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In my case as soon, as I start playing a guitar, because of fretting pressure, especially in the first three or four frets, I pull the neck of the guitar toward me. This produces a noticeable reduction in action at the 12th fret. Not a big difference, but quite detectable. Having said that, I intonate with the guitar on a flat surface on its back. Mind you, I never did sell one to Andres Segovia.

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Under Compensated Nut!

Most repair shops I been in have horizontal "set up stands/fixtures" several inches off the bench. For me, nothing compelling presented here, especially considering the actual relationship with the instrument's environment and playing conditions during performance -- so giving these techs the benefit of the doubt, I'd go with "myth."

I would suggest if it's set up on the bench, the player should lie on his back while playing.

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

'Way back in post #3, wbergman wrote:
'Somewhat related, I think I notice a difference on classicals if the guitar is played for a while, which I attribute to body heat warming up the wood and distorting it a little."

and I responded:
"That's something else; 'warming up' or 'playing in'. That is different from the setup, ..."

He's just informed me that he was referring to the setup, and not the tone. My bad.

I'm still not getting it. Why would the Neck move in a forward direction in playing position? If we are referring to weight/gravity (not string pull) surely the direction of the force is on the side of the Neck. Given that many Guitarists tilt the instrument slightly backwards (to view the fretboard) that would seem to suggest that the force is a little more backwards. Guitarists (at least good guitarists) don't push the Neck forward, they pull it back - using the so called 'weight of the arm'. All this suggests that the force is not in a forward direction at all.

Tens of thousands of guitars have gone across my bench, so I've had plenty of time to observe and measure and come to accurate conclusions about this.

They don't all change by the same degree, but yes lifting a guitar into playing position after making adjustments on the bench with the head being pulled back by gravity can have a noticeable effect.

I think it's somewhat interesting that the techs and people who do this for a living are puttng it in the category of "fact", while the home builders and hobbyists are calling it "myth" with far fewer samples.

Anyways, the skeptics can remain so if they wish, I know what I've seen over the past twenty years.

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Old growth, shmold growth!

So I set up a little experiment to show the effects of playing position vs flat. I encourage anyone to duplicate the experiment for themselves.
The testing fixture is a neck jig. The guitar is strapped in tightly with a band clamp. There is a dial indicator placed under the first fret to measure the amount the neck moves in both positions looked at in this mini study. Action measurements were taken using a stewmac action gauge and relief measurements were taken with feeler gauges. The guitar is a Gibson songwriter deluxe

The guitar was strapped in to the jig and tilted on its side. The indicator at the first fret was then zeroed. Action and relief measurements were then taken.
Then the guitar was tilted flat and the movement at the first fret dial indicator was noted. Action and relief measurements are taken again.

The results:
In playing position the action was .100"@ the 12 th, with .010" relief at the 7 th fret.
Flat,the dial indicator showed .013" movement which translated into a change in action to .090" with .008" relief
This shows that the position of the guitar does make a measurable difference. Some may argue that the difference is so slight that it doesn't matter and I wouldn't disagree totally. I set up in playing position because it's easier than bending down.

And you will have to take my word that I didn't falsify this experiment

I don't think that anybody would even consider that as a possibility, Sam.

What did occur to me as a possibility was the fact that your jig may also be reacting to the force of gravity and the 90 degree change in orientation. I mean, I am sure it is a very useful tool for you, but it is after all constructed out of 3x2 and sheet material, fixed together with screws. ... when it comes to measuring differences of only a few thousandths of an inch, you really need a more rigid base to function as a datum.

There is actually a much simpler and demonstrably more accurate way to test the hypothesis, a test which I shall do very shortly on all my guitars. I will take pics and post the results on here within a few days.

I do have an open mind on the subject, and am perfectly prepared to discover that my experiment will yield the same results as Sam's.

I couldn't imagine gauging specs in any position other than playing. Certainly makes a measurable difference in my experience - sometimes a little, sometimes a lot. A 12 fret short scale acoustic, eh, maybe a few thousandths. A Jazz Bass, it's not uncommon to see .050-.060" movement at the end.

In either case though, gravity has an effect. I can't see any sense in ignoring this, especially when it is just as easy (easier for me actually) to read measurements with the guitar in my lap than to crouch down to eye level with my bench. Sometimes it may affect no significant difference, but often times it does. I default to always including this factor.

So not a myth at all. Even if a headstock only moves .012" between horizontal and playing position, changing the action at the 12th by .006", that can amount to over a 10% change in action (or a greater proportional change in relief) for some setups. Can't see any sense in brushing that off as inconsequential.

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Eschew obfuscation, espouse elucidation.

Oh, as to the neck jig - yes, of course it is not entirely rigid and will see a few thousandths deflection on it's own. Still, compared to the neck it is relatively more rigid, and still a useful tool for observing changes in the neck.

More importantly though, is that once you get used to using one and develop a prescribed set of parameters which deliver ideal results, then it can be very predictable and controllable. The numbers displayed may not be absolute or entirely uncorrupted, but they are consistent and prove to yield very repeatable results once your methods have been developed with that tool.

I don't personally use one anymore, as I've developed some other control and gauging methods which although not at all easy to learn, can be carried out efficiently and predictably once mastered. For getting consistency of results with a much shorter learning curve however, I think the neck jig certainly has some great value.

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Eschew obfuscation, espouse elucidation.

I have to say, I don't get all this "crouching down " thing which so many posters seem to think is one of the downsides of setting up the guitar on the bench. I can and do set up guitars on the bench without once flexing my knees, let alone crouching down.

If you have to crouch down to eye level, that presumably means you are using a 6" rule to assess action ... if so, then discussions of thousandths of an inch are somewhat irrelevant ... there are other and better ways to measure action accurately.

How fine a point do you guys want to put on that pencil?

As fine as the edge of my blades...

Depending on what I'm checking, I typically use a rule at least 24" long, a Stew-Mac string height gauge, or feeler gauges. I don't know how to read any of these accurately without getting my line of sight level with the measuring device.


I would be interested in learning how this is accomplished.

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George :-)

Figures...

I think Murray uses the Stewmac nut slotting gauge for measuring action at the 1st and 12th frets? viewtopic.php?f=10101&t=44104#p583407

Myself, I spent nearly £3 and converted a digital tyre depth gauge for my action finder.

My last point on this subject is the same as the first. It does make a difference. No matter how you measure it, you will notice a slight difference. To some this may not matter and to others it does. You can get pretty close enough with either method

That about sums it up. You can decide for yourself whether it's enough difference to concern yourself with (case by case or general approach), but it does affect a difference none the less.

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Eschew obfuscation, espouse elucidation.

The easy way for anybody with a Peterson tuner to test the hypothesis that gravity exercises a measurable pull on the headstock of an acoustic guitar is as follows:

Tune the instrument up to pitch, with the instrument flat on the bench, ie with the headstock supported by whatever rest you favor, like you normally would when working on a guitar. Make sure your tunings are spot on.

Then, simply lift the instrument up and rest it on its side. Test the tuning again. If the hypothesis is correct, then every string will now measure flat. Lay it on its back again. Every string should now be back to exact pitch. If the hypothesis is correct, that is.

I have done this test, on more than one guitar, but I am not going to "publish" the results until I complete the actual physical measurement test, which as I said above will be completed within the next few days.

I would just like to observe that many long held beliefs have been destroyed by somebody coming along and performing a controlled experiment. Not that I am asserting that such will necessarily be the case in this instance.

For years, everybody believed that the break-over angle at the saddle on an acoustic guitar was a vital factor in determining volume and tone. Then along came Alan Carruth and proved that that whole notion was hogwash ; as long as the angle is enough to stop the string from slipping, the actual angle is irrelevant as far as volume and tone are concerned.

So, if somebody has already done what I am about to do, and could describe the test rig(or even better, show a picture as well) , the method employed, and the actual numbers, then all discussion would be silenced. Until then, assertions like "I have set up thousands of guitars so I know what I am talking about " are, quite frankly, irrelevant.

Numbers, not anecdotes.

Until next week, over and out ...

Care to show us what you came up with?

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Pat

The pitch reference would not be suitable - the length of the string is simply not affected to any notable amount relative to small movements perpendicular to the neck. By that reference one could tune a guitar, adjust the truss rod from .010" to .005" relief, and find no measurable change in pitch (which is a very subjectively gauged moving target from initial attack through decay anyway). This measurement could not then be used to conclude that the straightness of the neck and action did not change at all.

Bottom line is that this is a factor of influence. Whether you consider it to be influential enough to consider is up to each individual.

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Eschew obfuscation, espouse elucidation.

I'm also not convinced that gravity will change the tension on the string differently in different playing positions. Gravity will pull the string equally no matter which way the guitar is turned.

However, when the guitar is on it's back, supported at the neck by the nut, and by the bench at the tailblock, I believe the weight of the guitar is enough to cause a forward bow in the neck, often larger than the slight downward curve gravity will put into the strings, which would cause the strings to go flat while raising the action. Exactly like in the measured non anecdotal example in an earlier post. Though it is curious that the low strings were affected but not the high ones.

But while the string stiffness should be constant, the neck/body stiffness will vary from guitar to guitar. So it would not at all surprise me if the next guitar with a super stiff neck didn't flex at all, and the action went down due to the gravity induced curve of the strings pulling them closer to the neck (likely more on the low strings) without changing the tension (tuning) as the effect of gravity remains a constant on the strings no matter what position the guitar is in.

It would be interesting to take a straight edge and span it across the top of the nut and the top of the bridge, then measuring deflection of the neck at the halfway point, measuring the difference between on it's back and on its side. I would predict that some guitars will move, some won't, and there won't be a constant from guitar to guitar.

Anyway, I never kept a stat sheet, but I did do a lot of measuring at one point. My conclusion was that the difference between flat on back and upright was subtle, but more importantly unpredictable.

And, more importantly, it all became a moot point because it is more comfortably to take the final measurements with the guitar upright on the bench in playing position for me.

So that's how I do it.

YMMV

(PS, nearly all my experience is with acoustics, electrics may behave entirely deiffently, I wouldn't know...)

Tune your guitar. Pull back on the headstock. Is it still in tune?

Some of us neither call it fact nor myth. Sounds like a straw man argument to me...
Most all my customers play the instrument and find nothing wrong with either my action or playability and the instrument wouldn't go out the door if they didn't like it. I've been a "home builder" for 20 years (the rent is cheap), so don't be putting me in a category.
I find it hilarious that some of you load the neck with a couple of CF bars AND a T/R and then tell us that the necks move a few thousandths. If your actions are so critical that a few thousandths will bring the customer back complaining, I wonder what happens when the humidity goes up or down. Hope none of your customers hang their strap on the peghead.