Monday, May 10, 2010

Guitar Scale Length Basics Pt. 2 -- Fret Spacing, Intonation, and Drop Tuning

Last post I explained a bit about what scale length was and how it worked and why shorter scale lengths weren't automatically easier to play or snappier sounding. (Short version: because [on an electric, anyway] you can easily increase the string gauge to increase string tension, making the shorter scale guitar feel more like a longer scale guitar). This time I want to move on to the bigger differences that a guitar's scale length make. But first a quick review if you have not read the earlier post:

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.

One thing you should notice here is that scale length only refers to the length of the open string, and that the basic way that a guitar works is by pushing down on strings in order to change the speaking length of the string by pressing it against a fret. Shorter speaking length = higher pitch.

The second thing to notice from this is that a capo works by making your guitar into a shorter scale instrument. Tune down a half-step and put a capo on a 25.5" scale guitar and you essentially have a 24" scale guitar (with screwed up position markers). And since the notes of the musical scale are proportional to the length of the string you will notice that the 12th (octave) fret on the guitar changes from being 12.75" away from the nut to 12" away from the capo. In other words, as the scale length gets shorter, so does the distance between successive frets. If the frets are closer together it makes spread-out chords easier to play, but tighter chords become a little more tight as well. It feels like you're playing farther up the neck on a shorter scale guitar because (as the capo proves) you really are doing just that.

Next point, and one that is a little more involved. If you are trying to adjust your bridge saddles to intonate your guitar yourself you will have to adjust the longer scale bridge saddle just that much farther forwards or backwards to change it than you will the shorter scale guitar. It's the proportion thing again. Looking at the frets on each tells you that you have to move farther on a longer scale neck to change the pitch the same amount. So if an adjustable bridge has 0.25" of adjustment you will be able to adjust the shorter scale guitar more in that 0.25" than you can the longer scale guitar.

These are all reasons that I like shorter scale guitars. I have smaller hands and bad wrists, so the shorter neck and reduced tension makes things easier on me. So why would I consider a longer scale guitar?

Well, for one thing, as heavy music keeps going down in pitch the standard guitar tuning drops as well to give the music that bottom-end "chunk." For decades the guitar was built with standard E tuning in mind and string sets were engineered for that as well. If you decide to tune down to C or go all Sybreed and drop it all the way to Drop A#, standard strings get really floppy and you have to increase the string gauge by a lot to make up for this (which has its own set of issues). A longer scale means being able to use standard gauge strings and standard gauged strings are much easier to find.

Plus, going back to the comment about intonation, no guitar is perfectly intonated for every note on the neck in every key. It's all a big compromise. But since we know that smaller differences in length mean bigger differences in pitch for a short scale guitar we also know that a longer scale drop-tuned guitar is going to have less noticeable intonation problems than a shorter scale guitar would. This becomes even more apparent when lower string tensions make it more likely for you to make the string go sharp just from finger pressure. So the combination of higher tension with standard gauge strings and more forgiving intonation carries the day.

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.