Ebony bridge caps

[David Love]

There are a few problems I have with the theory of harder bridge cap
material influencing the sound as described.  First, the boxwood caps in
question are on average maybe 5-6 mm thick over a bridge that is 25 - 30 mm
thick.  That bridge material is made primarily of maple and other woods that
aren't as hard, laminated or solid as the case may be.  Even if the harder
boxwood cap transmits the higher partials (I assume that is what is meant by
brighter) more efficiently without filtering them, those frequencies still
must traverse another 80 - 85% of bridge body where there would be ample
opportunity for catching up on the filtering.  Second, the point of contact
for the termination is really the bridge pin (marginally) which is both
harder and denser than either material and extends through the cap into the
bridge body which, since it is not made of boxwood, would still have the
opportunity to filter out those higher frequencies.  Third, the piano world
is replete with solid bridge bodies of maple and a variety of caps made with
other than boxwood that don’t seem at all compromised in this way.  

The filtering of those high partials seems more likely a function of
inadequate stiffness in the board through the treble region and the board's
inability to reproduce the high frequencies transmitted through the bridge,
or, a function of inadequate mass in the rim and/or belly rail facilitating
unwanted bleed.  Whether or not some makers believed they could compensate
for killer octave problems with harder materials on the cap, I don't know.
I certainly do see the benefit of harder and denser wood on the cap to
resist compression damage from the strings over time and an eventual
compromise of the terminations.  If I am incorrect, which is entirely
possible, I would love to hear the explanation.

David Love
davidlovepianos at comcast.net
www.davidlovepianos.com 



Having said all of that, (I also love dichotomies),I think most would agree
that throughout the  conversations of boards, bridges, caps, etc, one theme
remains constant:  minimize the losses.  Lost energy is lost energy.

Michael C. Spreeman