Sam Harris said, "Each graduation in the Theme registers slightly
louder than the corresponding graduation in the Accompaniment".
You might have something here, Sam.

I have not been in all of your conversations but what I read into
this last paragraph is just as you suggest.  If the above statement is
absolutely true, then they are describing how the piano sounds to the
human ear and not necessarily how much vacuum is needed.  I take the
statement "each graduation" to mean that both the Accompaniment and
Theme accordions are compressed to the same intensity level (0-15)
and the vacuum level will be adjusted slightly higher for the Theme
regulator, such that a slightly louder sound will be heard when the
Theme holes are opened up.  You have to assume that this is for the
entire range of steps 0-15.  This suggests that the two springs are
nearly the same strength.   This is the case for some of the upright
Duo-Art's but not the majority.

Depending on the size of the piano, voicing of the hammers and the
action, will dictate the vacuum levels needed to achieve the "slightly
louder" difference between the Accompaniment and the Theme.  Your value
of 2" might be somewhat high for the lower vacuum levels but okay for
the higher ones.  You can detect a sound difference of 1/2" of water
fairly easily when the vacuum is at 5" but it is hardly noticeable when
the vacuum is at 10".  The percentage difference of 1/2 inch is much
lower as the vacuum level increases.  I did this test on my Duo-Art
Steinway today.  This is the reason that the two springs are of
different strengths in most cases.  Just because the wire diameters
are the same doesn't mean that they are of the same strengths either
-- be careful.

My Steinway has always played too loud so I have been experimenting
with different spring strengths because of our earlier correspondence
about one week ago.  Four or five years ago I sent my Duo-Art regulator
to Craig Brougher to see if he could solve the loud playing problem.
I believe he thought there was something drastically wrong with it
because of my vacuum numbers I was posting.  He did readjust the
accordions and bleed and reduced the maximum vacuum by about 10-15% as
shown on his graphs.  After installing the regulator, the piano sounded
great but was still very loud.  I also found that the separation
between the Accomp and Theme to be much larger than what I had
originally had set.  This difference didn't sound good to me at first
but I got accustomed to it.  This was probably because of one of those
listening preferences people talk about.

About six months ago I reshaped the hammers, lubricated the regulated
the entire action, re-pined about 25 sluggish bushings, and re-voiced
the hammers.  This helped quite a bit.  I can now reduce the zero point
to about 4-3/4" of vacuum but at that level a few of the keys still
don't hit.  This is probably stack problems which I haven't dealt with
yet.  The biggest change so far has been the voicing of the hammers.
I lightly needled them on the front face (1/16") and did some deeper
needling on the sides (1/8").

Just yesterday I got the weakest springs that I could fine and placed
them on the Duo-Art regulator.  After setting the zero point, the
results were excellent.  It brought the playing volume down another
notch but it still has lots of volume at the higher end.  When the
crash valve operates, at level 15, the volume seems to be good even
though level 14 vacuum level is much lower.  Because the spring tensions
between the Accomp and Theme is so low, it brought the separation down to
a level that sounds more realistic.  The piano roll coding still
separates the background and theme notes very well, even with the
Accomp-Theme suction values so close as seen in the numbers below.  It
would be nice to have about 1" to 1-1/2" separation at the lower end,
which can be done by changing the Theme zero setting.

For about $26 I just bought a digital fish weighing scale for measuring
the spring strengths.  Sam was using it to get his numbers and I
thought it would help us in "comparing apples to apples".

Note: I didn't regulate the spill with these changes.  The testing was
done in the piano using masking tape over the holes.  The Accomp and
Theme values were set to the same intensity level and the reading taken
with the theme hole closed and then opened.

These numbers were taken using the original stronger springs.  The
piano still plays loud with these springs.  It does take your breath
away because of the sure power of the playing.

Accompaniment spring strength  = 2.7 Lb./inch
Theme spring strength  = 5.4 Lb./inch

Level 0 - Acc. = 5"         Theme = 5-1/4"
Level 1 - Acc. = 6-1/2"     Theme = 6-3/4"
Level 2 - Acc. = 7-3/4"     Theme = 8-3/8"
Level 4 - Acc. = 17"        Theme = 12-3/8"
Level 8 - Acc. = 17"        Theme = 20-1/2"
Level 12 - Acc. = 23-5/8"   Theme = 30"
Level 14 - Acc. = 26-3/4"   Theme = 34-1/2"
Level 15 - Acc. = 28-1/8"   Theme = 36-3/4"

These numbers were taken using the weaker springs.  This is an attempt
to get the Accompaniment and Theme graphs to climb up at about the same
rate.

The playing volume is about where it should be for my Steinway with
these weaker springs.  The separation is very good but not as pronounced
as with the original ones.  If you graph these numbers, it shows that
the Accompaniment and Theme follow each other very closely between
level 0 through 12.  You still can detect a difference in the playing
volume when activating the theme hole and playing 3 notes at a time for
the entire range (0-15).   I believe this closely duplicates what is
found in the quote at the top of this message.

Accomp spring strength = 2.1 Lb./inch
Theme spring strength = 2.7 Lb./inch

Level 0 - Acc. = 5"         Theme = 5-1/2"
Level 1 - Acc. = 6-1/4"     Theme = 7"
Level 2 - Acc. = 7-1/2"     Theme = 8-5/8"
Level 4 - Acc. = 10-1/8"    Theme = 11-7/8"
Level 8 - Acc. = 14-1/4"    Theme = 15-1/2"
Level 12 - Acc. = 19"       Theme = 20-7/8"
Level 14 - Acc. = 21"       Theme = 24-1/8"
Level 15 - Acc. = 22" Theme = 27-1/4" (32" with Theme Crash enabled)

I don't know if this completely answers Sam's questions about the above
quote but I know what I will be doing to my regulator to solve the
"plays too loud" problem of my Duo-Art.  I also know a few customers
that have Duo-Art grands that have this same problem.

Pete Knobloch (Tempe AZ)