| I'm not a luthier and I can't really say what's going on with your bass. My bass has an extremely thin top and has significant sinkage (maybe a full 8-9 mm, but I haven't measured) around the F-hole on the treble (soundpost) side and a little bit on the bass side. A couple of luthiers have looked at it and said that at some point in the future, my bass's top may have to be reformed, an expensive and time consuming process.
The last luthier who looked at it decided it would help to increase the breakover angle, which is the angle between the strings above and below the bridge; you can imagine how this would reduce the downward pressure on the top. He also repositioned my soundpost, although not with that problem in mind. At the time, we knew that the bass bar was solidly in place. The increased breakover angle seemed to help a bit, but the problem still exists and I make a point of monitoring it.
My advice is that you should consider having it looked at, but it's by no means a certainty that your bass is in trouble. I'd be surprised if a new, quality bass had a sprung bass bar unless it was a particularly troubled or poorly maintained instrument. Assuming that your soundpost is in the right place and your bass bar is solid, it may be that your bass's top is thin and may tend to settle over time. If so, you and your luthier can probably take steps to minimize or manage it. It may also be that the bass simply has a little bit of shape to it naturally, and I'm not sure I'd be overly concerned about a few mm.
In the end, though, only a qualified luthier can tell you for sure, but I certainly wouldn't panic just yet.
As an additional data point, my bass was made in 1987 and the top has been quite stable in the three years that I've owned it - it may be that the sinkage occurred many years ago and has not progressed since.
Last edited by mjt0229 : 11-30-2010 at 09:39 PM.
Reason: clarity, extra info
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