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Old 03-20-2021, 12:08 PM
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KevinH KevinH is offline
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Location: Tacoma, WA
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Originally Posted by printer2 View Post
As Alan said the time domain is important. What if one guitar has a bright attack and the other one more sustain in the treble? Which one is brighter, you could sum the frequencies and get an average number. Will that one tell you which is brighter. Please excuse the plot being of a bass. I would like to see a plot done on some popular guitars...
I ran some spectra on a couple of my guitars recently - a Taylor 522ce (all mahogany, X-braced), and a Waterloo WL-S Deluxe (spruce/cherry, ladder braced). I did that because those are the two guitars I own that sound the most different to me. I figured that would be the best chance of seeing differences in spectra. To my ears the Taylor is much warmer (yes, a warm Taylor) with a rich sound whereas the Waterloo is more woody and a little brighter.

The difference is really apparent on the bass strings. So to try and simplify things, I ran a spectrogram on the Taylor when just the open E string is plucked, all other strings muted:
TaylorEStringSpectra.jpg

And here is the same for the Waterloo:
WaterlooEStringSpectra.jpg

The numbers show the locations of the partials for the E string, 1 being the fundamental. Because the string was plucked at 1/4 the string length from the saddle (near the center of the sound hole), the 4th, 8th, 12th... partials are muted. The A and T are the locations of the main air resonance and the main top resonance.

To my eye, the main difference between the two is in the relative strength of the orange spike (2nd partial, 165 Hz) and the yellow spike (3rd partial). The Taylor's 2nd partial is more pronounced - because its main resonance of the top is fairly close to this frequency. It decays faster than on the Waterloo probably because, as Alan has mentioned, the resonance sucks the energy out of the string. For a similar reason, the Waterloo has a more pronounced and faster decaying 3rd partial (247 Hz, yellow spike) because of its proximity to its (higher) top resonance.

Does this explain the deeper/warmer sound I hear on the Taylor? Maybe it's the added bass from it's pronounced 2nd partial. And maybe the higher-numbered partials (the green spikes) that seem to contribute more on the Waterloo add to it's brightness. Or maybe not. I suspect timbre isn't so simple.

And, for the curious, here is an E Chord strummed on both guitars:
WLoo vs Taylor E Chord1.jpg

I've heard other people describe the Waterloo WL-S as having a woody tone, attributed to the ladder bracing. I'm not sure how to describe the sound, other than I know when it when I hear it. For a while I thought it was a fast decay, giving more of a "thunky" sound. But, other than the yellow spike, the Waterloo seems to decay at about the same rate as the Taylor.

While looking at these spectra is fun, I agree that interpreting them in terms of warmth/brightness/etc isn't so easy.
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