Open string buzz doubt

[rodmbds]

Hi everyone, I got this classical / nylon string guitar, action is 3.5mm on bass side and 2.7mm on treble side, I guess you can call it low action.

Anyway, I don't get buzz (maybe just a bit if I dig in) but as I move my picking hand nearer the saddle , I start to get this buzz, sounds like a hiss, on the wound strings E, A and D.

It doesn't bother me that much, but I'm curious as I've learned so much here at the forum, I'm sure you can come up with some ideas.

Thanks a lot!

[Rodger Knox]

When you pick a string, it starts two waves going in opposite directions, and they get reflected by the nut and saddle. There are two points of maximum deflection where the peaks pass each other, one at the pluck point and one the same distance from the nut (or fretted string) as the pluck point is from the saddle. Getting near the saddle pushes the other max near the nut (or fretted note), where you might get a buzz. This behavior doesn't last long due to mass and stiffness of real strings(as opposed to ideal strings), but you would get some buzz on at least the initial transient.

[rodmbds]

Great, it makes sense! Yes, it does not last long, the buzz. So you could say it's something normal, no need for any kind of adjustments, right?

I mean, it plays nice and buzzes a little, nothing that bothers me, I'm aware it's a trade-off between nylon strings and low action.

[Bax Burgess]

I would take what Roger said to be a cue to at least check the nut slots.

[Ned Milburn]

Another thought... If the tie block is high compared to the saddle top (ie: little break angle across the saddle) then the strings could be jumping slightly on the saddle when plucked close to it. Also, if the saddle top is flat, rather than angled-and-peaked, it can cause sitar like tones...

[John Arnold]

All good suggestions. I would also check the string ends at the tie block to make sure they are not vibrating against the top or the bridge.

[Alan Carruth]

IMO break angle is less of an issue than is generally thought, at least on these lists. My own experiments showed that a break angle of only six degrees was 'enough' IF the pluck was such that the string vibrates 'vertically' with respect to the soundboard. If (as is usual) the initial displacement leaves the string with some 'horizontal' motion then it can roll across the top of the saddle, and a bit more break angle is needed to stop that. I have not tried to measure the limits there (which, I imagine, would vary somewhat with saddle hardness), but I strongly suspect that a 12-15 degree break angle will be 'enough' in any case.

Roger's description is the key. Suppose for your pluck you press the string down toward the top and then release it. The string makes a 'downward' angle toward the top at both ends. The useful limit of the pluck comes when the string hits the fret tops before you release it, so the angle at the nut end is limited. The limit of the down angle at the bridge end is set by how close you pluck to the bridge. In theory, if you pluck right at the front of the saddle the down angle at that end could be 90 degrees. In practice, the closer you are to the bridge the greater the force required to depress the string: it's difficult to get an initial down angle at the bridge end of as much as six degrees.

When you release the string the 'kink' from the plectrum starts to run out toward both ends of the string. If the initial displacement is a triangle then it becomes truncated. The two straight sides of the triangle that the string made just before you released it stay put, but as the kink travel outward there gets to be a longer flat joining them. Eventually the bridge end kink reaches the saddle and reflects from 'down' to 'up'. A little while later the nut end kink does the same. Now you have two straight sections joined by a flat in between that gets shorter, until, one half cycle after you released the string, the two kinks meet, and you get an inverted version of the initial string displacement that is also flipped end for end.

At this point the triangle of the string displacement points up. So long as the upward angle at the saddle never exceeds the break angle, the string will stay in contact throughout the entire cycle of vibration. As long as it's in contact it will transmit all of the force of the vibration to the top of the saddle, and thence to the guitar. Increasing the break angle beyond that won't produce more sound, and I've got the data to back that up.

Note that if you started the pluck by lifting the string up, the triangle will point down a half cycle later. Since you normally pluck near the bridge that puts the steeper down angle at the nut end, and the peak could hit a fret and buzz. As Roger says, that's brief.

It's also possible to displace the string sideways much further than the vertical displacement. In that case, feedback from top vibration can cause the plane of the string vibration to 'precess', becoming more vertical. If the amplitude is high enough the string will hit frets and you'll get that brief buzz, only it doesn't happen right away.

What increasing the break angle beyond the minimum does is to increase the tipping force on the saddle that is trying to break out the front of the bridge. That's a drag to fix when it happens; its best to just avoid it.

[rick-slo]

Hmm. Got a microphone?