Zero fret related intonation problems on headless bass

[wulf]

I got round to changing the strings on my Sei Flamboyant headless six string on Tuesday but noticed the intonation was seriously out when I was playing it at band rehearsal on Tuesday evening, with the fretted notes being about 20% sharp! Urghh...

The strings were Status double ball roundwounds (120 - 95 - 75 - 55 - 35 - 20), a shade lighter than the previous set (also Status double ball rounds but 125 - 100 - etc).

When I'd put the new strings on, I had a horrible buzz on the D string when it was tuned to C# or above and the B string sounded a bit flaky. Both of these issues were improved by using the grub screws that I'd normally use if I was using single ball end strings on the bass. This helped the strings make good contact with the zero fret.

Since discovering the additional intonation errors, I've tried moving the bridge saddle on the D string to limited effect (I picked the D string as it was the one I first noticed the problem on and its in the middle ground). Further experiments showed that the intonation was fine if I pressed the string down in the quarter inch or so between the zero fret and the nut.

I assume that my problem is something to do with not enough downward force meaning that fretted notes use the length of the string from bridge to nut rather than bridge to zero fret. It's similar to what's discussed in this thread but, being headless, a string retainer won't help.

I tied an old shoelace round the strings but was in a bit of a rush last night and didn't get it tight enough to make a difference. I'm going to ring Martin Petersen at The Gallery this lunchtime to arrange to take it up there (there are a couple of other other things I'd also like to ask him about) but was wondering if anyone else had come across similar problems on headless basses and what was diagnosed as the causes and solutions.

Wulf

[JMX]

My take is that the nut slots are not deep enough, so that the new strings don't touch the zero fret.

I never had those problems on my bass, but this has to be it.

[wulf]

It's been fine before, including with the very similar set of strings I've just taken off. I'm sure they're installed in the same way (I swapped the strings one at a time rather than taking all the old ones off before adding the new set).

Do you think such a minor step down in gauge could make such a big difference?

Wulf

[JMX]

Can't really tell without seeing the bass, but it could be that it was just the little difference between hit and miss.

[The Mock Turtle Regulator]

is there any noticeable wear on the zero fret?

if flat spots are appearing it could cause buzzes on open strings, and might cause fretted notes to be flat in relation to the open string notes.

could mean the zero fret needs replacing.

[wulf]

The zero fret looks to be in pretty good nick - the fretted notes are actually about 20% sharp rather than flat compared to open / harmonic notes.

I'm going to drop it off at The Gallery tomorrow - I spoke to Martin this lunchtime and he was wondering if it was something to do with how the strings fit through the nut, but I'll take it up there so he can do his magic.

I'll let you know what the upshot is, in case anyone comes across something similar in future.

Wulf

ps. It meant I left the Sei at home and took my Hohner B2A to the music group practise at church last night. Unlike others who've recently posted about converting back to four strings, I'm not that drawn back to less strings... but it was fun slapping and tapping away on such a wimpy looking little instrument