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Don Noon

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..... It turns out that the modes are not coupled as free plates.

 

Could you explain?

  I may of picked up something useful from the Curtin tap routine article.  Record M5, glue bass bar, record new M5, remove bass bar, remove the difference between the two and reglue bass bar.  Something else, remove more wood from M2 areas.  Just comparing to old Italian plates. 

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Here's the bowed semitone scale comparison so you can hear the differences (top #1 played first for each string): attachicon.gifArching comparison - broad vs tight.mp3

 

No. two gives me the sensation of more vowel change from note to note in the scales along with a rounder. more  defined sound. The effect is more musical and more interesting. 

 

I would like to predict that, for 2, a player will feel the bow more easily gets "right in amongst the resonances" where it can mess around with more creative opportunities.

 

Most interesting work.

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I feel somewhat responsible for the fact that I brought up bagpipes the other day.  Bagpipes bring out the nasty in everyone.

 

Yeah?

Well, you'll have to live with that from now on - won't you?

Bagpipes........ need I say more?

Now we'll probably never get over that, and every time somebody wants to start trouble here it'll be;

"Yeah, but what about those bagpipes?"

GREAT!

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I would like to predict that, for 2, a player will feel the bow more easily gets "right in amongst the resonances" where it can mess around with more creative opportunities.

 

 

#2 sounds better.

 

I agree.  Doug, in looking at the bowed response, the first one has higher peaks and deeper valleys; to me that translates to some "colors" that are overpowering, and others that are missing.  To continue the analogy, at the very high frequencies, you need some... but too much UV will fry your retinas.  #2 seems much better to me as a player, primarily by reducing the "yikes!" zone on the E string (which likely also colors the lower string overtones, too).

 

I think this all points out one of my other predictions:  the significant tonal/playing differences have nothing to do with the signature modes, which are only slightly different.  That leads to the logical (to me, anyway) conclusion that precise control of the low modes via tap tuning is not going to get anywhere in understanding these other critically important aspects of tone and playability.

 

For Uncle Duke:  the vibrating movements of the free plate do not show up in the assembled instrument, due to the attachment of the ribs, neck, chinrest, soundpost, etc.  The assembled instrument vibrations are that of a complex shell structure, not two plates kinda held near to each other.  So I view the free plate properties as only a rough way to get an approximate stiffness... and that's about all that's necessary.  The important things are elsewhere.

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So the conclusion is that "Cremonese arching" with recurve is best? :)

 

For this particular instrument, for those who expressed an opinion, and with the details of exactly the way I did it, and with this wood... it does seem that way.  Violas might be the opposite.

Howz that for a qualified non-answer?  :)

I think so too. But #1 has something I also like. It would be very interesting to hear them in a large room where I might see #1 ahead.

 

That might be difficult, as #1 and #2 both use the same back and sides.  And I trashed #1.

 

Thanks for the info.  -   Is the flat sawn bass bar going to stay or is it an experiment?

 

Grain orientation of the bass bar has been discussed before in other threads.  I have used both orientations; quartered is traditional and easier to fit, flat sawn has some possible structural advantage, and more difficult to fit.  Either way, I think there's no sound difference.  

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Don is right saying that there is no physical reason that they should be related. Years ago I was trying to use free plate tuning and came across this matching issue: M5 = 2 x M2. I wasted a lot time convincing myself that it is nonsense. I destroyed a lot of wood in the process. It turns out that the modes are not coupled as free plates. Moreover, the measurements by Joseph Curtin taken from classical instruments do not find any strict matching scheme.

 

Mike

 

Actually, in a flat plate these modes are related and are different superpositions of the same two underlying modes. What relationship they will have to each other in an arched plate will be complicated and most likely not useful to violinmakers but is probably saying something about the wood and arches.

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Yeah?

Well, you'll have to live with that from now on - won't you?

Bagpipes........ need I say more?

Now we'll probably never get over that, and every time somebody wants to start trouble here it'll be;

"Yeah, but what about those bagpipes?"

GREAT!

Oh, right, I posted a bagpipe Youtube video...  :rolleyes:   ... Italian Christmas music.   :rolleyes:  :rolleyes:  Shame on you, Addie!   :P  :lol:

 

Let’s try without bagpipes.  Better?   :wub:

 

https://www.youtube.com/watch?v=AfZkXntKY8k

 

Poor Don.   :(

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That's what I would try too... but I would thin below and to the side of the thick central area, and do the same above the thick area, on the bass side of the upper bout.  I believe that would put more meat on the D string; not sure about the A.

 

Happy to report some results about my regraduation effort for adding meat to D and A.

 

I have received suggestions from a few MNers.  Assimilating them all led to lopping off 0.3mm from the top plate almost everywhere and lowering the bass bar by a couple of mm.  I ended up getting significantly more meat on D and noticeably more meat on A.  Overall, the balance is fine.  Maybe a little bit of bridge tuning will suffice.  It's now a much more powerful violin than before.  M5 (with bar) is now 350 Hz.  The only annoying thing is that the Warchal Amber strings have this metallic twang that doesn't seem to go away.

 

So it looks like the top was just a little too stiff and too thick.

 

A big "thank you" to those who offered suggestions.

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For Uncle Duke:  the vibrating movements of the free plate do not show up in the assembled instrument, due to the attachment of the ribs, neck, chinrest, soundpost, etc.  The assembled instrument vibrations are that of a complex shell structure, not two plates kinda held near to each other.  So I view the free plate properties as only a rough way to get an approximate stiffness... and that's about all that's necessary.  The important things are elsewhere.

 

I disagree. The free plate mode shapes and frequencies do transfer into the final assembled violin.

 

Colin Gough has written some papers that will be published soon in which he does a finite element analysis (FEA) and follows the mode frequencies and shapes in this sequence: flat isotropic square plate, flat rectangular plate, flat violin shape plate, arched plate with various heights, anisotropic arched plate with different E ratios, same thing f holes cut, then with bass bar added, then with uniform thickness variations, same thing with different thickness graduation maps.

 

He then assembles the back and top with zero to full rib stiffness to show the effects of the ribs, then adds the sound post.  I think in the future he will add the neck and fingerboard, tail piece effects etc. The original free plate modes can be tracked all the way to the final instrument.

 

One of the difficulties of doing "what if" violin experiments when making real violins is that it is difficult to "keep everything else constant" because of the variation in wood properties and constructions. An FEA eliminates these problems and is very good for showing the effects of individual variables.

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