mfeng

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About mfeng

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  1. You can take a picture of the top or use a generic image - I just use a generic image these days. See attached for what a map looks like (cello top). You have to create the template first - put down mapping locations using the tool and point layers. You should use a separate layer to generate the outline (set at a fixed thickness for the contour - doesn't really matter what that thickness is but you need to put a finite value in). The template has a number of points in order that you just move the probe in place, click, and the measurement gets recorded. Move to the next spot, click again, repeat. Pro version of the software creates a contour. Hope that helps.
  2. I commissioned a custom instrument using his wood once. The wood was not good. Spruce wasn't stiff, maple was knotty and didn't have any ring to it. Instrument sounded terrible as a result. Live and learn...
  3. Mine works well. Software can be buggy at times but Liam is pretty responsive via email and has dealt with all of the issues I've encountered. Reasonably accurate, much easier to map plates once you have a template set up (I can take 80-100 measurements on a plate in ~5 min). The contour is useful to quickly see any high or low spots.
  4. More or less matches my data, back grads tend to be at least somewhat similar, whereas tops are easily confounded by bass bar. As an example, I've done a bunch of experiments around bass bars (on cellos) and found that I can cut down a bass bar (moving m5 from 188 down to 165 - both still quite high) and B1- only moved from 175 to 174Hz - I have other tops ranging in M5 from 136Hz all the way up to the 188Hz that land with a B1- of 174-176Hz. Where the stiffness and mass is matters quite a bit especially on the top.
  5. Word of caution about yitamusic - I've bought 3 cellos from them over the years, and have 3 badly warped fingerboards... I can deal with issues like that, but probably not worth the hassle for a regular cellist. Agree that CF bows will be on average better than the wood bow at those low price points. CF bows can feel very different from one brand to the next - just as much variation between CF bows as wood bows. The cheapest ones from China range from playable to surprisingly decent. At the lower price points, unless you are or know someone who knows what they're doing, I would advise renting. There are bargains out there, but you can easily end up with something worthless.
  6. Tension is a function of frequency and string length (distance from nut to bridge). Thus, as baroquecello mentioned, lighter gauge = thinner string, all else being equal, and easier to respond. Thick vs thin string depends on material (linear density of the string determines the frequency for a given vibrating length and tension) so different strings at the same tension can be different thicknesses. I don't have any scientific evidence of this either, but I've found that too high of an angle does choke the sound a little - similar effect to having the soundpost tension wrong, while noticeable, it's not a the end of the world. You might be able to compensate by adding a little more soundpost tension to balance the downforce from the strings. As for what to do, unfortunately I'm not in C'ville anymore otherwise I'd offer to take a look - but I will say that lowering the projection won't be cheap - if it's playable, practically I'd say just leave it.
  7. What are the grads like? I've seen split (or more accurately multiple) peaks plenty of times (but I only work on cellos). For me, usually this happens due to a large stiffness variance across the plate - I can tell this because the peak gets stronger or weaker depending on, for example, if I mic the upper bout, mid bout, or lower bout - each area seems to have a resonance mode correlated with it. With standard graduations and patterns typically these peaks line up pretty well, leading to a more uniform B1+. On the B1-, sometimes these converge after a few days of playing in, sometimes they split even further. Large deltas in along-grain vs cross-grain stiffness seem to be correlated to splitting at least the free plate frequencies; I haven't looked at how this affects B1- splitting specifically though at least off the top of my head there's probably a correlation. On cellos though splitting B1- is a good thing for reducing (splitting) the wolf. I've yet to determine whether the multiple peaks is a good thing or a bad thing - so far it just is. I think these peaks are more effect than cause.
  8. Does it change gradually or on a day to day basis? Gradual changes are usually humidity related, as the plate absorbs/releases moisture it changes the main top mode. Range of change is usually not more than a semitone or so. Can also be due to a mass damper wolf eliminator moving the wolf around with the humidity changes. I have seen top plates with split modes as well - two weaker top modes, but these are rarely strong enough individually to produce any sort of wolf. I don't think I've ever seen a top mode at a C - that's either insanely stiff or insanely weak.
  9. Two "best" and one "master". Definitely warped fingerboard. Here's a picture of the "master" one: https://photos.app.goo.gl/xn3Cu9YnMcM7LyXG7 (negative scoop?)
  10. I've had 3 of them. All three have had their fingerboards warp within a year. Yita chooses their wood based solely on visual properties, the maple they use is pretty crappy acoustically. As a result, the lack any sort of complexity to the sound. Honestly they sound exactly like their price. You can do much better than Yita. You're probably not going to find anything on ebay honestly - I've bought cellos from almost all the ebay sellers out there over the years, and none of them are worth the money. Buying an instrument sight unseen is a huge risk. I really wouldn't recommend it; the only reason I did was because I was looking for a new supplier and was willing to take that risk. Needless to say, none of them worked out. There are some great shops in China, but they certainly don't advertise on ebay. If you're dead set on buying something online, PM me and I can point you the right direction.
  11. So let me preface this by saying that most of my experience is with cellos, not violins. Yes, 494 is high for a B1- and more line with B1+. With cellos, B1- (the top mode) is always the wolf mode. I've never seen a B1+ strong enough to create a wolf - but I don't know yet if this is the case with violins as well as the modes are more closely coupled than with cellos. However, bass bar stiffness should have a relatively small effect on B1+, so either the stiffness has changed a huge amount (possible given the large change in sound), or this isn't a B1+ effect. Extra mass in the center of the bar can lower the freq, and coupled with a less stiff bar, probably accounts for the sound degradation. Mass/higher density of the new bar is probably a factor, but given the height of a typical bass bar and the h^3 stiffness relationship, I think a lesser factor than the stiffness, but still a factor nonetheless.
  12. The wolf going down a half step means the new bar is less stiff than the old one, assuming no other wood was removed from the top (for those familiar with instrument modes, B1- went down). Not surprised that the instrument has a thinner sound now - the stiffness of the top (especially on the bass bar side) has a big impact on the low frequency radiation, and half a step change alludes to a rather large decrease in bass bar stiffness. Could be because of less stiff wood, could be a smaller bar.