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Subwoofer damping

I didn't no whether to post this in the speaker or tech forum, but I'll ask my query.

I have a very large subwoofer which has 2 16 inch drivers. I fired this baby up today after having it in storage for many years. I played a reference recording of Frederick Fennell's Pomp & Pipes. Well I set the crossover pots at 10:00, 6 being the lowest and 5 highest. Everthing was ok till there was some low and I mean low frequency with plenty of dynamics. I could hear the drivers make a girgle sound that came out the 4 vents in the cabinet.

I can't recall if I've heard this before and I'm thinking that I need to add additional damping material. Doe's anybody supply speaker wool anymore? I can't imagine overdriving this thing....I think my house would collapse...so adding more material seems might help. Any speaker tech's with answers would be appreciated.

Roger
wavetrader
wavetrader OP
260 posts
 
Kirkus....I pulled the vents out...they were really tight. Things are not what they seem as far as the internal cabinet size. The HDF walls are 1-5/8 thick all around. It looks to have 2 chambers with a space about 10 inches high above the top of the chamber were there is wool stuffed in. One side has less wool than the other. There is thick padding on most surfaces. So I would say each woofer chamber is about 7 cu ft or a little less. I felt underneath and the rubber suspension feels fine. I probably overdrove the drivers as the present crossover does'nt provide a low pass filter and I have listened and there is alot more energy(frequency) being passed to the sub than is needed. So I will add a little wool and try the NHT crossover when it get's delivered....go from there.

Roger
shadorne's avatar
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shadorne
7,467 posts
 
the present crossover does'nt provide a low pass filter

IMHO, whay you may need is a "high pass filter" to prevent ultra LF reaching the drivers...I'd cut everything below 30 Hz....I don't think you have a "subwoofer" in the modern sense - I think you have something that was intened and designed to enhance bass reprodution in a large space like a club - it probably works best from 40 to 100 Hz.
wavetrader OP
260 posts
 
Interesting.......the NHT X2 should provide the needed flexibility.
shadorne's avatar
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shadorne
7,467 posts
 
Interesting.......the NHT X2 should provide the needed flexibility

I am not familiar with it. However a word of caution - I don't see high pass for removing ultra LF on the specifications. "50 Hz" is the lowest high pass filter which sounds like this is intended to provide a feed to mains.

You might need adjustable high pass at 10 to 40 Hz and adjustable low pass set from 50 to 90 Hz with various filter slope options.

Although I would expect the crossover that originally came with your box would take care of this...could one of the caps have dried out..you know certain caps don't like to be left in storage and will easily blow the first time you fire them up....that might be your only problem... a dud Cap...
wavetrader OP
260 posts
 
a 12 db slope from say 50 should start from 38 db for LF???

Crossover Frequency 50Hz, 80Hz, 110Hz high pass, 50Hz-140Hz adjustable low-pass filter
Crossover Slopes 12dB/octave high pass, 12dB/octave low pass
Phase 0/180 degrees switch, 0-90 degrees variable
Input Connectors XLR, RCA
Output Connectors XLR, RCA
Dimensions 2.125"H x 17"W x 11.5"D
Weight 9 lbs
Controls Gain, LFE Gain, Phase, LP, HP, Boundary (+/-6dB), Stereo/Mono, Trigger mode
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