Wound Trichords

[Ron Nossaman]

>I had actually been thinking one way to improve the tone of the last 
>couple notes at the low end of the long bridge on my M&H 50 -- C#3, the 
>lowest before the break, is 38-3/4" long -- would be to replace the plain 
>wires with wound ones.  Now it seems mayybe I am full of misconceptions 
>and this is a bad idea -- but why?
>
>Trent Lesher


Not a bad idea so much as a less than ideal fix. Putting the wrapped 
bichords on the low end of the tenor bridge will likely make it less bad, 
if it can be made to fit into the scale. For instance, that 38.75" C#-3 
with plain wire trichord will be at about 24% of breaking tension 
(regardless of wire size, within reason). That's pretty low, and will be 
very reactive to tension changes resulting from humidity fluctuations, 
meaning it will go out of tune quicker and farther than unisons farther 
up-scale, or down scale in the high bass. Tension will be determined by the 
wire size used there. For instance, unison tension with #20 will be about 
404 lbs, or about 369 lbs with #19. Going to a bichord unison, dropping two 
or three half sizes for the core, and figuring wrap to get back near the 
unison tension that was originally there will raise the break% to around 
40%. That's going to be a more stabile unison with humidity changes, and 
sound better too. The trouble is, that puts you at the bottom of the list 
of available copper wrap sizes, requiring about a 0.007" wrap to keep the 
tension down around where it was with the plain strings. Arledge uses as 
small as 0.006" for copper wrap. That takes care of C#-3, if the impedance 
and inharmonicity connects reasonably with the high bass. Now you'll 
probably want to go 2-4 notes higher with wrapped bichords to blend the 
impedance and inharmonicity into the rest of the treble. What happens? You 
maybe need 0.006" wrap for D-3, and smaller than is available for the next 
one or three. There's the problem, and the reason this doesn't always work 
that well, and the reason for transition bridges. The speaking lengths are 
too long at that pitch for wrapped strings. What you can get away with 
depends on the individual scale and what you have to work with.

Ron N