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As I have been trying to optimize setup of a couple of cartridges on my recently purchased Technics EPA-250 arm on SP10mk2,I played the resonance test tracks on the HiFi News Test Record. Based on the visible shaking during test track play one of the cartridges has a 7hz resonance on the horizontal test and a 13hz resonance on the vertical test. Is the fact that these two results differ widely indicative of any problem, either in setup or with the cartridge itself? IMHE, these two always measured near equal with other cartridges.
FWIW, mono summing of out-of-phase test signal shows that azimuth is not a problem. I get the same resonance test results at L-M-H range of recommended VTF for the cartridge and at a variety of VTAs.
If compliance of the cartridge is too high for the arm, would that be an explanation? I have heard that the dynamic damping of the EPA-250 makes compliance matching concerns somewhat less of an issue than with many other arms. I am getting 7hz/8hz results with another cartridge that is lower compliance, which leads me to believe that the arm itself isn't causing the variation in horizontal vs. vertical resonances.
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The answer is that it depends on the cartridge design - vertical and horizontal compliance are not necessarily going to be the same, but more commonly they will be similar. It depends on the intention of the designer.
In your case, I wouldn't worry too much about the difference. 13Hz is still well below the audible passband so you won't be getting any nasty modulation of your signal. In fact, the lower vertical compliance is going to be advantageous in maintaining a more stable VTA and SRA in the groove.
Stanton and Ortofon both have patents which enable the vertical and horizontal compliances to be adjusted independently of each other.
Ortofon's patent (which is used for the S-120) enables the suspension to tolerate an insanely wide VTF range from 1.5 to 10g. To be usable with a VTF of 10g, the compliance has to be sufficiently low so that the VTA is still correct and the cartridge doesn't bottom out on the record surface, but the lateral compliance must be sufficiently high in order to minimise the groove wear and enable it to achieve what is the highest LF tracking ability I have ever seen in a cartridge (120um should be achieved at the recommended 4g VTF). Otherwise, at 10g, you could imagine significant damage to accumulate quickly!
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
On a gimbaled arm like yours, the closer they are, the better. Big differences can cause some strange tracking problems as it will be stiffer vertically than horizontally or vice versa. It is a cartridge flaw most likely and is not usually an arm flaw on a gimbaled arm unless the bearings are bad.
I don't argue with what you say, but one could make a case in favor of having a higher effective mass in the horizontal plane than in the vertical plane, just as one can make a case for equal effective mass in the two planes. Frankly, this is an issue that I find confusing. Over time, I think Mike Fremer has gone back and forth on this issue, but he currently (or the last time I read one of his tonearm reviews) seems to be in the "nearly equal" camp. Obviously, most any linear tracker is going to have a higher effective mass in the horizontal plane; do we hear problems from that? What problems would one expect, even?I don't own a linear tracking tonearm, but I do own a Dynavector DV505, which was designed deliberately to have a high effective mass in the horizontal plane. It's a great tonearm for bass reproduction. Theory might predict that a high-ish effective mass in the horizontal plane would be favorable for bass.
Edits: 01/06/17 01/06/17 01/06/17
Thanks. Do you think that might be caused by age of the cart (early 80s), perhaps suspension tightening up? It's got great specs and a berylium cantilever.
You could send it to Soundsmith I suppose but, I would get an estimate first.
Not necessarily. It depends on the suspension design. As I pointed out in my post, at least 2 patents exist which specifically teach controlling lateral and vertical compliance values independently which frees the designer to adjust the VTF range without unduly compromising record wear and bandwidth. The lateral compliance indicates that the damping elastomer is likely fine. 7Hz is lower than ideal but shows that it hasn't hardened excessively (if at all). Commonly, it is suggested to aim for 8 to 10Hz, but at least 10Hz to 12Hz would be a better target particularly for the vertical compliance to achieve a more stable VTA/SRA.
Also, the specific resonance values need to be measured off an actual recording to determine the actual resonance frequency rather than making assumptions that the labelled frequency corresponds to the reproduced frequency (which ignores speed errors)
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Nt
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