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In Reply to: Shure V15VxMR Intermodulation Distortion Measurements posted by John Elison on May 24, 2004 at 10:20:46:
John,
I did warn you that the IM distortion would require you to be sitting when you saw the results for vertical modulation. (This was a while back so I don't expect you will remember). All is not lost however. The IM is greatly affected by the dynamic tracking angle of the cartridge. Also, does your test record STR 112 tell what the effective vertical modulation angle of the record is? (The cutter VTA is only a component of that figure.)
Anyway, by my measurements the VTA of the xMR is 28 degrees, give or take. So if the record is 15 degrees (say) then gross IM is to be expected.
I am still trying hard to get my charts to appear correctly in a posting. When I do we can exchange our xMR results! And then there is the ELP LT to be explored.
Keep up the good work and good listening, IM and all!
Bill
Follow Ups:
Hi Bill,I guess that I forgot about our previous conversation, although I suspected it might have something to do with VTA or SRA. I’m also hoping that the moving magnet principle might also have something to do with it because that would help explain why MCs usually sound better than MMs.
Regarding the graphs and pictures, I am now using the Gallery in Audio Asylum, but I am also having trouble getting them into posts. I had to store these most recent IM distortion graphs at another location in order to get them to come up in my post. They are also in my gallery and I can view them in my gallery, but they don’t seem to want to come up in messages from that location. Strange!
The STR 112 doesn’t mention anything about effective VTA. In fact, I had never heard of it until our discussion on the subject. I would love to find some better test records, but they seem to few and far between these days. I’m thankful that the ones I own are in such great condition from previous non-use. It was just too darn difficult to do this kind of stuff without computers and digital recorders, so I hardly used them at all. :)
Best regards,
John Elison
John,
I have looked up the spec '....STR112 has been cut with vertical angle approximating 15 degrees, which is representative of current recordings practice." Quote from CBS test records brochure. So the vertical modulation on the record will be less (by some unknown amount) than 15 degrees. This increases the mismatch between the record vertical modulation and the VTA of the xMR.
Do you have a figure for the dynamic VTA of the other cartridge (Denon?)? If it is less than 28 degrees then its IMD should be less than the xMR.
Bill
Well, these are both modern cartridges. The other one is a Dynavector DRT XV-1. Additionally, I will be testing the new Audio Technica OC9ML/II. I have no idea as to these cartridges' effective VTA. I believe that the goal nowadays is somewhere in the neighborhood of 20º to 23º.Everyone seems to think the Dynavector sounds noticeably better than the Shure so I suspect it might have less of the bad sounding IM distortion. It appears to definitely have more or the good sounding 2nd harmonic distortion.
Best regards,
John Elison
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