you are correct.  But I have spent hours replacing some of those drivers (from companies like Harbinger and Community) and indeed, there was ALWAYS fiberglass imbedded in the VC.  In an auto subwoofer application, with much smaller (generally) enclosures and high heat and SPL inside the cabinets, the problem is worse.

BTW, Infinity and JBL are both now owned by the Harmon International Group, but they are designed and manufactured in entirely seperate facilities.

Fiberglas tends to easily break into small, almost microscopic splinters.  That's why it gets under your skin and makes you itch.  Polyfil is a longer, less brittle fiber (usually Dacron), so it doesn't break off and go floating around inside the box.

Scott

Oh, I don't have any personal evidence that Fiberglas DOES cause a problem.  I'm like you, I've always used Dacron Polyfil.  I just figured if Fiberglas causes a problem, that would be why.

Scott

You say that using Acustastuff (and other products) make the speaker think its in a larger enclosure.  My question is how to make a larger enclosure smaller?

I built/ am building 2 fiberglass enclosures for 2 12in kicker comp XPL's and I think they are larger than necessary. 

any help is appreciated

Thanks for all your input, guys!  Now, instead of stuffing(polyfill), can somebody suggest a good LINING? Like something I could glue to the walls of the enclosure... The idea of sticking something into my box that would potentially touch one of the magnets bothers me... Call me crazy but it just doesn't sound like the best idea in the book.

Any suggestions?

--mindctrl

Polyfill is also available in the form of "quilt batting".  Any fabric shop should have it.  It's a roll of polyfill-type material that's maybe 1/2-3/4" thick, meant to be sewn between two sheets of fabric to make a quilt.  You could glue or staple it to the inside walls of your box, where it wouldn't come close your speakers.

Scott Gardner