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MMD > Archives > April 2001 > 2001.04.10 > 10Prev  Next

Duo-Art Expression Box Adjustment
By Sam Harris

I'm putting the finishing touches on an expression box from a Steinway
Duo-Art.  I'm a little confused about how the box should chart on the

Some have informed me the theme and accompaniment difference at the zero
intensity step should be around 1" H2O, and the difference at the 15th
intensity step should be around 13" to 15" H2O.  The lines should chart
almost straight with little or no curve being the most favorable.  Some
have said this is impossible to do, but it is not.  I have set the box
up this way and it is possible.  No, I did not make any modifications.
I did not shorten the springs or significantly alter the accordion

There are others who favor setting the box up so that when it is
charted the theme line and the accompaniment lines look more like a
divided highway, with the theme following the accompaniment line a few
inches H20 different.

Then there are those who say it's personal preference.  I agree that
the regulation of the box has room for personal taste, but surly the
roll editors work off a basic premise of how the box would "build up."

Did the roll editors expect the theme and accompaniment vacuum
differences to increase with each higher step? Did they edit rolls with
the expectation that the theme and accompaniment differences remained
about the same through out all the steps?

After reading a number of articles either E-mailed or faxed to me, I
decided to read again the Duo-Art Service Departments notes.  Here is a
quote I had read, but never really paid attention to.  It is the last
paragraph of page 4.

  "Each graduation in the Theme registers slightly louder than
   the corresponding graduation in the Accompaniment."

How would you interpret this passage?

Hmmm!  Does this mean there should be a 2" difference (or more)
throughout the entire chart, or should the charted lines diverge as
they approach the final step in order to get the same perceived
increase in volume?

If "slightly louder" at step 2 equals 2" H2O, would the same audible
difference at step 15 (without crash) be 2" also, or would you need to
have a greater difference in H2O to create a comparable increase in

I'm inclined to think the difference would not be more than 5" H2O at
step 15 if there was a 2" H2O difference at steps 1 or 2.  All of this
is speculation but according to the quoted passage, step 1 theme should
be a little louder than step 1 accompaniment; step 2 theme should be
a little louder than step 2 accompaniment; step 4 theme should be
slightly louder than step 4 accompaniment, and so on through each
step (without the crash valve).  I also realize each piano will have
different dynamic characteristics base on a number of other factors
that may or may not be related to the expression box (hammers, etc.).

Has anyone reading this ever regulated an installed box this way?
Have you ever compared the basic theme steps of 1,2,4 & 8 along side
the corresponding steps in the accompaniment to see if there was a
slight (personal preference) difference between the two?

If this was the philosophy one wanted to use as a basis for setting up
an expression box, would the lines diverge or would they be more like a
divided highway closely following one another?  I'm inclined to think
if one had a 2" H2O difference at step 1 and a 13" H2O difference at
step 15, the latter step would have a much greater increase in dynamic
level as compared to the first.

Here is my question:  "If slightly louder at the lower intensities lies
somewhere around 2" H2O difference, would the same audible differences
at the higher steps convert to 5" to 10" H2O difference?"  I can't say
until I get the box in the piano and hear it for myself, but maybe you
have already done the tests and can help me with the answer.

Maybe one should just make sure the box charts a good line with the
theme some higher than the accompaniment, then put the box in the piano
and then make sure the basic theme steps of 1-2-4-8 are just slightly
louder than the same steps in the accompaniment.

What are your thoughts about it?  Maybe this whole line of thinking is
a waste of time.  I'm sure I will get a few replies which state "Just
recover everything and set the gaps per the standard (which I agree
with), set the zero to just play with the damper raised, and not play
with the damper at normal, and be sure to get the spill to close at
step 10 and the crash to operates at 15, and let it go."

Others will say "let your ears be the guide," and to an extent I agree,
especially when one must "personalize" each box for the player action
and piano action it is mated with.  I'm looking for someone who has the
"secret" papers from Aeolian that gives the measured outputs of the
steps.  (Just kiddin'!)

I have read the Chester Kuharski article and have also looked at the
"WIND" program settings to see how they have interpreted the build-up
of vacuum.  I have even charted the "WIND" program settings and find
the lines do diverge some but not a great deal.  I have all my charts
in GIF format which are very small.  If anyone cares to discuss this
further I can provide the charts.

I will be installing this box in the next few days.  I will be
regulating the box to play the base theme intensities (1,2,4,8) a
little louder than the same Accompaniment step.  I will then use the
test roll to re-set the zero intensity and then chart the box and see
how the lines track.  Regulating the box this way may be a total waste
of time, and expression may be _awful_, but at least I will know that
the above quoted phrase is not really true.

Sam Harris - Greenville, North Carolina

(Message sent Tue 10 Apr 2001, 22:00:29 GMT, from time zone GMT-0400.)

Key Words in Subject:  Adjustment, Box, Duo-Art, Expression

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