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Confusion over linear-tracking and pivoted arms aside, I wanted to add
to the pivoted straight-arm versus pivoted curved-arm discussion.

From a tracking distortion point of view (Baerwald & Loefgren distortion
curves and nulls, etc.), the pivoted straight- and curved-arms are
identical.  If the connection between the pivot point and the cartridge
is rigid, its shape (straight or curved) has no bearing on the tracking
distortion.  It's all simply a matter of geometry, and specifically
the position and orientation of the cartridge relative to the pivot
point.  The shape of the rigid arm between the cartridge and the pivot
point really doesn't matter when it comes to tracking distortion.

However, from a structural dynamics point of view, the pivoted straight-
and curved-arms are different.  Structural dynamics is the study of
structural stresses, strains and modes of displacement (aka resonances).
See http://en.wikipedia.org/wiki/Structural_dynamics and skip down to
"Modal Analysis" to learn more about structural dynamics.

A pivoted straight-arm has very simple modes (aka resonances), with a
single fundamental mode, weak even harmonics, and yet weaker odd harmonics.

A pivoted curved-arm has far more complex modes because of its shape,
with multiple modes and a wider range of even and odd harmonics when
compared to a pivoted straight-arm.

Many would argue - including myself - that a pivoted straight-arm sounds
better than a pivoted curved-arm (all else being equal, such as the pivot
type and bearings, mass, etc.) because of the more complex modes and
harmonics associated with its shape.  Of course, things can be done to
minimize these resonances by adding resonance damping material to any
tonearm.

Aside from aesthetics, in particular the iconic look from the 1970s
when the LP dominated and "S-shaped" or curved arms were popular,
there are no sonic benefits to the pivoted curved-arm design over
the pivoted straight-arm design (all else being equal, of course).
There may be ergonomic benefits for some applications, although I
haven't found that to be the case personally. I don't believe there
are any pivoted curved-arm designs in present-day high-end audio.


Eric Jacobs

The Audio Archive, Inc.
tel: 408.221.2128
fax: 408.549.9867
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http://www.TheAudioArchive.com
Disc and Tape Audio Transfer Services and Preservation Consulting






On 12/17/11 1:18 PM, "Graeme Jaye" <[log in to unmask]> wrote:

>On 17/12/2011 Andrew Hamilton wrote;
>
>AH> I think Mr. Jaye meant to say "tangential tracking arms."   However,
>the
>AH> tangential trackers do move along the radius of the disc.  (: Better
>AH> maybe to call the straight and S-shaped arms, pivoting.
>
>Sorry to have confused anyone.
>
>In my original post, I actually referred to "a radial tracking system"
>- which means, of course, a linear tone arm (and tracks along the
>radius of the disc, as you rightly say) - not a radial tone arm.
>
>The main thrust of my comment was that Goran Finnberg had actually
>confused the original question (which concerned the differences
>between straight and curved radial tracking arms) with linear trackers
>and went to great lengths to prove that he was right (which he was)
>although not understanding the question.
>
>Graeme Jaye
>
>[log in to unmask]
>
>Audio Restoration and Location Sound Recording
>http://www.personal-cd.com
>