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
timwat

Showing 4 responses by twl

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.
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?
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.