rear string lengths

[Ron Overs]

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Hi Dale,

As usual, I get around to replying to a topic by the time you've 
probably forgotten that you wrote it.

At 10:22 PM -0500 24/11/02, Erwinspiano@aol.com wrote:
>Although there are many reasons for the usually generous sustain 
>times heard on Mason &Hamlins

Indeed the heavier rim construction and thicker plate webbing (at 
least when compared to the slightly built S&S instruments, and the 
later offerings from Kawai and Yamaha) would also contribute to 
sustaining qualities. I was quite impressed with these aspects of the 
M&H B I saw at Reno.

>  all this talk of rear duplexes got my attention the other day as I 
>tuned one of my recently bellied Mason A's. All the backscale lenths 
>in the plain wire are generous. I found the sustain very good in the 
>K- ovtave as is usual for these pianos with decent boards.  I also 
>note that the first 9 notes of the first capo section had  tuned 
>duplexes corresponding to a 6th partial and the rest of the section 
>double octaves. . . .the rear string lengths of the first nine notes 
>were quite long. Starting at about 4 inches down to about three then 
>back up to longer lengths again.

The ultra short back scales used by some makers would seem to be 
effective in reducing sound board panel response (since the short 
back-scale lengths would function like a group of small bars, holding 
on the bridge - I just imagine them controlling the panel - don't 
move).

>Although these segments were fairly well in tune the greater 
>attributing factor I believe is the long backscale lengths.

Yes I suspect that it is important also. Although they can to be too 
long also, which causes terrible back scale noise problems (the 
Yamaha CFs of the mid '70s had high noise trebles which were shockers 
in this regard). When we rebuilt a KG6 Kawai (a piano known for its 
intrusive back scale noise) in '99, we relocated the hitch pins and 
set the bearing blocks to a shorter tuned layout (filling the 
original pin holes with car body filler). The new hitches were 
located 20 mm (which is a standard figure we use) behind the revised 
block locations. The outcome was very pleasing indeed.

>Other contributing factors would be wide cases/board

What do you mean by wide cases/board ?

>  good scales (mostly)

The M&H cross over is somewhat old worldy, complete with 
diving-tension-syndrome as the treble bridge approaches the crossover 
- like so many other makers, some of whom consider that they are 
modern piano manufacturers.

>, good bridge location in the center of the board etc.) (As a side 
>noteRecent discussions on Mason a's very short bass backscale 
>lengths didn't however in this case render the tone unacceptable by 
>any means. Tail thinning helps greatly on these pianos with 
>conventional belly's)

Indeed, but if it had a longer back scale it might have been even 
more impressive.

>   Finally the question. What are adequate backscale lengths  capable 
>of giving  increased freedom/sustain. The lengths in this case are 
>much longer than the average stwy. It seems like 3 to five inches on 
>any piano(in the capo) would allow more bridge and board freedom.

Agreed, but five inches or 125 mm would be getting towards the longer 
length which might be appropriate for the rear duplex - any longer 
and there is some risk of intrusive back scale noise.

>   If I removed the duplex on the average stwyL and changed nothing 
>but the string lengths.(forget the tuning) what would happen?

You'd probably get some improvement. But I suspect also that the 
smallish bridge dimensions could be a likely factor in the less than 
impressive sustain of many Steinways. Back in 1990 I re-bridged a 
circ. 1925 New York D which had amazing board crown, but the bridges 
were shot (a well known Australian piano maker had previously 
'rebuilt' this piano by inserting shortened balance rail pins into 
the split treble bridge, presumably in an attempt to gain a tighter 
fit between the 'bridge pins' and the split bridges - the outcome 
seemed to be somewhat less than impressive). Furthermore, I suspect 
that this piano might have been one which the belly man built while 
he was thinking about lunch, since there was virtually no bearing but 
substantial board crown. There we also major disagreement between the 
bearing on bass bridge relative to that of the long bridge. Since the 
board appeared to be relatively undistorted with age, I could only 
conclude that it had been poorly assembled.

So I took the opportunity to rectify the down bearing by building 
taller bridges instead of lowering the plate, since already I had 
begun to suspect that tall bridges helped sustaining qualities. When 
the bearing was finally set this piano ended up with a nearly 40 mm 
high treble bridge in the mid section (with an unstrung down bearing 
setting of 6 mm - 4 of which typically sinks out during the 
stringing). The sustain of this piano is very good. One old timer 
local tech (John Rocks), who has - since rest his soul - graduated to 
harp tuning, claimed that I'd transformed the piano into a European 
style singing piano which had a slightly smaller upper dynamic range. 
I agreed. It was an important lesson for me on the importance of 
bridge rigidity, since nothing else on the piano was altered (apart 
from reshaped capo and duplex bars - which were unhardened since we 
only started this practice in '94-95).

>      I'm looking for suggestions and expeience from whomever.

I that while I still feel somewhat unsure about this topic, I have 
developed hunches. I feel that the back scale length should mirror 
the requirement for the excursions necessary to produce the lowest 
harmonic of the adjacent notes. In other words, in the bass where a 
significant ' board displacement is required to generate effective 
sound pressure level of the fundamental, the board must be at its 
most moveable. This doesn't necessarily mean floppy, since we do want 
the board to move as a homogenous whole as much as possible. But the 
edges or perimeter of the board should be very flexible. As the 
frequency of the fundamental frequency increases as we move up the 
scale, the sound board should become progressively stiffer. If the 
back-scale lengths gradually shorten they will work with the 
stiffening sound board panel to help raise the impedance of the board 
for the higher notes. But I do not think we should use 30 mm 
back-scales unless we are looking for less sound pressure level in 
the treble. Of course, this might be a legitimate goal when designing 
a small grand for the home environment.

Interestingly, while still on this matter of appropriate sound 
pressure level for the environment, the buyer of our piano no. 001 
has it housed in a largish music room at his home. This piano 
produces so much volume that it sounds somewhat like it is trapped in 
a biscuit tin. I suspect that 225 cm is too large for a home 
environment piano. So it may be that a suitable design for a 200 cm 
grand might incorporate slightly shorter back scale lengths to reduce 
the sound pressure level to more acceptable levels for the home.

Just a couple of thoughts from down under.

Best,
Ron O.
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OVERS PIANOS - SYDNEY
Grand Piano Manufacturers

Web: http://overspianos.com.au
mailto:info@overspianos.com.au
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