[CAUT] Duplex angle

[Alan McCoy]

Thanks Del. I will do just that. Read it again, that is.

Just made a device as described by Mark. One line is at 15 degrees, and on
the other side of the "V" cut-out is a line at 22 degrees.

Kawai GE-1 varied from 15 at low end of capo up to 22 degrees at A7.
S&S D varied from 22 to about 24 degrees.

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


-- Alan McCoy, RPT
Eastern Washington University
amccoy at mail.ewu.edu
509-359-4627


> From: Delwin D Fandrich <fandrich at pianobuilders.com>
> Organization: Piano Design & Fabrication
> Reply-To: "College and University Technicians <caut at ptg.org>" <caut at ptg.org>
> Date: Tue, 14 Nov 2006 11:03:23 -0800
> To: 'College and University Technicians' <caut at ptg.org>
> Subject: Re: [CAUT] Duplex angle
> 
>  
> 
> | -----Original Message-----
> | From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On
> | Behalf Of Alan McCoy
> | Sent: November 14, 2006 9:13 AM
> | To: College and University Technicians <caut at ptg.org>
> | Subject: Re: [CAUT] Duplex angle
> | 
> | Hi Mark,
> | 
> | Yes you are making sense. I like it!
> | 
> | So how did you arrive at your 15-22 degree parameters? If the
> | angle is less you get more unwanted noise and if too steep,
> | it is less tunable and the string digs into the capo more?
> | 
>  
> I don't know where or how Mark came up with his numbers but I did write about
> this in the Journal. Check the June and/or August 1995.
> 
> Del
> 
>