Polyester Fiber Stuffing is an old trick used to trick a sub into thinking that the box is larger than it is. I would recommend adding polyester fiber stuffing to sealed boxes although some ported boxes benefit from adding it. For sealed boxes, using the roll or weave polyester fiber stuffing is recommended. For ported boxes, using the rolled polyester fiber stuffing is recommended as the weave will break apart and escape through the port.

Recommended amount is 1lb of polyester fiber stuffing for every cubic feet

I was extremely skeptical when I ordered this stuffing. I went ahead and did it because it was cheap and the two 10's under the back seat of my chevy truck just didn't sound very good. I had previously had the same two subs and the same amp hooked up in my car in a type 2 trunk box and they were awesome, but in the truck they just weren't very loud and seemed to distort way to easily. I ordered two pounds of this stuffing and it surprised me how big it was when it came in. As I started to stuff my box with it, I thought "man, this is rediculous! There's barely enough room in this box for all this stuffing." But I stuffed it all in because my box is two cubic feet and a pound per cubic foot is recomended. I put the subs back in, and man what a difference! I can turn my system up twice as loud as before with no distortion and much deeper, fuller sounding bass. In addition to being able to up the volume, I was able to turn up the gain considerably on my sub amp. This is the cheapest and one of the best improvements I've ever made to my system.

I originally purchased 2 lbs of this to fill a box that I built that had over 2 cubic feet of volume. Well I didn't hear much of a difference. Then I Took the Polyester Fiber Stuffing out of my box and used it for my friends box that we had cut apart to make it smaller to fit in his camaro. When it was installed in that box....MAN What a BIG difference! It sounded like the subs were getting an extra 75 watts! Anytime you have a small box I suggest the use of Polyester Fiber Stuffing, especially truck boxes.

I bought two pounds for a custom built 52 inch box holding two Kicker Comp 8 icnh subs. I noticed a much smoother and harder hitting bass after I stuffed the two separate chambers. I would recommend this for any custom built box. I think it definitely absorbs the sound waves and my two 8s' now sound better than the two 10's previously had in my truck!

Recently I purchased about 2 lbs to stuff in a 2 cubic foot total, 2 chamber downfire box that was pre-fabricated to fit in my 2000 Dodge Ram. After a side-by-side comparison of two trucks with my (2)Infinity 10" 1030w's & my neighbor's (2)Infinity 12" 1230W's, there is a BIG difference! With the same exact voltage running to our amps, same voltage cd players, same caps, and everything MINE is significantly louder and deeper. Not only does the bass hit harder because of this Polyester Fiber Stuffing, but you can turn the volume up even more without it distorting.
WITHOUT the Polyester Fiber Stuffing the sound from the subwoofer seems to resonate throughout the box and create a hollow effect.
WITH the Polyester Fiber Stuffing the sound from the subwoofer is more precise and more air is able to be pushed through the subwoofer cone, thus able to generate more bass.
Overall, this is a great product & I would recommend this to everyone with a small or truck box.

Once I had my enclosures finished, Type #1 sealed box, one JBL GTO 8" sub per box, .35 cubic foot inside dimension, 200 watts RMS per sub, I put the Polyester Fiber Stuffing in one. I read a review on the website that said the it made a huge difference between a box with and without it, so I had to check it. I took both boxes, (one with polyester fiber stuffing and one without), and hooked the subs up to the amp. in my other vehicle since I had the boxes done before I had my amp. wired up in my Jeep. I hooked up the box filled with polyester fiber stuffing first and cranked it up. The sound produced was a tight, kick in the chest pound. I pulled the wires from it and hooked up the one without the polyester fiber stuffing. The sound wasn't as loud and it was muddy. The sub was vibrating and working WAY too much for what I was getting out of it. The polyester fiber stuffing made a HUGE difference in the sound quality of the sub. If I could give this a rating higher than 5 I would. It made that much of a difference.

This makes bass really nice and crisp. Would recommend anyone to buy

After replacing my entire Bose premium (?) sound system on my 350Z I started
having a lot of distortion especially from the sub I mounted behind the driver
seat. I started my distortion killing project by spending 2 days on covering the
doors and all around the sub box with Dynamat. I got pretty good results, but I
was not satisfied. Then I started checking the specs for the sub and sub box and
figured my sub box is a little smaller than it is supposed to be comparing the
specs of the sub. I decided to get a bigger custom sub box for my sub and
installed it behind the seat. Again, I had an improvement but there was still
distortion coming out of the sub. I was pretty frustrated after spending about
$300 and days for Dynamat and sub box replacement and I started checking for my
options and I decided to give this polyester stuffing a try. My sub box is about
.7 cubic ft. so I put 1 pound of this stuff in the box and turned the system on.
The result is UNBELIEVABLE!!! Distortion was completely gone and I was able turn
the volume on a lot more than I did before with no distortion from the sub at
all. Don't get me wrong, not only this stuff but everything I did on the system
helped to have a nice system. But this stuff made the biggest difference for me.

I have 2 JL's in tightly sealed box with only .7 ft^3 space, so I thought this would do
little to improve my sound. Man was I wrong!! I added a 1lb. to each woofer and I
can't believe how much tighter and accurate my subs sound now. Not to mention it
really makes it easier when setting up your front stage. WHY DIDN'T I GET THIS 5
YEARS AGO?!?!?

i have a sony 10in xplod truck box. when i first hooked it up, it sounded
fairly decent, accurate, and handled my hard rck music well. i decided to put
some filler in it...stuffed it FULL (the filler was coming out of the speaker
cutout! lol) hooked it back up, and the sound was louder, very tight and
accurate, and it doesnt distort as much if at all. i HIGHLY recomend this stuff
to anyone with a sealed box looking for less distortion, higher volume, and
deeper, tighter bass.