[CAUT] Bass bridge, string scale, cantilevered bridge, tone

[Delwin D Fandrich]

 The B is one of my designs. At least the original was. When built well -- which
was seldom, if ever, the case -- it was a decent little piano. The undercut bass
bridge is one way of coupling the vibrating energy from the strings to the
soundboard in an area with just a bit more mobility than it would have had if
the bridge contact were right up next to the inner rim. It takes the place of a
cantilever by moving the contact point of the bridge out away from the inner rim
without introducing the rock and roll motion of the cantilever. Did it work?
Well, yes, for the most part -- keeping in mind that the piano also has a
laminated soundboard that is just a bit too thick for that area. Everything is a
compromise. The low bass performance is certainly better than it was with a
cantilevered bass bridge. (Yes, I tried both.) 

Could it be done differently with still better results? Perhaps. Were I doing
another piano of that size I'd now do it differently. If you've taken one of my
all-day seminars recently you might have a CAD drawing of how I would have done
a piano of that size in the late 1990s. It's on the last page or so of the
hand-out. And I've moved on a bit since then. 

This stuff has its greatest value in small and very small pianos. These --
assuming even moderately sensible design -- are the only pianos where the
cantilever shows up. With very few exceptions the backscale in larger pianos
(say from 200 cm on up) is long enough, and the bridge contact point is far
enough away from the inner rim, that cantilevers are not used. Even in the 185
cm to 200 cm range where cantilevers were used in the original design they can
be dispensed directly without much, if any, major surgery. 

It's from there down that the problem of the ever-shorter backscale begins to
significantly impede bridge motion and low bass tone performance. But even here
everything is relative. If the backscale length in the low bass averages, say,
100 mm, making it 20 mm longer will give the low bass a noticeable, but probably
not dramatic, increase in clarity and pitch definition. After all, you're only
making the backscale length 20% longer. And the low bass performance should
already have been at least reasonable. 

Increasing the backscale length from 25 mm to 50 mm, however, is a 100%
increase. And decreasing the cantilever overhang by even that much will
substantially improve its energy coupling efficiency. The combination will give
you a dramatic improvement in low bass clarity and pitch definition. Even
considering that we have made the speaking length of the string 25 mm shorter.
Most pianos in the 150 cm range will have an A-1 speaking length of around 1,100
mm (give or take some). Making this 1.075 mm, or about 2.3% shorter. I doubt
anyone could hear any tonal difference that could be attributed to this amount
of change in length. Will this piano end up with a great sounding bass? No,
probably not. But it will be a whole lot less bad than the original. 

There are a whole lot of pianos out there in the 150 cm to 180 cm range that
have low bass backscales in the 25 mm to 40 mm range. (Remember, it's the
effective backscale length we're talking about. Not the physical distance from
the back bridge pin to the c/l of the hitch.) Most of these pianos have
extremely short backscales and their bridges are all mounted firmly on a floppy
and lossy cantilever. In my opinion they can all be given a more
pleasant-sounding low bass by lengthening out that backscale and shortening up,
or removing entirely, that cantilever.

ddf


| -----Original Message-----
| From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On 
| Behalf Of Fred Sturm
| Sent: May 01, 2008 5:52 PM
| To: College and University Technicians
| Subject: Re: [CAUT] Bass bridge, string scale, cantilevered 
| bridge, tone
| 
| The answers to Alan's question I have read don't really deal with the
| topic: an especially short scale instrument. On the topic, I 
| happened today to see a Baldwin grand from around 1995, I 
| think it said model B with a number after it, not something I 
| had ever seen. It was a 4' 11"  
| or so, and had a bass bridge without apron or cantilever, and 
| the bass end almost touched the plate, but was undercut for 
| the lowest eight unisons (not contacting the soundboard). I 
| guess that is one way to do something or combination of 
| things. It did have accujust pins so that probably helped 
| matters. Not too bad a sound. Not too great either, but it 
| could have used some voicing, so maybe there was potential.
| 	But to Alan's question, there does seem to be a 
| tradeoff when you get to a really foreshortened scale. Would 
| the sound really be better if you foreshortened the scale 
| more in order to lose the cantilever? (No argument about 
| changing to German loops - that's likely to be an 
| unquestionable improvement). It seems like a tradeoff between 
| what the string is producing and how the soundboard is 
| transmitting, and if the input from the string is bad enough, 
| the better transmission isn't going to make for a better 
| overall sound. That's just pure "logical thinking based on 
| limited experience in related matters." Could be dead wrong, 
| but I think what Alan wanted was experience in this realm of 
| the mini-scale, and I haven't seen it addressed: will the 
| bridge change with the corresponding shorter scaling be 
| capable of a better overall sound, worth the trouble?
| Regards,
| Fred Sturm
| University of New Mexico
| fssturm at unm.edu
| 
| 
| 
| On Apr 30, 2008, at 2:18 PM, Alan McCoy wrote:
| 
| > Hi Jim and Ron (and others),
| >
| > I do not have enough first-hand experience with especially 
| short-scale 
| > instruments that have been recipient of the kind of 
| treatment that the 
| > Brodmann thread was about, namely new string scale with a shorter 
| > speaking length, longer backlength, no cantilever. But I am curious 
| > about what kind of tonal change I might anticipate if I were to 
| > rescale, say,  a Kawai GE-1.
| >
| > Would anyone be interested in describing what would be the likely 
| > tonal result with these changes to this short-scale piano? I know 
| > words won't likely do justice to it, but I'd be interested to hear 
| > anyway.
| >
| > BTW, this isn't idle curiosity.
| >
| > Thanks.
| >
| > Alan
| >
| >
| > -- Alan McCoy, RPT
| > Eastern Washington University
| > amccoy at mail.ewu.edu
| > 509-359-4627
| > 509-999-9512
| >
| >
| >
| >
| 
|