Currently in my workshop I’ve an instrument in Italian style having 2 x 8’. The owner wants to have the instrument restringed. Currently it’s strung very lightly in bronze but from what I measure, restring it in yellow brass should work perfectly. Note that the current sound is pretty awful (kind of vibrato in the sound, dull sound). This was the foremost reason the owner asked me to look at the stringing.
My concern is the soundboard is caving in from the bridge towards the bentside. I’m afraid that stringing it in yellow brass will increase the tension on the soundboard and might eventually lead to the soundboard collapsing.
What does the wisdom of the list propose? Should I use backpinning, add extra bars to the soundboard,…
Maybe some photos can help the professionals here to devise a remedy.
I’d say no “happiness bar” if you can avoid it (had bad experience: the caving of the soundboard was beautifully fixed but one single note became “dead”).
Maybe one or two lightly arc’ed ribs would do the trick. Control the humidity (more on top, less on the inside, the usual) and glue the rib(s) when the soundboard is “crowned”. It should stay there from now on.
But DON’T take it as an advice, let’s listen the pros.
Maybe I’m too concerned. But anyway, to give an idea I did the following. I’ve placed a straight plank over the instrument and used a steel ruler to measure the distance to the soundboard. On the left of the bridge I have 5,5 cm. On the right side (closest to the bentside) I measure 6 cm.
I’ve worked on several instruments of this maker. In general they are cheap and often made from plywood,MDF and plastic parts. Corners are cut when it comes joinery, red brass or bronze is used from the bass and -in my opinion - too far in the treble,etc. In general the instruments have a very metallic sound. I could improve some using Rose wire. My worry comes from one of his other instruments which had a huge problem with bridge cave-in. A collegue of mine removed one of the 8’ registers to fix this.
I’ve included a photo. It doesn’t look all that bad but remember that the stringing is very light (0,17 mm in the treble, around a1 0,21 mm, thickest string in the bass is 0,44 mm)
I wouldn’t worry about it. Many harpsichords have minor dipping in the area between the bridge and the bent side, I’d say the majority of those I have worked on, with no perceptible negative effect. This dipping happens in large part because harpsichord soundboards are not ribbed under the bridges - I would definitely not add ribs. And that degree of dip is not enough to warrant back pinning, IMO (and I’m not sure it would work with that bridge design).
I’ve also been thinking about the pressure: bronze has a higher density than yellow brass => bronze puts more pressure onto the strings.
Indeed at the end of the story I might end up with the same dip but hopefully with a much better sound.
Have a nice week!
This instrument doesn’t have a hitchpin rail, which would reduce downbearing on the bridge. It might allow greater string tension with less pressure on the bridge.