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E36 /7 Z3 (1996-2002)
E36/7 Z3 roadster and coupe talk with our gurus here.

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  #1  
Old 08-09-2012, 12:18 PM
Rykster Rykster is offline
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Location: Las Vegas, NV
 
Join Date: Dec 2011
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Mein Auto: Infiniti M35, 2001 3.0 Z3
Unhappy Subwoofer "Stuffing"

My H/K sub sounds like a goose honking. Thinking it must be the foam surround and/or cone, I checked the foam surround and cone, and both look brand new. (The car has about 34,000 miles.) Inside the box there was a piece of what looks like carpet padding, about 1" thick, cut to fit around the speaker. What is the purpose of this? I assume it's there for a reason. If I take it out, will that make any kind of a difference?

I also read somewhere that filling the box actually makes the sub more efficient because it absorbs sound waves or gigabytes or gamma rays or tax write-offs or something. Anybody know anything about this?

Short of replacing the speaker itself, is there anything I can do to make it sound better?

Thanks.
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  #2  
Old 08-09-2012, 12:59 PM
Wertles Wertles is offline
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Location: Rochester, NY
 
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Mein Auto: 1999 M Coupe
Replace the amp. That is the weakest point in the system followed by the speaker itself. Kicker makes an affordable and quality replacement speaker. Adding additional stuffing in the box does make it more efficient.
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  #3  
Old 08-09-2012, 01:24 PM
dkindig dkindig is offline
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Mein Auto: '01 Z3 3.0i Roadster
Quote:
Originally Posted by Rykster View Post
My H/K sub sounds like a goose honking. Thinking it must be the foam surround and/or cone, I checked the foam surround and cone, and both look brand new. (The car has about 34,000 miles.) Inside the box there was a piece of what looks like carpet padding, about 1" thick, cut to fit around the speaker. What is the purpose of this? I assume it's there for a reason. If I take it out, will that make any kind of a difference?

I also read somewhere that filling the box actually makes the sub more efficient because it absorbs sound waves or gigabytes or gamma rays or tax write-offs or something. Anybody know anything about this?

Short of replacing the speaker itself, is there anything I can do to make it sound better?

Thanks.
Okay, I know something about this, as speaker-building is a hobby. First off, the honking sound is likely an air leak at a box seam or at the speaker flange. It has also often been called a "farting" sound.

Check the seams and the driver flange-to-enclosure joint for air leaks/looseness. The carpet padding stuff is actually a valiant-but-misguided token effort at enclosure damping. It's all wrong for this application. In a speaker that is destined to produce the upper frequency ranges that type of padding can prevent standing waves inside the speaker cabinet by dampening internal reflections. That works well for those instances but only for frequencies where the wavelengths are shorter than the internal box dimensions.

For a sub, the damping is designed to slow down the transmission of sound from one side of the enclosure to the other. This, in effect, makes the enclosure act acoustically like it is slightly larger than it really is, therefore lowering the resonant frequency of the entire assembly. For this, you need a loose, fibrous filling. Polyfill is used most of the time for this. Anything with those characteristics will work, though, and when I did my sub upgrade I had fiberglass batts laying around so that's what I used (loose fiberglass).

The trick is to not pack it in. You fill so that the internal space is occupied but it can't be so tightly packed in that the material is heavily compressed. It should result in a resonant frequency for the assembly that is in line with an empty enclosure approximately 20-30% larger.

Last edited by dkindig; 08-09-2012 at 01:26 PM.
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