Measuring Guitars

[Purité Audio]

I thought it might be interesting to acoustically measure some guitars, I have been reading how different Woods affect the tone, I can understand how a larger enclosure will alter the Fr and perhaps hoe lacquer might change the resonant frequency.
What would be a good piece of software to capture an initial frequency response examine sustain etc?
Keith

 

[RayDunzl]

Audacity can record the waveform (or analyze one already recorded) and give a spectrum.

Examining the waveform over time would give hints to sustain and how the harmonics fade.

One problem would be making everything else equal.

Strum or pluck repeatability.

Tone (harmonics) changes with where you pluck the string on the same instrument.

Different acoustic guitar designs may project their sound differently (different polar response), so, where do you measure?

Could be interesting, but other than just listening to them (or playing them) subjectively, it might be difficult to make good comparisons.

 

[RayDunzl]

I just tried it, for grins, with a pluck on an unamplified bass guitar G string, about 2 inches from the mic.

A pluck near the neck (more mellow) and a pluck near the bridge (twangy). Way different tonalities.

Here are the spectrums. Lots of harmonics with strings.



Recorded waveforms (zoomed in, after the initial attack, during the sustain). They're both quite repetitive, both have the same 97Hz fundamental, both quite different looking.



Is that enough to discourage or encourage you?

 

[Purité Audio]

That’s really interesting and encouraging, I realise it can’t really be scientific and choosing a guitar is purely subjective, I just bought it might be interesting to compare body shapes, top, back and side materials.
See if there is any correlation between response and preference.
Keith

 

[DonH56]

The problem is likely to be getting a consistent strike/attack. How you hold it, how you press down the strings, how you pick/strum, all impact the sound. I would rig up some sort of mechanical striker to generate a consistent attack/pluck/whatever and ensure it is placed at the same place on each guitar. Failing that, I would use a pick on an open string or use a capo (to avoid differences from finger fretting), and strive for the same measured amplitude as well as consistent speed of attack.

I have a vague memory of doing this ages ago back when I was building effects boxes and was curious. IIRC I modify a rat trap (bigger version of a mouse trap) by stopping or replacing the spring (too much force as-is) and putting a little rubber foot on the trap bar (cut a slot in the foot and glued it down with a small square of wood). I added wood strips and clamps to attach it securely to the neck, then used a string to trip it. I think I extended the part that the spring attached so it stood an inch or two higher than the bottom plate so it could fit around the neck. It's hard to describe but was not too hard to make and use.

 

[Purité Audio]

Thanks Don, I have been thinking about the repeatability issue, perhaps I will just go for the blinded comparison, like the Stradivarius link that Vincent linked too in my other guitar thread, can a musician pick the expensive guitar etc etc?
Keith

 

[Blumlein 88]

I've done some of this. Basic resonance is easy everything else is messy. Looking at spectrograms in Audacity is more instructive. For the body you get cleaner results with a small speaker playing tones or pulses into the back or soundhole. I wouldn't say you can evaluate quality very well that way. Maybe basic resonance and harmonic tone structure

 

[Speedskater]

Microphone placement will be a problem. It will be hard to get repeatable reading on just one guitar let alone several. Maybe some sort of placement jig.

 

[DonH56]

For my tests the guitar was laid on a table (actually on a foam "egg crate" mat for protection and to let it vibrate better) and the mic was on a short stand over the sound hole (or where it would be for an electric). That way measurements were consistent. I also measured from the pickup, and kept a couple of pickups to use so I had comparable schemes, but of course that means the pickup's transfer function is in the response.

When I mic a guitar I prefer to use a couple of mics if possible; one aimed at the sound hole and one aimed at the neck to get plucking sounds and such. You don't really hear the latter in the audience but everyone expects to hear them on a recording, so... Kind of like close-mic'ing a piano; the hammer strikes get accentuated much more than sitting at a "real" performance but people like that (me too, guilty as charged).

 

[harlo11]

Hi everyone, I want to start playing a guitar but I don't have any idea. I might need some help to decide which brand to buy since I don't have much of a budget. I have been searching online and found several reviews like https://musicadvisor.com/?s=guitar+brands
It would be a great help to hear some opinions for those who really plays. I am open to any suggestions. Thanks

 

[RayDunzl]

Go to a local Music Store (if there is one) and talk to somebody and touch some.

Guitar Center, Sam Ash are some brick and mortar suspects.

 

[Wombat]

An acoustic guitar is convenient for a beginner as it frees you from being tied to amplification and thus you can more easily play/practice wherever you wish.

 

[Purité Audio]

The whole guitar thing is interesting, once you move into solid wood guitars, the actual manufacturing process doesn’t appear to be that different, some manufacturers Taylor for instance have a modern automated plant , labour costs determine price so anything non European/American is cheaper.
I am going to be measuring and ‘blind testing’ some guitars with some musician friends, I have purchased some guitars that range in price, same body size but different woods and prices.
Keith

 

[Wombat]

Th

The whole guitar thing is interesting, once you move into solid wood guitars, the actual manufacturing process doesn’t appear to be that different, some manufacturers Taylor for instance have a modern automated plant , labour costs determine price so anything non European/American is cheaper.
I am going to be measuring and ‘blind testing’ some guitars with some musician friends, I have purchased some guitars that range in price, same body size but different woods and prices.
Keith

The application of 'tone-woods' in stringed instruments is a historical reality. The old favourite tone woods because of limited availability are being replaced by substitutes or laminates.

Can technology match tradition? Strads. and Strats. change in tonality as the wood ages. For the better- we can't know, can we?

 

[harlo11]

Thanks guys. I heard Yamaha is a great brand too. I found this https://musicadvisor.com/yamaha-fg800-acoustic-guitar/ and read some of the article about this instrument. Will this one do for a beginner like me?

 

[SpeedyRodent]

Thanks guys. I heard Yamaha is a great brand too. I found this https://musicadvisor.com/yamaha-fg800-acoustic-guitar/ and read some of the article about this instrument. Will this one do for a beginner like me?

I have a FG 800 as a practice guitar in my living room. It is a very good guitar overall. The most significant Change from the previous generation is the scalloped bracing.

I do have one suggestion. Regardless of the guitar you choose, make sure you add in the budget to have a good luthier 'setup' the guitar. The string height (action) at the nut end of the fg800 is fairly high from factory. Adjusting this down makes a significant difference in playability. A lot of beginners give up learning due to bad setups. Many guitar shops will throw in a free setup if you buy the guitar from them.

Personally I'm very picky with my setup specs and do all my own setups.

 

[Wombat]

Go

I have a FG 800 as a practice guitar in my living room. It is a very good guitar overall. The most significant Change from the previous generation is the scalloped bracing.

I do have one suggestion. Regardless of the guitar you choose, make sure you add in the budget to have a good luthier 'setup' the guitar. The string height (action) at the nut end of the fg800 is fairly high from factory. Adjusting this down makes a significant difference in playability. A lot of beginners give up learning due to bad setups. Many guitar shops will throw in a free setup if you buy the guitar from them.

Personally I'm very picky with my setup specs and do all my own setups.

Good advice.

 

[Purité Audio]

I have ordered three Furch Guitars to experiment with Spruce/rosewood, cedar rosewood and spruce mahogany!
More when they are delivered,
Keith

 

[Wombat]

I have ordered three Furch Guitars to experiment with Spruce/rosewood, cedar rosewood and spruce mahogany!
More when they are delivered,
Keith

You may end up on an endless mission like amirm.

 

[rebbiputzmaker]

That’s really interesting and encouraging, I realise it can’t really be scientific and choosing a guitar is purely subjective, I just bought it might be interesting to compare body shapes, top, back and side materials.
See if there is any correlation between response and preference.
Keith

Good luck. Probably easiest to stick with acoustic guitars and measure the difference sizes shapes and materials. When you get into electric you open up an entire set of different variables. You now have different pickup styles, and amplifier types which come into play. When looking you will still see that many players use tube amplifiers. This brings into play the different sounds of the tube amps, Fenders Vox Marshalls Etc. The harmonics interface (loop) between the guitar and amplifier also comes into play to affect the sound. Solid state tries to mimic these effects be imo it is not the same. Maybe good for some but far from traditional. Feel is also an important part of choosing a guitar. Body styles also effect player flexibility, something like a thin line ES225 can be more easily used for different music styles than an L5 as an example.