[CAUT] Tuning the back duplex

[Jim Busby]

Hi Ric,

 

Scott Jones and I had a rather lengthy discussion about his "string
couplers" and the backscale. Not in the tuning of the backscale but in a
new concept; tuning stability. He asked that I try to determine which of
the trichords seemed to go out seasonally (typically the left or right
string) and couple that one in the backscale to act as a "spring" of
sorts and possibly aid in overall stability. The hope is that the string
that seems to "go south" (my words) will not go quite as far out and the
tuning will at least appear to be more stable. He's not "selling" this
idea but wants try this out. I think he may be onto something.

 

So... the reason I'm adding this to your post is that I do believe this
is worth a try and will also help in "tuning" the duplex. It works
wonderfully for the front and may work in the back. If you've never
tried these they definitely have a place in pianos. My 2 bits.

 

Regards,

Jim Busby BYU

 

________________________________

From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Richard Brekne
Sent: Tuesday, May 29, 2007 3:14 PM
To: caut at ptg.org
Subject: [CAUT] Tuning the back duplex

 

Hi Daniel

I wonder if you might share your reasoning as to why the tuning process
will not allow for tension in the back length to remain higher then in
the speaking length once the back length is set to a higher tension. It
would seem to me that if one was careful not to move the speaking length
tension overly much in tuning, that this would have no affect. Playing
would tend to pull on the string... if anything tending towards more
tension on the back length... tho perhaps if the tension on the back
length was overly high  friction might slip and an evening out of the
two segments might occur.

Another thing that strikes my thinking is what about the tension on the
segment of string on the bridge surface itself.  Today I was working on
a 7 year old D which has early stage killer octave problems developing.
There was a good deal of phasing going on and some amount of bonified
false beats (single string beating).  I virtually eliminated all of this
by first pulling up the back length segment, then tuning with quite hard
test blows with sustain pedal down to let loose any that I'd over
pulled, followed by finding a pitch for the back lengths in which there
was no false beat apparent for these lengths and tuning them as unisions
to that pitch.  None of the resultant pitches for backlength unisons
were consonant with the speaking lengths... so the problem you allude to
with ringing after damping was not apparent.

I just got back from the concert where I heard the whole thing from the
studio of the National Broadcasting company here in Norway at the
concert hall in town.... not a hint of change through the whole concert.
I'll see the piano again in the morning.  Interestingly enough tho...
the experience did open my eyes a bit more into the world of the
percussive problems of the killer octave.  Nothing like a high class
studio to shed a kind of acoustic-microscope on piano sound.

Cheers

RicB



	
	> just what is the most optimal frequency relationship to the  
	> speaking length to tune these lengths too is another question.
I'm  
	> getting the feeling that if one assures that the tension is
higher  
	> in the back length then the speaking length.... that you end
up  
	> with a cleaner sounding instrument.... but I am still  
	> experimenting.  Any thoughts would be greatly appreciated
	>
	> Cheers
	> RicB

	I have not tread lightly here but delight in joining a fine mind
in a  
	study in which many have indulged in passing as have I.
	I find as have you that higher tension is favorable, variable  
	tensions (read variable pitches) not commensurate with the
series of  
	the speaking length are not too noticeable, but any piano with  
	tunable back lengths cannot stand perfectly tuned back lengths
for  
	the resulting stridency of the ringing after damping.
	
	Again, my own experience indicates regular tuning process rarely
can  
	keep the residual tension higher than the speaking length and
that  
	higher tension on the back length could aid soundboard collapse.
	
	Your contributions are greatly appreciated and look forward to a

	continuation of same.

	 

	Daniel Gurnee  HSU Ret.

	 

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