Poul Ladegaard's Air Bearing Tangential Tonearm!
Graph one (upper):
Arm resonance measurement, executed with the regular test record. Note the
very smooth response in the lateral ("vandret") plane all the way down to
3-4 Hz. The arm resonance in the lateral plane at about 2.8 Hz could be
damped to prevent susceptibility to vibration. The sound will hardly benefit
from this, since the flat response from 4-5 Hz on upwards already guarantees
a perfect reproduction of bass transients.
Graph two (middle):
The high level sweep is unable to provoke bad behavior or flexing in the
carbon fiber arm.
Graph three (bottom):
With a special vibrator developed for the purpose, the arm's behavior at low
frequencies can be studied more precisely than with a test record and with
better flexibility. By connecting the air pump to a variac it is possible,
simply and repeatably, to study how the damping of arm resonances depend on
the thickness of the air film. Curve A is with normal air flow (220 volts on
the pump). At 160 volts curve B is obtained and at 150 volts, curve C.
Apparently, a curve between B and C would seem ideal, but the situation is
unstable. The suspicion is that beginning friction between slide and arm base
is what 'helps' here. A damping concept must be based on something else than
the thickness of the air film.
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