Article about bridge agraffes - function, types

[Ron Overs]

Hi Calin,

>I think Stuart's claim regarding longer sustain is quite correct. I heard
>his piano on recordings compared with other famous concert grands. The same
>piece was played on different pianos by the same pianist. The Stuart piano
>struck me as having probably the longest treble sustain of them all.
>
>I believe longer sustain is a direct consequence of using bridge agraffes,
>as I tried to explain on my website and in my other replies to this thread.
>Simply because you loose less energy with a bridge agraffe and put it to
>better use because of its large footprint.

While I agree the improvement in sustain may in part be due to less 
energy being lost, when compared to lossy bridge cap wood, I still 
suspect that the added mass may be of more significance than the 
termination improvement. I am inclined to this opinion since we gain 
very large increases in sustain time by mass loading an otherwise 
conventional bridge.

>What I'm trying to say is that it's not only the increased mass that
>accounts for the longer sustain, it is the stiffness of the agraffe which
>allows it to transmit much more of the string's energy to the soundboard.
>The traditional termination looses too much of it at the string/wood
>interface.

Perhaps so.

>. . . However, mass is not the only factor when using bridge 
>agraffes. Otherwise,
>one could mass load a bridge imagine adding weights to the treble end.

One can, and we do.

>Maybe they will improve sustain a bit, but not as much as a bridge agraffe,
>because the string still bears on wood.

I can tell you from experience that adding mass to the treble end 
increases the sustain by a considerable amount. At this point in time 
I haven't done A-B tests with two instruments, one with agraffes and 
one with a standard bridge mass loaded. But I can tell you that we 
have direct experience of deliberately mass loading the treble to 
arrive at a desired balance between sustain and power. Here's an 
image of a re-manufactured piano which was mass loaded in the treble 
for this very reason.

http://members.optusnet.com.au/ronovers/overskawai8r.jpg

This piano was re-manufactured for the pianist, Gerard Willems, who 
has done a number of recordings using the Stuart piano here in 
Australia. Gerard had a Yamaha G2 in his home studio which was worn 
out. When he asked me about the possibility of rebuilding it for him 
I suggested finding a Kawai KG5 shell to re-manufacture it with our 
action and I-rib board with a new scale. We routinely mass load the 
high treble to achieve the sustain we're looking for. Those of you 
who saw our no. 6 piano at Rochester would have seen the mass loaded 
bridge.

>  And the string/wood interface is
>inherently flexible and absorbs much of the string's energy rather than
>transmitting it to the soundboard. The agraffe improves sustain because it
>offers a clean termination, high stiffness (=little loss within it) and
>transmits the string's energy via a large footprint to the bridge.
>Just look at the footprint of a bridge agraffe and compare it to the
>footprint of a string on a wooden cap. The difference is huge.

Yes, I agree that the larger and less lossy footprint probably does 
allow for more of the higher harmonic spectrum to be transmitted to 
the board, but I am still unsure if we want that to occur from a 
musical perspective. My impression from speaking with Udo 
Steingraeber, when he was here a few months ago, was that he was not 
yet convinced that the agraffed version of his concert grand is 
suitable for all repertoire. But I'm sure many of us are unfamiliar 
with the qualities which bridge agraffes bring to the mix, since most 
of us haven't had a lot to do with instruments which are fitted with 
them. Even in Udo's case, he is mostly used to building instruments 
with conventional bridges. But I was interested in his impressions 
since he is one of the few people on the planet who has built 
instruments with conventional and agraffe equipped bridges.

>By the way, I'm always talking about the treble end because that is the
>place where sustain is insufficient even in the best pianos.
>Lower down the scale, the situation changes, as the frequencies to the
>transmitted are lower and the string/wood interface becomes less of an
>issue. It can transmit lower frequencies much better than high ones.

I agree.

As I mentioned in a previous post. I believe that bridge agraffes 
should be given serious evaluation as a possible way forward in piano 
evolution.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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