[pianotech] Tuning the duplex sections

[PAULREVENKOJONES at aol.com]

Makes much more sense now and closer to my understanding. Thanks. Large  
vente to go. :-)
 
P
 
 
In a message dated 3/16/2011 3:28:12 P.M. Central Daylight Time,  
del at fandrichpiano.com writes:

 
Actually  “sustain rate” should be “decay rate.” The rate at which the 
sound energy  dissipates whether into the bridge or elsewhere. In general a 
note with a high  decay rate will also have a short sustain time but this is 
not always the  case. Sometimes the energy in certain partials—usually the 
higher partials—can  decay at a rapid rate while energy in other partials—
usually the fundamental  and lower partials—can continue sounding for a 
reasonable amount of  time. 
Not enough  coffee. 
ddf 
 
Delwin D  Fandrich 
Piano  Design & Fabrication 
6939  Foothill Court SW, Olympia,  Washington 98512 USA 
Phone   360.736.7563 — Cell  360.388.6525 
_del at fandrichpiano.com _ (mailto:del at fandrichpiano.com%20) —  
_ddfandrich at gmail.com_ (mailto:ddfandrich at gmail.com) 
 
 
From:  pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On 
Behalf Of  PAULREVENKOJONES at aol.com
Sent: Wednesday, March 16, 2011 12:36  PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Tuning  the duplex sections

 
Actually,  I'm unclear on this terminology. Can you distinguish "sustain 
rate" and  "sustain time"? Thanks.
 

 
Paul
 

 
 
In a  message dated 3/16/2011 1:11:13 A.M. Central Daylight Time, 
_del at fandrichpiano.com_ (mailto:del at fandrichpiano.com)   writes:

 
My tests  demonstrated that when the tuned front duplex system is working 
as  advertised sustain rate increases and sustain time decreases. Think of it 
in  terms of conservation of energy. 
ddf 
 
Delwin  D Fandrich 
Piano  Design & Fabrication 
6939  Foothill Court SW, Olympia,  Washington 98512 USA 
Phone   360.736.7563 — Cell  360.388.6525 
_del at fandrichpiano.com _ (mailto:del at fandrichpiano.com%20) — 
_ddfandrich at gmail.com_ (mailto:ddfandrich at gmail.com) 
 
 
From:  pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On 
Behalf Of  PAULREVENKOJONES at aol.com
Sent: Tuesday, March 15, 2011 10:46  PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Tuning  the duplex sections

 
Del:
 

 
I  just wanted to thank you for your articulate and concise statement. My  
understanding has always been that the open front counterbearing increased  
the sustain in the speaking length because of the transfer of energy  back 
and forth across the capo. Am I reading you  correctly?
 

 
Paul 
 

 
 
In  a message dated 3/15/2011 11:50:34 P.M. Central Daylight Time, 
_del at fandrichpiano.com_ (mailto:del at fandrichpiano.com)   writes:

1)   With an inefficient termination--i.e., a V-bar with shallow string  
termination angles and "tuned" front duplex string segments on the other  
side--energy can be transferred back and forth across the V-bar. Because  the 
duplex string segments are tuned (in theory, at least) to some  calculated 
partials of the speaking lengths, vibrating energy at or around  the resonant 
frequencies of the duplex string segments will pass back and  forth across 
the V-bar with relative ease. Among other things, this has  the effect of 
increasing the rate of decay in the desired speaking lengths  because some of 
the energy that is transferred across the V-bar to the  duplex string segments 
is absorbed into the plate at the front bearing  bar. This loss is in 
addition to whatever amount of energy is absorbed  into the plate at the V-bar.

Since the so-called "tuned" duplexes  are rarely, if ever, accurately 
tuned, these vibrating portions of string  can, and often do, produce sounds at 
undesirable pitches that are close  to, but not quite on, some harmonic of 
the normally speaking strings. As  well, because the string deflection angles 
are shallow and vibrating  energy is being transferred back and forth across 
the V-bar, any slight  imperfections in the shape or surface texture of the 
V-bar can, and often  do, create undesirable vibrations or "string noises." 
In an effort to  control both dissonant vibrations and the string noises it 
is a common  practice to mute the front duplexes. This damping absorbs some 
of the  vibrating energy in the duplex string segments but it does not stop 
the  transfer of vibrating energy coming from the desired speaking lengths 
of  the strings to the duplex string segment. That transfer continues but 
it's  now a one-way street; energy is being dampened on the duplex side of the 
 V-bar and is now unavailable for any transfer back into the speaking side  
of the V-bar so the decay rate in the speaking string increases even more  
and the sustain time further decreases.

2)  When the string  angles are greater than about 15˚ to 18˚ and the 
duplex string segments  are kept reasonably short energy is not freely 
transferred back and forth  across the V-bar between the speaking string segments and 
the duplex  string segments. The termination of the speaking strings at the 
V-bar is  more efficient and most of the energy arriving at the V-bar is 
blocked and  reflected back into the speaking string segments. Some energy, to 
be sure,  is still absorbed into the V-bar and/or capo tastro bar but very 
little  makes past the V-bar it into the duplex string segments. In this 
case  damping the duplex string segments makes little difference because there  
is little energy there to be damped. 

As an added benefit, because  the strings are not "rocking"  back and forth 
at the V-bar, its shape  is less critical and string noises are virtually 
unheard of.  

3)  The back scale is a whole other issue. Energy is not  being transferred 
from the speaking strings across the bridge terminations  and to the 
backscale portion of the strings. The backscale is set in  motion by the motion of 
the bridge(s). Whether or not the backscale string  segments are tuned does 
not materially affect the vibrating energy in the  speaking portion of the 
strings or their decay rates and, hence, will have  little, if any, effect 
on how they vibrate or how long they vibrate.  

Whether tuning the backscale string segments has any positive  effect on 
overall piano performance is, for me, at least, an open  question. I have yet 
to see it conclusively demonstrated by even the most  ardent supporters of 
the scheme. Keeping an adequate backscale length is  clearly important but 
deliberately tuning the backscale to some partial  lengths of the speaking 
strings has long seemed an exercise in futility.  Besides, given the broad 
spectrum of fundamental waveforms and partials  driving the bridge(s) at any 
given moment (while the piano is being  played) it would be well-nigh 
impossible to avoid finding backscale  lengths that are not "tuned" to some 
fundamental or some partial of some  note or other. 

ddf

Delwin D Fandrich
Piano Design &  Fabrication
6939 Foothill Court SW, Olympia, Washington 98512  USA
Phone  360.736.7563 — Cell  360.388.6525
_del at fandrichpiano.com_ (mailto:del at fandrichpiano.com)  — 
_ddfandrich at gmail.com_ (mailto:ddfandrich at gmail.com) 


-----Original  Message-----
From: pianotech-bounces at ptg.org  [mailto:pianotech-bounces at ptg.org] On 
Behalf Of David Love
Sent:  Tuesday, March 15, 2011 4:10 PM
To: pianotech at ptg.org
Subject: Re:  [pianotech] Tuning the duplex sections

Yes, that's right of course,  went too far with that idea.  

So then why exactly does muting  the front duplex kill the tone?  Even a 
light muting in which the  rocking motion is presumably unimpeded.  What does 
the front duplex  contribute in that case (when it's unmated) and how does 
it  contribute.  Similarly, why does muting the front duplex in a piano  with 
a very short duplex not kill the tone nor does the tone suffer,  seemingly, 
from having a very short front duplex.  

David  Love
_www.davidlovepianos.com_ (http://www.davidlovepianos.com/) 






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