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MMD > Archives > April 1996 > 1996.04.25 > 04Prev  Next


Re: Wire Size Calculation: Bass Strings
By Craig Brougher

Just a note on the stringing scales for wound strings: There are many different ways to build bass strings, and they all have _slightly_ different characteristics. The software takes into consideration basically the desired frequency of each string according to the length prescribed and just uses the old high school formula plus a database to generalize the desired sizes. It will compute the tension and then search its data to find a core wire size that will give you a certain safety factor for that, first. Then it will add the mass with copper windings. No biggie. But there are tradeoffs, and they exist because different pianos use different tensions in the same length scale.

The "cello-like" tones of a Mason-Hamlin are built around a very high tension scale. So you can build a somewhat thicker bass string with more mass and stretch it tighter to raise the pitch. This changes the partials and ideally puts them more equidistant along the string. This, I believe, favors the even harmonics, strengthening them over the odd harmonics. Even at that, you have tradeoffs, because you can give the core wire an extra gauge or two and decrease the copper accordingly, or you can go the other way.

When you slim down the core wire to the bare minimum safety factor and increase the copper, you change the anti-node width because you have changed the shear angle. A higher shear angle supposedly perfects the high partials of the string, which in turn resonate better with the rest of the tenor and treble section. This sympathetic resonance creates the quality that old timers named the "foundation section." It colors the piano's tone, even when those notes are not being played. The more balanced way in which they ring in sympathy, the more color they bring to the scale.

A good piano will have a rather "chameleon-like" bass section that produces different coloration, depending on the intervals played and how loud they are hit. Steinways are like this. They sound differently, depending on who is playing them. As long as that instrument continues to fascinate the ear, then it will never get tired of hearing it. That means the tone must be both pleasing and very complex. A complex set of partials means there are many overlapping partials and they are therefore impure. So what seems, to a tuner, to be a perfect instrument is not necessarily all that great to a musician.

The overall point is this: It doesn't matter whose software or books you buy. None of them can give you the exact scale of the original piano strings. But basically, unless you wind your own, what good is that information going to do you by the time you have sent a pattern to the string maker? He is going to use his own scale in any event. And he isn't even going to mike the original strings! He has what is called a "scale stick." Once he has laid out your strings, he will know how to duplicate them.

The redeeming factor of all this is, 90% of the tone in the foundation comes from the scale of the piano and how the bass bridge is cut, not the ratios of core to winding of the bass strings (unless something is really wrong with those strings). The scale of the piano is literally cast in iron (with its associated bridges). If you fitted a Steinway plate into a Kimball piano and mounted Steinway bridges on its board, it would have the coloration of a Steinway. As a matter of fact, Kimball did just that with their Bosendorfer-- which I call a Kimballdorfer, or a Bosenballer, depending on how I feel at the time. The better and more precisely detailed a piano scale is designed, the less affected it is by string differences.

The more important factor of a tenor/ bass section is the vowel tones "spoken" during the decay of notes and intervals, but this gets into another subject altogether.

Craig B.


(Message sent Thu 25 Apr 1996, 13:15:03 GMT, from time zone GMT.)

Key Words in Subject:  Bass, Calculation, Size, Strings, Wire

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