Questioning Ortofon's OM Weight Recommendations

[dumptruck]

I thought I had the compliance-to-arm matching concept down, but maybe I don't... from Ortofon's brochure:

With the weight plate, the mass of a Super OM cartridge will be 5 grams - a perfect match for most "S" and "J" shape tonearms with detachable headshells. Without the weight plate, the mass is a mere 2.5 grams - suitable for low mass tonearms with detachable or fixed headshells.

Well, with the weight plate, if you have a medium 12g eff. arm mass, the estimated resonance should ~8Hz with a 25 µm/mN OM, or ~7Hz with a 35 µm/mN OM. A little low, right? Taking off the weight moves that up almost 1Hz, so why do we want the weight here?

Say the arm mass was a feathery 4g or so, now they look pretty good with that weight, but if you take it off, the resonance moves up too high. Why does the Ortofon brochure seem to have it backward?

 

[flavio81]

In any case, just adding or removing 2.5g from the headshell won't turn a 14g mid mass arm into a 7g light arm...

 

[dumptruck]

No, but that's really not the question...

 

[lini]

dt: I could imagine that in this paragraph Ortofon might rather have had a match in terms of balance range limits in mind - and less a match in terms of compliance, which would depend on the exact model anyway.

Greetings from Munich!

Manfred / lini

 

[luckydog]

My 2p worth : I just think it's marketing misphrasing. The original purpose/benefit of the removable mass plate seems just to enable proper use in a true light mass arm, especially relevant when using some of the older OM high compliance stylus variants. That's all.

 

[ConradH]

IMO, the OMs work best with a fairly low mass arm and there's nothing you can do about that except get another tt or arm. The main purpose of the weight plate is to let the counterweight work at some reasonable location on its post. If the counterweight is too close to the pivot so that it doesn't have adjustment range, I add the plate. If I can run without it, so much the better.