[W9TR]

Originally Posted by robd2

This was a great share. The last few years I’ve learned a lot about cart output to stage gain/overload matching but I still don’t fully get the mass/compliance compatibility. Does everyone agree with this statement from the article about my arm?

The 10cc’s higher effective tonearm mass of 8.5g requires a lower compliance cartridge to put the pair in the resonant frequency sweet spot. Think of the suspension system of a car. A compromise must be found between the smoothness of the ride and the driver’s ability to feel the road. A heavier car (arm) necessitates stiffer suspension (lower cartridge compliance) whilst a lighter car can play it a little looser (with higher compliance).

The statement above is not correct. Plus Darko doesn't like Dire Straits so he's dead to me.

The mass compliance thing is simple but seems to be a mystery, so let me try to explain it.

All cartridge suspensions are necessarily 'springy' - the needle/cantilever and coil (MC) or magnet (MM) are suspended by an elastomeric material that allows them to move freely to trace the record groove. This springy-ness is called compliance.

All arms have effective mass, that is the mass the cartridge 'feels' at the end of the arm, not the whole mass of the arm, which would be much higher.

Also of course cartridges have mass. This is what Darko missed. The sum of the tonearm effective mass and the actual cartridge mass is what the cartridge suspension 'sees'.

Since there is mass and springiness together, you have a mechanical resonance. Remember the weight (mass) on the end of a spring (compliance) from high school physics? It's that.

So you want to adjust this resonance to be low enough that the cartridge picks up the lowest audio frequencies, but high enough that the cartridge is not sensitive to warped records or footfalls. The ideal range is from 8 to 11 Hz.

The Vinyl Engine has a nice tool you can use to evaluate cartridges for compatibility with your arm. It is the combination of cartridge mass (including mounting hardware), tonearm effective mass, and cartridge compliance that is important here.