[Harp-L] Re: The Comb Debate



Hi Aongus,

The story as told to me by a well-known player is that he used a high-end,
customized harp during a recording session, which the engineer found to be
too bright.  He switched to a stock Special 20, whereupon the engineer was
happy.  An exotic comb material would have been only a small part of the
customization of the instrument in question.

I doubt that the comb material per se affects the sound of the harmonica,
but I do think that the comb's mass and hardness can affect the efficiency
of the reeds' performance, by how much the comb either absorbs or reflects
their vibration as transferred through the reed plates.  And if a reed plate
can't transfer a reed's vibrations, why is it that when plucking the reeds
of an unmounted 270 Super Chromonica reed plate, the reed tuned closest to
the resonant frequency of the plate itself always sounds dull, only to ring
normally once mounted onto the comb?  It seems as if the loose reed plate is
vibrating sympathetically with the reed tuned closest to it, thereby
absorbing some of its energy.  Once mounted directly onto a comb, the reed
plate has no effective resonant frequency itself but rather contributes to
the resonant frequency of the plate/comb assembly, which is lower than the
pitch of any of the reeds and unlikely to vibrate as much.  An unmounted or
insecurely mounted reed plate may to a lesser extent vibrate sympathetically
not just with the reed tuned closest to it but with the other reeds, insofar
as the upper partials of its resonant frequency are close to those of the
reeds.

So a comb vibrating along with the reeds is thus perhaps not a good thing in
that, like the reed plate, it would thereby absorb energy from the reeds and
detract from their ability to swing freely, affecting
their response and loudness, if not tone.  A hard, high-mass comb might
resist vibrating along with the reeds more than a flexible, low-mass comb,
leaving the reeds unimpeded and unaffected.  A soft gasket between the reed
plate and comb would partially isolate the plate from the comb, preserving
some of its ability to vibrate sympathetically and absorb energy from the
reeds.

Best regards,
Rick




> ------------------------------
>
> Message: 4
> Date: Thu, 2 Sep 2010 10:02:49 +0100
> From: "Aongus Mac Cana" <amaccana@xxxxxxxxxx>
> Subject: [Harp-L] The Comb Debate
> To: <harp-l@xxxxxxxxxx>
> Message-ID: <A63E009F389B43789703E2C2C8D1B671@fujitsu2bq5kq4>
> Content-Type: text/plain;       charset="iso-8859-1"
>
> At the Willie Clancy School a year or two ago, I remember that Rick Epping
> remarked in passing while discussing another topic, that he had
> participated
> in a recording session where a harmonica player presented with a harmonica
> having some exotic comb material (i.e. not wood). He said that the sound
> engineer picked up right away that the sound of the harp was as he put it
> "too bright"
> As Rick has fettled, designed, and built - not to mention played more
> harmonicas than I have had hot dinners I am prepared to defer to his
> opinion
> that there may be a perceptible sound difference to the educated ear or the
> audio instrument arising from the use of different comb materials.
> I recall that he also did not think much of my simplistic engineering
> proposal of achieving air tightness by using a paper gasket between reed
> plates and comb.
> BeannachtaÃ
> Aongus Mac Cana
>
>
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