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Cartridge Loading and Compliance Laws

After reading into various threads concerning cartridge/arm compatibility, then gathering information from various cartridge manufacturers I am left feeling confused with head spinning a bit.... Ok, cart compliance I get, arm and total mass I get, arm/cart compatibility and the whole 8-12 Hz ideal res. freq. range I get. But why on earth then do some phono cartridge mfgs claim their carts are ok to use with med. mass common modern arms when they are in the highish 20-35cu compliance range? Am I missing something??

Ie. Soundsmith, VanDenHul, Ortofon and who knows, maybe more??

From what I gather, below 8Hz is bad and above 12Hz is bad. If one is less ideal than the other, which is worse I wonder, too low res. freq. or too high?
jeremy72

Showing 4 responses by fleib

fleib
1,124 posts
 
Hi Jeremy,
From VDH - Static Compliance: 35 Micron/mN

To estimate arm/cart res use dynamic cu @ 10Hz.
Regards,
fleib
1,124 posts
 
Jeremy,
Static compliance is always higher than dynamic. It's dynamic compliance that is used to estimate arm/cart resonance. The standard used in these calculations is measured at 10Hz. Some Japanese cart manufacturers measure dynamic at 100Hz. Those figures are not directly comparable to 10Hz figures.
Regards,
fleib
1,124 posts
 
There is no formula to convert static compliance to dynamic. In fact dynamic cu can be different laterally than vertically. For resonance estimates vertical is normally used. Most specs are dynamic cu. For example, most Benz carts are 15cu (dynamic). VDH only gives static, but tells you eff mass range of arms for the cartridge.

The only examples of both static and dynamic I could find listed is AT. The 33EV has a static cu of 40. Dynamic is 10 @100Hz. That's equivalent to approx 17, 18 @10Hz. There is no reliable formula to convert 100Hz to 10Hz.
www.lpgear.com/product/AT33EV.html

IMO it's better to find out what makes a good match from other users. Resonance estimates are often wrong and great sounding combos can be outside of the recommended range. If you want to find out exactly what res freq is, get a test record. You're more likely to get bad results with a low cu cart on a light arm. When res is near the audible band it can impact on the music.
Regards,
fleib
1,124 posts
 
Jeremy,
Halcro said it more succinctly than I. That's what I mean. Resonance calculators are just an estimate. I've calculated combinations that should resonate at 8Hz, and they tested at 10Hz. Effective mass is will change with things like the distance of the counterweight from the pivot (moment of inertia). Cartridges might vary somewhat or age. If you're really interested in the math I suggest that you go to Vinyl Engine and do a search or ask in the forum.

Re: 100Hz conversion. There doesn't seem to be an exact formula for conversion. Carts in the 10cu range (100Hz) have 10Hz cu approx 1.75 x that. The AT-150MLX, 33EV (10cu @100)have cu = 18 approx. An AT-95 or Clearaudio MM has 6.5cu @100Hz and approx 15cu at 10Hz. The DL-103 has 5cu at 100, and seems much stiffer. An old Pioneer PC-401MC has static cu of 16 and 100Hz dynamic of 12cu. VTF range (1.7 - 2.3) would indicate a stiff suspension. None of this makes much sense for arm matching. 100Hz cu seems more like a measure of tracking ability at 100Hz (bass), than cu around res freq which is near 10Hz. The only correlation I can come up with is a sliding scale. Low 100Hz cu is more than doubled for conversion. Med - 10cu is x 1.75. Higher, around 12 to 16 @100 is closer to to that number.

There are other things to consider as well. Certain combinations will work better, in some cases, than others, even though compliance/mass would seem OK. That's why it's really more effective to ask or read what the best matches are.
Regards,
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