The Curious “Break Angle”

This means nothing to me without a formula but it shows me what the break angle is and where the force (F) vectors are. The bridge would be the perpendicular. The dotted line, the string where it vibrates and theta, the break angle.

I’ve read a lot about how the angle that the strings take when they cross the bridge or the nut can affect how the guitar plays. I’m not sure I understand completely the mechanism for the phenomena described but, as a college Physics major (for a year, anyway), I have some insight. I’ve read that the strings are easier to bend if the angle is less and I’ve read that they stay in tune better if the angle is shallower. I’ve read the opposite as well. Here’s my take. I recently acquired a wide neck ’65 ES-355 with a Maestro. The break angle behind the ABR-1 is almost zero degrees meaning the strings go straight back to the tailpiece. Compare that to a trapeze which has a steeper break angle but still relatively shallow, maybe 3-5 degrees? I’m guessing here since I don’t have the tools to measure exactly. Compare that to a stoptail screwed all the way down. That looks like at least 20 degrees. What is clear is that the downward pressure on the saddles is totally different in each case. That’s simple physics and it holds up on inspection. The E string on the Maestro with the almost nonexistent break angle kept jumping out of its saddle slot when I bend it (so I made the slot a little deeper and its fine). The Bigsby and stoptail do not. I’ve had the problem on occasion with the trapeze and light strings. But does the increase in break angle change the tension on the part of the strings between the saddle and the nut? A lot of folks say that it does. My findings are different. Let’s look at the common sense part of the equation. A string is brought to pitch by tightening it to a particular tension point. I don’t think the string tension really cares what angle the string takes when it leaves the saddle and heads to the tailpiece. The bridge  can tell-no doubt about that but once the string hits the “open road” where you play it, it seems to be exactly the same no matter what the break angle. Then there is something they call “compliance” which throws a bit of a monkey wrench into the theory. Compliance is the is the resistance to bending. Increasing the break angle increases the downward force at the saddle and nut and in so doing,  it

The roller bar on a Bigsby B7 increases the break angle but its a lot less acute than a stop tail but less flat than a trap tail or a Maestro.

distributes the load over a smaller distance. That, presumably, would make it harder to bend, even though the tension on the “open road” of the string is the same.  That begs the question of whether that changes the distance you have to push the string to get, say, a half step change in the note. I’ve done more than a few side by side comparisons of stoptails, trapezes and Bigsby ES-335s and find that the differences in how hard it is to bend a note are pretty minimal. On the first subject, I’ve also found no perceptible change in string tension (assuming the string gauge is the same). I have to admit I like playing stoptails over the others but not because of any perceived tension difference. I do find some small variations in sustain but that’s another post. I really prefer the stop because it makes for a lighter guitar that’s a lot easier to string and I don’t use a trem anyway. That said, my favorite guitar has a Bigsby, so go figure. On the string tension issue, I do find a change in tone when you go from 9’s to 10’s to 11’s because, in that case, the string tension does change. There is also the issue of the path of the sound waves produced by the instrument with the various tailpieces. Are they transmitted effectively to the wooden mass of the center block (like a stoptail) or do they allow the top to vibrate (or try to) freely like a trapeze would?  The Bigsby (or Maestro or sideways) would probably be closer to the stoptail as it’s mounted into the center block. I always thought this would make a big difference in tone and that the break angle would have something to do with it. But now I’m not so sure. How does downward force on a saddle translate into tone or does it? I need a physicist or an engineer to tell me how it works because I’m pretty much just a player like you who has a lot of question and enough knowledge to be dangerous.

You can see how acute the angle is on a stoptail? It's not entirely clear if this is a real advantage. I think it is. I prefer to play stoptail guitars and I usually keep the tail screwed down close to the body

15 Responses to “The Curious “Break Angle””

  1. Chris W says:

    As an engineer, here’s my take on it…

    The break angle can not effect string tension for unbent strings, period. Charlie’s analysis of tension = pitch for a given string construction is correct. The only way that the break angle could effect string tension during bends, is if the angle is shallow enough that the string is allowed to slide over the saddle during bending. In this case, the string is capable of stretching both in front of the saddle, and behind it, which would change the effective spring constant of the string by changing the strings effective length during bends. In other words, the string between the nut and saddle and the string between the saddle and tailpiece can be modeled as two springs in series, where the compliance is additive. If the string can not slip over the saddle, we are back to a single spring model with the compliance being the function of the string construction, length, and tension (i.e. pitch).

    With a stop tail, none of this slippage matters much since the distance between the saddle and tailpiece is short, and the second spring in the two spring model is negligible. Also, the break angle is always high enough where string slippage is probably not happening significantly due to the high coefficient of static friction resulting from the high downward force resulting from the vector sum of the tensions in front of and behind the saddle.

    On the other hand, a guitar with a short Bigsby and a roller bridge would fit the two spring model better (low friction on the “saddle”, long second spring), and I would expect it to feel slinkier bends on that guitar. Another slightly different example of a two spring model is a guitar with a Floyd Rose. Bends are easier on a Floyd because the second spring is complying in addition to the string. And as Floyd players know, there is also the extra effect of the tension being non linear during a bend due to the second spring giving. A string has to be bent further to achieve the same pitch, complicating the analysis some more. Nothing is simple, right?

    Regarding tone, any archtop builder will tell you that down pressure at the bridge (a function of break angle) has a strong influence on tone. Stronger down pressure excites the guitar top more and brings more resonance and damping into the sound. In other words, it becomes more of a complex hollowbody sound. The degree of the effect this has on a solid top or a semi hollow is debatable, but it should have some.

    And for my last engineering comment: This is easy stuff to measure. If I were really into this stuff and were going to assert or argue it on the internet (I’m just doing thought experiments here), I’d take some force vs displacement measurements as a function of break angle for a few different tailpiece setups. This could be done simply with a luggage scale (simple force gauge).

  2. OK Guitars says:

    Resident genius Chris W., folks. Nice to know one year of college physics wasn’t a complete waste for me.

  3. Instead of trying to “solve” the question of what effect string break angle has on tone with formulas and physics theory, why not just “experiment” with a guitar that has a tune-a-matic style bridge with an adjustable stopbar tailpiece behind it. Raise the stopbar tailpiece up pretty high so that the strings’ break angle is quite low, and “listen” to how that actually sounds and feels; then screw the stopbar tailpiece down really low (loosen the strings first of course), tune back up to pitch, and “listen” to how the same guitar/same strings sounds to see if there’s any difference. Use your ears to get real “data.”

  4. OK Guitars says:

    Good idea. However, I don’t think the break angle makes any tonal difference at all. It’s just that every time I play a 335/345/355 with a Maestro and virtually NO break angle, when I bend a string it pops out of the saddle. If you make the saddle groove deeper, you lose resonance and sustain because the sides of the groove dampen the string if its too deep. I think break angle with regard to tone is overrated. As long as it’s adequate to keep the strings where they belong and keep things from buzzing and rattling, then I don’t give it much thought. I will say this–I have no intention of ever buying another one with a Maestro. They look wrong, they play poorly and I don’t use a trem anyway.

  5. wB says:

    My experience tells me that the break angle must be at the best spot for tone.
    If too much the top is restricted and too less not enough force to excite the top.
    on a semi like a 335 the Best thing to do is put it in the middle and then adjust up or down for the best tone or where yu think the best tone is.WB

  6. OK Guitars says:

    I don’t find that the break angle has much to do with the transmission of sound but it has a lot to do with sustain and how well the strings stay in the saddles without having to make the notches too deep. That said, your system makes sense. If you hear a difference, then by all means, adjust the break angle with the stop tail.

  7. Peter says:

    I’ve been playing guitar for 30 years. I’m also an engineer. I own many guitars with stop tailpiece incl. a 335. Adjusting the height of the tailpiece could make a lot of difference, not only to pick attack and how you feel the strings, but also to tone and sustain. This is how it works:

    * The break angle depends on the neck set angle, the bridge height and the height of the tailpiece.

    * A steep break angle increases the pressure on the bridge. More of the strings energy is transferred to the body/top of the guitar making it acousticly louder but with less overtones and harmonics. The bridge will collapse under pressure over time. Before that it might tilt. Strings break more often.

    * If the strings are in contact with the rear edge of the bridge, the tailpiece is to low. This kills sustain

    * A steep break angle leads to the dead portion of the string behind the bridge becomes less elastic and therefore makes more resistance when picking near the bridge, or bending strings. The guitar gets a firmer feel, comparable to using heavy strings.

    * Guitars with 4+ degree neck angle has a higher bridge than a guitar with less neck angle (but it would also depend on the height of the fretboard and the frets). These guitars would often benefit from a higher tailpiece or even a top wrap in some cases for optimal sustain and a smoother feel.

  8. OK Guitars says:

    Thanks for your input, Peter. I appreciate it when folks with more knowledge than I have-especially scientists-help out the with the real technical stuff. I understand physics pretty well (I was a physics major when I started college) but I understand writing and guitars better. Feel free to chime in or correct me any time.

  9. Rob Heinink says:

    As a player for over 40 years I’ve noticed a big difference in the playability of my 335 with regard to the break angle. When the angle is steep the feel of the strings is stiff and as soon as I raise the tail piece the strings have a more relaxed feel and it’s also easier to bend the strings. As far as tone, I have found that the more drastic the break angle the better the tone is acoustically but I’m not sure if I hear that the tone difference when the guitar is plugged in.

  10. OK Guitars says:

    This is a place where physics and real life seem to diverge. Many people have the same experience you have. Physics says the tension on string that’s tuned to pitch is always the same. Players say the shallower the break angle, the easier it is to bend. It is not a simple equation, however. There are all kinds of forces at work and simple logic seems to be less than adequate for explaining why the physics and practical application are at odds.

  11. Stefan says:

    (sorry for the double post, I edited a bit of the text)

    Very interesting information on this website!

    Mr. Gelber, what do you make of the common perception that a stoptail has to be all the way down for optimum sustain? Personally, I can’t adjust my 335 so that the stoptail is all the way down without the strings touching the back of the bridge. Makes me wonder if I should have a luthier have a look at it.

    And I really second the steep break angle/acoustic loudness point.

    Isn’t a guitar supposed to sound better plugged-in if it sounds loud acoustically?

    I am a little confused…

  12. OK Guitars says:

    I’m not a physicist, so I can’t give you formulas and force vectors and such but I can speak from experience. I usually lower the stoptail as far as I can without the strings touching the back of the bridge. If that isn’t all the way, it’s a function of the neck angle, not the break angle. The shallower the neck angle, the lower the bridge, the lower the stop can go. I think the relationship is more important than exactly where the stoptail sits. It seems logical that the more downward force on the bridge, the more sound will be transmitted to the centerblock. The same logic that says tighter strings are louder than loose strings applies here. I’m sure there’s physics afoot here. The last point is a bit tougher. I don’t think the acoustic sound of a solid or semi makes that much difference in how the guitar sounds amplified. After all, the pickup is not a microphone. It doesn’t directly respond to the acoustic property of the body as much as it does to the movement of the strings in a magnetic field. I know, more physics but there are websites that explain the workings of the pickup that will clarify this. There is clearly a relationship between acoustic tone and how the guitar will sound amplified but I can’t say that a 335 that sounds great acoustically will always sound great plugged in (and vice versa).

  13. Stefan says:

    Thanks a lot for your insight! ^This makes a lot of sense.

    It does make me wonder though about top-wrapping though considering the break angle is not very steep…

  14. OK Guitars says:

    I’ve tried it and the break angle is much shallower but still OK but the guitar didn’t sound as good.

  15. Patrick says:

    Old thread but I thought I’d chime in… I am a guitar tech and have set up many a Gibson in my time. The formula that seems to work for me is to set the break angle at the bridge to duplicate the same angle at the nut, usually 17 degrees. This will result in the stop tail being raised higher on the bass side than the treble side. Seems to strike a balance…

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