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Old 11th August 2003, 08:45 AM   #1
Howard is offline Howard  United Kingdom
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Default Stuffing

What will be the effects of adding some acoustic "stuffing" into a sealed subwoofer enclosure as opposed to leaving it empty?
I'd like to maybe extend the bass response down a bit on my DIY sub.
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Old 11th August 2003, 09:00 AM   #2
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My guess is that would work if your trying to soften the "boom" that some times sounds sharp effect. or it might sound like you put your sub in mud i don't know. try it. not a pro.
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Old 11th August 2003, 09:21 AM   #3
Howard is offline Howard  United Kingdom
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I just reckon it could sound a bit deeper considering how much the driver moves

Any way of doing this?
Would stuffing make any difference?
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Old 11th August 2003, 11:18 AM   #4
Beggar is offline Beggar  United Kingdom
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Hey

Adding stuffing effectivly makes the enclosure seem bigger to the driver, this results in a lower Qtc, meaning the response will be 'smoother' and more drawn out. Typically i have found i can get between 25% and 30% extra effective volume from stuffing.

There's loads of info on this around on the forum already (i think ) Also you might want to check out http://www.diysubwoofers.org

Heres a pic of interest, its actually for a midrange cone, but the same trends still apply
Attached Images
File Type: gif response.gif (13.6 KB, 254 views)
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Old 11th August 2003, 11:21 AM   #5
Howard is offline Howard  United Kingdom
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I'm sorry but I don't really understand all this Qtc business, etc. You'll have to explain it to me in newbie terms!

I just had a bit of a play with the SW Episode 2 DVD and the real low frequencies are certainly there, but considering how much excursion is involved with my poor subwoofer cone, I feel there could be more output, if you see what I mean.
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Old 11th August 2003, 11:52 AM   #6
Beggar is offline Beggar  United Kingdom
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On the graph the red line indicates the frequency response one would get with a larger box (i.e. by adding stuffing to an enclosure)

The dark blue line indicates the response of a smaller box, and the other lines are somewhere between the two

Notice that the red line shows higher output at lower frequencies, this is due to the extended, smoother 'curved bit.' As you add more stuffing/make the box bigger this curved bit extends more and more, and also becomes more smooth, giving you greater output at lower frequencies.....

However there is a catch (a few others too actually) Adding too much stuffing can have the opposite effect, making the enclosure smaller

I strongly suggest u do as much research on the topic as possible before you do anything, that link i gave earlier is a good starting point. (Toying with the sealed.xls file avalible from that site might help clear things up a little)
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Old 11th August 2003, 02:35 PM   #7
Guss is offline Guss  Canada
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Default IB IB IB IB

As 0.5 Qtc mean critically damped, do I need to add stuffing and or wall damping ?
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Old 11th August 2003, 03:18 PM   #8
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How large is the woofer?
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Old 11th August 2003, 03:26 PM   #9
Howard is offline Howard  United Kingdom
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12"
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Old 11th August 2003, 03:37 PM   #10
Guss is offline Guss  Canada
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mine is 5.5" alu cone. It is used as a mid/woof unit.
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