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RE: Interesting! Thanks!...

Posted by flood2 (A) on October 23, 2014 at 01:25:30

In Reply to: Interesting! Thanks!... posted by John Elison on October 22, 2014 at 19:13:28:

I used the white noise response that is part of the phasing test on the Ortofon Test Disc. There is a lateral cut with a bandwidth of 23kHz and a vertical cut with a bandwidth of 29kHz - I don't quite understand why there is the discrepancy! I also have the CBS test disc STR-112 that you used for the square wave tests of your Shure V15 plus HFNRR test disc and the Analogue Productions Ultimate test LP. Of them all, I prefer the Ortofon as the most versatile. For me a pink noise test is a nuisance as, like you, I don't have a good phono amp with switchable EQ. I have verified the EQ accuracy of my phono stage with an inverse RIAA network so I'm comfortable with the accuracy of the Ortofon cut. The HFNRR disc is not as accurate I believe (based on the pink noise response characteristic) - I originally just used it for the +16dB and +18dB tones and the broadband channel separation measurements. This is mainly because I don't think much of The Exchange cutting engineers and don't trust their ability to make a high quality/accurate cut based on my experience with their commercial work.

To answer your question, putting the Shure "x" modified response bodies aside, yes, I think that a "good" (high impedance) MM design can extend the response beyond 20kHz quite easily. The issue I feel is the quality and uniformity. Given the target price point for the majority of MM designs, most designs available today have a rather higher tip mass than is ideal and the mechanical resonance is also not as high as a good MC. Based on my white noise meansurements, most of my mid price MM designs have a mechanical resonance in the range 20 to 28kHz (at a guess). On that basis, I would have to agree with your previous posts on the subject that low output MC or low impedance MM is the way to go to put the electrical phase shift as high as possible. Although the Stanton LZS claims to be designed for a 100ohm input resistance, this puts the cutoff at 16kHz and a 5dB loss at around 18kHz. When this is corrected by increasing the input resistance to 2k, this design does show off MC like qualities in the treble region. The FR is absolutely ruler flat up to 10kHz before a slight 2.8dB dip at 18kHz then rising gently above 20kHz towards the mechanical resonance (the response at 29kHz is some +5dB above the 1kHz reference level). This has proven to my satisfaction that a good MM can be passed off as a MC.

The Shure "x" bodies are curious in that the pseudo pink-noise like rolloff was deliberately engineered. I don't know what they did with the magnetic circuit to achieve the response, but my M97xE does actually have a ruler flat response from 10 to 23kHz whilst following the same general trend you show from 1kHz to 10kHz. The inductance is 650mH giving a resonance at ~12.1kHz and the damping factor is 0.52 (275pF load).
Apart from the poor quality of the cantilever alignment and the woeful tracking that doesn't meet specification.....It does make reasonably pleasing noises, but can't compare to my OC9 or Denon DL301!



Regards Anthony

"Beauty is Truth, Truth Beauty.." Keats

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