[78-L] Tonearm/Cartridge Mismatch - Compliance Remedies?

[Iñigo Cubillo]

The place where you add the mass in the tonearm is not so relevant, given
that you get a more massive tonearm but also well equilibrated by a
counterbalance, so you end with a given effective weight at the
needlepoint, say, 2.5 grams or 3.5 grams or maybe even 4 to 5 grams for a
Shure SC35C.

The groove moving the needle sees only the needle point, which it moves
side to side. If the needle support is flexible enough related to the mass
of the arm above, the groove will move the needlepoint and not the tonearm,
resulting in a more effective sound production. If the tonearm is too light
related to the flexibility of the needle support, the needle mounting is
seen by the groove as a light and stiff thing, then the groove moves the
needlepoint and the tonearm also, resulting in a non effective vibration
that migrates along the tonearm instead of producing sound.

The effective sound production goes along with the movement of the
needlepoint relative to the cartridge. So a light tonearm needs a very
flexible needle mounting, and a massive tonearm needs a more stiff
cartridge. If the needle support is too flexible for the tonearm, then the
groove prodices sound, but cannot displace the tonearm across the record
properly, starting to skip and mistrack.

All the play is related to the transmission of vibrations thru a system
formed by coupled springs and masses, and if you know physics it is
relatively easy to see how the thing works. Then there is the famous
electromechanical analogy, used by Maxwell at Bell Laboratories to
calculate and design the revolutionary Ortophonic soundbox. With this
physics you convert masses and spring constants into electrical impedances
(actually capacities and inductions) so the calculation becomes that of the
transmission of electrical vibrations thru an impedance circuit.

These things are amazing... In any case, if you think about it, the issue
is pretty much intuitive. To provoke an adequately effective vibration in
the needle you need certain resistance behind it.

Iñigo