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Wildly fluttering woofer

Without any kind of warning the left woofer of my Thiel 7.2 speaker started fluttering-the excursion was at least two inches. Won't happen with a CD. Tried another record and the same thing happened again. I have not switched speaker cables.
System: VPI Mark IV turntable with Graham Phantom arm and Dynavector XX2 cartridge, McCormack DNA 500 amp, Audible Illusions Modulus 3B pre-amp, Thiel 7.2 speakers, all wires are Audience. HELP!
katz1
sbrownnw
699 posts
 
Did you move the table recently? If not, probably something in the cartridge or phono stage (tubes?).
atmasphere's avatar
atmasphere
11,834 posts
 
Its not a speaker cable :)

Its in either the phono section or the setup of the cartridge itself. Since its only in one channel I suspect the phono section, which may have a noisy tube.
heyraz
177 posts
 
It sounds like subsonic feedback. Move the speakers to see if it improves. Also try to isolate the turntable.

You can easily isolate the problem by swapping channels from the speakers back to the turntable.
mechans
3,048 posts
 
It is almost certainly sub sonic feedback as mentioned before. I have seen this using test records on my own gear which can't produce a sound below 28 cycles but will wobble violently between 20 and 26 cycles.
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