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How much of stuffing/damping for sealed bookshelves?

post #1 of 8
3/10/06 at 8:10am
Thread Starter 
I have some SEALED bookshelves with 12 cm woofers that i have stuffed with pillow silicone stuffing . The cabinet is stuffed to the brim;enough so that the stuffing doesnt want to come out.
Now my question is whether i have put too much of it inside the cabinet ? The woofer has a frame such that the stuff wont get into the spider coils........
so as long as the coils arent being obstructed,there should be enough air for the driver to breathe right ?

Please reply.Becoz the people at diyaudio SO DONT want to help........

Thanks !
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post #2 of 8
3/10/06 at 9:20am
Don't stuff the cabinet too tight. If you do, the stuffing starts to decrease the apparent size of the cabinet, not increase it. Here are some measurements showing this:
http://www.diysubwoofers.org/talksho...ages/41415.htm
Basically, the most you should do is 1.00-1.25 lbs/cubic foot of stuffing.

(If you have a meter, you can determine the exact maximum amount of stuffing by measuring the resonant frequency of the speaker. When it stops decreasing, you've reached the maximum amount of stuffing. Any extra will be detrimental.)

Another thing: you should make sure to keep stuffing a certain distance away from the back of the woofer. There needs to be space, otherwise the apparent Qts of the woofer changes because the airflow gets constricted.

Finally, remember that stuffing lowers the Q of the entire speaker. This lowers the bass cutoff and lowers the group delay (improves transient response), but it also leads to a slightly leaner sound. So you may or may not like the change.
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post #3 of 8
3/10/06 at 10:30am
Thread Starter 
Hmm.....looks like i am gonna have to remove some of it then.......Thanks !
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post #4 of 8
3/10/06 at 10:38am
Thread Starter 
Another thing :
Since the speakers are modded aka factory made and the woofer hole is only so wide,the pillow stuffing is not one large mass.Multiple layers stacked till the top of the cabinet.Does that make a difference in the heat dissipated by the fiber ?
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post #5 of 8
3/10/06 at 11:03am
No, it makes no difference whether the stuffing is one mass or a bunch of pieces.
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post #6 of 8
3/10/06 at 11:31am
Wodgy - I don't know if you remember but you gave me some suggestions on what to do with my sub in this thread:

http://www6.head-fi.org/forums/showthread.php?t=155748

I stuffed the port and filled the cabinet with poly-fil. I put in 60oz. of stuffing into a 16x16x16" (external) cabinet, thinking the more the merrier. Now reading this thread it seems that I probably should take a bit out. According to my calculations I have nearly 2 lbs/ft^3 in there now.

Once I start removal is there any way to know how much I should actually take out without doing measurements?
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post #7 of 8
3/10/06 at 12:10pm
If you think you've got about 2lbs/cu.ft. in there right now, you could just eyeball it and remove about 1/3rd of the stuffing. Personally I'd just take it all out, weigh it, then put as much back in as you think is appropriate.

Though if it sounds good to you right now, you could also just leave it the way it is. Looking at Tom Nousaine's measurements, if your box is small, optimum fill is around 1.75lbs/cu.ft. It's only large boxes where the optimum fill goes down to 1-1.25lbs/cu.ft. 2lbs/cu.ft. is close enough to 1.75lbs/cu.ft. so that the extra really won't make that much difference.
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post #8 of 8
3/10/06 at 2:28pm
What negative effects will overstuffing do to sound quality?

It 'reduces' box size so, that means it will decrease the low bass response?
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