Tools

Effective Mass from Resonance

Effective mass is the figure every resonance calculation needs, and for many arms it is not published. It depends on the headshell and counterweight fitted, so there is often no single number a maker can quote. If yours is not in our register, you can measure it instead of guessing: play a test record, find the frequency where the arm and cartridge resonate together, and the arm's effective mass falls out of the same arithmetic run backwards. Enter what you measured and the cartridge you measured it with.

Between 3 and 30 Hz. Most arm and cartridge pairings land between 6 and 14.

Leave blank for 0.5 g, a typical set.

Arm effective mass

Enter the frequency you measured and the cartridge you measured it with, and your arm's effective mass appears here.

If your arm is already in the tonearm register you do not need this page. It is for the many arms with no published figure: effective mass depends on the headshell and counterweight fitted, so there is often no single number to quote.

How to measure the resonance

You need a test record with a low-frequency sweep or a set of tones between about 6 and 14 Hz. Play it and watch the cartridge from the front: at resonance the arm and cartridge visibly wobble together, the cantilever moves most, and a light hand on the plinth feels it. Take the frequency at the worst of it. Read the lateral track rather than the vertical one if the record offers both, since lateral is the figure the usual formula describes. Two readings a hertz apart are worth repeating rather than averaging, and be honest about the precision: half a hertz of reading error moves the answer by roughly a gram, which is enough to matter.

What comes out is the arm's effective mass including the headshell and any hardware you had fitted at the time, which is what a resonance calculation wants anyway. It is a measurement of your arm as it stands rather than a maker's figure, so it can legitimately differ from a published number: a heavier headshell, a different counterweight or an armboard spacer all move it. The answer is only as good as the compliance you fed in, and cartridge compliance is published three different ways, so check the standard before you trust a surprising result.

Check the tonearm register first, in case yours is already there →

Convert a compliance figure to 10 Hz before you use it →

Who makes these

Bool Audio is a father and son making hi-fi components in a small UK workshop. We build the Clear Wave unipivot tonearm and the Clear Wave 2.0 tonearm cable, both for the Linn LP12. These calculators began as our own bench arithmetic. They are free to use, there is nothing to install, and they take no view on which cartridge or tonearm you should own.

The Clear Wave tonearm → Clear Wave 2.0 tonearm cable → Shop →