[pianotech] Baldwin Front Duplex

[George F Emerson]

Hi Barb, et al,

On closer examination, you will see that the randomness that you observed is 
not in the speaking lengths, but only in the duplex lengths.  Another 
interesting phenomena is the sound emanating from the duplex segment.  If 
you pluck the front duplex length of most other pianos, the predominant 
pitch that you will hear is defined by the duplex segment length.  In the 
Baldwins with termination pieces, when you pluck the duplex length, the 
sound is "fuzzier" and less distinct, but the predominant pitch is that of 
the speaking length, not the duplex length.  If you search the archives you 
will find more discussion of the Baldwin "termination piece."

Before I went to work at Baldwin, I was a university tech.  We had a few SF 
and SD Baldwins (7' & 9').  Tuning the top two sections of these pianos was 
always troublesome to me.  I found that if I muted out the front duplex 
segments through the termination pieces, the tuning worked out better for 
me.  I used flange bushing strips to mute in this range.  It weakened the 
tone a bit, but "cleaned it up" in my judgment, as a tuner.  Nobody 
complained, so I left the mute strips in.  I didn't know why, but it worked 
for me.

When I went to work at Baldwin, I found a partial answer.  I plotted a graph 
of the FFT (Fast Fourier Transform) for each note in the termination piece 
sections.  As expected, there was a peak for the fundamental and each of the 
harmonic partials of each note.  The magnitude of the peaks was random, but 
this was also to be expected.  What was unusual was an extra inharmonic peak 
for each note roughly at the frequency of C88.  For some notes, this was 
harmonic to the fundamental, but in most it was inharmonic.  I believe this 
is what troubled me in tuning these pianos.

In the original design for the termination piece, the idea was to make the 
termination more rigid.  The termination piece provided a bridge between the 
vbar and the main body of the plate between each note.  In that respect the 
concept was sound.  Another part of the design intent was to use a very hard 
material for the termination, harder that the string itself.  This would 
result in less risk of the string, moving across the termination surface, 
damaging the termination surface.  If anything, Baldwin proved that you can 
get away with a harder material by using a larger radius at the termination. 
Just because you can get away with it doesn't mean it is the best practice. 
I prefer the termination to be less hard than the string.

The termination piece was developed before I came to Baldwin.  As I 
understand it, in the early prototypes, there were a few notes with an 
"objectionable" sound.  Experimentally, they found that increasing the 
duplex length resolve the problem.  Consequently, they designed a 
termination piece "type B" to substitute for "type A" for those notes deemed 
to have this objectionable sound.  Consequently, you see mostly type A, with 
random substitutions of type B to resolve this objectionable sound.  To me, 
every note with a termination piece has an "objectionable" sound, whether 
type A or type B.

The good news ..... and the bad news, is that there are still pianos of this 
type in use, but no more are being produced.  Baldwin piano production is 
now out-sourced to China.  While there are poor quality pianos from China, 
there are also good pianos from China.  In my present work, for a Chinese 
company, we are constantly striving to raise the level of quality.

Frank Emerson

----- Original Message ----- 
From: "Barb Nobbe" <barbara at pitchperfectpianos.com>
To: "PTG" <pianotech at ptg.org>
Sent: Monday, November 16, 2009 7:26 PM
Subject: [pianotech] Baldwin Front Duplex


> Hello list,
>
> I just have a curiosity question. I was tuning a 1999 Baldwin SF today and 
> was noticing, what I thought, was an oddity of the front duplex system.
>
> If you can see from the picture, some of the duplexes are wider and the 
> speaking length starts a little more back than the others. Surely, this 
> has some affect on the scaling and such, but what seemed odd was that in 
> the first section of duplexes, there seemed to be no pattern of how they 
> were set, wide versus narrow.  It just seemed like a random placement to 
> me.  (Sorry, the picture doesn't show the full section. I was trying to 
> get a good close up to show the difference in the duplexes).
>
> In the 2nd section of duplexes, (the high treble) they were all the same, 
> narrower ones and the start of speaking lengths seemed to look more 
> uniform.
>
> Did Baldwin have a reason for placing the duplexes in such a seemingly 
> random way?  Or does it even effect the scaling design with such a nominal 
> amount of distance difference that the duplexes were just placed in 
> whatever fashion they were placed?
>
> Again, just curious. The piano tuned fine, with whatever rendering 
> problems most Baldwin grands have. :-)
>
> Thanks.
>
> Barbara Nobbe, RPT
> Pitch Perfect
> 859-489-4793
> barbara at pitchperfectpianos.com