[CAUT] Duplex angle

[Alan McCoy]

OK. I hear you. So you must have devised some kind of experiment to prove
this to yourself - that the buzzing that we hear is not excessive leakage
across the capo, but is leakage to the capo instead. I'd like to be able to
do that experiment myself. Can you describe your experiment so that I might
be able to duplicate it?

Alan


> From: RicB <ricb at pianostemmer.no>
> Reply-To: "College and University Technicians <caut at ptg.org>" <caut at ptg.org>
> Date: Wed, 15 Nov 2006 09:11:48 +0100
> To: <caut at ptg.org>
> Subject: [CAUT]  Duplex angle
> 
> Alan.
> 
> I think if you look closer at what I said you might want to rethink your
> statement that your experience doesnt jib with mine.  <<Duplex noise>>
> is NOT the same thing as leakage ACROSS the capo.  Duplex <<noise>> is
> leakage TO the capo.
> 
> There are two things going on here that are commonly (and mistakenly
> IMHO) humped into one box called Duplex noise. The first is real
> bonified noise... buzzing, zinging, crashyness... whatever you want to
> call it.  That is leakage TOO the capo itself.  Leakage ACROSS the
> duplex simply excites the front length and doesnt make any <<noise>> in
> this same sense of the word at all.  You can-not prevent this leakage
> ACROSS the capo to the front length no matter what you do. And frankly,
> I suspect if it was measured in all the various termination
> configurations out there you would find it does not vary significantly
> at all. Heck... even with an agraffe you can excite the speaking length
> by plucking the small front length appropriately. This shows leakage
> ACROSS the termination from one string segment to another.  All you can
> really do is decide what you want to do with this leakage.  That is
> indeed rather central to the whole front duplex idea.  Exploiting it
> rather then trying to inhibit it.  Inhibiting it only really means
> absorbing that (roughly) same amount of energy through some method of
> damping it... but it is still energy that has gone across the termination.
> 
> Of course the angle is important to the termination from the standpoint
> of buzzing.. ie leakage TOO the capo. But even here the picture is a bit
> more complicated. Capo profile, hardness, and counterbearing angle all
> contrive to achieve a situation that allows for a good termination that
> wont cut the string in half and allows for tuneability.   A great
> example..... I just ran into grand a few days ago that had a constant 20
> mm front length counterbearing by way of a half round brass bar for the
> entire capo region. Counterbearing angle was quite steep... rougly 20
> degrees.  I dont think I have ever run into an instrument with a more
> buzzing front duplex in my life. It was simply horrible.  Now this is a
> short length... and steep degree... but still lots of loss TO the capo.
> 
> Touching the finger and changing the quality of the sound influences
> BOTH these issues.  You can touch a non buzzing string and it will
> change its quality as well.  Many will say to the detriment of the
> sound... at least in pianos designed with a front duplex in mind.
> 
> In short... Leakage ACROSS the termination and leakage TOO the
> termination are too different things.  Thats why the angle is quite
> important on the one hand and not nearly so on the other.   In fact....
> If one could prevent leakage TOO the termination by some other
> device...  it might actually be quite usefull to not have any
> counterbearing angle at all.
> 
> Cheers
> RicB
> 
> 
>     RicB said:
> 
>     "In my view, this angle does not significantly prevent leakage
>     across the
>     capo to the duplex segment regardless of its degree.  It DOES get into
>     how much leakage occurs to the capo itself and is inter-related with the
>     capo profile and hardness in this context."
> 
>     My experience doesn't jibe with this statement. I've noticed (haven't we
>     all?) that duplex segments that have a shallow angle are more prone to
>     duplex noise. The other part of this observation is that longer
>     segments are
>     also more prone to noise. I can't help but think that the angle has
>     everything to do with forming a termination to the speaking length.
>     Picture
>     a string with zero deflection at the capo, where the capo is just
>     touching
>     the string at the "termination" point. That would not provide good
>     termination, right? String energy lost to the duplex and string
>     noise. Now
>     raise the duplex segment up 1 degree. Still not good termination as
>     evidenced by loss of string energy into the duplex. Keep
>     incrementing the
>     duplex angle and at some point there will be better termination and less
>     energy lost to the duplex. Obviously the segment length, radius of
>     the capo
>     and the capo hardness enter into this issue, but I can't help but
>     think that
>     the angle is an important factor in termination. How else do you
>     explain the
>     phenomena that touching the duplex with your finger, or muting it
>     out with
>     felt, can drastically alter the tone quality of the speaking length?
>     If, as
>     you say, the "angle does not significantly prevent leakage across
>     the capo
>     to the duplex segment regardless of its degree", then why have any
>     angle at
>     all, if not to form a solid termination?
> 
>     Alan
>