String Buzz Emanating from Bridge Groove

[William Hoffman]

hey y'all, i've got this question and would appreciate any and all help.

the bass has Spiro Mittels on it and sounds great, both pizz and arco. when playing at a low volume, no buzz is audible. but when i pluck the open A (and now sometimes the G) string loudly and really dig in, after a short time i can hear a distinct string buzz coming from the area of the bridge groove. the bass is otherwise set up perfectly and has no cracks or loose parts that could cause this buzz. so i am assuming it is the bridge groove cuz just about everything else has been double and triple checked.

if so, how in your experience can this happen?

could it be that the groove is not deep enough?

or what about the angle of the groove edges? my luthier told me to be sure and give the string an angled surface so the strings won't be pinched over too sharp a corner there. could it be that the angle of the top side of the groove wasn't filed correctly? what is the correct angle to file the top and bottom edges of the grooves?

thanks!

[bigolbassguy]

My guess is that you have some loose winding on the string. Try wrapping a piece of electrical tape tightly around it. If the buzz goes away, it's probably time for a new string.

[William Hoffman]

thanks for the alternative. but it can't be that. the Spiros are fairly new and are not unwinding. i've also changed the strings many times in the past years and the buzz is there with new or old strings. the buzz sound, which i've been listening to for about 2 years now, emanates directly from the string groove in the bridge. i have to assume the source is the string rattling on the bridge groove. i just want to know if anyone has ever experienced that and what can be done about it.

[Greg Clinkingbeard]

Originally Posted by William Hoffman

what is the correct angle to file the top and bottom edges of the grooves?

thanks!

I'm no luthier but this is what I like.
The grooves should be nicely rounded so that the string rides in the entire groove. It should be a bit wider than the groove and mine are probably .3mm wider than the strings at the top of the bridge.
The radius is tough to explain, but think of a dinner plate with the outer fourths cut off. There should be a definite witness point but the string should come off the bridge at the correct angle and not bind at all.

[bejoyous]

Maybe it's time for a new bridge.

[Jake deVilliers]

Originally Posted by William Hoffman

thanks for the alternative. but it can't be that. the Spiros are fairly new and are not unwinding. i've also changed the strings many times in the past years and the buzz is there with new or old strings. the buzz sound, which i've been listening to for about 2 years now, emanates directly from the string groove in the bridge. i have to assume the source is the string rattling on the bridge groove. i just want to know if anyone has ever experienced that and what can be done about it.

Sounds like low frequency 'sitaring'! Is your bridge thin enough at the top ie 3/32" or so?

When I file bridge slots I come up from below and rotate around the bridge in the same way that the string comes up from the tailpiece and goes around the bridge on its way north. At a guess, I make a 10" - 12" radius arc.
That way the string can find its own perfect seat, with clean entry and take-off, no matter the height of the bridge or position of the tailpiece.

[arnoldschnitzer]

As you mention the problem happening only on open strings, the culprit is most likely the nut. My guess is that the nut grooves are either too low, or too horizontal.

[bribass]

Originally Posted by arnoldschnitzer

As you mention the problem happening only on open strings, the culprit is most likely the nut. My guess is that the nut grooves are either too low, or too horizontal.

+1. When I've experienced mystery open string buzzing like you describe it most often turns out to be the nut, even when it really sounds like it coming from much lower down on the instrument.

[Andrew McGregor]

Spiros have three layers of windings... I've had one of the middle layers break and cause this, with no visible damage. So, while I agree it's probably the nut, if you can't find a problem there, change the string.

[JtheJazzMan]

I have this same issue on a spiro solo B (tuned to A) string.

It comes and goes depending on whether the string twists slightly. I have a marvin tailpiece which allows the string to twist.

I believe Andrew Mcgregor is on the right track, it could be an internal problem with the windings. Perhaps not broken windings but loose or twisted.

[William Hoffman]

thanks to everyone for your replies.

on listening again yesterday, the location of the buzz is either in the area of the bridge or just above the end of the FB at about mid-string. in fact, i've also always wondered if the string itself is rattling on the FB.

it is not just on open strings, for example a low "C" on the A string can produce this buzz, too. but does only happen if i pluck hard enough to produce a loud note.

could that be the nut? or can it be that the string itself is rattling against the FB? the string height is not really low, the A string is at about 8mm. any thoughts?

thanks again!

[bigolbassguy]

I have two questions. What does the buzz sound like; is it shooshy, clacky, like a sitar, etc. - and where, exactly, is the noise coming from? It would be helpful to pinpoint it. I do this with a length of surgical hose (a trick I learned from a mechanic) Put one end against your ear, and search around with the other. It's worked without fail for me. Any kind of tubing will work, if you have enough hands You might need an assistant.

[William Hoffman]

that is a good tip. i'll have to use that next time.

this time i went by process of elimination and (1) checked out the bridge grooves, and the A and G string grooves were too tight and not deep enough. i remedied the situation and took a gentle swipe or three at the angle of the afterlength strings on the bottom side of those bridge grooves. so far, this appears to have been the solution to the "buzz" (it was a faint string rattling that came from the general area of the bridge tip).

that being so, i have not needed to go to (2) the second suspected area, which was, as Arnold suggested, going to be the nut grooves.

thanks again for all your great help! TB is a great thing!