12 String Buzz Behind The Saddle

[TomT]

Hey guys.

 

I have a Yamaha 420 12 which has a few strings that always buzz behind the saddle.  I try wadding cotton back there but then it mutes the string.  Can't seem to find anything online about this; it's always about fret buzz.  Any suggestions? Tia.

 

Tom

[john]

Buzz behind the saddle? Are you sure it isn't the saddle itself? Check how it is seated in, that the bottom of the saddle is smooth and flat, and that the seating area is also nice and smooth and flat. Equally you could look at the seating of the ball string ends. To get buzz (other than fret buzz) you need something that is either:

 

• not seated correctly, so it moves, even under tension
• where the string is routed through or next to something with insufficient space so that string vibration touches the close surface

Granted, depending on how the ball ends are secured it is possible that the string could touch another surface, I would think it unlikely as the length of string between the ball end and the saddle is very short so string movement will be limited.

 

Is it an electro acoustic? Most electro acoustics have the bug under the saddle. If that is not seated correctly it could provide a pivot point allowing saddle movement.

I must have written my post at the same time as Hobo, and it looks like we are thinking in a very similar way.

[TomT]

It's pretty weird. Acoustic, no pickup, new saddle, everything is nice and tight.  The buzz makes the damned thing sound like a sitar. The worst culprits are the 11th E and 8th D.  Last set of strings I had it was only the E that was a problem.  The only thing I can think of is maybe the saddle grooves aren't deep enough because whatever is going on between it and the pegs affects the whole string. It's definitely behind the saddle.  If I place my finger on the string back there the noise is gone.

 

I pinched a little cotton in there again and it seems to work.  At this point that's all I care about.  I'm just wondering what all the mystery is.

[john]

Ah... So the noise created also depends on the fretted notes being played? That would suggest something much harder to diagnose and correct... Harmonic induced sympathetic resonant frequencies. By touching behind the saddle that might just be enough damping to mute what is in essence a design or build flaw.

If it is that it's not easy to correct. I had a problem on my Martin acoustic that was and is annoying, although I did address it partly. I played specific notes on the G string or E string and it set up a resonant frequency on the A string. Likewise touching the A string at saddle would dampen the resonant coupling.

This article explains some of the factors:

http://www.phys.unsw.edu.au/music/guitaracoustics/construction.html

String choice can also affect it but less so than the construction. That said changing string gauges or from phosphor bronze to bronze flat-wound is nice and quick as an experiment.

A good luthier might be able to source it and charge you lots or you can experiment with damping in the sound cavity (other approaches are more permanent and more expensive. Whatever you do (damping, strings, bridge mounting etc. will affect tone. The trick is to do something that pleasantly alters it, and for the layman that takes trial and error.

Chances are it will be some damping material (experiment with type), placed somewhere on the backboard or soundboard towards the tail of the guitar. Changes to the saddle mount are more likely to change the volume and tone of the higher notes, the E1and B strings. The annoying part is the experiment usually involves loosening or even removing strings for each experiment. Persevere and you should be able to improve the issue without destroying the overall tone or volume.