It's used for dampening. If you've ever played drums or known someone who had a drum set, you might have noticed that they threw a couple of blankets in the kick drum. It's used to give a little warmer, more solid sound.
It helps out the sound a little bit when used properly. You don't want to overdo it, meaning you shouldn't stuff your sub box with it like you're stuffing a pillow.
stuffing a box makes the box appear to be a little bigger than it is to the sub. it is because it changes the total Q of the system a little. it only makes a box seem about 10% bigger than it really is. the rest is too technical and too much for me to type right now but basically that is what it does.
I thought it was only for sealed boxes as well, what the stuff is is not cotton but polyfil it is used to stuff pillows, it slows down the sound waves as they hit the wall and come back, in essence making the box seem bigger, because there is more travel time for the sounds waves, used in moderation it is good, but you don't want too much, that's just overkill, and if you're not careful when installing it, it is possible for it to damage the sub.
I'd say it can't hurt...the benefits, they are arguable...I would like to see the double blind results on that one....richard clark..hello, you there?!?!?!
I have yet to experience one benefit from stuffing a box...that's just my personal experience. Maybe it's because I always build my boxes a bit larger then the smallest advertised spec. Often times it's there to help your sub believe that the box is smaller....personally, I can't think of how cotton will help change the compressibility of the air inside the box...From a sealed point of view, the air in there is to damp the cone....that's about it....Possibly the loose weave of the polyfil can shift and whatnot...blah, blah, blah....BM, I'd like to hear any technical reasoning behind this one....not calling you out, just asking for the scientific jargon behind it.
If your box is producing a rattle it's your box that's the problem, not the lack of some polyfil.
Things like dacron, wool, or deflex pads are more beneficial when used in midrange and midbass cabinets...it's very popular in highend home audio. It's used to breakup the back wave and deflect it....this keeps the backwave from exiting back out through the driver's cone. I have yet to experiment with deflexpads either....we'll see what happens when I start the kickpanels soon.
i copied this out of my users guide and found it to be informative enough to put here
Why should a box be damped? If the speaker is a subwoofer and will only be used to produce low frequencies, then it should probably not be damped because most damping materials will have very little effect on frequencies below 100 Hz and virtually no effect below 50 Hz. However, the woofer in a two-way speaker must often operate to 1500 Hz or higher before crossing over to a tweeter. In this case, the addition of damping material or fill inside the box can have a significant effect. The rest of this discussion will assume that this is the case.
Let’s look at what damping does to a box and then we’ll answer our question, “Why should a box be damped?” The presence of “fill” or “stuffing” inside a box will have two principal effects:
• The acoustical absorption inside the box will increase.
• The box damping will increase, making the box seem bigger than it really is.
Now lets answer our question: First, a box that is damped with “fill” will have less of a problem with standing waves inside the box because the “fill” will absorb and attenuate them. How well it does this will depend on the frequency of the standing waves and the absorptive properties of the “fill” at those frequencies. Remember that one of the main purposes of a box is to prevent the sound which emanates from the back side of the driver with inverted polarity from interacting with the sound emanating from the front of the driver. Second, a properly damped box will produce a smoother response and will respond better to transients. This contributes to a third benefit: A box with a proportionally large amount of “fill” will sound bigger than it really is. In other words, a smaller box with lots of “fill” will damp the driver in similar fashion as a larger box with no “fill”. This trick has often been used with closed boxes to achieve a smooth response from a smaller box.
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