Killer Octave Question

[Delwin D. Fandrich]

----- Original Message -----
From: "David Love" <davidlovepianos@earthlink.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Saturday, April 12, 2003 10:07 PM
Subject: Re: Killer Octave Question


> I'm just following along on this discussion and don't have much to
> contribute in terms of whether the bridge does or doesn't support crown.
> But, assuming that it doesn't, the question that comes to my mind is
> whether or not you could build a bridge that does support crown, and,
> assuming you could, would there be any benefit.  In addition,  I recall
> reading a few days (at least) ago a comment by Del in which he mentioned a
> piano in which the original bridge had tapered down to a relatively
reduced
> height was being replaced by a bridge of fuller height (in the treble)
that
> would add stiffness in the upper area and that he expected it to improve
> sustain--assuming my memory is serving me well here, which it may well not
> and I am open to being corrected.

There were two reasons for adding some height to this Steinway Model L
bridge. First, these pianos are notorious for their relatively weak killer
octave and high treble under the best of conditions. Rarely do they have
what I would call good to excellent sustain. This particular piano was not
that old but the treble sounded more like a tuned drum set than a piano. I'm
not necessarily an advocate of excessively tall bridges, but this one was
really quite short. Even for a Steinway. The new bridge will add both
stiffness and mass and, yes, I do expect it to help improve sustain.

The second problem was one common only to Steinway and is related to the
first. The plate is fitted to the pinblock after the pinblock is fit and
glued into the piano rim assembly. For whatever reason this pinblock had
been planed down quite a lot and the plate was set quite low, especially on
the treble side. Since the bridges are planed to fit the elevation of the
plate after the plate has been fit to the pinblock this meant that the
bridge had to cut down rather far to accommodate. It also meant that the
string plane would be lower than normal. Since the height of the action
stack is more-or-less preset by the design of the keyframe the slack is
taken up either by boring the hammer really short or by pealing the hammer
rebound felts off the back of the wippen. Or, as in this case, some of both.
The new hammers are now bored per normal.


>
> ... If that's true, and if the bridge can be
> made of stiffer material, or supported in some manner, why would you not
> want to use the bridge to support crown and, while your at it, have the
> thickness of the bridge increasing as it goes up the scale (rather than
> tapering down) to add stiffness and better impedance characteristics to
the
> treble section.   I realize there are problems to be considered in terms
of
> altering the bridge height, like what it does to the plate position,
string
> height, action elevations and such.  But assuming we're talking about a
> full remanufacturing job, it seems these problems could be solved.
Anyway,
> the basic question is, is there any benefit to considering manufacturing a
> bridge of materials, shape that will support crown and/or contribute to
the
> kind of impedance characteristics we're looking for whether in the short
or
> long term.

Unless we can make the bridge straight, Ron's point about the curve of the
bridge precluding its crown supporting functions seems pretty valid. Even
making the bridge of some modern super-composite wouldn't help much.

Besides, it doesn't really need to serve this function. It is quite easy to
build any needed crown supporting capability needed into the ribs.

Del