Official Luthiers Forum!

Tone will always be subjective. Amplitude can be measured.

Might be something leftbrainluthiers@yahoogroups.com would sink their teeth into?!

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Dave
Milton, ON

Michaels right. Gotta love him for that quality.

I would thinks so Todd.

With tone being subjective...well how about testing for things like

-longer sustain
-increased partials in the harmonics
-a scope on the sound waves will show change in bass mid and treble response

Now them things you can measure.
but yup, tone quality ... got me there.

Oh and by the way ...me gotts a great deal on blindfolds if you guys need them for your umm testing.

Personaly I like the Voo Doo approach ...is more fun.


blessings
the
Padma

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Audiences and dispensations on Thursdays ~ by appointment only.


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Todd,

I posted something recently about sensory evaluation recently - my wife spent about 20 years designing tests related to subjective qualities of food and drink.

To get good data you either need large numbers of random testers and a test that can be statistically analyzed or a small number of very highly trained experts.

My advice would be this: contact a local audiophile club and see if they would agree to do some focus groups with different instruments. These people often have very highly developed listening abilities. A second thought is to find a violin building school. A bunch of students might make a really good panel to determine if there are differences between instruments and what the quality of those differences are.

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

Just for the sake of argument, does it really matter what scientific analysis tells us here? If you hear an improvement but a computer generated graphic analysis shows no change, which is more important? If you hear no improvement but the computer shows a big one, will you go out and buy it?

Or put another way, would you rather your illness get better from the placebo effect or would you rather stay sick in the comfort of "knowing" that the drug you are taking is scientifically unproven?



That's the only test that matters as far as I can tell and the one I plan to do. I have a couple of friends with ears as good as any I know. If they hear a clear difference, I'll be satisfied that it works. Only problem is if I disagree

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http://www.chassonguitars.com

I've done a lot of testing of guitar spectra over the years, and so far as I can tell, the effects of 'playing in', no matter how it's done, are of the same sort in every case. Basically, the top 'loosens up'.

The effect is most pronounced in the low range: the 'main top' resonant mode tends to drop a bit in pitch (on my guitars, usually about 1/2 semitone or a little less), and the amplitude increases, so that it pumps more air. I see this on my own guitars, whether they're played 'by hand' or driven artificially, and the same sort of differences between 'new' and 'old' guitars of similar design.

In the spectrum of the guitar the 'main air' and 'main top' output peaks tend to become taller and, perhaps more importantly, broader. These are the two lowest resonant peaks, and account for a large part of the total power output of the guitar, even up into fairly high frequencies, simply because they're the most effective sound producers.

Subjectively, I associate these changes with a more 'full' or 'solid' sound generally: this 'puts a floor' under the tone. However, a lot depends on where the guitar started out: if it already had a lot of bass, and the treble was not really clear, it might just descend into 'tubby'.

What this suggests is a two-pronged appraoach: we could see if some agreement could be reached on the correlation between objective measurements of output and the subjective impression of tones that contain more of these particular frequencies on the one hand. One nice thing about this is that there are a number of ways to go about it that may not require playing in a bunch of guitars. For example, recordings of guitars could be digitally filtered to see if enhancing or reducing the signal strength below, say, 250 Hz, really makes a difference in the perception of 'tone'. With luck this could set thresholds: we could get some idea of how much change you need to have before it's noticable. Once some agreement had been reached about what a particular tone 'looks like', in terms of the spectrum, then we could see which features of the guitar give these spectral outputs.

The other prong would be to get more data to corroborate or refute the measurements I've got. This is not too difficult at some level: if you have a computer with a sound card an 'impulse spectrum' or 'step spectrum' test can be done in about ten minutes. The key is to have the setup ready, so you can do these tests at the drop of a hat: if it's too hard to do, you won't do it. The other really important thing is that you do the test the same way every time. One of the reasons I have not published anything on this is that I've moved, and, perforce, changed my setup, a couple of times in the past few years. The charts I get now look very little like the charts I was getting six or eight years ago, so that can't be compared directly. You have to get a bunch of data with the same setup. Then you look for commonalities in the data, and try to correlate those with subjective impressions of tone.

There is also a 'direct' test that could be tried: build a 'matched pair' of instruments that sound the same, and then play one and not the other. I tried this once, but the instruments turned out not to sound the same when they were completed, so I never followed through. A factory won't be able to do this unless, by shear chance, they get matched sets of wood coming through the line and built them into the same model, and even then it's not guaranteed. You could, of course, take the opposite tack and play your way through Martin's or Taylor's wearhouse until you find two that sound 'the same'. That's a less trustworthy setup than building identical instruments from the get-go, IMO, but may be more plausible, since they make so many and their QC is pretty good. Now, if you could get an 'in' with Chris or Bob, and convince them to build several guitars with 'matched' wood, that would speed things up.

If anybody's interested, I can go into methods of looking at guitar spectra. As I say, it's not hard, and only requires minimal equipment and some free software.

Finally, in no way do I mean this to cut off further discussion, or suggestions of other ways to do this. Part of being a good scientist is being open to the notion that you might be fooling yourself: it's all too easy to see what you expect to see. The best way to find out if that's the case is to get a bunch of people with different approaches all looking at it, and arguing about (sorry, 'discussing': we don't 'argue' on this list) what they see.

Yeah... We save our Knock Down Drag Out Fights full of yelling, cussing, calling eachother out, and Broken Beer Bottles for the Left Brain Luthiers group! It's all in the name of Science!

How did that whole Bridge Rocking vs Pumping "Discussion" finally end anyway?

Anyway, A tonerite is on the list of stuff for me to buy. I think the basic idea has some merit... it just has to wait for it's turn behind "Workbench" and "Band saw"

Thanks

John

It just makes sense. At least, it just makes sense to any luthier or player that has had the opportunity to test/play "before" (right off the bench instrument) and "after" (once the top has had the chance to vibrate a little while.) I suspect the majority of people in the camp of believing that vibrating an instrument to help it "break in" or "loosen up" is hogwash are people that have simply not had the experience of hearing an instrument "open up."

Anecdotally, I was told years ago that the memory of sound is perhaps the most difficult sensory experience to recall, so it is very difficult to make A/B comparisons with a gap in time between A and B. I am sure there are a number of disbelievers that can't reliably remember the before and after well enough to agree that the change is real, and don't want to feel like fools for ascribing to a notion they cannot prove.

Dennis
p.s. I think we should quiz David Hurd some more, about a cheap, down and dirty solution to this that we can cob together for $15 instead of $150.

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Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

Here is a question. Has it been established that guitars will not "open up" unless played? I mean, if a guitar is strung up, can it be that just the string tension alone can account for stressing the top, etc., and causing the top and associated structure to change to accommodate to the string pull? It just seems to be that the tension of the strings is a much greater force than the relative change in force exerted by the vibrations of the strings.

If I was going to spend money on a gadget to break in a guitar, I would want to be pretty sure that the guitar won't break in all by itself and in the same amount of time just by virtue of the fact that it has been put into a state of stress just from being strung up!

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"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

OWW!!!!! Great question Steve. My past experience tells me that an excited plate will open up quicker than a plate left passive so intuition tells me that a plate under continuous by static loading will take longer to reach the same elasticity as one that is respectively variable loading.

If the companies don't have the confidence in their products to spend the money and time to do a professional study (that they make available to the public for scrutiny), then why the hell would somebody want to do it for them? It's not like making guitars is a time consuming process enough.... but hey if you're willing to work for free, I have grass in my front yard that is so special, that cutting it imparts a state of euphoria... anyone want to see for themselves?

Gee it looks like you dudes are really serious about testin out this here gadget thing...
so me gonna wish you success in this, shut me mouth and go run amuck elswhere on the forum.

All joking aside, me really hopes you get positive results...the physics say you should.

But if you run into a snag, PM me and I'll go dig out that book on secret chants and incantaions...you never know. (sorry just coulden't help meself with that last line.)

good luck
the
Padma

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Audiences and dispensations on Thursdays ~ by appointment only.


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Aloha All,

I think I referenced this in an earlier thread but here's my inexpensive take on a "Guitar Dildo" from a number of years back:

http://www.ukuleles.com/Technology/HulaGirlShaker.html

In general agreement with Al Carruth, I suggest that the top in particular will both try and take time to adjust to the compressive and tensile stresses placed on it when the strings are brought up to pitch. In all likelihood vibrations from either playing or some secondary source (loud speaker, vibrator, whatever...) will simply speed up the process so that the instrument will be at some equilibrium state and not "fighting" the top vibrations quite as much. In all honesty it is inconceivable to me to pay $150 for a device such as the Tonerite or anything similar (and similarly priced).

With respect to chiming in on the bridge torque business, I've learned not to throw myself between individuals with strong, diametrically opposed opinions.

But my understanding from Pete Licis and Brent Gallagher (who did the heavy lifting on this issue and both came to the same conclusions regarding the bridge torque model) is that from a torque standpoint, it is as though the strings were only attached to the saddle.

aloha,

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David C. Hurd
http://www.ukuleles.com

Alice laughed: "There's no use trying," she said; "one can't believe impossible things." "I daresay you haven't had much practice," said the Queen. Through the Looking Glass by L. Carroll

"Since my house has burned down, I have a much better view of the moon"

How to analyze it....?

I think you'd want to quantify the tonal "maturity" or the magnitude of change as a function of time. The spectral data can be obtained by using an accelerometer (the smaller and lighter the better) and by analyzing the data using a FFT (Fast Fourier Transform). This would basically show you the different modal frequencies and their amplitudes. You would need to develop a history of guitars that have not been "Tone Righted" as well as a history of those that have. You could get your FFT results at various points in the guitar's life (don't they seem to change the most the first week or so?) and compare the differences between them.

If your numbers indicate that the tone-rite cause more significant change in the vibration than just letting the guitar sit around...and your gut tells you that it sounds better...then maybe it does.

Personally, I'd rather play the thing than to stick some gizmo on there. God knows I need the practice...

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http://www.PeakeGuitars.com

We need two guitars made by the same company on the same day. These need to be as new as possible.

We need to put them in a humidity and temperature controlled room (with data monitors).

Then, we need to charaterize these guitars over a period of time, say a week (given stable environmentals).

Next, attach a tonerite to one. Continue characterization over the next week.

Finally, (double blind), get folks to subjectively judge the guitars.

If the objective data and subjective data correlate positively, we have the answer.

So, who can get the guitars? Who has access to a studio quality room? Good mics?

Mike