Cartridge/Tonearm matching fundamentals?

TWL made a comment on a recent thread about two very nice cartridges (Shelter 501 and Lyra Lydian Beta) not being suitable for a unipivot tonearm like the JMW.

I know nothing about the concepts of matching cartridges and tonearms (nor much about tonearm types) and was wondering if TWL (or a similarly knowledgeable soul) could share some of the basics on the topic with the unenlightened.

I don't understand either the term "higher compliance range", not the different tonearm types (unipivot vs. ?) and thus why, in the thread in question, neither the 501 nor the Beta won't work on a particular tonearm.

As a point of reference, I recently acquired a VPI HW19 MKII with RB600, have purchased but not received a Dynavector 20XH.

Thanks in advance,

Tim Wat
Tim, the term "compliance" relates to the flexibility of the suspension of the particular cartridge. Generally, a number of 12cu or under is considered low compliance. Low compliance means a stiff suspension, and often accompanies a heavier cartridge. Over 12 and under about 25 is medium. And over 25 is high compliance. Actual numerical values of these definitions may vary by some opinions, but this is approximately the values.

Many observe the proper guidelines for arm/cart resonance matching, which would give a combined mass/resonance in the 10Hz-12Hz area. But this is not the only thing that needs to be accounted for. Compliance will affect some tonearm designs in different ways. For example, you don't put a super-high compliance cart on a high mass tonearm. You don't put a super-low compliance cart on a low mass tonearm.

What I referred to in the other thread was low compliance incompatibility with unipivots. The lack of rigid horizontal orientation of these arms precludes use of very low compliance carts, due to the propensity of the cart compliance to cause the tonearm to change azimuth during play. Outriggers and fluid damping, and higher weight "cups" have mitigated this somewhat in the better designs, but the basic rule holds in the more extreme cases. All unipivot designers are aware of this, and readily admit this mismatch with low compliance carts. I even recently read an interview with Harry Weisfeld, the designer of the JMW arms, and when asked about the disadvantages of unipivot tonearms,he said in the interview," as the arm rides up and down on the record, the aspect ratio can change. In other words the arm tilts."

This is not much of a problem with medium and high compliance cartridges, because they do not generate the same amount of deflection to the arm as a low compliance does. So, the result is that medium and higher compliance carts are better matches for these types of arms than low compliance ones.

Very low compliance carts like the Denon DL103, present a challenge to even the better gimbal-bearing arms, due to the energy transmitted to the arm and bearings.

In the case of a "borderline" match, where the numbers are on the edge of compatibility, it is potentially a problem. You should not go there unless you are willing to sell the cart or the arm in case of a mismatch.

For a rookie, the best bet is stay in the "happy medium". A medium mass arm, a medium compliance cart, will usually provide good results. When you start to get into the exotic stuff, you should have gained enough knowledge and experience to make the correct matching decisions.

In your particular case, the Dynavector will be very happy in the RB600 on your VPI.
Nice summary of the "ins and outs" of arm / cartridge matching Twl. I would only add that very high compliance cartridges need very low mass arms. Moving Magnet cartridges with "dampers", "stabilizers" or "brushes" tend to be less finicky about this but one should not stray TOO far from the above "formulas" that Twl was kind enough to provide. Sean
There is a simple (grid) graph available (should I find it I could fax it to you) that matches cartridge compliance with effective tonearm mass. I do believe the resonance frequency (between tonearm/cartridge) should be between 9-12 HZ --the figure simply out of the range of record warps (5-HZ) and below the audible range of 20 HZ.

peter jasz
Peter, I was looking for that graph, but couldn't find it. If you find it on the net, could you please put a link, or URL up for us, so we can all see it?
I must disagree with the assertion that low compliance cartridges are incompatible with unipivot arms. Those unipivots which are oil damped are completely stable with this type of cartridge, the viscosity of the oil offering enough momentary resistance to minimize any momentary torsional forces exerted on the arm by the cartridge. The well tempered, although not a unipivot, is a good example of the physics of this and is completely compatible with the lowest compliance cartridges as is a well damped unipivot. To understand the physics, imagine trying to quickly move an oar through water; just won't happen. Now imagine slowly pulling it. Works right. The science also is backed up by my practical experience with the Audiocraft AC-300, Graham and Well Tempered arms. No problem with the Denon 103D, Koetsu Rosewood and older Kiseki.
I've seen / used that "gridded graph" and it did not work out correctly. At least not in the one case that i relied on it. That was enough to teach me that not all "tools" are accurate. While i don't know if it is the same graph ( which i would assume that it was ), If others have used that graph, and it worked for you, please let us know. It is possible that the manufacturer's specs that i used were incorrect or that i just ran into a "freak situation". It would be far too convenient to "write off" such an easy method of arm / cartridge matching if i was the only one that had problems with that specific formula.

For further reading on the subject, try checking out this link to Galen Carol Audio. I think that this has been posted here in the past but wasn't sure, so i figured that i'd throw this one in as another point of reference. Sean
Is the lydian beta very different to the origional removeable body lydian? I'm curios because I had one and it was one of my favorite cartridges, can't get it now.
I'm also curious, although I'm not sure it will apply. I found the old lydian a good match to the older immedia rpm arm. Same with the clavis d.c. I understand Mr. Perkins used the lyra cartridges for his design of the rpm arm. Is there something different about the behavior of the rpm arm as opposed to the vpi?
Okay, regarding the "oar in the water" analogy, this is a mitigating factor as I mentioned above, as are the weighted "outriggers" on some unipivots. It can help to improve things. However, I would point out that even if the "oar" is greatly slowed by the "water", it still moves(azimuth). And then when it tries to come back to normal(azimuth), it is slowed in it's return, by the "water". Neither of these is optimal performance. So yes, it does help out, and these arms that Viridian mentions are better performers, under stress of low compliance, than ones without the damping.
Certainly no oil damped unipivot is optimal. But then is the implication that captured bearing arms are, in fact, optimal. Certainly not. No captured bearing can be infinitely free moving in the horizontal and vertical planes and completely without play. That is why the ABEC standard is used in measuring the accuracy of bearings in this type of arm. Essentially, it measures just how far from optimal the performance of captured bearings is. By definition there is either some degree of chattering or friction in the horizontal and vertical planes. We can certainly disagree on the magnitude of this phenomena, but my practical experience indicates no practical advantages for captured bearing arms over damped unipivots with low compliance cartridges.
Okay.Just my opinion.