[pianotech] GH-1s

[David Love]

Correction, this sentence, third paragraph of #4 below, show read "will be"
less than 1.5%.

The board does deflect and the residual measureable bearing will not be less
than 1.5%, as it should be in my view.  

David Love
www.davidlovepianos.com


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of David Love
Sent: Wednesday, December 19, 2012 1:11 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] GH-1s

Ron:

My responses (I've numbered yours below so that will be easier to follow):

1. What you said was that there was never a reason to use trichord wrapped
strings.  If they sound better, that's a reason to use them.

2. I wouldn't consider the Asian lacquer clang the current standard.  If you
are rebuilding a Steinway piano then the best of the Steinway pianos is the
standard unless you decide that it isn't.  The scale doesn't change
appreciably, meaning you aren't converting a 155 lb plain wire string to a
175 lb string or a 145 lb one.  So the board will need to be designed
accordingly.  We don't need to revisit the inconsistencies of certain
methods and procedures, I think we agree on that. 

3. Yes they do, we agree on that. 

4. Yes, here is the heart of the matter.  I wouldn't consider my rib scales
light, nor heavy but just right ;-).  We haven't gotten into side by side
comparison of rib scales and I'm not sure this is the time for that but I
wouldn't consider my rib scales light at all, but nor are they heavy.  They
are calculated to carry the full downbearing load by themselves.  Once major
difference is that I happen to think that fixed ends formulas are a more
realistic approach than you do based on your use of simple ends formulas and
so and so my rib scales may well be lighter than yours.  But I wouldn't
consider them light.  

The boards don't have a lot of compression.  If you are thinking that my
panels ribbed at 5.5% and yours ribbed at 6% have a significant amount of
difference in terms of compression at any given time, I think that's
overstating the significance.  That amounts to about 5% difference in RH.
This difference between hybrid and RC&S is somewhat artificial to me.  Your
6% board has compression when the humidity is above 35%.  Mine has
compression when the humidity is above 30%.  I don't want the board going
under tension but neither do I want it in an environment where the humidity
is 80%.  Some modest amount of compression is desirable to keep the board
from going under tension.  I crown the ribs but not as much as you do.  I
just want enough crown that I can flex the board and still have some crown
left.  Much more than that is unnecessary, in my view, and may even create
too much stiffness, though I'm not sure as I haven't really ever researched
that, but I've thought about it in light of other assemblies I've made with
tighter radii.  Of course with a smaller cutoff, or without one, a tighter
radii can create too much crown so that you have a problem with plate and
bridge height.  So I don't see any reason to overdo it.  

Did I say I use light bearing??? I don't think so.  The preset bearing
settings I use are 1.5 degrees through the piano.  In actual practice the
bearing in the bass ends up a bit lighter when you account for the string
looping and felt placed over bass shelf.  This is not particularly light
bearing in fact from what you wrote it's probably a bit more than you have.
I don't see the need to go to 2 degrees in the top of the treble though.
The configuration and rib scale make that area stiff enough.  I don't like
jangles.  I definitely want the board to be loaded, the spring compressed.
When all is said and done I go through and tweak the bearing based on what I
hear.  Do I need a bit more stiffness here or a bit less.  One and a half
degrees, just to clarify, is the preset bearing.  The board does deflect and
the residual measureable bearing will not be less than 1.5%, as it should be
in my view.  That's not to say the load associated with 1.5% has
disappeared, but it has been transferred to the board.  This is a broader
topic though.  Ideally I would end up with about 1/2 of the preload crown
but it can vary slightly.  The rib calculations in the design phase, btw,
will not yield a deflection of 1/2 the crown but something less than that.
The panel (and the bridge) do add stiffness to the assembly.  So even with
the board being thinned and the ribs being scalloped, the deflection in real
life will be less than the beam calculations would suggest.  When you glue
on the panel and then glue the panel to the rim, the entire assembly takes
on more stiffness than the rib scale alone would suggest.  As it should be.
But if you aren't taking that into account then, in my view, it's very easy
to over design the ribs.  

So taken all together we clearly have some differences in our design
approaches.  In my view it doesn't necessarily have to do with cut off bars
or bass floats or the addition of certain redesign features that I've
mentioned before or even the EMC at which we rib the boards, since those
aren't significantly different.  I think our differences are more
fundamental and boil down to how we approach designing a rib scale.  That's
really at the heart of any soundboard design, the ribs.  The other things
add up collectively to impact certain tonal aspects but it's the rib scale
first and foremost.  The rib scales I'm using are not light, in my opinion
at all, to restate.  They are adequately designed to carry the load by
themselves.  Thus I don't worry about panel thinning, in fact I think it
adds to a fuller tonal spectrum.  Were I making a compression crowned board
I would definitely think about not thinning the panel except maybe in the
bass.  The full thickness of the panel would be needed.  But the rib scale
would be lighter as well, likely, or at least they seem to be when you
analyze them.   As I said, spring rate is something that I look at but there
are other criteria that must be used to put the spring rate in context.  I
think the contribution of the panel must be considered because no matter how
you slice it, it contributes.  More, if it's thicker, narrower and not
diaphragmized, less if it's thinner, diaphragmized and wider.  But it
contributes and, in my view, must be considered in the equation.  

Sadly, at this point anyway, none of us are quite willing to give up our
spread sheets and design specifics because they remain somewhat proprietary.
Even if we did share them coming to a consensus is always difficult because
we may essentially have very different tonal goals, which is what I think.
Since we can't climb into each other's heads to know what we are looking for
and or experiencing this is always a challenge.  And, btw, that doesn't
bother me but that doesn't mean I don't have a strong opinion about it.  

I think we would both agree that making a rib scale that is inadequate to
the task of load bearing would be a mistake.  Where we may disagree is how
much margin there is and far we can go before we have a problem on the other
end.  You have commented favorably before about boards designed such that
they can't be overdriven.  But a board that can't be overdriven is quite
possibly a board that can't be driven enough.  I think there's as much
danger in that from an esthetic standpoint as making a rib scale that is too
light.  The target is fairly narrow, in my view, if the goal is the maximum
range of expressive possibilities.  While we evidently disagree on how
narrow that range can be and still be acceptable my goal is to make the
range as wide as possible even at the risk of being able to overdrive it
slightly (emphasis on "slightly").  And my standard for that is determined
by what I believe the piano literature actually calls for.   

David Love
www.davidlovepianos.com



Nossaman wrote:

1. Sure, maybe trichords might actually sound better in some instances, but
I never objected to how they sound tonally. My objections were in the
successful matching and hammer mating of three strings, which is enough for
me when I have the option of avoiding them.

2. Yet one of the common observations is that my pianos sound like what the
older folks remember from when they were kids, before the Asian and lacquer
clang became the standard.

3. Then they need to try a few things and think for themselves, don't they?

4. Okay. Some context. At last this is all fitting into something that makes
sense. You're building a much more nearly conventional rib crowned board
with a very light rib scale and moderate panel compression, loaded with a
light bearing. This explains your preference for a light bearing. 
The board couldn't take much more, and a partially panel supported board
(this would be a hybrid RC, rather than an RC&S board) will change more in
tonal character as the load increases than will a RC&S board. That follows.
Eliminating cutoff bar and fish also follows, as panel support allows this
where a light rib scale RC&S board wouldn't support much load without a
cutoff. This follows too. I'm not entirely sure, but I expect this accounts
for your insistence that thinning the panel is necessary, as you have a
minimal bearing load, you need as much panel flexibility as you can get just
above minimal acceptable stiffness. This also follows, if it's correct. This
is also why spring rate doesn't mean much to you because the rib stiffness
isn't nearly as important to quantify with a very light load and the panel
compression doing a fair share of the work of load support. It also somewhat
accounts for your insistence that the ribs in a CC board are doing the same
thing as a RC board. In a low crown light rib scale assembly, partially
panel supported and lightly loaded, they more nearly are, where a CC board
bears no resemblance to an RC&S assembly where the ribs are supporting the
load.

Taken all together, I now understand much of what you're doing. Your
preferences in bearing load, rib sizing, bass cutoff and fish, however, have
little to nothing to do with what I'm doing, which as I've said, is putting
a 6% or slightly above MC panel on a rib scale that will handle a bearing
load graduated from 1/2°-3/4° in the bass, to 1-1/2° to 2° in the treble
without any help from the panel.

Ron N