Classical String Action Specifics, Please
 

Hi, I am curious after seeing typical string action specs for the 1st and 6th strings, how the inner strings might vary.

Since the guages progress in different ways from acoustic, how do the string actions vary.

Does the action move progressively lower from say 4mm (Low E) to 3mm (Hi E) or do they stagger because of the staggered string guages?

I realize player's feel is paramount to any standards.

Classic action...
 

As a typical classical saddle is flat, tapered perhaps toward th high E string, once the two E strings are set the other are where they are. I have never had a client complain or even comment on the variations in gauges. Most common in my experience is 2.5mm under the high E string to the top of the 12th fret, and 3 to 4mm under the low E string. The higher action is generally preferred by experienced concert players, as it is with players who prefer high tension strings. Electric acoustic instruments and of course Flamenco instruments are typically lower, 2mm under the high E and 3mm under the low (at the 12th fret). Another problem I found common was that players coming from steel stringed guitars often asked for the nut slots to be filed too deep, which is a mistake on a classical guitar.

Sounds good, now is that measurement of action with the 1st fret held or unfretted with 12th fret action?

The measurement is taken with the strings to pitch but without fretting. Well trained players who do not use electronics sometimes prefer slightly higher action to produce the volume required for live performance.

Really ?

The conventional thinking on a steel string acoustic is that the floor of the slot on the nut should be on the same plane as the top of the first two frets.

Why should this be any different for a nylon strung guitar ?

I would suggest that to be relative to the rest of the setup, gauge and tension of the strings, and most importantly the enthusiasm or strength of the player. Nylon strings are typically 30 to 50 lbs less tension than steel strings (per set), on an instrument that typically has no truss rod and fluctuates somewhat with the seasons. Some players have separate string nuts for summer and winter, others add or subtract paper or veneer shims under the nut to account for these variations. Too low at the nut with a strong technique and you will have some string buzz. Perhaps a player who relies on electronics and a light touch could be happy with a low action classical guitar but someone who needs to project acoustically would be unhappy with the string noise.

I am familiar with the practice of having separate saddles for winter an summer (leastways on steel strung guitars) ... this is because the soundboard swells or shrinks and the height of the bridge and the saddle varies accordingly.

I have never heard of the practice of changing out the nut according to the season , and tbh I cannot see why the change in humidity should have anything to do with the height of the strings at the nut.

Perhaps one of the classical luthiers could comment here.

I think you mean to say players change out string saddles for the season not string nuts. Nuts are almost always glued in. I strive to get the nut slot heights to the exact same height of the frets immediately in front of it. On some occasions I'll go higher on the bass strings only by a hair and that's almost always on steel string guitars. Some Pete Townsend style hard hitting players might benefit from a slightly higher string as would those who use a slide.

Seasonal change is of no concern regarding action at the nut. Just think of the nut as another fret, the zero fret or the very first fret in line. Then ask yourself why you would ever want it any higher then the frets?

I have nothing to contribute to this discussion, other than to say that in my experience many Spanish made guitars have a "floating" nut held down only by the pressure of the strings. I've had more than a few flop off the guitar during a hasty string change...yay me.

I don't believe in starting a thread and then becoming a "ghost" so i will thank everyone for their input.

I was mainly curious if anyone in setting up the action of a classical took the string gauges into account as they do not progressively get smaller like steel string.

But as far as the stream of conversation, I think steel strings have small variances in nut action so classicals and obviously flamencos would to. And by variances I mean thousandths of an inch.

Also I don't speak for anyone, but i don't see the positives of gluing in a nut, unless it enhances the bond/sound of the bone to wood. Like the previous poster stated, the tension of the strings is enough to keep in place.
Only in basses have i found the tension works against holding the nut in place.

Gluing the nut in has nothing to do with the sound of the instrument. Like dosland said, it's just annoying when you go to change the strings and they fall out or if it's a really loose fit and you start to tighten the outside strings and the nut slides over. If you are like me, and most people, when you drop something you watch as it falls, it hits the ground right where you saw it hit the ground and then it takes 5 days to find it. ;)

I only put one dot of glue on the bottom of the nut for that very reason.

You want it higher than the 1st fret because on a classical guitar the open strings will buzz once the clearance to the 1st fret is less than about .4mm. Granted that is not much, but unless you play with a super light touch .5mm's clearance is standard for E-G and a touch more for D-E.

So you achieve freedom from buzz at the expense of accurate intonation? .5mm ( = .020") is huge, and unless the nut is compensated, I would think the pitch at the first fret is guaranteed to be sharp. If the open strings are buzzing, then surely the relief need to be greater, or else the saddle needs raising?

Admittedly, my experience is only with steel strings, which is why I would like the opinion of a bona fide classical luthier.

I have never seen a nut that was not glued down

You're welcome to take my opinion or not, I am a classical guitar luthier. The excursion of nylon strings is huge compared to steel strings, partly because of the strings themselves and partly because the top is generally much more flexible which contributes to string excursion... there is not a classical luthier that I know that would set up a guitar with no clearance at the 1st fret because it will buzz regardless of how much relief the neck has. As an aside, the nut is usually compensated forward .5mm in classical guitars.

Typical concert level action on a classical guitar is 3mm high E to the 12th fret, 4mm low E to the 12th fret, and at least .5mm above the 1st fret for all strings. That enables a good player to dig in and not buzz too much, although many players will use a higher action than what I've listed.

Cheers,

Chris

And how do you measure the .5mm above the first fret?
You just measure the top of fret to bottom of string. In steel string we measure by fretting 3rd fret and measuring 1st fret with feeler gauges .002-.-004. I assume classical would be a little higher.

Gotcha, I didn't know that. Yes, we measure from the bottom of the string to the top of the fret. I just use one of the LMI digital action measuring gauges to do it.

I'm wondering if earlier in this thread we were talking past one another by assuming the same method of measurement for the 1st fret clearance. I'm guessing measured like you mention it would be a lot lower than .02. When I'm back in my shop from the holidays I'll pop a measurement off that way and post the results.

Thanks,

Chris

I wonder if we're talking about different ways of measuring 1st fret action... see the posts above and tell me what you think.

Chris

I've been making both steel string and classical guitars (and lutes, dulcimers and other stuff) for 30+ years. As you are aware, a "true" classical guitar - in contrast to a "crossover" - has some significant differences in setup and playing technique. The strings, themselves, don't require as much compensation for intonation as steel strings do, partly due to the composition of the strings and partially due to the longer scale length typical of classical guitars (650 or 660 mm).

A good setup for a classical guitar is pretty much as Chris stated. Setup well, the intonation on a classical guitar will be as good or better than steel string guitars.

I am still perplexed as to why the floor of the nut slot needs to be .5mm higher than the plane of the tops of the first two frets, which is what I assumed you meant ( ignore the fretting at the third and measuring the gap at the first fret ... that wasn't what I was talking about )

When you do a fret dress and crown on a classical guitar (which I have never done, although hundreds on steel string guitars) I assume that you set the neck straight first of all, by whatever method you choose (I use a specialized jig when doing steel string guitars) then dress the frets level (ie the tops are all in the same plane) and then crown them, and you then rely on string tension to pull the neck into correct relief (since classical guitars do not normally have adjustable truss rods).

But the nut slot floors are not in this plane, they are .5mm higher, and this is to prevent buzzing. So the question arises, why don't the strings buzz when they are fretted at the first fret ... take it one step further , if you used a capo to hold the strings down at the first fret, would the strings then buzz? And if not, why not?

The nut, after all, is in essence only another fret which has the additional function of maintaining string spacing.

So if you built a classical guitar with a zero fret, are you saying that the zero fret would have to be .5mm above the level of all the other frets? By that logic, the second fret should be .5mm below the level of the first fret, and the third fret .5mm below the level of the second fret, und so weiter.

I am quite sure that there is something I am missing and I eagerly await elucidation. Specifically about the zero fret question.

The strings don't buzz when they're fretted at the first fret because there is clearance of at least a few 1/10ths of a mm to the next fret. The strings are obviously not co planar with the frets as the action above the frets increases as you move down the fingerboard towards the saddle. If there was no action above the next fret the string would be damped because the string still has a small amount of amplitude even right next to its nodal points. Anywhere you fret on a fingerboard the string will have a small amount of clearance above the fret in front of it or it would buzz.

The strings don't buzz when you CAPO them because they are being fretted at that particular fret. That's different than the strings being able to clear the fret in front of them. There will still be clearance to the frets in front of the frets that are being capo'd.

Chris

I see what you're asking... no, the floor of the nut slots is going to be just a hair (not .5mm's) above the 1st fret, but there will be .5mm's of distance between the 1st fret and the bottom of the strings because the strings are climbing towards 4mm's at the 12th fret. That's what is mostly creating the space.

I'm thinking along the same lines as murmac on this one. I don't get it? I've built 12 classical guitars, including flamenco, over the last 25 years and I don't have buzz issues on any of the nut slots. Like I said I do tend to go higher on the bass strings, especially for SS guitars, because some players like to really bang on the open strings. But if you treat the nut just like a zero fret for example then in theory the nut slots should be at the same level as the frets in front of it.

Just like the first fret is level to the second and third so should the nut be level to the first and second or at least real close.

It's all about the difference between nylon and steel. A zero fret on a nylon string guitar does not work, the action has to be exceptionally high to avoid buzzing on open strings. It's better to have the nut a bit higher, and then the action doesn't have to be quite as high. Nylon strings have larger excursions than steel strings, which requires more height above the frets, and they also change pitch less due to the stretch from fretting. It's a complex geometry problem, and I believe that fretting a string causes it to rise a bit as it crosses the fret, which explains why fretted notes don't buzz. I've only built one nylon string guitar, and I've always used a zero fret, but it did not work with nylon strings.

The significant point here is that with nylon strings, which are much more flexible (compliant?) than steel, high nut slots do not degrade playability on the first few frets.

The only way I could understand that argument is that you are saying that for any given force applied to a string equally more energy is imparted to an open string on a bone nut compared to a fretted string on a metal fret.

Such that if the vibration from bone nut to bone saddle is greater (larger circles) then from metal fret to bone saddle.

Otherwise I'm struggling to understand why a nut should not be treated just like any old fret in regards to string height.

Rodger, your posts are almost always a model of sense and lucidity, but I have to say I am confused with this one.

I just googled "classical guitar zero frets" and one of the first hits was this one ...http://www.classicalguitardelcamp.co...c.php?t=49669l

It would appear that not every luthier shares your aversion to zero frets on a classical.

If you look back in the posts, I never argued that the nut slots are .5mm over the first fret. You're both putting words in my posts so to speak. It is, however, an undisputed practice that a classical guitar needs more or less .5mm clearance from the bottom of the strings to the first fret. That's the universal practice because much lower than that buzzes, no matter how good the setup is.

The zero feet construction on classical guitars was more popular in the 30's and 40's and actually works quite well. You can still find some Hauser guitars with zero frets installed in then, and I know a few players who currently prefer them.

Chris

It's almost New Year in Scotland, Chris, so no time to debate further. I wish you a very good New Year, and hope to see further contributions from you on the AGf !

That seems kind of odd. I've never seen a classical guitar with a glued-in nut. Are you talking about classical or steel string guitars?
-Bob

Cheers! I wish you a good new year and look forward to learning from you folks.