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Old 8th February 2012, 12:07 AM   #1
jjl is offline jjl  Australia
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Default difference between padding and stuffing

Why do some designs call for stuffing the speaker box with a certain weight of stuffing and some call for padding on the surfaces.
What different roles do these two methods play in the general scheme of things.

Jeremy
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Old 9th February 2012, 10:15 AM   #2
jjl is offline jjl  Australia
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Come on guys, this is not a trick question. I just want to understand the reasons you would use one or the other and the effect(s) they may have on the performance of a cabinet.
Jeremy
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Old 9th February 2012, 11:36 AM   #3
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Quote:
Originally Posted by jjl View Post
Why do some designs call for stuffing the speaker box with a certain weight of stuffing and some call for padding on the surfaces.
What different roles do these two methods play in the general scheme of things.

Jeremy
Quote: stuffing the speaker box with a certain weight of stuffing This seems to be the case with woofers, where is need a heavy stuffing material to fill space(inside enclousure air) and increase, up or boost the bass.

Quote: some call for padding on the surfaces. This seems to be the usual procedure used with cone midranges enclousures or even tweeter enclouseres.
The light weight stuffing will no fill inside space enclousure(Litrage will be the same) and will attenuates the resonances;
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Last edited by FullRangeMan; 9th February 2012 at 11:40 AM.
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Old 9th February 2012, 01:18 PM   #4
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Basically, what FRM said. There's a bit of crossover (pardon the pun) in purposes, but generally you pad the surfaces to reduce resonances and you stuff the box to increase it's apparent volume. In the old days, we used Fibreglas for both, but we've learned that acoustically opaque materials with high internal losses (carpet pads) work better for damping and acoustically transparent materials with a high R value (wool) work better for stuffing.
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Old 9th February 2012, 02:17 PM   #5
sreten is offline sreten  United Kingdom
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Hi,

Its simple. You stuff anything that is sealed and line vented bass boxes.
You can add light stuffing to vented boxes but keep it away the port.
Excessive stuffing and stuffing near ports reduces the ports effectiveness.

You can also line sealed boxes if your using something like "sonic barrier".

rgds, sreten.
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Old 10th February 2012, 07:07 AM   #6
DrBoar is offline DrBoar  Sweden
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The best place to absorb standing waves and reflections inside a box ( or a room!) is well into the free volume at velocity maxima. The worst place is at the walls were we have pressure maxima and velocity minima.

So for a closed box absorbing all back radiation is just fine and stuffing the the whole volume is just fine.

However, if you want to use the back radiation to increase the radiation resistance. That is get more sound out for a given input/cone motion, the stuffing in the middle of the box will give losses to that increase in radiation resistance and thus defeat the purpose of the bass reflex, horn och quarter wave resonantor that you build.

So in a subbass box you have no stuffing at all. For pipes and reflex boxes there is a trade of were you add stuffing along the walls to reduce midrange reflections/standing waves while minimally interfering with the "bass boost". How you balance these two conflicting requirements very a lot depending on design requirement, intended applications and so on.

Felt glued to the walls can also reduce tranmission and vibraton to a surprising degree (Hobby HiFi 2/2002) they use Nadelfilz that google translate to Needlefelt, and that is plain wrong. Nadelfilz is a short filber wall to wall rug/carpet in this case 8mm thick that is 1/3 of an imperical inch, hmm 1/3 sound to uncomplicated make that 5/16 of an Inch...
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