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

[John Delacour]

At 22:39 -0700 2/5/08, David Love wrote:

>...Del just posted something on shortening the cantilever on the M, 
>not eliminating it.  The factors that have been discussed have not 
>been limited to the cantilever alone but also include the backscale 
>length, proximity of the low tenor bridge in relation to the bass 
>bridge, scaling, soundboard design especially in the bass end of the 
>piano, hitch pin arrangements to name a few...

And there are others, not touched on.  If there were some intrinsic 
virtue in a suspended bridge, we can imagine a lot of makers over the 
years would have suspended the bridge on grands over 6 ft. including 
concert grands.  Tastes in tone colour have varied and do vary from 
age to age and from place to place, but taste has never led piano 
makers to cantilever the bridge except as a compromise, to get the 
best possible performance out of short pianos.

In the case of the 5'10" Steinway 'O' with a suspended  bridge and a 
bottom A length of 139 cm. it could well be argued that, all other 
things being equal, the apron could be considerably reduced or even 
removed altogether, resulting in a bottom A length of, say, 130 cm. 
and tonal results achieved which most people would see as an 
improvement.  This is a plausible hypothesis because it still leaves 
the piano with string lengths that are quite acceptable and even 
common in a piano of that length.

With verticals and short overstrungs or grands with maximum string 
lengths less than, say, 105 cm., the question is different.  Every 
centimetre's reduction in the string length will tell tonally and I 
know of no maker that has managed to get away without suspending the 
bridge to some extent.  There are extreme cases, such as Lipp and 
Bechstein verticals with an apron almost 6" wide and I have a Lipp 
overstrung upright with a curved apron and strings as long as on a 
Steinway model B! which, surprisingly?, does not sound quite the same 
as a B.

The Coblenz maker, Knauss, whose pianos have a exceptionally warm and 
clear bass, rejected the apron and had a tall, curved bass bridge 
that is quite steeply angled, to allow for string probably 4 cm. 
longer than would be possible with a bridge at 90 degrees to the 
board.  I have not seen this from any other maker, though there may 
be other examples.  With such an arrangement there is a worthwhile 
gain without the loss inherent in an apron.

At the moment I am working on two Brinsmead overstrung grands of 
different periods, both about 5'8" in length, which is about the 
length where questions begin to be asked.  Brinsmead refused to 
suspend the bridge and instead judiciously floated the soundboard.  I 
will post some pictures, but the 'floating' is differently done on 
the two pianos, one from 1870 and one from 1905.  The result on both 
is good.  I have just fitted hammers recovered with Wurzen AA felt to 
the 1905 piano and am slowed down in my work of regulation by the 
strong temptation to play the piano for long periods instead of 
turning screws etc.

I will also post some pictures of English arrangements on verticals, 
where the optimum was achieved by a combination of freeing the 
soundboard from a rigid fixing to the back and some cantilevering of 
the bridge.  I think the only German upright I have seen that floated 
the board was a Thürmer.  There may be others but generally the 
Germans seem to have stuck religiously to a rigid fixing of the board 
all round.

With a fixed soundboard, an apron, and a short string back-length it 
strikes me there is bound to be a stifling or impairment of the tone, 
since vibrations that are destined for direct transmission to the 
soundboard are used up in bending the apron.  I would be interested 
to know if a short back-length has any bad effect on the tone of a 
piano where the soundboard is made flexible enough, by springing, to 
respond to the direct impulses through a straight-down bridge.  I 
think the bad effect would probably be far less, if not actually 
negligible, than in a piano with a soundboard rigidly fixed to the 
rim.

JD