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View Full Version : great idea?



somekook
03-29-2007, 09:57 AM
i hear about you guys putting polyfill or whatever into your boxes and trying differnt **** to "fool the box into thinking its bigger. but i dont buy any of it. sure polyfill can be compressed but its only because its full of air. the actualpolyfill is a solid so it cant be compressed. what im saying is that all youre doing is actually making the box a neglegable amount smaller, and possibly fooling youself into believing that its louder or whatever you might think is happening. i dont know though, if i saw a legitimate experiment that proved it would make it louder i would believe it.

somekook
03-29-2007, 10:00 AM
anyways, heres where my idea comes in. put something to the box that actually CAN be compressed more easily than the air in our atmosphere. I.E. a gas. does anyone know of a gas that can be compressed with a good amount less pressure than air? if so, try filling a balloon with as much as you can to still fit in your box, and then install a sub and see if its louder. because if the sub can compress and expand the volume of the gas inside the box more easily, it will be moving more, hence creating a greater pressure difference outside the box. make sense?

skadude016
03-29-2007, 10:06 AM
makes sense but in the lanes this is illegal ;)

helotaxi
03-29-2007, 10:09 AM
Its the resistive property of the poly fill in the box in regards to the air in it that allows the box to act as if it were bigger.

Gas is gas and it all compresses the same.

SCIVIC94
03-29-2007, 10:10 AM
how would u make the bax airtight enough to contain the gas?is most gases flammable anyway?so the slightest spark with the right conditions would probly make a nice number on the scales.

somekook
03-30-2007, 08:10 AM
gasses do not all compress the same. also i said you could put the gas in like a baloon so it would be easily contained but still able to contract and expand.

resistive property of the polyfill? resistive to what?

W8 a minute
03-30-2007, 08:59 AM
I don't think you understand the purpose of polyfill. Or maybe I don't? Anyway, here's my take on this.

Polyfill slows down or breaks up the back wave thereby fooling the sub into thinking its in a larger box. It really has nothing to do with compression or pressure at all.

As an example:
If I blindfolded you and locked you in a closet you could tell you were in a small room by the sound of your own voice when you screamed. The reverberations off the walls would tell you the room is very small. Much like a bat uses sonar. Now if I locked you in the same closet and lined the walls so it was acoustically "dead" you would assume the room was much bigger because your voice would never echo back to you when you screamed.

I don't think putting gas inside a box will increase output. It WILL change the T/S parameters of your setup though since box calculations are based on the compliance of the air on BOTH sides of the sub.

So either one will change the sound or tuning of the box but neither will make it louder per say.

helotaxi
03-30-2007, 09:59 AM
gasses do not all compress the same. also i said you could put the gas in like a baloon so it would be easily contained but still able to contract and expand.

resistive property of the polyfill? resistive to what?

Talk to Mr. Boyle, I think he's probably a bit smarter than you and he would tend to disagree about gases compressing differently. Disagree to the point that he defined the expansive properties of a gas in relation to temp and pressure and number of molecules present. It's defined in a law bearing his name and contains a nice little thing called the universal gas constant. Could hardly be universal or constant if all gases behaved differently now could it. 3 semesters of A's in college chemistry, FTW.

Thread on polyfill:
http://www.soundsolutionsaudio.com/forum/index.php?showtopic=7168

req
03-30-2007, 10:07 AM
owch.

major burn by taxman.

Omarvelous
03-30-2007, 10:18 AM
Well... do the experiment yourself....

I listen to my box with out polyfil, and then added polyfil.... DEF heard an improvement.

Why not just try it urself? That's not legitimate enough? We don't need to get too fancy with it, ur ears are good.

GemaRastem
03-31-2007, 03:04 AM
physics>you

Trixter
03-31-2007, 12:06 PM
true that all gasses compress the same...though they may contain larger or smaller molecules, there will just be more or less of them in a given space. if you wanted to present a negative pressure inside your box, for the theory that the sub would move more freely, then you would need to consider a type of negative pressure box by using a vacuum pump, and, of course, an absolutely are tight box that can with stand a vacuum atmosphere without imploding (would only take a few mmHg to do this). however, now the problem is with the sub it self....the cone is ****** into the box. to prevent this from happening you would need to provide an equal atmosphere outside the box for compensation...dam near impossible in a car. at this point your back to square one....with both sides being equal, just to find out that there was no point to doing it anyways.