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

[Delwin D Fandrich]

| -----Original Message-----
| From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On 
| Behalf Of John Delacour
| Sent: May 03, 2008 2:55 AM
| To: College and University Technicians
| Subject: Re: [CAUT] Bass bridge, string scale, cantilevered 
| bridge, tone
| 

| 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.

Our standard practice on the Models M, O, L and all of the various As is to
remove the cantilever entirely. The bridge is moved forward as far as is
practical in each case. Even if a small amount of plate grinding is required. 


| 
| 
| 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

The short backscale restricts the motion of the bridge while the cantilever
reduces the energy transfer efficiency of the bridge assembly. In other words,
the short backscale makes sure the bridge assembly is unable to move in response
to the low frequency vibrating energy in the strings while the cantilever
ensures that whatever low frequency vibrating motion might make it to the bridge
body will not be efficiently transferred to the soundboard system. It will be
dissipated as heat.

Freeing up (or "floating") the soundboard eliminates any possible need for a
cantilever but it can not overcome the restriction to low frequency motion due
to a short backscale. 

ddf