Weird sudden back-bow on Essence 5

[tomhug]

I have an Essence 5 which has been getting a lot of playing time with a relatively new jam band I'm in.

This one is unusual for my experience with Alembics, so I figured I'd tap into the Santa Rosa "hive-mind". For me it's unusual to experience such a radical change in relief so suddenly. This bass played fine at rehearsal on May 14th. Pulled the bass out for a gig on the 18th and it had suddenly developed a weird back bow. At the gig I thought I might have popped out a high fret, but this morning, in the quiet, with coffee at hand, I see now it's a back-bow.



The above pic represents a straight edge, pressed flush against the 1st, 2nd, and 3rd frets. Obviously the neck has a back bow.

I've given both truss rods a healthy 1/4 turn to loosen, and I'm going to let the strings pull it into position and see if it needs any more.
I do my own setups, and this bass usually has just the right amount of relief. Nothing else on the bass has changed, same strings, same bridge height, same nut adjustments. I pretty much follow the advice on Joey's setups tips, on the Fender site, and this very useful eBook.

Not sure I have an actual question, but I wouldn't mind some eyeballs virtually looking over my shoulder while I make these adjustments.

[jwright9]

loosen both truss rods another quarter turn.

[tomhug]

loosen both truss  rods a quarter turn.

Yup, that's exactly what I've done. Now, I'm just waiting to see if any more loosening is needed, after the strings have had some time to exert some force on the neck. Thanks!

[jwright9]

My Martin acoustic just did the opposite.
Last time I played it a month ago it was perfect. Just opened the case last night and found that it had a significant forward bow. I had to tighten 1/2 turn to get it straight.
Makes sense, It was so dry here during the winter and now it is more humid.


Did the humidity change drastically where you live in the past week or so?

[tomhug]

My Martin acoustic just did the opposite.
Last time I played it a month ago it was perfect. Just opened the case last night and found that it had a significant forward bow. I had to tighten 1/2 turn to get it straight.
Makes sense, It was so dry here during the winter and now it is more humid.


Did the humidity change drastically where you live in the past week or so?

Not drastically, no. Dew Point of 59 on the 14th, 49 on the 18th.

I've noticed humidity having a far greater effect on my acoustic instruments than on any of my solid-body instruments, although no doubt there is some effect.

[David Houck]

Not only can such a change be the result of seasonal changes in humidity, but the difference in the environment at a gig from that at your house can also cause a sudden significant change in neck relief.

I remember a gig at a bar, must have been in summer, where I arrived to set up just after a rainstorm, and  bar staff opened all the windows and doors.  By the time we were into the third song of the first set, the strings were practically lying on the neck; so we took an early set break and I adjusted the truss rods.

My house doesn't have air conditioning, and my bass tends to move with changes in humidity; and the last couple of weeks or so, I've been making truss rod adjustments practically every day, as we've had a lot of passing spring showers.

[tomhug]

Not only can such a change be the result of seasonal changes in humidity, but the difference in the environment at a gig from that at your house can also cause a sudden significant change in neck relief.

I remember a gig at a bar, must have been in summer, where I arrived to set up just after a rainstorm, and  bar staff opened all the windows and doors.  By the time we were into the third song of the first set, the strings were practically lying on the neck; so we took an early set break and I adjusted the truss rods.

My house doesn't have air conditioning, and my bass tends to move with changes in humidity; and the last couple of weeks or so, I've been making truss rod adjustments practically every day, as we've had a lot of passing spring showers.

I've been very fortunate so far, all of my instruments, Alembics and non-Alembics, have not exhibited that much sensitivity to environmental changes. This Essence seems to be the most sensitive one of any that I've owned. In spite of harsh and extreme Chicago-area temperature and environmental swings, I think I've lucked out with a pretty stable bunch of basses, all things considered.

[gtrguy]

I had this happen once with the 1996 Stingray that I gig with a lot. Turns out I had hung it on a bass hanger on the wall and the otherwise rock solid bass just did not like that at all. Live and learn...