Double Bass Unwanted chorus sound

[Kristian]

Hi,
I have a 5-str bass with a high C, after changing to a thinner c-string I got some kind of chorus sound in the first 7 positions.
I've heard that a sound post adjustment possibly can cure this phenomenon but i would prefer to try other possible solutions first, since I don't have a luthier living close by.
Thanks

 

[robobass]

Afterlength? Wolf eliminator? Other tailpiece alteration? I'd try daming your afterlength with foam to see if this is a "south of the bridge" phemonemon.

 

[DoubleMIDI]

Most steel core high-C strings I tried are either hard to press down in thumb position or weak in the lower fifth of its range.
My personal minimum diameter is 1mm (not less!) and the same tension as the G string, which is often hard to get. Too thick and the higher positions loose sustain.

 

[Kristian]

The after length is damped with a cloth, so it can't be that.
It's a very nice gut string made by Gerold Genßler, thicker than any steel string c I've seen.

 

[Robert Strickland]

What kind of pickup? Try repositioning it.

 

[Kristian]

No pickup. It's a acoustic sound.

 

[DoubleMIDI]

Seems that a sound post adjustment is a good idea to try.
Before the sound post adjustment on my bass, I needed a two element pickup for a balanced sound over the strings, after the adjustment it worked also with only one element.
It also might be cheaper than a new set of strings.