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Happy New Year everyone. This is the first time I'm building my neck and bridge from scratch and I'm very close to having the neck angle correct but I then realized I could build the bridge any thickness I chose to match the neck angle, and vice versa.

Right now, neck bolted on, with no frets, when I run a straight edge along the fret board (FB) I have a 3/8" gap where the bridge will be located which from reading various sources would mean a similar 3/8" thick bridge and would also match someone else's (from reading) version of the perfect bridge height. LINK HERE.

I've also read different interpretations of the proper bridge height and clearance from the fret board so my question is, since I can still change neck angle and bridge height, what height should the bridge be? Higher for more drive? Lower? What clearance over the bridge with a straightedge should I look for - no frets? With frets?

It's small guitar, 9.5" UB and 13/5" LB, 24.9" scale, 12 fretter..

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Thank You and Best To All

I use a 3/8" bridge, with 1/8" saddle height gives 1/2" between bottom of E string and top of sound board. So with a fretted 1/4" FB, a straight edge down the center pf FB will leave a 1/16" gap above bridge on my guitars before strung up. There are other variables, such as how much the top will rise under string tension, and stiffness of the neck. So you may need to adjust these figures.

Chuck

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Thanks Chuck. Do you use a 3/8" Bridge from experience with different heights? Or is that an agreed upon standard of sorts? As I write that I understand the fairly universal "1/2" between bottom of E string and top of sound board" which seems to be, again, a standard of sorts. Any reason (tone differences) to go higher with the 'E' to sound board dimension? Lower? With associated neck angle of course.

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Thank You and Best To All

Thanks Todd. Do you go little higher with more bridge or more saddle? Both?

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Thank You and Best To All

Thank you again. I think I'll leave my neck angle as is and shoot for the figures you've (and Chuck) suggested.

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Thank You and Best To All

I would love to hear from someone who has played with different string heights at the bridge assuming they also weakened/strengthened the soundboard to match the new string height.

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Formerly known as Adaboy.......

I did a long experiment a while back to see what effect raising the string height off the top had on the sound, as compared with changing the break angle. The bottom line was that it was easy to hear, and measure, a difference when the string height off the top was changed, but break angle doesn't seem to matter unless you don't have enough.

Basically, the main force driving the top is the up and down 'transverse' force that is maximized when the string vibrates 'vertically' wirth respect to the plane of the top. There is a 'tension change' signal that tugs the top of the saddle toward the nut twice for every full cycle of the 'transverse' wave, but it's generally a lot weaker, and the top is built to resist that sort of movement. THere is also a high frequency 'longitudinal' compression wave in the string when it's plucked off center in it's length.

You need to have some break angle (or do something that's equivalent) to keep the string in contact with the top of the saddle as it vibrates in the 'transverse' motion. It doesn't take much, maybe six degrees or so, but you need it, or the string will hop off the saddle top.

As the string height off the top rises, there is more leverage for the 'tension' and 'longitudinal' signals to deform the top, and you get more of those frequencies in the output of the guitar. Since the tension signal is octave-doubled, and the longitudinal signal is 'way up in the higher harmonics (although it's not necessarily a 'harmonic' itself) these tend to add to the high end color. Of course, you have to balance the desired tone with structural considerations: it might seem to be a benefit to make the strings 3/4" off the top for the sound, but you'd have to beef up the structure a lot, and use a bigger bridge, to take the stress, and that would cut into the gains.

The bottom line is that having the strings come out around a half inch off the top seems to work pretty well. A bit higher or lower won't hurt the sound too much, and you can adapt the string height depending on what you think of your structure.

So, how do frets work?

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

The same way as the saddle. If you don't press the string hard enough, you get a dead sound.

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John

To me having 3/8" over the bridge location from an unfretted fingerboard is ideal. I would make the bridge 3/8" and expect having a little over 1/32" clearance once the board is fretted. That will allow for a 1/8 saddle and around 1/2" string clearance over the soundboard with normal action.

At least that is what I'm thinking but I could be wrong

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Joe Beaver
Maker of Sawdust

My tops rise .012" in the bridge area and I like a low action so I leave a bit more ( more like .060 ) I did the just clearing thing with the frets installed and found that I had a bit less saddle than I wanted.

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Fred
Actually I shoot for 1/32 to 1/16 from an unfretted keyboard to the top of the bridge on my SJ body. (15 1/4") lower bout. I may have to add to that for my new build. (16 1/4' lower bout)

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Joe Beaver
Maker of Sawdust

Yes, but synthesisers are a whole different ball-game ...

Murry,

Not sure what you mean by synthesisers?

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Joe Beaver
Maker of Sawdust

I believe it's a play on words from Joe Beaver's post about keyboards

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http://www.bobmatthewsguitars.co.uk

Post about keyboards? Yes, I think I might have done that. And just when I thought I had this posting thing down pat. Oh well, time to get back to the piano.

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Joe Beaver
Maker of Sawdust

...which is right, of course, but I was hoping to promote a bit more discussion. What I was getting at was that it's pretty hard to get 6 degrees break angle on a fret (and if you try it, you'll have a significant tuning problem). So there is more than just the break angle involved and that becomes very apparent on classical strings. Getting sufficient down pressure on the fret (or saddle) becomes a function of break angle, string tension, stiffness in bending of the string and finger position behind the fret when fretting and these parameters factor into playability, because they can be altered by choice of fret height and string type. FWIW.

Carry on!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I've found for my guitars that if I set the neck so the plane of the fretted FB (fret tops) is .425 high at the saddle location then once it has pulled in once strung I will have a .5 string height right in front of the saddle. I like to have more than 1/8 saddle showing on a new guitar and I radius the bridge to more or less match the radius on the saddle. I think my thickest bridges are .35 in the middle but are usually a bit lower.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Trevor wrote:
"...which is right, of course, but I was hoping to promote a bit more discussion."

I suspect that the damping of the finger behind the fret has more than a little role in stopping string motion, and thus reduces the need for break angle.

Jim Woodhouse found that classical guitar strings tend to make a slightly lower pitch when they move 'horizontally' than when they move 'vertically', and suggested that they are 'rolling' on the fret tops. The pitch difference corresponds to a change in length of about one string diameter. Evidently the fret doesn't make a perfect stop.

Yep, all of that, too.

Which makes me think of that (so far unproven, scientifically) theory of mine about why the sound of a guitar changes as the break angle changes (and nothing else). The physics says it shouldn't (which is more or less what Alan has proven experimentally) but it does! How much the string wraps around the saddle (the wrap angle - different from the break angle) makes quite a bit of difference, IME, and tends to change as the break angle is changed unless you take steps otherwise.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Trevor wrote:
"Which makes me think of that (so far unproven, scientifically) theory of mine about why the sound of a guitar changes as the break angle changes (and nothing else). The physics says it shouldn't (which is more or less what Alan has proven experimentally) but it does!"

First: you know you've 'arrived' on these lists when people just use your first name: Mario (or even 'Grumpy') doesn't need any further introduction, and neither does Trevor, IMO.

What I saw, in tests of _one_ classical guitar, was that altering the break angle had some effect on the the way the top vibrated, but not enough that anybody in the listening tests could hear it. Your mileage will almost certainly vary. In particular, I can see where 'threshold effects' could come into play.

Altering the break angle without changing string height off the top changes the way the top distorts slightly, and this, in turn, alters the vibration mode shapes and frequencies a bit. The changes are small, but it's conceivable that a mode that is near another in pitch, for example, could be shifted enough to move into, or out of, a half band width, so that the coupling could be altered quite a lot. This could change the sound, particularly if the modes in question are close to the pitch of a played note. That's a whole string of 'ifs', of course, but it's bound to happen once in a while. That's when you get the testimonies about how important break angle is by itself. You get the same thing, I think, in changing machines or bridge pins: usually it doesn't matter, but when it does, it can matter a lot. So, just a bit of scientific CYA.

The best explanation I can come up with ATM is that with a large wrap angle (longish contact length on a widish saddle) the string has a "clamped" end condition, and you get all the effects of having to flex the string at the ends as it vibrates, which throws up a lot of intonation issues. With a short wrap, approximating a knife edge contact (same break angle and saddle height) the string end is more of a "pinned" end condition and there is much less end moment and less intonation issues. The string tends to rock on the knife edge rather than flex. I think that this affects the damping of the high harmonics in particular and is what I hear, along with less intonation issues (which is something that IS supported by the physics - discussion, maths etc. in the usual place).

Typically, as one changes the break angle (saddle height constant), the wrap angle also changes unless you change the saddle top geometry, and I'm hearing the change in wrap angle rather than the change in break angle, IMHO.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Can someone explain to me how this works? Is it true for non-pinned bridges?

I can't see how the top can "notice" a change in break angle when string height, string tension, bridge footprint and string angle relative to the top are the same...

Edit: Or is this change in top distortion caused by something other than torque?

Thanks,
Sondre

I don't play, much less build, nylon string guitars, but on steel string guitars, I have no doubt that the string doesn't "stop" cleanly/completely at the saddle(nor the fret). The steeper the break angle, the more complete/clean the 'stop', much like a musician can improve/alter his/her tone(and intonation) by paying attention to how they fret a note(finger pressure and placement). On guitars with very low or nearly non-existent break angles(older guitars with the saddle cut down to nothing) I've even noticed a distinct intonation issue dependent upon how hard a note is played(plucked); played lightly, it would intonate correctly, but played aggressively, the intonation would go flat, suggesting that the string's active length would no longer "stop" at the saddle. On inexpensive guitars that aren't worth the cost or bother of a neck reset and still had decent action with the cut-down saddle, I've cured the above and improved the overall tone by simply slotting the bridge(slotting the pin holes) to bring the strings closer to the saddle, providing some reasonable break angle. Even at the same height above the soundboard, there was a very noticeable change by changing the break angle.

Even capo placement(are capos ever used on nylon strung guitars?) can have a dramatic effect on tone; while placing the capo mid-way between frets can appear to work just fine, listening closely(and with a responsive guitar, of course) while moving the capo closer and closer to the fret does change the tone, to the point where many of us will place the capo right -over- the fret. Using a high quality capo with a small and hard sleeve, like a McKinney or Elliot, allows it to be placed right over the fret without muting the open notes(a bit of trial and error is necessary to find the 'sweet spot'...). A lot of us first learned of this through Tony Rice, BTW. Many would think that as long as the notes(fretted or capo'd) aren't buzzing that all is fine, but fact is, getting a clean/buzz-free note is just the beginning...
Soft rubber and/or spring-loaded capos need not apply(and shouldn't even exist, in my opinion, but I digress...).

As for the ideal bridge height, as well as string height above the soundboard, that will depend upon the whole of your build and design as well as its intended use/goal, and not any -one- factor.

On flamencos, quite often. But indeed rarely on classicals.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)