Re: [Harp-L] Cahmber size in combs - was injection molded combs

[Winslow Yerxa <winslowyerxa@xxxxxxxxx>]

When designing the Discrete Comb, I found that chamber size had a big effect on response. Dividing the standard diatonic comb chamber into two halves made the reeds unresponsive to all but the softest playing (i.e., lowest air veloicities). I had to thicken the comb and then widen the chambers internally to achieve an acceptable response to normal breath volumes.
 
It seems that a larger chamber size has a sort of shock absorber effect that dampens the effect of trying to push a large volume of air quickly past the reed. Some double-reeded harps likewise have holes or slots punched in the dividers between upper and lower reeds. Blocking the slots for the lowest-pitched reeds will make them choke.
 
Going in the other direction, most chromatic harmonica combs have ramps installed to reduce chamber size for the midrange and high reeds, with the ramps reducing the chamber size more and more for the higher pitched reeds. As the high reeds need less air for activation, they also benefit from a smaller chamber. I've tried adding ramps with modeling clay to ramp-less combs and noticed that the effect is easier reed activation and slightly brighter tone.

Winslow

Winslow Yerxa
Author, Harmonica For Dummies, ISBN 978-0-470-33729-5
            Harmonica Basics For Dummies, ASIN B005KIYPFS
            Blues Harmonica For Dummies, ISBN 978-1-1182-5269-7
Resident Harmonica Expert, bluesharmonica.com
Instructor, Jazzschool for Music Study and Performance


________________________________
From: Jonathan Ross <jross38@xxxxxxxxxxx>
To: harp-l@xxxxxxxxxx 
Sent: Monday, October 29, 2012 2:41 PM
Subject: [Harp-L] injection molded combs

"Another facet of the comb discussion that has been discussed before is
thickness.  We could start a whole other debate about that. "

Comb thickness is basically a factor of chamber size.  How chamber size effects the performance of a harmonica is an interesting thread.  Chambers can have an effect at times (see some of the resonance issues with regards the XB-40).  Are the sizes enough to have an effect?  Hard to say.  I doubt the small differences mentioned here would have a huge effect, but it's possible.