[CAUT] Baldwin SD-10

[RicB]

Hi Jim.

Every time this front duplex subject comes up I hear at least 5 
different versions of what it is or isn't.  Grin... I think I give up 
trying to find a real life original type what it was meant to be 
definition.  That said.... my inexperience with front duplexes agrees 
with what Ed McMorrow wrote 20 years back. To begin with, he agrees that 
the front duplex will deliver the best sound when it is not tuned to an 
harmonic of the speaking length. He speaks of de-tuning the thing.  On 
the other hand, he disagrees with you about the profile not making a 
significant difference.  I've been comparing capo bar profiles with 
string noises ever since reading his book, and keeping track of how 
re-profile jobs I've done hold up over time.   I simply can not conclude 
otherwise then the detuned front duplex with a sharp "V" profile on iron 
not overly hardened yields the best results.

The basic precept of the duplex idea as I understand it is that string 
energy is going to bleed past the capo no matter what you do.  The front 
duplex length then is meant to store some small amount of this and 
reflect it back to the speaking length.  Whatever relationship between 
speaking length and front duplex length was originally intended is 
perhaps less important then whether or not there is some positive effect 
for any given front length

What I've noticed about front duplex lengths also agrees with what Ed 
writes.  If they are tuned to a harmonic... then a whistle-sh kind of 
string noise is apt to occur. If de-tuned as per Ed's suggestions  then 
this does not occur.  Sizzling, buzzing  or string noise on the other 
hand seems to me more a product of the profile of the termination. Thats 
my experience anyways.

As far as instruments very short front lengths like the Bechstein.  They 
have a different character to their sound.  One either likes it or does 
not... but comparing the two in the context of this discussion strikes 
me as difficult.  They are completely different types of playing fields.

Interesting to note that Schimmel pianos now incorporate what they term 
a triplex scale, which puts front, singing, and back lengths into 
theoretical specified relationships with each other. The front duplex 
lengths are very quite indeed.

Cheers
RicB

    As for the sizzling front duplex, regardless of make of piano:  The
    primary
    problem is not the shape of the capo-bar string-contact area, whether
    radius, sharp, not sharp, or whatever, as long as it's within
    reason.  The
    basic problem is a fallacy of the duplex theory in the first place.  I
    know:  To say this puts me in danger of being accused of "heresy". 
    After
    all, this system has been proven for the past 134 years, and copied by
    several manufacturers after the original patent expired.  

    In my opinion, this fallacy becomes apparent when, contrary to what
    duplex
    proponents teach, we notice that the tones are better in those unisons
    where the duplex is NOT resonant with some partial of the speaking
    length
    than in those where it is.  To go into more detail, I'd need to get into
    the physics of critical coupling of resonant circuits, and I'd
    rather not
    go there just now.

    Jim Ellis