M97xE laminated pole pieces?

Date Updated: September 7, 2017 FAQ #5007
Question:
Why does the M97xE use non-laminated pole pieces?

Answer:


Response from Shure phono engineering:
The frequency response of a phone cartridge is the result of:
1)  The mechanical response of the stylus, which typically has a resonance just past 20 kHz, and….
2)  The electrical response of the coil in the cartridge (resistance and inductance) loaded by the cable and preamp it’s attached to, and…
3)  The magnetic response (eddy current losses) of the pole pieces in the cartridge.
#1 raises the frequency response as you go up in frequency.
#2 lowers it (with a high slope - 12 dB/octave)
#3 lowers it (with a low slope – 3 dB / octave)
The V15 cartridges from the Type III to the TypeV had laminated pole pieces, which indeed reduced the amount of loss via #3. Given the contributions of the other 2 parts of the frequency response (those varied considerably from one model to another even within the V15’s), this was appropriate, but,,, as it turns out, a little magnetic rolloff gave a better result. These cartridges had small shorting rings added (different for each model), which introduced a bit of carefully controlled magnetic loss, as a tweak to get the freq response “just right”.
The M97xE does not have laminated pole pieces, so indeed it has some gentle roll off from the pole pieces. Given the mechanical and electrical responses , the whole is fairly well dialed in frequency response wise. If you laminate the pole pieces, but leave the rest the same, you’ll end up with a rising frequency response at high frequencies – not as ideal as the balanced performance the M97xE currently has.
It’s about balance – tuning things to work together. A sports car has different suspension parts than a family sedan – intentionally, as each works best with its own set of parts. Using parts from one in the other is not a good idea.