[CAUT] Baldwin SD-10

[James Ellis]

Stan Kroeker asked some questions re a Baldwin SD-10, and Ron Nossaman made
some appropriate remarks in reply.  Also, I think someone else had some
questions earlier about sizzling noises in front duplex sections, whether
Baldwin or another famous make.  I would like to add a comment or two of my
own.

In some SD-10s, in the top two treble sections, the muting felt between the
tuning pins and the string rests is only cosmetic, and is not thick enough
to touch the strings.  That leaves the leading sections of the strings free
to vibrate whenever they just happen to be resonant with some partial of
the speaking lengths.  Enough energy can bleed past both termination
contacts, the front termination and the string rest, and get to the leading
end of the strings (in front of the tuning pins) to make them sing like
crazy when they just happen to be resonant with a speaking-length partial.
The bandwidth over which this resonance will occur is very narrow, but it
does happen now and then, and it really sounds wild when it does.  The
remedy for this is simple - thicker felt under the leading ends of the
strings between tuning pins and string rests, so it will actually touch the
leading sections of the strings, and not just look pretty.

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.

Also, notice those pianos where there is no front duplex, and the spacing
between capo bar and string rest if fairly close.  Chances are that you
will also notice those strings do not sizzle.

So, what are the solutions for a sizzling front duplex?  There are a few
that will work:  However, they are NOT muting the duplex (which will make
the tone dull and decrease the sustain), NOR raising the string rest so
high that it will put the angle across the capo bar so steep that the
string will dig in and make deep grooves.  The trick is to put those duplex
string sections OFF resonance with the partials of the speaking lengths
without muting them.  I'm told that Scott Jones' "PitchLock" clips will
sometimes do the job, but I have not tried them myself.  I have my own
method, but it's still under development, so I'm not recommending it just now.

Sincerely, Jim Ellis, RPT