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PostPosted: Thu Oct 26, 2017 10:57 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
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First name: Ed
Last Name: Bond
City: Vancouver
Country: Canada
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The thing is, all tops can be made the same stiffness, so stiffness is just one aspect. You can design that in. If you do deflection testing, then all your tops can be the same stiffness (if you want) but the weight/mass will be different.

Choosing the 'stiffest' wood is not always the best choice, at least not how I work.

As we know, stiffness and density are pretty much correlated enough to rely on.

So if you measure your density, you're basically measuring stiffness at the same time. But playing with density is a great way to tinker with the timbre, which is our job.

So if you have two tops, one at .03, another at .05, and take them to the same stiffness by deflection, you would be building two very different guitars. Yes the .05 top will be stiffer wood, but it will also be heavier at the same deflection as the .03 top. The .03 top might be better than the .05 top for fingerstyle whereas the .05 top may be better than the .03 top for a heavy handed strummer.

I think it's really valuable to be able to quantify such stuff and develop knowledge of what those numbers actually mean to the timbre of the instrument, and how to use such data to bring your guitar in line with what the customer has asked of you.

I've been doing exactly that for the past 220+ guitars with a very, very high rate of customer satisfaction, which, at the end of the day, is what it's all about.



These users thanked the author meddlingfool for the post: Clinchriver (Fri Oct 27, 2017 5:15 am)
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PostPosted: Thu Oct 26, 2017 11:03 pm 
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Brazilian Rosewood
Brazilian Rosewood

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Though when I say by measuring density you're measuring stiffness too, perhaps I should say rather that you are 'discovering' something 'about' the stiffness, since you're not actually quantifying it.

Same as you can learn something about stiffness by tapping. If you have two tops of equivalent dimensions, whichever has the highest pitch tap will be the stiffest.

Or learn something about stiffness by weighing. If you have two tops of equivalent dimensions and weigh them, the heaviest one will be the stiffest. And will also have the highest tap tone.

I think I blathered again.


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PostPosted: Fri Oct 27, 2017 1:03 am 
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Old Growth Brazilian Rosewood
Old Growth Brazilian Rosewood
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Location: Ann Arbor, Michigan
First name: Hesh
Last Name: Breakstone
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jfmckenna wrote:

Ok I think I understand. So you stuck to a thickness for ALL tops (even regardless of species?) and then looked for a certain number in deflection based on what ever weight it was that you religiously stuck to over the years?

This is kind of a chicken and egg thing but how did you know what to look for? What weight to use? What deflection to get, and what thickness to use as a base? Or is this all just an accumulation of personal data over time?



You have to start accumulating your own data, that spread sheet I mentioned and then pair it with your own admittedly subjective evaluation of how the instrument turned out. This is also taking into consideration what body size it's on as well and that's recorded too. So it's an accumulation of personal data over time.

We could share data provided that all variables i.e. are eliminated including exactly how the deflection testing is set up, the dimensions of the plates AND RH control. I'll add that how long something has been seasoned is a variable as well. Has it been baked, torifaction, etc.

Although not the end all to be all generally speaking the stiffer the top wood generally speaking.... the more likely it was to be suitable for what I wanted to see and eventually listen to. This goes back to getting that feel for the wood and flexing it using your own experience over time. Not scientific I know but a good cursory check making me want to test it with the rigid and controlled parameters.

We will forever have the disparity of how an individual builder sees what they are trying to accomplish by building. If you are keen to go for WAY higher performance than say a factory instrument (even defining this is dicey... and subjective to a degree...) acceptance and use of any old top IME won't get you there.

Lastly selective is relative too. Picking one best testing top out of the ten that you have does not have the possibilities of one out of a hundred or one out of a thousand but it still has value in the elimination of the lesser performing tops.



These users thanked the author Hesh for the post: Clinchriver (Fri Oct 27, 2017 5:21 am)
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PostPosted: Fri Oct 27, 2017 8:20 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Tue May 13, 2008 10:44 am
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The scientific measurements and tools help narrow things down but in the end I don't think we will ever dispel of the magic and the mystique that goes into building an instrument :D

If anything it's great for the marketing department.


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PostPosted: Fri Oct 27, 2017 10:03 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sun Mar 30, 2008 8:20 am
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"The scientific measurements and tools help narrow things down but in the end I don't think we will ever dispel of the magic and the mystique that goes into building an instrument :D

If anything it's great for the marketing department."

[:Y:]
The last refinements of tuning the soundboard rely on the tips of my fingers to "measure" the responsiveness and make adjustments accordingly.


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