Official Luthiers Forum!

Hi there friends! A friend of mine gave me a very good loud and quality sounding instrument. I would like to replicate the sound in my instruments. I also own strobosoft software and a good microphone.So my question is what kind of measurements should i make other than neck angle top thickness, bracing etc? I mean is there any frequency based test that i can make and later reproduce it (or search for) in my next built? Thanks in advance for any help and sorry for the large post.

I would suggest reading "Contemporary Acoustic Guitar Design and Build - 2nd Edition" by Gore and Gillet to get a good idea of what gives with this.
Stewmac membership will save 50% on the non membership price.
https://www.stewmac.com/luthier-tools-and-supplies/supplies/books-plans-dvds/guitar-building-and-repair-and-setup/contemporary-acoustic-guitar-design-and-build-2nd-edition.html?utm_source=google&utm_medium=shopping&utm_campaign=2021-06-gp&pref_currency=P&shipcalc=UK&gclid=CjwKCAjwtdeFBhBAEiwAKOIy5_ieCJ2DYekBGGAROj-FW8lyEtj7B4gkfrX-A7BqT9qQfqycpAVfBRoC8fMQAvD_BwE
BTW, yours in not a large post at all - you might try a search for "Hesh" to see some of his (very informative) posts, mostly on repair.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

So there is a way then. i will have to search more i guess but it is too complicated.I have seen also the o brien gore videos?Do they worth buying?

Don't know about bought Robbie O'Brien/Gore videos, I've only seen the free Youtube ones.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

The O'Brien/Gore video complements the book. It might mean very little without reading the books first.

Frankly, I don't think this is possible to do. Not to the degree that it seems you want it too. You can copy traits of a guitar, maybe, but you can't copy a guitar like say an artist can copy a Van Gogh or something. You can't even make two guitars sound the same if you use the exact same timbers cut from the same stock. I've tried it.

Wood is too variable to simply copy the thickness, bracing size and so on to yield the same or even similar results. That's why a lot of luthiers use deflection testing or the Gore/Gillet method for determining the top thickness. Those methods determine the top thickness for ANY given piece of wood so that you can maintain at least some consistency between guitars regardless of the material properties of the wood. So a stiff top would be thinner then a floppy one, and so on. Before measurements luthiers would do this all by feel, most still do probably.

the book as i can see is very expensive,...i cant buy it at the moment maybe at another time i will...thanks alot for the replies they are really helpfull. I think that modern luthiers shpuld have something like a patern to know every instrument is going to be good...

I get what you’re saying, however it’s not that simple. There are plenty of plans that give dimensions, however there is a lot of tubing the instrument that happens after those general dimensions are reached. As stated above your brace wood may be less or more dense, the top may be stiffer or not as stiff, and there is a host of other variables.

I would suggest searching for plans for the particular guitar you want to duplicate and then build as closely to those plans as you can.


Sent from my iPhone using Tapatalk

The OP would do well to pay more attention to this point. This is why a pattern is not enough.

Imagine trying to bake a cake when the amount of flour or sugar needed will vary, depending on the physical properties of the specific flour or sugar you are using. That's what it is like when you try to build a guitar that sounds good, in addition to looking good and not falling apart. Even pieces of wood from the same part of the same tree will be different from each other, in terms of how they generate sound. You can get to the point where most of the guitars you build (assuming the same general shape, dimensions and features) sound pretty similar. But that takes learning how to build to criteria other than strict dimensions.

i dont know if it is good to ask or not but maybe someone that has the gores book could tell me the procedure of taking frequencies and measurements and how it is done....?

You'll find it here, in the on the ANZLF for a free software, visual analyser 9.0 seems best version for this.
http://www.anzlf.com/viewtopic.php?f=1&t=3696&p=44370&hilit=using+visual+analyser#p44370

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

thanks!!!! it says that you get three frequencies. But what are they? how do i use them?

You've embarked on a long road, and need to learn about the signposts.

A useful introduction would be 'Acoustics for Violin and Guitar Makers' 4th edition, by Erik Jannson, which can be downloaded free from:
http://www.speech.kth/se/music/acviguit4/
Get part1.pdf through part9.pdf.

It includes instructions for a sound recording and analysis program called 'Wavesurfer', also free, from the same site.

A friend of mine wrote an Android app that he calls 'Luthier Lab' which contains a module for recording sounds and doing a spectrum analysis. Again, it's free. There's actually a ton of useful stuff for a modern luthier in that app.

Basically, my experience echos that of jfmakenna. It's possible, by duplicating the low-order resonant behavior of a guitar, to make one that sounds similar, and the more like the original it is, the greater the similarity. Usually that's 'good enough', and I've built a couple of acceptable 'tonal copies' that way. But even matching the wood exactly, by cutting the pieces from the same boards and so on, and matching the dimensions and the weights and the resonant behavior of the parts to very close tolerances won't produce 'identical' guitars. In the last such pair I made virtually everybody could hear the difference, although there was no consensus as to which instrument was 'better'; they were different, but equivalent in quality. I seriously doubt you could do much better using wood as a material, particularly for the top, and it may even not be possible with synthetics.

thanks alot again!I want to be able to reproduce a good instrument...not excactly the same.Just have a formula that can tell me that the outcome will be good sounding....without wolfnotes and lound as the instrument i have on my hands right now...i think this is what gores book promises...consistency. The link does not work i dont know why...maybe i am doing something wrong?

Sent from my iPhone using Tapatalk

Try this:

https://www.speech.kth.se/music/acviguit4/index.html

As far as copying good sound. There is no formula. you just get everything in the ballpark, and make a bunch of them, hopefully paying attention to what you are doing, what you are changing, and keeping track of everything on paper, or some kind of file. I would imagine the good sounding guitars can be made the high tech way, or the low tech way. Consistency can be achieved either way as well. Done well, neither way is easy, but it is a lot of fun trying to get there. Otherwise people wouldn't keep doing it!

_________________
Why be normal?

Pikolo. You are asking exactly the right questions. Unfortunately there are no short answers. There is a large body of knowledge that needs to be absorbed to understand how the guitar works and thus produces the sound that we hear - and that we want to hear. That’s why the Gore Gilet books are such substantial volumes.

However if you want to make a good sounding instrument then using a tried and trusted design is a good way to go. Getting the craftsmanship as well as you can, using material that doesn’t have to be the most expensive but has the right characteristics such as being properly quarter sawn.

And note that designs based on commercial, factory made guitars are very likely to be too heavily built (to avoid warranty issues) We beginners almost always err on the overbuilt side, tops a bit too thick, braces a bit too high. Look towards lightness all the time.

Anyway do enjoy the process. Dave

Well put.
+1, and enjoy. Building can be very Zen. Most of the time anyway.
There's really no short cuts, at least as far as many of us have found.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

As other noted, the variable qualities of wood make it impossible with one go to copy an instrument. You can do studies on the instrument you like and perform a set of tests, to characterize the instrument you like. First of course is to document the instrument, size thickness, bracing pattern … Document the resonances of the guitar by creating a spectrum graph and understand lower frequency resonances, a combination deflection and tap test to determine the monopole mobility an maybe chladni patterns to understand the modes in the spectrum graph. Even with that information there is not a method I know to replicate the sound, but it can be a target. Physically build the same instrument and use a method to thickness the top and back plates, and document the physical attributes of the wood for the plates and braces, young's modulus and density.

With a built instrument you can do all of the tests you did with the original and see where your at. With a base line of your own work you can start to modify your procedures to target the attributes of the guitar you like. I personally find that the biggest difference is getting the top thicknessed optimally and with an active back the back plate thicknessed properly. I set the brace height to a spec. I do tune the braces, but alas it is in an intuitive way.

_________________
http://www.Harvestmoonguitars.com

johnparchem wrote:
"Document the resonances of the guitar by creating a spectrum graph and understand lower frequency resonances, a combination deflection and tap test to determine the monopole mobility an maybe chladni patterns to understand the modes in the spectrum graph. Even with that information there is not a method I know to replicate the sound, but it can be a target."

That's essentially what I did in making my 'tonal copies'. If you stick closely to the overall design of something you like you'll end up with an instrument with similar 'character'; that's what Martin and Taylor and all do. Matching specific resonances gets you closer.

But how i do it ? I have a mic and visual analyzer. i taped the bridge on the top and fount the three basic tops(whre it makes a spike?) then what else?

Here is some information from Trevor Gore's website on using VA to make and use a spectrum graph https://goreguitars.com.au/attachments/Tech_note_on_data_collection_R1_2018_A4.pdf. I do not know a simple explanation about what to do with that information. It might take a whole book to explain it from the ground up.

I think your best option is to first build a guitar as close to physically possible as the one that you like.

_________________
http://www.Harvestmoonguitars.com

Thanks! This is something I will definitely do but i wanted to know if i got qny other options.I will try to find the gore book also...maybe a used one?We will see..

Some more info that may be of interest
https://goreguitars.com.au/main/page_about_design_modal_tuning.html
https://www.tommillerguitars.com/post/voicing-via-frequency-spectrums

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Hi again! So i took a measurement with a rubber hummer from punching the top of the bridge instrument and the spectrum analysis is like this. So whick is the air frequency , top frequency and back?