Damping material - big differences in poly fill types - diyAudio
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Old 23rd May 2011, 03:44 PM   #1
zman01 is offline zman01  Bangladesh
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Default Damping material - big differences in poly fill types

Hi,

I've been playing around with my Castle Micro Towers for the past fews days. the build was relatively easy, and I have a thread on that here:

Castle Microtower build

One things I was not being able to accomplish satisfactorily is the level of damping. Sharp highs, low bass, boomy bass, lower SPL, chesty sound - I experienced all of these during my attempts to get the amount right. Tried reading up on the Internet, tips and tricks seemed to work partially, sending me only back to more experimenting. I basically experimented with 3 types:

1. HCF (Hollow Conjugated Fibre): This fill is very springy. The texture feels like nylon and color is a bright white. Can come in big lumps, but clumps separates from one another very easily. With HCF, bass was flabby with medium levels of stuffing, tighter but chesty sound with more stuffing; also highs became shrill. Bass was not accurate (though deep).

2. Polyester batting: Made into a roll and used it to stuff the cabinets. Sound becomes thin and shrill, listening fatigue inducing. Bass lacks in quantity, quality, and warmth.

3. Denser Poly fill from a stuffed toy: Obviously not all toys will be stuffed with the same stuff. Out of exasperation in my search for a denser stuffing, I took some filling out of an old discarded soft toy, half expecting that to be full of HCF too.. The fluff was made of finer strands and was less springier than HCF. The texture was different - softer and tended to form small clumps. It felt kind of like a synthetic cotton. Color was a bit dull too, compared to the bright white of the HCF. Stuffed the mid section of the Castle MT ML-TL and bingo - tight bass is back! Bass has much better definition and accuracy, overall the music is much more dynamic.

So, what I have learned is that quality and type of poly fill matters a lot - it affects the bass most, and in my case also affected the mids and highs of the CHR-70.

The toy wasn't that big and not enough came out of it to stuff both cabinets - so I am now searching for the same type of stuffing.

Would love to hear experiences from others also.

-Zia
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File Type: jpg Poly_batting_lump.jpg (95.1 KB, 452 views)
File Type: jpg Good_polyfill_lump.jpg (74.4 KB, 456 views)
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Old 23rd May 2011, 04:52 PM   #2
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4. Try memory foam glued to internal walls, it is very different.
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Old 23rd May 2011, 05:18 PM   #3
zman01 is offline zman01  Bangladesh
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I don't have any memory foam with me now - will try to get hold of some.

This is the first time I am hearing memory foam. This is for any cabinet?
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Old 23rd May 2011, 05:32 PM   #4
FrankWW is offline FrankWW  Canada
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Wavebourn is right about the memory foam, it will work. It's what's used in upscale foam mattresses that keep the indentation after a weight has been removed and is quite dense.

I don't know how easy it is to get stuff where you are.

That poly fiber you found useful is probably the same stuff that's used to stuff cushions. So you might want to look in places where they sell cloth or manufacture toys.

Wool which has not been spun into yarn is good, also. Wool is actually quite dense - has Specific Gravity of 1.3 - the downside is that insects like to eat it. so you might want to seal it in a plastic bag.

Fiberglass will work, as well. It comes in batts of varying density. Glass has an SG of about 2.5

The effectiveness of fibre stuffing depends on the density of the material, how fine the strands are, and how close together they are.

Polyester, the fiber you've probably been using has a SG of 1.25, so it's effectiveness depends on the fineness of the strands and how many strands are gathered together in
a bat.
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Old 23rd May 2011, 05:50 PM   #5
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anyone tryed rockwoll (like the one you use on drywall isolation) ?
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Old 23rd May 2011, 05:57 PM   #6
zman01 is offline zman01  Bangladesh
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Quote:
Originally Posted by FrankWW View Post

The effectiveness of fibre stuffing depends on the density of the material, how fine the strands are, and how close together they are.

Polyester, the fiber you've probably been using has a SG of 1.25, so it's effectiveness depends on the fineness of the strands and how many strands are gathered together in
a bat.
Yes, I am finding finer strands that are gathered closer together give me better performance. You are right about the cushion material - that's the type that was driving me crazy.

BTW, I have my walls padded with poly batting (~1") and that seems to be doing a decent job in damping the internal wall reflections... the line stuffing is the main problem.

Wavebourn, for memory foam what thickness do you suggest?

-Zia

Last edited by zman01; 23rd May 2011 at 06:04 PM.
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Old 23rd May 2011, 06:42 PM   #7
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I have tried memory foam.....works quite well. I just cut up a $10 pad from Target. I have also tried self adhesive cork with mixed results.
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Old 23rd May 2011, 07:02 PM   #8
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I spoke with people on AES convention that demonstrated sound isolating server rack mount box, they confirmed my finding about memory foam. It is the one of the best damping materials available. My concern was how long it lives, but in my experimental speakers made in 2006 it still works like new without signs of degradation.

I use 2 inch mattress pads. Unfortunately price is going higher and higher, even for factory rejected pads on ePay.
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Old 23rd May 2011, 07:15 PM   #9
jlsem is offline jlsem  United States
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A used one that's been pissed on is probably a lot cheaper.

John
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Old 23rd May 2011, 07:19 PM   #10
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Not a Lady Gaga soaked pad.......those bring big epay $$
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