Grado "wobble"...?

I've experienced this phenomenon on several Grados, all the way up to a Reference/Reference model in a JMW 10.5 arm. It is consistent in the fact that the same records always induce the wobble and, yes, it seems to happen more often with 45 rpm records than with 33 1/3. It's something Grado owners simply have to learn to live with, apparently. At least I've never been able to stop it. And yes, it's annoying.

For the record, it's the Grado "Wiggle".
And yes, mine did it too (I always thought the damn thing would bust loose and leave a huge scratch on my LP -it never did...)

The problem is one of improper cartridge/arm matching.
Grado cartidges will resonate visually and audibly (check out what your woofers are doing during the "dance"...).
Your amp is reproducing that stuff!

As "jlazart" accurately points out, you need a medium effective mass tonearm or a tonearm that utilizes dynamic damping to get the best out of the low compliant Grados. Arm/cartridge matching is critial to getting the best performance and sound out of an analog front-end.

Hmm. Though I know very little about this stuff and am highly math-phobic, I ran a calculation according to the figure on Galen Carol's "tonearm/cartridge capability" web page and came out with a resonant frequency of 8.635, which though lower than the recommended 9-11 range doesn't seem to miss by much. I didn't think the Grado's compliance of 20cu was considered "low." But admittedly I have a lot to learn in this regard. Thanks for all the help so far.

OK, I've had a chance to look through the archives at VA, and am more confused than ever. Some posters there suggested that the wobble was due to unclean vinyl (my soul, perhaps, but never my records). Others suggested that the VTF was set incorrectly (I'm at 1.55g; Grado recommends 1.5). Still others suggested that the 'arm/cartridge match was improper. This last point is what has me still concerned.

Factoring in an effective mass of ~16.5 grams (11 g for RB-250, 5.5 g for cartridge, plus some miniscule amount for two mounting screws), and Grado's published rating of 20 cu for the cartridge, I calculated the Grado/Rega resonant frequency at about 8.6 Hz. The chart at the bottom of Van den Hul's phono FAQ webpage essentially confirms this.

Is this really too far outside the recommended 9-11 Hz range?

And, isn't the problem that the Grado has slightly too *high* a compliance for my 'arm, rather than too *low* a compliance?

It seems that Jlazart's recommendation of a total effective mass of ~14 g is spot-on, but also that I'm in the ballpark. So I have to think the Grado wobble (or wiggle) is due to something other than 'arm/cartridge matching, at least in my case. (My latest theory is that the slightly wider grooves of a 45 RPM pressing and/or the wider lead-in grooves prove difficult for the Grado to track.)

I'll certainly look for something a bit lower in compliance when I upgrade (soon).

Thanks again. Sorry to beat this topic to death--just trying to learn something from it.