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Don Noon

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Notice I said it's what "I would try", and what I believe it would do.  At the moment.

 

I make absolutely no claim that it is true or it would actually work. :P

So we'll call them “Noon Theoretical Areas of Interest.”   I’m OK with that.   :P  :lol:

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So what is going on in the dungeon?  :D

 

Glue is drying on the bass bar. ^_^

 

While I'm here...

 

I just noticed that the new top weighs exactly the same as the previous one (after regraduation).  Since they are of the same log and nearly the same properties, any significant differences should be primarily associated with the arching (graduations are about the same).

 

The new top incorporates all of the arching and graduation features I think should maximize the "bridge hill" amplitude.  If it turns out the same as the previous one (which was not very strong on the high end), then I'll have to join Melvin in pitching out those theories and re-focus on the wood.

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Wow. What kind of wood is that?

Low density processed Sitka, as detailed back there in post #59.  Not that it matters, but the bass bar is .38 density processed European, slab orientation.

 

 

Anyone care to guess at the tonal difference between the two tops, based only on the weight, taptones, and arch height?  Same spruce, installed on the same fiddle.

 

Top #1:  57.0 g,  94, 174, and 366 Hz   arch = 14.7mm

Top #2:  56.7 g,  89, 162, and 386 Hz   arch = 15.6mm

 

I will guess that #2 will have slightly lower B1- frequency and slightly higher B1+.  And I will further guess that these differences will have absolutely nothing to do with the quality of the sound or how it plays.

(I already guessed that #2 would have much better high frequency/clarity based on the SHAPE of the arching, not so much the height, weight, or taptones).

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I'm trying to figure how you get a low plate weight with high hz m5 

By using extremely low density wood with high(ish) stiffness.  Here it is on a map of normal wood:

post-25192-0-42683400-1427337431_thumb.jpg

 

 

I'm thinking why isn't m2 double m1 or why isn't m2 the double of m5. 

Because there's absolutely no physical reason why it should be.

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 Addie and carl - if it's not my business just say so and I'll drop this  - 

 

If I'm not mistaken, we (both of you and I) have come to grips with our problems in the past and become, if not on-line friends, then, at the least friendly towards each other. 

On-line problems are just not worth it. If we (any of us) were to meet, face to face, in person, over a beer, (or tea) we'd probably become fast friends.

Any of us.

That's been my take on things. So now, if possible, I try to be as innocuous as possible, which is, very often, somewhat, ahhh, difficult - as both of you know from dealing with me and my (big) mouth in the past.

Shake hands and give it a new start - forget what you think of 'the other', as it's probably mistaken.

 

We good?

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I'm thinking why isn't m2 double m1 or why isn't m2 the double of m5.  I'm following.

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

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Life’s but a walking shadow, a poor player

That struts and frets his hour upon the stage

And then is heard no more. It is a tale

Told by an idiot, full of sound and fury,

Signifying nothing.

I don't want to get in Don's way here Mike but here's my m2/m5 belly comparisons without trying for a specific m2.  They just happen.

 

    M2          M5

1.  163        330

     174        348

     164        347

     174        347

     174        348

     174        346

I quit keeping track of m2 after these figures. Plates were lowered another 8-10 hz depending on the plate stiffness index method- PSIM.

I should add that m1 numbers were all above 90 hz and half were still above 100hz.  

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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

 

This was my reply to you, not the one to Ernie. 

I don't want to get in Don's way here Mike but here's my m2/m5 belly comparisons without trying for a specific m2.  They just happen.

 

    M2          M5

1.  163        330

     174        348

     164        347

     174        347

     174        348

     174        346

I quit keeping track of m2 after these figures. Plates were lowered another 8-10 hz depending on the plate stiffness index method- PSIM.

I should add that m1 numbers were all above 90 hz and half were still above 100hz.  

And your point is?

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We definitely need a separate thread for hotheads to flame away at each other.  This has been rather annoying.

 

Back to the topic...

 

We might need a reminder about what the current test items are:  top #1 is smoothly arched with no recurve at the channel and no flat zone in the broad arch.  Top #2 is more "Cremonese", with a flat zone in the middle of the long arch, and some slight concave or recurve in the crossarch out near the channel.

 

It's still a little early (i.e. first day glued up), but as best I can tell, but I'll give tentative results.  First, a low-resolution spectrum of bowed semitone scales:

post-25192-0-39272100-1427390069_thumb.jpg

 

Bridge hill power:  Top #2 does not have more power (yet; see weasel wording at the end of the post).  In fact, it has less; but the reduction is all at the very high end, which may be a good thing for reducing harshness. 

 

Transition hill:  a little weaker (good), and shifted more to higher frequencies (good too)

 

Low end:  not hugely different.  B1- frequency dropped 17 Hz (yay, I got a prediction right!), and B1+ stayed exactly the same

 

 

None of these differences are huge, or obviously good or bad just looking at them on charts or numbers.  I'll give my player's impressions:

 

My main problem with top #1 was excessive power around 800 Hz, or in first position on the E string.  It was intolerable, both from a tonal (ugly/boxy) and playability standpoint.  It just jumped out and assaulted my ears.  Top #2 has reduced power in that zone by about half, so it is much better.

 

Lost power at the very high frequencies is not really a loss, unless you like harshness.  I thought there might be a loss starting ~4 kHz, but top #2 showed some loss down to 3400 Hz.  I might claim another prediction success, except I have very little confidence that the result is due to what I though might cause it.  It might just be coincidence.

 

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

 

Now for the caveats:

  • Although I tried to keep things the same... same strings, same bridge... I did need to fit a different post, and it is likely in a different spot
  • For top #1, it was a regraduation, and had been previously assembled and strung up for a week prior to the regrad.  So in addition to possible pre-settling, the ground coating had a longer period to dry (the present top still smells of ground).
  • As a consequence of the preceding difference, I might expect top #2 to brighten and open up more.  I'll see in another week or two what happens.

 

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