[Harp-L] comb dimensions

[Zombor Kovacs <zrkovacs@xxxxxxxxx>]

What about comb depth? Or maybe we call it width. I am
talking about the length of the chamber, not the
height. How does that affect the sound?


--- Winslow Yerxa <winslowyerxa@xxxxxxxxx> wrote:

> There are two aspects to comb thickness:
> 
> - player comfort
> 
> - effect of reed chamber geometry on reed behavior 
> 
> The standard diatonic thickness seems to be the most
> comfortable for
> players. This may be due to what diatonic players
> are already used to -
> many different types of harmonica have many
> different overall
> thicknesses in the mouth - chromatics, bass
> harmonicas, Auto-Valve
> style octave harps, and single reed diatonics, among
> others. But people
> who play primarily the single reed diatonic seem to
> be physically
> uncomfortable with anything significantly thicker.
> 
> When I first started desiging the Discrete Comb, I
> took two wood-combed
> Marine Bands, removed the top cover and reedplate
> from one and the
> bottom cover and reedplate from the other. I then
> sanded the exposed
> comb top of one and bottom of the other to
> half-thickess, and glued
> them together with a thin sheet of plastic in
> between. 
> 
> The resulting harmonica was within a millimeter of
> standard thickness
> for a diatonic, but the reed chambers were only half
> as tall and half
> the total volume. The harp was comfortable enough in
> the mouth but
> would only respond to a very light breath attack and
> would not produce
> much volume.
> 
> As I developed milled combs with discrete upper and
> lower chambers, I
> started at nearly double the thickness of a standard
> comb, then
> progressively thinned the comb. The optimal thicness
> turned out to be
> abourt 1.5 times the standard thickness. Any thicker
> and no gain was
> realized; any thinner and response and volume
> suffered. Chamber volume
> was increased by carving more volume out of the
> walls of the "teeth" of
> the comb, which were structurally supported by the
> horizontal separator
> between upper and lower chambers.
> 
> Of course this is in a case where upper and lower
> (blow and draw) reeds
> are physically isolated from one another and
> expected to interact in
> the same air-filled chamber. Tremolo harmonicas in
> fact function with
> much smaller chanbers than in the Discrete Comb, but
> the same sort of
> response is not expected from them, and the player
> typically has four
> such chambers in his/her mouth at any given point,
> allowing for greater
> absorption of excess breath force. Also, the
> Knittler-constructions
> AutoValve harp has dual-reed chambers of a very low
> height but greater
> width as the blow and draw reeds are side by side.
> 
> For a dual-reed chamber such as found in the
> standard diatonic, larger
> mouth holes may actually  help in overall response -
> the bigger the air
> passage at the interface between the instrument and
> the player's body,
> the better. But the question of reed chamber height
> and the related
> question of overall chamber volume are ones that
> have not, to my
> knowledge, been systematically addressed.
> Anecdotally, chambers that
> are too large are known to cause problems, as in the
> reed chambers in
> Holes 9 and 10 of the XB-40 in higher keys. In most
> keys this does not
> cause a problem, but in the keys of C and above, the
> chambers have a
> resonant frequency that is lower than the pitch of
> the reeds and pulls
> their pitch down.
> 
> Winslow
> 
> --- J Compton <jofjltn4@xxxxxxxxxxx> wrote:
> <snip>
> >  
> > As for what does (or might), how much work has
> been done
> > experimenting with changing the comb thickness? 
> Most production
> > harps seem to have about the same comb thickness
> (opening the door
> > here for someone who has measured dozens of them
> to correct me and
> > ridicule me for speculating where real data
> exists).  Is this an
> > optimal thickness or just a traditional thickness?
>  I'd search the
> > archives, but can't get there from work at the
> moment.  Please
> > forgive me if a search would have yielded this
> info.
> >  
> > Also, what might be the next big development?  The
> recent Seydel with
> > the stainless steel reeds is an example...maybe. 
> Any prediction on
> > what might be next?
> >  
> > Jonathan "the future is hazy" Compton
> > 
> > 
> > 
> > > Date: Fri, 20 Apr 2007 08:28:46 -0700> From:
> zrkovacs@xxxxxxxxx>
> > Subject: Re: Subject: Re: [Harp-L] comb material>
> To:
> > harp-l@xxxxxxxxxx> > WHen? Im not gonna check
> back. If it is so, I
> > am> sorry. I thought it was me. But to me it
> doesn't> matter who it
> > was. If it was you, its probably all the> same. >
> > Zombor> > > ---
> > Jeff roulier <jroulier@xxxxxxxxxxxx> wrote:> > >
> At 12:36 PM
> > 4/19/2007, you wrote:> > > > >It seems I have
> stirred up still water
> > (if there is> > >any saying similar to this in
> english) with the> >
> > comb> > >material topic :-)> > > > > > Check the
> archives... I was
> > the one who started this> > debate. > > > > > > >
> >
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