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Regulars
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Yesterday, I got my viola back from the shop after having the fingerboard replaned. My viola had a slightly high action (or at least my luthier said so), and I have short fingers. When I brought my viola in I asked her to lower my bridge a little more than the amount taken off the fingerboard, so as to lower the string height at the end of the fingerboard by about a millimeter.
Although I tested my viola for a few minutes at the shop yesterday to see if it was comfortable, tonight was the first time I actually practiced for an extended period. I expected my intonation and overall comfort to improve. But I also noticed an interesting result: the low strings sounded darker and richer than before. It's the same viola with the same strings, but it seems to have changed from a "big violin" to more of a "small cello" timbre. I'm a little surprised at how much difference a tiny reduction in string tension seems to make! I'm wondering if there's a certain ideal string tension range for each individual instrument that I just moved into...
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I'm not sure if it's (only) a matter of string tension. String height also affect the locus where the sound is emitted and possibly the whole way it resonates inside ?
From what the luthier who made my viola told me, the angle that the strings make on the bridge should be around 155 degrees but does depend on each instrument. There are just too many variables, gave up on trying to understand precisely... It's like the (huge) sound difference when I first got a carbon bow, I told myself, who would have thought... ?
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AndrewH said
... I'm wondering if there's a certain ideal string tension range for each individual instrument that I just moved into...
Sounds like you're liking the change so congrats, AndrewH!
I'll share some thoughts for further debate based on my fledgling experiences having had Felix at Fiddlershop tinker with my Sima Traian:
I think it's the strings themselves (depending on brand and whether they're weich, mittel or stark) that each have their own ideal tension range for a given vibrating string length - VSL (326 mm for a violin, for example.)
Hypothesis A: Lowering the bridge shortens the vibrating string length. If yes, is this the main cause of the reduced string tension and richer sound you are experiencing?
Hypothesis B: To accomplish the fingerboard work you had done, the sound post was removed and reset which could also influence the "mini-cello" sound you mention.
As for the notion of "ideal range" here are a couple of observations from my personal string length mod experience:
- My strings are made for a VSL of 326 but my actual VSL is 351 (fatter nut, bridge moved north.)
- My bridge was set to as low as possible (3.5mm on the E, just under 5mm on the G)
- When I use weich strings the sound is most mellow but the G string gets very floppy, even hitting the fingerboard when bowing with gusto. (Clearly below the "ideal string tension" range.)
- When I switched to Warchal Timbres with higher tension, the floppy G string problem is almost entirely gone.
- "Almost entirely" isn't good enough for Felix. When I visit Fiddlershop and work with him on my bowing, I've noticed that he tunes my violin to A 443 (hence upping the tension:) For his taste, this produces the best sound my violin has to offer.
- So whether one tunes to A 440, higher or lower is another variable in finding the "ideal tension" range.
So those are some of the variables I notice. Since you didn't change strings or reposition your nut or bridge, I'm betting on a combo of Hypothesis A with B as a wild card 
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Interesting. It's possible the soundpost was reset because the strings had to be removed to access the fingerboard.
I currently use Vision CGD and Larsen A strings, all medium gauge, so the tension is a little higher than Dominant but definitely within the average range. The string height above the fingerboard is now 4.5mm on the A string and 6mm on the C, and was about a millimeter higher before.
I had the nut replaced in 2014 because it was starting to wear down, which raised the strings by a fraction of a millimeter but would not have increased the vibrating string length.
Now that I think about it, Hypothesis A might need some modification because lowering the bridge by a millimeter reduces the vibrating string length by less than a tenth of a millimeter. That's insignificant in terms of string tension. But it also slightly reduces the angle at which the string bends at the bridge, which means the same string tension produces less pressure on the bridge.
If bridge height matters so much, I'm surprised that the shop where I bought the viola would set it up so high to begin with. (Not the one I go to now -- I bought the viola in the Los Angeles area in 2005, and moved to Sacramento in 2010.) I'd expect more thought to go into showing the viola at its best at that shop, seeing as it was a $15,000 viola (modern but well used, made in 1979) at a shop that services instruments for multiple Los Angeles Philharmonic string players. It's possible the luthier preferred a more violin-like sound for a slightly small (15.75") viola, or set it up for lower-tension strings.
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Has the instrument’s volume remain the same before and after fingerboard replaning/bridge height lowering? I would suspect a slight reduction, but I realize that this is a subjective judgment.
If the viola was left at the shop during a seasonal humidity shift, you might be hearing a slight dimensional change in the wood components as well.
From the criteria mentioned in your original post, I suspect it is due to a position change in the sound post. Keep in mind that your instrument costs many powers of ten more than mine, but the physical principles remain consistent throughout.
Success is the progressive realisation of a worthy ideal. —Earl Nightingale.
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AndrewH said
...
Now that I think about it, Hypothesis A might need some modification because lowering the bridge by a millimeter reduces the vibrating string length by less than a tenth of a millimeter. That's insignificant in terms of string tension. But it also slightly reduces the angle at which the string bends at the bridge, which means the same string tension produces less pressure on the bridge.
OK, you've convinced me that Hypothesis A is probably not significant...
... but your comment about more pressure on the bridge probably is.
More pressure on the bridge would mean more pressure on the top plate and a tighter fit for the sound post. So with your very slightly lower bridge -> less pressure -> less tight fitting sound post (assuming it's the same sound post in the same position.) I think that would have a mellowing influence on the sound (up to a certain point after which it becomes too little pressure).
Another nutty thought. Wouldn't taking mass off the fingerboard during the replaning tend to influence the sound too?
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Irv said
Has the instrument’s volume remain the same before and after fingerboard replaning/bridge height lowering? I would suspect a slight reduction, but I realize that this is a subjective judgment.If the viola was left at the shop during a seasonal humidity shift, you might be hearing a slight dimensional change in the wood components as well.
From the criteria mentioned in your original post, I suspect it is due to a position change in the sound post. Keep in mind that your instrument costs many powers of ten more than mine, but the physical principles remain consistent throughout.
I can't hear any difference in volume. If there is one, it's slight.
No seasonal humidity shift -- the viola was at the shop for two days, with no precipitation and virtually no change in daily temperature or humidity in that time.
The reason I mentioned the price was mostly my surprise that the shop in Los Angeles set it up with such a high bridge and high action, which seems to have been detracted a little from the tone quality. They carved the bridge that is currently on my viola (which was made by someone else).
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Just me thinking out loud, people have different opinions on the height of the strings, if I was selling a instrument and the normal height was X that's how I would cut the bridge. If the customer wanted lower then that, you can always take wood off can't put it back.
Mark
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