What does "high compliance" mean in respect to a pickup cartridge

[crackle]

Copied from this thread: https://www.vintage-radio.net/forum/...d.php?t=155403

Can someone please explain the difference between the 9TA and the 9TA HC.

Thanks
Mike

[BRASSBITS]

The HC version is high compliance

[crackle]

What does "high compliance" mean in practical terms? What is better high or low. What difference does the mass of the arm make, and how does a high compliance help?

thanks
Mike

[Herald1360]

For a given applied force, a high compliance part will deflect further than a low compliance one. What that means in practice for cartridges, I've no idea. Over to the experts.....

A high mass arm with a high compliance cartridge would hold the cartridge steady as the record waggled the stylus and low mass arm with a low compliance cartridge would presumably let the cartridge waggle with the stylus.

[crackle]

Thanks Chris, that makes some sense.

So a high compliance cartridge is always better than a low compliance one.
But a low compliance cartridge is not too bad if used in a high mass arm.

Am I correct in thinking that high compliance just means it takes less force to vibrate the stylus and ceramic elements.

Presumably age could cause a stiffening of the rubbers used in the stylus suspension and yoke, and turn a high compliance cartridge into a low compliance one with age.

Mike

[Hartley118]

Am I correct in thinking that high compliance just means it takes less force to vibrate the stylus and ceramic elements?

Yes - true in general at low frequencies, so discs with heavy bass modulation are generally tracked better with a high compliance cartridge.

However, as usual, spring/mass resonances do make matters more interesting. The mass of the arm will resonate with the cartridge compliance at a low frequency. This can be quite critical: if it's in the audio range, it will boost the bass. In fact, back in the day of heavyweight low compliance pickups in the 1930s, the high head mass and low armature compliance created an LF resonant peak sufficient to more or less provide the right bass equalisation to compensate for the 78 recording characteristic.

Returning to the present day, there's an issue that one can overdo the stylus compliance. With a high mass head, such as those generally on autochangers, a very high compliance cartridge could push the LF resonance so far down that it coincides with the 'bounce' frequency of the turntable mounting springs, or a warped or off-centre record. That in turn can lead to the stylus leaving the groove. So a substantial massy pickup head may do better with a stiffer (lower compliance) cartridge.

And there's of course another thing - if the cartridge/arm combination needs a fairly high tracking force for decent mid and high frequency groove tracing, excessive stylus compliance can result in the cartridge 'bottoming' on to the record surface, which is clearly a bad thing.

At high frequencies, stylus compliance leaves the picture and stylus tip mass is then the significant factor. Our mass/spring resonance of interest becomes now the stylus mass 'bouncing' on the compliance of the record groove material. The lower the tip mass and the stiffer the record material, the higher the HF resonant frequency; it's this HF resonance which generally sets the upper limit to the cartridge HF response. Interestingly and paradoxically, when compliant vinyl began to replace stiff shellac as a disc material, it was more difficult for manufacturers of top-grade cartridges to achieve the extended HF response that the new-fangled LPs demanded. A well-recorded 78 could typically give a wider HF response than a vinyl LP because the cartridge HF resonance is higher on hard shellac.

Martin