Did you change the settings on your phono stage to what the specs call for on the new cart?
Is the at 150mlx a bad match on the jmw9 tonearm
I am asking because I just installed the at150mlx on my vpi scout 1.1 and am getting woofer pumping. I had a ortofon 2m blue before this and had no pumping. The table is on a flexy style stand with 4 butcher block shelves and a laminated top shelf of 1/2" acrylic ,1/2" aluminum, 1/2" acrylic. The table sits on the top shelf on top of a sand box. The stand is spiked into carpet on a concrete slab. It is located about 12' away from the right speaker behind the listening position. I am not sure what other information would be helpful but it seems to happen at normal listening levels( slightly louder than conversation).If it is a bad match I would like to figure it out ASAP and return it for something else. Thank you for any help.
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- 12 posts total
Effective mass of the JWM 9 is 7.7g. The AT150MLX weighs 8.3g and the mounting hardware add 0.5g for a total effective mass of 16.5g. AT150MLX dynamic compliance is 10. If you run those figures through the resonance frequency calculator, you get a resonance frequency of 12.29 Hz, which is at the upper end of the 8-12 Hz recommended frequency range. If you can see the woofers pumping, that may be a damping issue of some sort, the kind moderated by a fluid-damped tonearm. You can also lower the resonance frequency into the 10's by adding headshell weights to bring effective mass up to around 20-25 Hz. |
What doesn't look right to me is flexistand? Don't know what that is, but VPI's don't like flex. You're right with the other stuff...a solid connection to Earth. I would take it off the flex stand and see what happens.. Also damping may cure this. Add just 1 drop at a time and listen. If the sound becomes soggy...take out one drop with a Qtip and try again. |
- 12 posts total