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Strange subsonic rumble problem?

Hmm.... I have 2 arms on my TW Acoustic Raven AC, a Reed 3Q and FR 66S sitting on Minus K platform. Yesterday, I took out my Koetsu cartridge and put on Ikeda Kai on my FR 66s. After the usual setup routine, I noticed significant subsonic rumble with the woofers pumping like mad when using the FR 66s. No such problem when using Reed arm playing the same record. I never had subsonic rumble problem in my system for a long time now and no problem with FR 66s in the past. The setup seems to be fine, all the joint, screws, etc are tightened properly as far as I could tell. Overhang, VTF, VTA, etc has all been checked several times so I am out of idea now what else to check to eliminate the problem. I assume airborne vibration, acoustic feedback should not be an issue since the problem was not there before and the turntable sits in the same location for years now.
Thanks for any suggestion.
suteetat
yogiboy's avatar
yogiboy
5,467 posts
 
Is this the first time you had the Kai with the FR? Rumble is usually caused with arm and cartridge mismatch causing the cartridge to resonate. If you have a test record with that test track it will verify this. I found this out the hard way after blowing woofers!
suteetat OP
435 posts
 
I used the Kai with FR 64s in the past with no problem but never tried it with 66s. After I put the Koetsu back on, the rumble was still there also. Koetsu/Ikeda was connected to
Audio Tekne SUT into Asthetix Io. Using resonance evaluator on vinyl engine, resonance is somewhere between 8-9 Hz with effective mass 38g for FR 66s so it should be ok though.
yogiboy's avatar
yogiboy
5,467 posts
 
That resonance is on the low side close to record warp frequency! Nine times out of ten this will cause woofer pumping. You should get a good test record so you can see this for yourself.
I use Shure ERA 1V TTR115 test record, it is invaluable for this test.
You can find them on Ebay for about $20.00. It would be a wise purchase for someone like you who is into vinyl.
sarcher30
596 posts
 
Maybe that arm/cart combo does not like that record? Does it do it on other records? If so, you may have a problem with the arm.
11flat6
55 posts
 
have you checked if your FR66s arm is properly grounded?
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