[CAUT] Duplex angle

[RicB]

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