Poly-Fil box stuffing?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=62288
Printed Date: April 28, 2024 at 10:20 AM
Topic: Poly-Fil box stuffing?
Posted By: glacious
Subject: Poly-Fil box stuffing?
Date Posted: September 06, 2005 at 3:29 PM
I recently constreucted a new box out of 3/4 MDF for my Rockford Fosgate Stage One Subs. I built it to the best of the specs the sub required, and I guess it turned out good. It hits a whole lot harder than my old box, but then a friend of mine told me that if i stuffed it with some filling, that it would help it to hit harder. I found some stuff called Poly Fil and at 13 dollars a pound, I am not sure if it is really worth it. I mean I have a Rockford Fosgate P5002 pushing them, and I just think that they can't handle the power. Not to mention that I added a Power Cap as well, and well I don't think that the filling would help much or would it?? That is my question. I am also considering maybe upstaging to the Stage 2's which really don't handle that much more power, but maybe that is my problem. Bottom line is, my system hits, but not to my xpectations, so should I use some filling in the box or should I just get the Stage 2's. Thanks for the help...
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JP
Replies:
Posted By: geepherder
Date Posted: September 06, 2005 at 5:15 PM
Check to see if Rockford recommends using stuffing. Some manufacturers do- JL, for example. Basically what stuffing does, is slow down the air that's moving inside the box, to simulate a larger volume (bigger box).
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My ex once told me I have a perfect face for radio.
Posted By: redpeppers
Date Posted: September 07, 2005 at 12:00 AM
poly fil is only need it box is too big or too small for subs spec.
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Where theres is a wire there's a way.
Posted By: stevdart
Date Posted: September 07, 2005 at 7:24 AM
redpeppers, I like your sig line :) But if the box is too BIG how is polyfil going to benefit? If it's too big one should physically reduce the volume with a solid fill like a brick or a block of wood, or another interior baffle, or more bracing. If it's too small by more than 10% of the RANGE of volume needeed for the woofer to perform properly, the box should be rebuilt. But, as long as the box volume is in the proper range, polyfil can be used to enhance the quality of the tone. It is easily removed if the results aren't satisfactory...
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: placid warrior
Date Posted: September 07, 2005 at 7:15 PM
geepherder wrote:
Basically what stuffing does, is slow down the air that's moving inside the box, to simulate a larger volume (bigger box).
Allright...can someone PLEASE clarify what the fill does! Origionally this is what i was telling people too, makes sense....but another topic which had a link where some guy used an MLSSA analyzer to measure impedence of 3 different enclosures stated that "the air inside your enclosure actually heats up as your woofer moves, making the air stiffer. When the enclosure is stuffed with fiber, the fibers wiggle, dissapating some of the heat and making the system work as though the box were larger"
Posted By: Poormanq45
Date Posted: September 07, 2005 at 9:35 PM
[;acid: Of course the air is going to heat up. There's usually a few hundRED / thousand watts going through a voice coil, which is like 1~2% efficient. ~98% of that electricity is going directly to heat.
Now, about the poly fil wiggling: WTF is that guy smoking?
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Posted By: stevdart
Date Posted: September 07, 2005 at 11:12 PM
(Poorman, another doozie!! We're still waiting for your answer to how resistors will lower current flow in THIS TOPIC. The guy's not smoking anything.) placid warrior: both answers are essentially based on the same principle. I first read about the fibers of the polyfil vibrating when I ordered AcoustaStuf and read the paper insert in the package. It told (IIRC) of how these specifically-designed fibers reacted to the air flow in a way more beneficial than regular polyester fill. The reaction was a vibration as the fibers dissipated the energy of the sound waves. Now, this post led me to do a quick search through the Web for more specific information, and so please look at In the first, look at this line: When a sound wave strikes an acoustical material the sound wave causes the fibers or particle makeup of the absorbing material to vibrate. This vibration causes tiny amounts of heat due to the friction and thus sound absorption is accomplished by way of energy to heat conversion. The more fibrous a material is the better the absorption In the second is a description of Isentropic flow (which is way past me but not past some of the others who frequent this forum...) The third is geared more toward my level of intellect and I will point you specifically to the section titled "Friction". In it you'll see that friction causes a liquid (including the gas: air) to slow down when it passes over a rough surface. This should help clear up how polyfil makes a box volume seem larger. The air, indeed, is slowed down because of friction, and the polyfil "wiggles" as it absorbs energy and dissipates it into heat. At least, it clears it up for me! (...glacious - $13 lb for polyfil is high. You should be able to get regular polyfil for $5 or less per lb.)
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: mrmsudawgs
Date Posted: September 08, 2005 at 10:36 AM
Let's keep it simple. Buy some polyfill at Wal-Mart - the stuff they put in pillows - for about $3.00 for a huge bag. Jump in your vehicle and set your volume level to where it is bumping pretty hard. Make a mental note of how every thing sounds - maybe use a meter to take a few db measurements. Now, turn everything off, remove your subs from the enclosure, pack some polyfill in and repeat the test. Notice any difference? If so, good! If not, well - there you have it. :>)
Mike
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2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.
John 3:16
Posted By: DYohn
Date Posted: September 08, 2005 at 11:25 AM
stevdart wrote:
(Poorman, another doozie!! We're still waiting for your answer to how resistors will lower current flow in THIS TOPIC. The guy's not smoking anything.)
I answered that one for you, Steve.  ------------- Support the12volt.com
Posted By: glacious
Date Posted: September 08, 2005 at 5:33 PM
Simple enough I think. The specs for the speakers in a sealed box, are from .75 to 1.25 cubic feet of air. The box I built is about +/- 1.13 cubic feet of air. So I don't think the box is too small. But then again, if it was smaller than the speakers specs. then it would be a nice tight bass. But in this case..it has the boom...boom. Like a loose boom, but not muddy boom. Maybe I just have the wrong size box..LoL. For what its worth, mrmsudawgs, I guess I will just take your advice and try it and see what happens. And thanks to everybody else's opion. I appreciate all the help.. By the way, does anybody have any thing good or bad to say about the Stage Two Subs?? I might just need to upgrade... ------------- JP
Posted By: mrmsudawgs
Date Posted: September 08, 2005 at 6:30 PM
glacious - one more thing...
If your subs are in separate chambers and sealed independently of each other you can simply put polyfil in one sub's enclosure and none in the other. Get your music going then adjust your balance to the left or right to hear the difference.
Better yet, disconnect the left sub then play the music (be careful to cover the bare wires if you disconnect at the enclosure instead of the amp) to see how it sounds. Then reconnect the left and disconnect the right (the one with the poly) and see how that sounds. This method will keep your mids and highs in balance instead of moving them to the left or right side of the vehicle.
Let us know what you find out. Good luck!
Mike
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2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.
John 3:16
Posted By: stevdart
Date Posted: September 08, 2005 at 6:47 PM
DYohn] wrote:
P>I answered that one for you, Steve.
Ha ha, that's classic. And so is kgerry's response.... Can't be improved upon! ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: glacious
Date Posted: September 09, 2005 at 1:43 PM
mrmsudawgs Thanks for the info. I am on a somewhat tight schedule, but maybe next weekend that will be my project. And I will let you know xactly how things came out. On a side note...do you happen to have any sort of xperiance with capacitors?? ------------- JP
Posted By: haemphyst
Date Posted: September 09, 2005 at 2:23 PM
stevdart wrote:
https://www.grc.nasa.gov/WWW/K-12/airplane/isentrop.html
What? You didn't understand all that? Sheesh...  ------------- It all reminds me of something that Moličre once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: mrmsudawgs
Date Posted: September 09, 2005 at 8:59 PM
Capacitors? I know more about them from the engineering/design side than audio applications. I know from several threads in this forum that some of the more knowledgable members do not buy into the hype around caps. I understand why they should work in car audio but I question whether or not they actually do as well as they claim.
Stevdart: please - no isentropic flow calculations I had hoped that I would never see those equations again after I took my professional engineering exam. Yuk! Actually, those equations are for air or water flow through a nozzel or orifice and really do not apply to the "flow" we are discussing. In this case, our "flow" is just air moving inside a sealed enclosure instead of a definate flow from point "A" to point "B" and never returning to point "A". It also assume constant entropy (sort of a measure of chaos of a system) and it assumes the process happens very slowly and is isothermal (no heat loss or gained). Yeah, it gets pretty deep real quick. Dang - now I'm going to have to design a rocket engine nozzel just to expunge these stinking thoughts in my head!! Ha! Ha!
Mike
------------- 2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.
John 3:16
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