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Any half-decent modern RIAA stage can get to within 0.5dB of the RIAA curve, very few cartridges are that close, especially at HF, and almost none at LF due to arm/cartridge/compliance resonance.
I've tried measuring the frequency response of cartridges, but always fall down with the accuracy of the test LP. Using white noise or pink noise rather depends on how white or how pink the noise actually is. In many cases, they're not particularly good.
Many years ago I had the Decca Frequency Response LP, on which it was stated that the bands above 10kHz were good for 5 plays (yes, only 5!) if the accuracy was to be maintained, which if I recall, was something quite good like 0.25dB. Decca were probably being a bit pessimistic, but nevertheless, it's indicative that LP's HF is pretty fragile. Thay may explain in part why the noise-bands of test LPs aren't reliable for frequency response measurements.
As an aside, this was found to be the case with the old CD-4 quadraphonic LPs where the ultrasonic carrier carrying the rear channel information was destroyed after only a few plays.
Consequently, I question the accuracy of any of the reviews of cartridges as I can't believe they change the LPs that frequently.
S.
Haven't thought of this in years. I had an all in one system when a teenager. It was Quadraphonic including Quad phono and Quad 8 track. The CD-4 type LPs didn't have lots of rear channel to start with on such a TT. After a few plays there was nearly none. The Quad 8 tracks were much better for Quad effect as it used a pair of the stereo tracks to have 4 channels.