Bass cab design problem - help! - tmcconnell

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Bass cab design problem - help!

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I am working on a bass cab. Its a sonotube covered with carbon fiber, front ported, well damped internally. The bass driver is a front firing, front loaded Eminence omega - a pretty good 12" pro driver. The vb is about 3.5 cubes, port about 4dx7l (all per bass box pro). High pass at 2500 on a piezo tweeter, and a 1000mf cap in series on the woofer to prevent dc issues. Tuned to 32 hz (probably too low to appreciate but the design goal was hi fi for a small club bass player, lightweight etc). Baffles are end plugs of 1" mdf, 19" in diameter.
Sounds beautiful on a 4 string. Low B rings true on a 5 string.... until you crank it way up with a 400 watt amp and kick in subharmonics (knob), and pluck the low B like a bow and arrow. It does not bottom out - but makes this big ocillating wooshing sound. I covered the port and it still does it (ie not port noise). I can't make the thing behave under such abuse. The damping is not glued in (its 2" foam) - could it be the damping moving back and forth - its in tight. I just can't figure out where the bad sound comes from. It does this with or without the cap. Do I just need to more aggresively roll out the infrasonic stuff? Have I forgotten something in the design? Its likely not the amp because another commercial cab I have cab (which seems to be ignoring everything below 50 hz) does not do that. It's not the driver because the cab acts the same with a delta 12 lfa as well (except that bottoms out under the same stress). It does this on the low open B, and the three frets above that, and then goes back to being normal.

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Topic - Bass cab design problem - help! - tmcconnell 16:27:40 06/24/04 (7)

Re: Bass cab design problem - help! - Yury 05:50:19 06/25/04 (1)

Re: Bass cab design problem - help! - STUART 10:05:22 06/29/04 (0)

Re: Bass cab design problem - help! - Centauri 03:07:05 06/25/04 (3)

Re: Bass cab design problem - help! - Bill Fitzmaurice 04:50:20 06/25/04 (2)

subharmonic device - tmcconnell 21:42:26 06/25/04 (1)

I'd bag that toy. - Bill Fitzmaurice 07:15:29 06/26/04 (0)

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