Wednesday, May 5, 2010

Scale Length Basics -- A Simple Explanation

Of all the things on my blog the one that seems to have brought the most people here is my discussion of scale length and pickup placement on the guitar. It seems that a lot of people have questions about scale length that are in need of some simple answers. Think I can manage that.

First off, a guitar's scale length is the length of the string from where it leaves the nut towards the fingerboard to the place where the string crosses the bridge saddle. This distance is (more or less) the same as the "speaking length" of the string -- the part that vibrates when the string is plucked. The strings speaking length and gauge form the basis for all the math that goes into acoustics that I'm mostly going to ignore here because we don't need all that math to get a basic understanding. Just wrap your head around this one thing:

If two guitars have different scale lengths but are using the same gauge of string, the one with the longer scale length will need more tension on the string to reach the same pitch as the one with the shorter scale length.

Put another way, comparing the same string on two guitars:


Longer string - same gauge - same tension = lower pitch

Same length string - heavier gauge (thicker string) - same tension = lower pitch

Same length string - same gauge - lower tension = lower pitch

Therefore: longer string - heavier gauge - same tension = even lower pitch


As you can see the pitch is determined by all three things (length, gauge, tension) and not by any one of the three alone.

The first myth, or truism about guitars that lots of people throw around but nobody seems to explain:

-- Guitars with longer scale lengths sound snappier or punchier than guitars with shorter scale lengths. Or, closely related, guitarist with shorter scale lengths are easier to play than guitars with longer scale lengths because the strings are looser.

This is sort of true, but only if both guitars have the same gauge strings. A longer scale guitar with extra light strings may have less tension on the strings than a shorter scale guitar strung with heavy strings. It depends on the ratio. That's why D'Addario publishes a spring tension guide -- so that you can keep string tension relatively the same between two guitars with different scale lengths by choosing the appropriate string gauges. Players who play both a Stratocaster (with a 25.5 inch scale length) and a Les Paul (with a 24.75 inch scale length) often times string the Stratocaster with .009s and the Les Paul with .010s for this very reason.

So if the reasoning behind saying that a Strat is more punchy than a Les Paul is because of scale length it's really only true if you have one set of strings to choose from.

Next time -- more about scale length and why players who play drop tunings often choose guitars with longer scale lengths.

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