# Audio Tube Packing



## TankLT (Sep 7, 2011)

Does adding packing behind the speakers in an audio tube help?


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## Polaris425 (Dec 16, 2004)

I know I've heard of people putting packing of some kind (usually quilt batting) in their truck boxes.... not sure what affect it would have on the tube.


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## tony1j (Mar 11, 2011)

I tried packing mine, I have two tubes that each have 2 6.5's in them. I couldnt notice any difference..


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## Polaris425 (Dec 16, 2004)

Plus if for some reason you ever had a leak, that would a MESS.

However........ and this is just an idea that popped into my head just now...

What if, you rolled a little bit up, and kind of bound it in the corner or end of the tube..

If you ever did have a leak and a little water got in there, the batting would soak it up, instead of it sloshing all around and getting all over your electronics... Might just soak up enough to keep from damaging them...


Dang... I tell you what I dont have 'em often but when I go it's a goodun! :bigok: haha!


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## TankLT (Sep 7, 2011)

It makes a difference in sub boxes but I've never tried for full range speakers.

Polaris has started another idea. Sponging or dessicant to absorb stray moisture or even sealing the sections of tube off from each other so if one part leaks the others are ok.


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## whoolieshop (Mar 22, 2011)

The short answer is yes, it cost like $1.70 a bag and one bag will do 10 tubes. You can also use fiberglass insulation it works just as well, and if it helps improve the sound quality even a little bit it was $1.70 well spent.

The long answer:
The theory behind polyfill/insulation in a SUBWOOFER enclosure is it will help out if your box is slightly too small by tricking the subwoofer into thinking it's in a larger enclosure, improving bass response. 

But we're not stuffing subs into audio tubes we're using coaxial speakers which are designed to work in an infinite baffle or free-air setup, this means the enclosure can be very large or very small. When the cone of a speaker moves, it produces two sound waves, one from the front and one from the rear. These are exactly 180 degrees out of phase;
A infinite baffle speaker works well as long as the sound waves leaving the rear of the speaker never meet the ones coming from in front of the speaker. Which will eventually happen if there is no type of enclosure, ie you're holding the speaker out in the air letting it play. When these two sound waves meet we experience cancellation, meaning the two waves are nullifying each other. We get around this in our cars by mounting speakers in the doors and dash, the interior panels serving as a barrier between these two sound waves. 

The other advantage of using a filler material is it it helps to defeat standing waves inside the enclosure, in this case it would be a sound wave that hits the back of the tube being reflected right back at the cone. Polyfill will absorb this and should improve bass response a little.

I personally like using polyfill in tubes, it *sounds* better in my opinion with them, perhaps that's just my brain telling me that because I put it in there it sounds better, but they will never sound worse when using it!


*Edit* and one other thing, be sure when you're hooking up your speakers you wire them both up the same! Reversing the positive and negative on one speaker will cause massive cancellation!


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## Coolwizard (Feb 28, 2009)

I wonder what would happen if you filled it with expandable foam??


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## Polaris425 (Dec 16, 2004)

^ Air wouldnt be able to travel through it then. And IIRC air has a good bit to do with how it sounds???


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## whoolieshop (Mar 22, 2011)

Yes foam would fill the voids and cut down on the available air space behind the speaker, it would effectively make the tube smaller inside. The insulation or polyfill is made up of lots of individual fibers that will disrupt the soundwaves but not cut back much on the available air-space. I've found that a longer tube has a little better bass response than a very short tube, although an inch or two doesen't seem to make a whole lot of difference.

The ONLY part of the sound spectrum we're affecting at all is the mid-range bass area, a 6 1/2 woofer can only produce a specific mid-range area of frequency it's all about cone area. Nothing you'll do to a 6 1/2 will make it pound like a 10" or 12" woofer but you can improve the mid-bass a little which is not a bad thing at all.


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## todbnla (Jun 12, 2012)

I ordered some _Acousta-Stuf Polyfill _from part express which is made for speaker enclosures, this is not pillow foam but made for speakers, I will report on how it works out.


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