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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

Showing 18 responses by wavetrader

wavetrader OP
260 posts
 
Thanks for the responses...I ordered 3 lbs of wool to start.
wavetrader OP
260 posts
 
I have a Velodyne also and that rattles all the dishes in the house. My big sub....sounds different...as instictavley you look around and say what the hell was that.

I am going to add some wool as the cabinet is about 40+ cubic feet and I don't think there is enough material in it. It could have been overdriven but I think not..but my mono amps will output about 1800W each. Kinda overkill.
wavetrader OP
260 posts
 
Audiokinesis

They are Scanspeak 16's. I don't know the model but the sub was built in about 1992. They have 2 scanpeak vario vents on either side. The box is about 20"Wx48Lx56H. I talked to the designer years ago and he mentioned that they needed more damping material. There were 2 of these made and were used in a resturant/disco-bar. They would litterly shake the whole building like a earthquake. When I had the cabinet sent to my cabinet maker the sub was dissasembled so I don't think enough material was put back in.
wavetrader OP
260 posts
 
AudioK

If you click on my system there is a picture of the sub.
wavetrader OP
260 posts
 
The vents are 4 inch.
wavetrader OP
260 posts
 
Acually I got out a tape and measured the box: 20WX41Lx50H
wavetrader OP
260 posts
 
I took a look at the vents and they have a spiral design. If I remember correctly they were manufactured by dynaudio. I think I'll try adding some wool and see if I get an improvement. Typically is there a rule for the amount of material? Say not over 60 pct of the box volume for example.
wavetrader OP
260 posts
 
I have been playing some classical music and the soundtrack from the movie "Charlotte Gray" BTW is a great disc.Anyway I tried different levels and 7:30 setting works very well with no noise out of the vents. At that level the sub still vibrates the floor through the house. I've noticed the Bass has become more defined and delivers alot more punch so maybe the drivers needed some break-in.

Shadorne intersting setup. I have a friend that has a 24 inch Hartley loaded into his crawl space....the most incredible bass I have ever heard....a strike on a tympany sounds like a gun going off.
wavetrader OP
260 posts
 
Duke thanks for all your insights.

Roger
wavetrader OP
260 posts
 
Kirkus thanks for your thoughts. I havent talked to the designer in a year but I will have to see if I can contact him. He definately is capable as a designer and audio engineer. He designed me sattelites and their crossovers along with my mono block amps. They are incredible speakers.

I guess I'll have to inspect this. I know for sure Scanspeak made the drivers. I will report back as things progress.

I am going to replace the current crossover. Probably with a NHT X2 as it looks to be the best fit for my system.

Thanks
Roger
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
wavetrader OP
260 posts
 
Ok let me point out that...and I am sorry I didn't earlier that these drivers are mounted on a thick plate that secures to the bottom of the box. They fire downward and are completely visible if you had the box on it's side. It's been a long time since I actually had it apart...but I seem to remember 2 chambers and corner bracing and so on. The box is made of HDF I recall and weighs about 200 lbs. The plate with drivers is probably 100 lbs+. If I was really industrius I'd pull it apart and check but it is a bear to handle.

Roger
wavetrader OP
260 posts
 
Kirkus, Power is not a problem....you can weld with these amps.
wavetrader OP
260 posts
 
Kirkus your a good man with good advice.

Roger
wavetrader OP
260 posts
 
Interesting.......the NHT X2 should provide the needed flexibility.
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
wavetrader OP
260 posts
 
I meant...a 12 db slope from say 50 should start from 38hz for LF???
wavetrader OP
260 posts
 
Once you're familiar with some of the lanugage and parameters, you can then approach the designer to figure out whether or not he was smoking something when he built it . . . and maybe exactly what he was thinking.

I 'll say thanks......but do you really know everything.
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