RE: [Harp-L] The shapes of the covers



What comes to my mind is that the covers can only contribute to the tone
if they are allowed to vibrate freely; as with the top of a fine violin.
But, by nature of the beast, the covers are compressed (squeezed) when
playing. Even in a neck rack, your lips would lightly compress the cover
plates. What ever they may be made of could not vibrate freely anyway.
Therefore, to me, the only contribution a cover could make to tone would
be via the "shaping" of the sound leaving them in the same way different
horns connected to a PA speaker's tweeter would "throw" the sound
differently.

Yet, in the case of the harmonica covers, this "shaping" would never
really happen, in my opinion, for the shaping of the sound would require
a bit of distance for the phenomenon to occur. So, how would the shaping
take place if we are playing up against a vocal mic or compressed and
tightly cupped with a bullet mic? I just don't see it happening.

The comb material I can kind of see, however; even though it too is
compressed while playing. (We squeeze the cover plates, which transfers
the pressure to the reed plates and ultimately to the comb.) When you
play an acoustic guitar, your arms, chest, abdominal area and perhaps a
thigh if your are seated, are restricting a lot of the guitar body's
ability to vibrate freely, yet there is a huge difference in volume and
tone between different woods and a steel resonator body. This would tend
to substantiate, to some degree, the comb material "argument"; although
a guitar body presents a lot more surface area than does a harp comb.

John Balding
Tallahassee, FL

-----Original Message-----
From: harp-l-bounces@xxxxxxxxxx [mailto:harp-l-bounces@xxxxxxxxxx] On
Behalf Of Vern Smith
Sent: Friday, July 11, 2008 12:46 PM
To: harp-l@xxxxxxxxxx
Subject: Re: [Harp-L] The shapes of the covers

As harp-l's self-appointed, skeptical old curmudgeon, I hear the call of

duty to bust another myth.

There is nothing about the acoustics of the harmonica that suggests that
the 
covers play any role in the generation of the sound.  The covers define
the 
shape of the sound passage from the reeds to your ear.  They might 
conceivably affect the coupling of the sound to the outside air as does
the 
bell of a horn.  They might have a slight effect on loudness but not
tone.

Because the human ear has a logarithmic response, small changes of sound

energy are imperceptible.

I predict that in a blind comparison of machine-blown diatonics,
listeners 
could not distinguish between groups of harps with covers and no covers 
(much less covers having minor design differences) by the sound alone.
I 
suggest that any effort to achieve nuances of tone (warm, bright, etc.)
by 
means of cover design is wasted.

Vern
Visit my harmonica website www.Hands-Free-Chromatic.7p.com

----- Original Message ----- 
From: "John F. Potts" <hvyj@xxxxxxx>
To: <lavoie@xxxxxxxxx>
Cc: <harp-l@xxxxxxxxxx>
Sent: Friday, July 11, 2008 2:57 AM
Subject: [Harp-L] The shapes of the covers


> Mark,
> What effect do vented covers (Big River, Marine Band) have as
compared to 
> unvented covers (Mesterklasse, Golden Melody, Promaster)  or very
slightly 
> vented vented covers (Proharp)?
> JP
> _______________________________________________
> Harp-L is sponsored by SPAH, http://www.spah.org
> Harp-L@xxxxxxxxxx
> http://harp-l.org/mailman/listinfo/harp-l 


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