Double Bass Sympathetic vibration on an after length.

[Who da Ville]

I've not been using my plug-in pickup for a while, so I finally took it off yesterday; the plug receptical has been mounted on the A/D after lengths for as long as I can remember. After removing the pickup, it seemed that the bass opened up a lot, and even sounded louder to me.

But while playing, I started noticing a sympathetic tone. I soon discovered that whenever I played an open D, the after length of the D string also vibrated. No problems with any other string.

Can someone please suggest an adjustment I can make to correct this problem? My luther is a long ways off, & I'm hoping I can do this myself. I re-installed the pickup yesterday for an acoustic practice to deaden the vibration, & that doesn't seem right.

Thanks for the advice.

 

[KUNGfuSHERIFF]

Weave plastic tubing or a hankie between the strings and see what happens.

 

[TroyK]

Clint, you're about to fall into a deep well!

Check this...

Tune your bass and then "play" the afterlengths and see if you can recognize the pitch. Ideally it would be an 11th + some number of octaves above the open string. If it's a little sharp or a little flat, you can "tune" them with a little shim between the string and the tailpiece. I have part of a matchstick under one of mine now. The right way to do that is much more complicated and involves (at least) changing the length of your tailpiece wire, but a luthier who was into that sort of thing, could go a lot further with it. Not all of them are and some people reading this won't be either.

As you've already discovered and KFS has pointed out, you can also dampen the afterlength with some (pickup jack, tubing, towel, wolfetone eliminator, etc)

 

[Greg Clinkingbeard]

This is a deep hole. The after length on my bass is exactly 1/6 of the string length (7"/ 42"). The after length notes are: D, A, E and I forget. This is with Spirocore Mitts and a Stark E. The after length tuning was much different with EP weich.
The bass is very even now other than a bit of a wolf tone and the tendency to feedback around the B and C on the G string. My solution is to stuff a towel behind the tailpiece.
A friend was having a similar problem with Bb. I fit a new soundpost which took care of it. My soundpost is in a good spot and fits well so I live with it. If the issue persists, I'll adjust the post.
The issue of tuning the after lengths is valid but changing strings, string heights and weather make the pursuit a bit challenging in my experience. I tend to believe in setting up a bass 'textbook' and going beyond that with caution, finding that changes may have trade offs.

 

[Who da Ville]

Thanks for the great advice, guys. I thought about trying a Wolf Tone eliminator, & now I also have a matchstick in my bag of tricks.

And, I might dip my toe into the well by measuring the after lengths and determining their tone...