[pianotech] GH-1s

[David Love]

I guess I don't approach it quite that way.

The design starts with the scale, we probably agree.  In a piano that
averages 160 lbs per string in the plain wire section the low bass tensions
won't differ that much whether the piano is a Steinway M or a Steinway B.
What will be different is the manner in which the tension is achieved.  In
the M you will have to rely more on increased string diameter, in the B you
will rely more on string length.  The character of those mono and bichords
then will be somewhat different.  This is not unlike achieving higher
tension in the plain wire section by increasing the diameter of the string
(going up a half size for example) versus increasing the speaking length.
Those both will yield higher tensions but the character of the sound will be
different.  

The fact that one piano has less soundboard area is of no consequence in
determining the string scale except to the extent that you are limited in
terms of bridge shape and overall string length.  The tension targets will
be roughly the same.  In the small piano the amplitude problem is dealt with
by thinning the panel in the low end of the piano, insuring that the bass
bridge isn't too close to the rim, and/or installing a bass float.  The bass
float will probably require a change to the rib array but that's another
matter.  Lowering the tension in the bass artificially because the piano is
smaller will just create something that is unpleasant or out of balance, in
my opinion.  Avoiding gnarliness can result is a bass that sounds like a
rubber band.  

I'm not sure why you would want to create a quieter bass sound just because
the piano is smaller anyway.  It probably will be somewhat quieter already
owing to reduced soundboard area and perhaps less string mass.  Compensating
for clarity that is lost to diameter when sacrificing length can be done by
insuring the core diameters are not too large, that the bass bridge is
positioned as far from the rim as is functionally possible (at some cost for
reduced string length) and that the bass end of the soundboard has as much
mobility as possible by careful thinning or adding a float.  

The smoothness and difficulty of scaling of the transition will be limited
by the bridge shape possibilities and choices about how (and whether to)
install a transition bridge.  There are hazards to third bridges to be aware
of.  Positioning a separate bridge can put it in a place where the impedance
characteristics are quite different from the high end of the bass bridge and
the low end of the tenor.  Tying the bridges together can create excess mass
or stiffness at the low end of the tenor and into the transition that can
make it sound thin.  You can end up with something that sounds a bit odd,
more like a lute than a guitar, if you are not careful.  Or, you can end up
with two breaks instead of one.  Better is probably creating a semi
transition bridge that keeps the long bridge and the transition contiguous.
You'll be making a compromise of the scaling but you will anyway no matter
what.  If you shorten the length of the transition considerably sometimes it
will be better to have wrapped trichords rather than bichords (at least in
my opinion).  

Bottom line is that I don't think I would alter the lower bass scale because
you think it will accommodate a smaller piano better.  I would address the
small piano soundboard issues in order to make the impedance characteristics
more amenable to the reduced area that you have to work with.  That means,
to me, careful diaphragmizing which you can safely do if you are creating an
assembly with limited compression crowning needs.  I'd probably thin the
bass end below the bridge to something like 5-6 mm and thin the panel around
the bent side and up the straight side as well.  Judicious use or
elimination of soundboard shaping devices such as cut-off bars.  If you
install one, keep it small.  A careful analysis of the rib scale (as would
be expected anyway).  Optimal positioning of the bass bridge away from the
rim balancing speaking length needs or create a bass float.  Optimizing the
scaling at the low end of the tenor bridge to the extent that the plate
allows with careful consideration before creating separate transition
bridges both in terms of placement and support as well as the scaling that
connects bass to tenor.  

Better would be to remake the plate to allow more bass notes (of course not
realistic).  It's amazing what a 32 note bass does to solve scaling problems
in small pianos.   

David Love
www.davidlovepianos.com


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Jim Ialeggio
Sent: Monday, December 17, 2012 1:26 PM
To: pianotech at ptg.org
Subject: [pianotech] GH-1s

David L wrote:

<So, I guess I'm not sure what you mean by "this disconnect continues to
this day, to define and unfairly limit small belly design, and, mind
bogglingly, define upright design as well".

My comments mostly have to do with wrapped strings, as the small piano
"problem" becomes problematic in the transitions and low tenor through the
bass. The square acreage of the small soundboard limits the amplitude of
that belly. Trying to drive that amplitude when it is not there to be had is
to my thinking a problem. So, my take is that since the board simply cannot
physically comply with amplitude requirements to the degree a large belly
can, the strings in a small belly are asked to make up the difference by
making a more complex, noisy, and thus loud sound.

At least according to my messing with the spread sheets, the lower end of a
workable low tension scale in the bass, using modern wire, is or has been
defined by the need to effect a smooth transition into the plain wire.
Smooth in terms of loudness, as well as other string scaling parameters.
Since the in the plain wires low tension trebles are about 160lb/string
(480lbs/ plain wire unison) the effective bottom end of a modern low tension
bass scale ends up being around 190/unison to approx 300lbs or so at the
mono to bichord transition, and then the transition from 300 to 480 by the
trichord transition.

If you were to try and drop the bottom end of the tensions in the bass/low
tenor curve,  in order to create a quieter bass sound, with less noise, a
sound which makes up for lack of amplitude with stronger but still
relatively soft presence of real low partials (fundamental still remains
mostly absent because of belly size limitations), the transitions both from
tenor to plain becomes problematic in terms of BP% and loudness. The
differential in loudness between wraps and plains becomes problematic as
well.

So in this case, where the lower end of the wrapped string tensions are
determined by needs higher in the scale at the wrap/plain transition, the
material itself, ie the tensile strength of the wire, becomes in and of
itself the decision making entity, as the BP%  cannot be appropriately
messed with. In this case a key aesthetic decision is being made not by me,
but by the steel available to me.

My experiments with dropped tensions and lower tensile strength wire in the
bass on small pianos have been encouraging, and I am continuing them. But it
does mean having the freedom to explore sounds other than the bass growl,
which in a small belly, to me sounds more like a caricature than the growl
of a lion.

At least that's my take.

Jim Ialeggio




-- 
Jim Ialeggio	
jim at grandpianosolutions.com
978 425-9026
Shirley Center, MA