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Author Topic: Preferred Subwoofer Damping Material?  (Read 1833 times)

Tim Gurske

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Preferred Subwoofer Damping Material?
« on: April 25, 2017, 06:12:55 pm »

It seems like there are many options. Is there a preferred material that "the pros" use or does everybody have a different preference? As always I am looking for cheap and best, although I realize that those might be mutually exclusive in most situations.

And, before the "it depends" answer :-), I will give some details about the application: I am building a basic ported cabinet for a single 18" subwoofer that will be used for playing general music (top 40 mostly) sometimes indoors and sometime outdoors.

Thank you in advance!
« Last Edit: April 25, 2017, 08:49:18 pm by Tim Gurske »
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Lee Buckalew

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Re: Preferred Subwoofer Dampening Material?
« Reply #1 on: April 25, 2017, 06:16:55 pm »

It seems like there are many options. Is there a preferred material that "the pros" use or does everybody have a different preference? As always I am looking for cheap and best, although I realize that those might be mutually exclusive in most situations.

And, before the "it depends" answer :-), I will give some details about the application: I am building a basic ported cabinet for a single 18" subwoofer that will be used for playing general music (top 40 mostly) sometimes indoors and sometime outdoors.

Thank you in advance!

I like water for dampening. 
Now for damping...  ;D

I will let some of the speaker builders chime in with their preferences and why and in what context they like/don't like the various options.

Lee
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Tim Gurske

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Re: Preferred Subwoofer Dampening Material?
« Reply #2 on: April 25, 2017, 08:49:45 pm »

I like water for dampening. 
Now for damping...  ;D

I will let some of the speaker builders chime in with their preferences and why and in what context they like/don't like the various options.

Lee

Ha! I fixed it.
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Michael Thompson

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Re: Preferred Subwoofer Damping Material?
« Reply #3 on: April 25, 2017, 09:55:59 pm »

It seems like there are many options. Is there a preferred material that "the pros" use or does everybody have a different preference? As always I am looking for cheap and best, although I realize that those might be mutually exclusive in most situations.

And, before the "it depends" answer :-), I will give some details about the application: I am building a basic ported cabinet for a single 18" subwoofer that will be used for playing general music (top 40 mostly) sometimes indoors and sometime outdoors.

Thank you in advance!
It depends!  LOL  Seriously though...Manufactures use all different things.  The first question is does your design need any at all?  Many don't.  Personally if I need it, I like polyester because it doesn't rot from ozone exposure like charcoal foam, but it does hold more moisture than the foam.  Fiberglass works, but it can be a mess and heaven forbid your design has open ports and a mouse gets in there.  They love that stuff.

some examples:
JBL SRX712m (polyester)
Various D&B cabinets (Foam)
JBL SRX728 (None)
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Tim Weaver

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Re: Preferred Subwoofer Damping Material?
« Reply #4 on: April 26, 2017, 04:06:08 am »

For subs I wouldn't use any. Fiber material won't do anything at those frequencies. You're better off building a solid, dead, rock-hard cabinet.

So I guess the best damping material for subs is more wood for bracing!
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Ivan Beaver

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Re: Preferred Subwoofer Damping Material?
« Reply #5 on: April 26, 2017, 06:03:05 am »

The first question is does your design need any at all?  Many don't. 
Think of it like this.

Low large are the waves being produced in the cabinet?  Think 10-30' long.

Is 2" of "stuff" going to do anything?

Stuffing can help on higher freq freq that are shorter, but will not do anything at the longer lower freq
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Stephen Kirby

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Re: Preferred Subwoofer Damping Material?
« Reply #6 on: April 26, 2017, 07:25:10 pm »

In the box modeling software I have, adding "stuffing" material has the effect of a larger air volume.  My understanding is that the resistance to air flow kind of acts like a capacitor lowering the resonant frequency of the volume.
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Tim Weaver

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Re: Preferred Subwoofer Damping Material?
« Reply #7 on: April 26, 2017, 07:59:55 pm »

In the box modeling software I have, adding "stuffing" material has the effect of a larger air volume.  My understanding is that the resistance to air flow kind of acts like a capacitor lowering the resonant frequency of the volume.

Yes, but it's not enough to worry about when dealing with subs.

Imagine this. You have a big sub playing 10 feet in front of you. Now hold up a blanket of whatever material you want. Did the sub get any quieter? Did it change in tone?

No. Because the wavelengths are huge. You would need about 2.5 FEET of damping material to even begin to have an effect at 100 hertz. At 50 hertz, you'd need 5 feet of the stuff. Are you going to add 5 feet of stuffing to every wall of your cabinet? Probably not.
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Stephen Kirby

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Re: Preferred Subwoofer Damping Material?
« Reply #8 on: April 26, 2017, 08:15:26 pm »

I don't think it's about wavelengths.  It's about the effective volume of the box and the tuning.  Air is a spring and the larger the volume of air the lower the natural frequency of that spring.  If stuffing actually does behave as a way of faking additional volume then that changes the tuning of the box.  Having done bunches of models of boxes, it does show up in the software as extended LF.
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Tim Weaver

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Re: Preferred Subwoofer Damping Material?
« Reply #9 on: April 26, 2017, 08:31:25 pm »

I don't think it's about wavelengths.  It's about the effective volume of the box and the tuning.  Air is a spring and the larger the volume of air the lower the natural frequency of that spring.  If stuffing actually does behave as a way of faking additional volume then that changes the tuning of the box.  Having done bunches of models of boxes, it does show up in the software as extended LF.


How many boxes have you built and measured with and without stuffing?

Stuffing in subs used to be a thing. Now it's not so much. The drivers are so much stronger that the box has much less effect on low frequency output nowadays. Sure, it still needs to be a tuned system, but the motor driving that system is a big-block chevy compared to the old days. IOW, the woofer's now have all the low end you need. The box doesn't need to extend things any lower. In fact, often times you can extract a good, flat low corner freq by tuning the box extra low. Since most modern woofers will easily hit under 40hz. You don't need to tune the box (and have a group delay hump) at 40ish hertz. You can tune it lower, push the GD lower so that the port tuning is below the HP filter of the cabinet. You'll have better phase response down low like this.

Older drivers needed all the help they could get to hit under 40. So we lived with group delay and itchy fiberglass.
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Bullwinkle: This is the amplifier, which amplifies the sound. This is the Preamplifier which, of course, amplifies the pree's.
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