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In my opinion a significant source of the rumble on
non-moulded wax ones also are / were the lathe on which a given
cylinder was cut or dubbed. Add to that, the aberrations (that
develop as time passes) in concentricity from wax & celluloid
moulded ones & you've got considerable low frequency crap
that ordinarily would not be detected by acoustical
reproducers. Filtering the signal is thus often warranted.
Mechanically adjusting for improved concentricity
is often not as simple as one would hope. The physical distortions of the
tubes are not uniform: a setting for one end is not necessarily optimal for the
center or other end. Theoretically, adjustments for portions of the
cylinders should be made individually (in whatever increments you deem
desireable: every 1/2", 1" etc of grooves) & the file then assemble
edited. I do this comparably for disks when changing the arm's tangent
(for disks with extremely disparate radii of inner and outer most
grooves).
Another effective technique for dealing with
cylinders' tubular eccentricites is to run them at 1/2 speed and then double the
pitch for playback.
I don't know if anyone's undertaken to make for
themselves, or to offer them to others, but it'd be smart to have a
machinist precisely (accurate to .0001") mill a suitably configured
cylinder that'd be analagous to a test record or alignment tape. It'd be
made out of something soft that would retain its shape but not jeopardize styli
& their cantelevers, i.e. teflon. It wouldn't necessarily have to be
grooved, but would provide a baseline of measurement determining how much
rumble's generated from any playback mechanism versus that emnating from a
particular record.
Also, it's important to not assume that any
given groove is "vertical". As with all mechanical devices, tolerances are
involved. IF a groove induces a stylus to meaningfully oscillate at some
angle other than true perpendicular (+ or - the theoretical standard), then
unnecesary low and high frequency noises will occur. This is remedied by
continually adjusting the phase relationship of the stereo cartridge being used
to track the grooves. I call the process "vectoring". It's extremely
beneficial for ALL monaural grooves.
Best,
Shiffy
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