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I wanted to get the EMI fret calculator in an offline format so I ended up making an Excel spreadsheet that includes the basic 17.817 output...plus string stretch compensation output. The only input required is the scale length. It solves for 24 frets.

The two outputs and the compensation factors are laid out clearly so it's all there and easy to analyze.

The stretch compensation aspect intrigued me initially but having adjustable intonation, very light strings, and very low action kind of makes this aspect moot. In hindsight however, I can see that the stretch compensation would definitely serve acoustic guitars. I'd love to hear comments on this. The stretch compensation is highest at the first fret and then tapers off until fret five where it remains constant for the rest of the frets. That makes sense, especially with nut string heights that are slightly safe and high.

If someone has an idea where I can publish this .xls file so I can link to it here...please say so. Otherwise anyone is welcome to e-mail me and I'll happily share it.

stuartgortsr@gmail.com

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Hi Stuart, Thanks for sending it over! I wonder if, for completeness, you should add the conversion to millimetres and bridge locations for classical and steel strings? Just so it's all in one spreadsheet?

Just a thought,
Thanks!
Nick

Actually, it would be great if anyone could run through the pros and cons of string stretch compensation? I assume not everyone is doing it? Is it worth it on a [small ] classical?

Ah...well converting to metric is simple enough....except I'd never use it.

But whatever subtleties are involved with bridge placement beyond scale length are lost on this electric builder.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Yeah, I put the metric conversion on mine. So is stretch compensation more of an electric thing? I've never really heard of it before. Showing my ignorance again.

Stretch compensation would more benefit acoustics than electrics.

The idea is that since you are bending the string when you fret, you are stretching it in the process and increasing the pitch. The compensation shifts the fret toward the nut to compensate for the stretch and maintain the proper frequency for that note/fret.

The stretch issue would be more acute on an acoustic with higher action, thicker, tighter strings, and a non-adjustable bridge.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

I would like to take a look at it also. I did one several years ago on excel but I'm not sure what the stretch factor is all about

Thanks
joebeaver@cox.net

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Joe Beaver
Maker of Sawdust

http://windworld.com/features/tools-res ... alculator/

In case you might want to see the original calculator from wence my Excel file originated.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Cheers, That makes sense. I'd be interested to know how many acoustic builders use stretch compensation...
I've got my fret positions from the SM calculator so far. Have I been missing a trick?!

Is there any reason not to do it?

Stuart, I received the spreadsheet just fine. Thank you for that. I read the write up on it you posted on the concept. It is very interesting stuff!

It seems that guitar setup, string size and type and which string (low e, high e, so forth) we are talking about would play a role. Have you put the theory to an actual test? I would be interested in hearing the results.

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Joe Beaver
Maker of Sawdust

Heavens no. That would require building two instruments...one with compensation and one without...and then testing with something capable of very subtle analysis.

All I can say is that I've included the stretch compensation in everything I've built and the intonation has been lovely down the line. The cnc cuts the fret slots so placement is never in question. When I draw the model in cad, I copy and paste the fret placement values straight out of the Excel file into the cad software. It's hard to screw it up.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

If it works than that is the real test. Good job!!!

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Joe Beaver
Maker of Sawdust

I'm assuming you're using straight frets, Stuart?

If you are, there's a big problem with this method, which is that you've only compensated for the sharpening of one string at best, because, in general the longitudinal stiffnesses and hence sharpening on fretting of all the strings in a set are different and so will need different stretch compensation.

When I first started working on intonation/compensation, I worked out where all the frets would have to be for all the strings to play the equally tempered scale accurately. Each fret ends up in a slightly different position for each string (stepped frets) because of the different string stiffnesses. However, as it turned out, the spacing between all the frets remained the same as standard for each string. So if the frets were placed in the "right" position it's as if you had to slice the fret board longitudinally into six segments, one for each string and shuffle them a bit relative to each other. That's effectively moving the whole fretboard segment relative to each individual string. But that is actually the same thing as moving the whole string up or down relative to the fretboard, which means that all the frets can be aligned again, in their conventional positions with the strings shifted slightly up and down the board relative to the frets. And, magically, that is the same as nut and saddle compensation, whilst retaining standard fret distributions. So you don't have unconventional fret spacings and each string has its own, correct, nut and saddle compensation.

All the maths, modelling, testing etc. in Section 4.7, usual place.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Ya...they call it "true temperment" when they're trying to sell it to you.

http://www.truetemperament.com/site/index.php

...and it's silly the way they present it in the video. I get excellent intonation on straight frets and can fret chords at high registers with open drone strings and maintain perfect intonation...at least it's perfect to these better than average ears.

Not that you're wrong because you most certainly are right...but what the average ear can actually hear might argue against the hassle of doing this.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

You should look into design tables in SW. No cutting and pasting required, the dimensions are read straight from the spreadsheet.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

I can't get through the barrier Microsoft has erected to make me buy the newer Office products. I can open older .xls files using their provisional launcher but Solidworks can't get past their new roadblock. It pisses me off I have to pay $100 to restore functionality and productivity by having to upgrade to new software that I don't want to upgrade. So...for the moment I'll just stew about it and sulk with my principles.

It takes all of five minutes to get the data from Excel to Solidworks. If I had integrated cam software it might be worth getting it all wired down.

One note...design tables require knowing intimately the functions of relations and parameters. I've never had any training on Solidworks but I'd need it to use drawing tables efficiently. I'd of gotten that training many years back if I'd have purchase integrated cam software with Solidworks. Having new tool paths generated instantly with model changes would have been the bees knees back in the propeller days. I kind of blew it buying separate cad and cam packages...but I get by well enough.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic