Last month we covered high frets, and other possible reasons for fret buzz. We then went on to discuss several flaws that cause high notes to be out of tune. I’ve kept the last influential factor for this month’s issue – and THAT, my friends, is the bridge’s mounting position. I’ll conclude with a word about nuts.
Even in our day and age (a time of computer controlled production processes), guitar bridges are sometimes mounted in the wrong position. It’s hard to believe, but nonetheless true. Over the years, I have witnessed a substantial amount of such guitars coming into my shop. These are instruments you DON’T want to buy. They play hopelessly out of tune, and reversing the error is only possible at high cost and usually with permanent esthetic damage. Don’t think lightly of glue remains, screw holes, finish imprints and other lacquer damages!
Nonetheless, when buying guitars, checking bridge position is much overlooked. Don’t make that mistake. I know it seems clumsy, but you should bring a long steel ruler to the shop. That, or at least a tape measure, made of a non-stretchable material.
And this is how to proceed.
Place your ruler up against the nut, adjacent to the thinnest string, and check the distance to the middle of the 12th fret (the octave position).
Now move your ruler so that it starts at the octave and add the distance you just measured.
RIGHT THERE is the theoretical spot where the string should “lift off” from the saddle (note that this is not necessarily the front edge of the saddle!).
In real life though (and again, I’ll explain why in another blog post), you need to back off a bit. The correct spot differs from one guitar to the other, depending on string gauge and bridge height. For guitars, expect to add 0.5 to 2 mm or so, for basses some 2 to 4 mm. These are rough guidelines, and they only apply to the thinnest string.
For the thickest string, the point where the string should make contact with the bridge is even further back: expect 4 to 5 mm when it’s a guitar – but it could be up to 7 or 8 mm (sometimes even more) when it’s a 4-string bass. Add extra for a 5th string.
So if you’re buying a guitar with a fixed and non-adjustable bridge (like most acoustics), don’t forget to measure the lengths of both the thinnest AND the thickest string. If those lengths match what I set forth in the previous paragraph, don’t worry. If they don’t: move on to another instrument. (I mean it!)
When you’re considering a guitar that DOES have adjustable bridge saddles, it’s not important whether they’re already in the right spot – they usually aren’t. What matters is: do you have enough play to move them there? Using your ruler and my guidelines, you should now be able to check for yourself. Probably even on sight.
But if the store owner is willing to let you adjust the two outer saddles (use a screwdriver that matches the bolts!) – or is willing to do it for you – then I’d suggest the following: move the thinnest string’s saddle as far TOWARDS the neck and the thickest string’s saddle as far AWAY from the neck as they will go. Then check whether the distances you’ve measured before fall within these boundaries. If they don’t, move away. If they do, you’re set for the next and final test…
Last month, I wrote the following phrase: “A guitar or bass that won’t play in tune is useless, unless you want to hang it on the wall for decoration. It SHOULD play in tune, ALL the way up, and ALL the way down.”
So now it’s time to talk about the lower regions of the neck. To keep matters simple, I’ll assume that the frets of your test instrument are in the exact spots they’re supposed to be in. (If you’re not willing to make that assumption, you may use this handy fret position calculator and verify.)
Supposing the fret positions are fine, there are now several possible situations.
Okay, let’s make things a bit more objective. I’ll suppose you’ve checked and approved the neck’s upbow. I’ll suppose that bridge height is optimal. Now show me those feeler gauges from Understanding Guitars’ December issue! If you haven’t bought them yet, do it NOW. You need them, really. Can’t stress that enough.
Measure the distances between each individual string and the first fret. On a guitar, these should roughly be around 0.4 to 0.6 mm (thickest string), gradually decreasing to some 0.25 to 0.4 mm (thinnest string). On a bass guitar, strive for 0.5 to 0.6 mm on all strings. But show some common sense, and most of all: in combination with those feeler gauges, keep using your ears! On some instruments, the lowest value may already generate open string buzzing. On others, the highest value may already cause notes to sound off-key. And always keep in mind that a hard-hitting playing style may seriously mess with those numbers!
Let’s keep some perspective here. If the price is right, a bad nut shouldn’t keep you from buying a guitar that’s otherwise perfect for you. It can be replaced, at a relatively low cost. Still, it’s not a bad idea to know a thing or two about the subject. So let’s go nuts for a bit!
The slots’ width should be just right for the string gauge you’re using. If you’re moving on to lighter or heavier strings, prepare for some nut work or even a replacement.
Strings move around in slots that are too wide. That may affect tuning, AND it may hinder your playing. You need control over string movement. When bending a note, you want to do that with precision. When you DON’T want to bend it, the string should stay put. On top of that, when the bottom of the slot is uneven, you may feel (and even hear) some grinding or popping when the string moves sideways in it. That’ll get on your nerve, over time.
Narrow slots are even worse. I’m sure you’ve been there. You’re turning and turning that tuning peg, but nothing happens until… ping! The string that sat stuck in its slot suddenly jumps free, and that previously flat note is now way too sharp. The problem gets worse if your guitar came with a tremolo bridge (as you may or may not know, that thing should actually be called a vibrato – but that’s a whole different subject) but lacks a locking nut. Then, when you’re rocking that tremolo arm, the strings move back and forth in their nut slots. The friction of those narrow slots WILL prevent the strings from returning to their exact starting position, and the result is an out of tune guitar. THAT will surely drive you nuts, indeed.
Conclusion: nut slots should be just right. Each string must be able to slide back and forth without friction, but it may NOT be able to move sideways.
Slot bottom angle, although much overlooked, is also of great importance. Strings, especially thicker ones, aren’t perfectly flexible. When they pass over an object and are thereby forced to make an angle (yes, I’m describing what happens at the nut), you won’t see crispy clean corners. The string will sort of bend or lean into its new direction. (The same thing happens when the string takes off from the bridge saddle.)
Therefore, the slot bottom should “help” the string to proceed on its natural path. It should round off the corner, so to speak. A slot bottom that’s not curved may provoke string buzzing: this time, the string won’t buzz against a fret; it’ll just be buzzing in its own slot. This isn’t hard to understand. Take a look at the photograph for an impression of what happens inside a nut slot with a flat bottom.
The somewhat curved shape of the string passing over the flat surface of the slot bottom results in a slight gap. When the string is plucked, this gap allows the string to vibrate against the nut material, and this, my friends, generates a buzzing sound.
Yes, nut making is a job of precision.
Bring your arms
After reading my mini-series, you are now well armed to tackle the potentially hazardous task of buying a new guitar. You’re armed with knowledge, and (should be) armed with tools. Bring them to the shop, and use them well. Practice beforehand. And don’t forget to use your senses, and your common sense as well. Now go out and get her.