Re: [Harp-L] comb dimensions

----- Original Message ----- From: "Zombor Kovacs" <zrkovacs@xxxxxxxxx>
To: <harp-l@xxxxxxxxxx>
Sent: Friday, April 20, 2007 1:03 PM
Subject: [Harp-L] comb dimensions

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?

I think that the dimensions are important only because they affect the volume of the reed chamber. The chamber and your embouchure can form a Helmholtz resonator whose frequency is a function of its internal volume and the area of an orifice opening to the outside. My experience is that chamber shape doesn't affect sound very much but I would not say that it has no effect at all. The manufacturers, like Douglas Tate, who put ramps in the high pitched reed chambers obviously believed that it makes a difference.

I attached a large syringe to a single chamber that could be placed over any reed of a loose redplate. I blew air in through a plastic tube through the end of the chamber where it usually enters. The setting of the plunger in the syringe had major effects on the response of the reed. At some settings the reed would not sound at all and at others it responded enthusiastically. In this case, I think the syringe acts more like the player's embouchure than it does as variations in chamber size. It demonstrated to me the importance of embouchure and/or chamber volumes. It may be that chamber volume has a small effect because it is small with respect to the player's embouchure.

When tuning, I often "kiss" the loose reedplate to sound a reed without putting it back on the comb. Here there is no chamber at all but the opening in my mouth. I find that the very high-pitched reeds respond best when I hold my mouth as though there were a golf ball in it. The very low pitched reeds respond best when I put my tongue close to my lips and minimize the open volume in my mouth. The middle pitches will respond well to almost any embouchure. This demonstrates that the volume of the chamber is an important variable. However, it is puzzling and the opposite of what I had predicted. Go figure!

Incidentally, the fact that I can "kiss" the reedplate and produce a note that sounds exactly the same as it does when the plate is in the harmonica convinces me that the comb material plays no important role in sound generation and propagation. You can produce a note with a wind-instrument reed or mouthpiece from a trumpet or clarinet but it sounds nothing like playing the whole instrument.

Visit my harmonica website

This archive was generated by a fusion of Pipermail 0.09 (Mailman edition) and MHonArc 2.6.8.