Spectralayers signal observed at 60, 180, 300 and up.

Kirmeth Dugger

Kirmeth Dugger

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Mar 22, 2022
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I was at a friends house and to record his guitar. He is all electric. Huge amps all around. His son is a programmer I thing and got into my facebook somehow. Not worried about it. I thought it was funny. Oddly though in the signal I was working on I had an awesome sounding when isolated but still appeared very odd in it spread. It was at base level then 60hz then 180 and so on. What is it? Is that just how all the amps and whatnot display at that level? Thank you for your input. Just joined the forum and am very interested in more conversations!
 
Hi Kirmeth,

Not sure exactly what your question is, or what display you are looking at.
The low "B" on a five string bass is 31Hz, it's harmonics are at multiples of that frequency.

Many guitar amps and speakers are actually designed to progressively add more harmonic distortion with increased volume level, so if you were to put in a 30Hz signal, looking at the response on a RTA (real time analyzer) the fundamental (30Hz) and multiples of the frequency would be visible, 30x2=60 (second harmonic), 30x3=120(third harmonic) 30x4=180 (fourth harmonic) etc.
The levels of harmonic distortion added at high levels in guitar amps often exceed the fundamental, THD can be well above 100%.
This makes the amp sound louder than it actually is in SPL (sound pressure level).

A "clean" subwoofer would not exceed 10% THD (harmonics would be more than 20dB lower in SPL than the fundamental frequency) if operated within it's linear range, driver excursion not exceeding Xmax.

Art
 
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What has Facebook and a programmer got to do with it. If I understand correctly you recorded a guitar through big amps and looking at the guitar track you are seeing a spurious signal at 60, 180, 300 and higher frequencies. I'm guessing you are in North America? If you were in Europe/UK you would have said 50, 150, 250 etc - the common harmonics from the mains power frequency - or at least I think that's what you are saying, no idea what the 5 and 10Hz signifies related to these harmonics? What exactly is the question again?
 
Paul Johnson said:
What has Facebook and a programmer got to do with it. If I understand correctly you recorded a guitar through big amps and looking at the guitar track you are seeing a spurious signal at 60, 180, 300 and higher frequencies. I'm guessing you are in North America? If you were in Europe/UK you would have said 50, 150, 250 etc - the common harmonics from the mains power frequency - or at least I think that's what you are saying, no idea what the 5 and 10Hz signifies related to these harmonics? What exactly is the question again?
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I thought the same except for it not being in 60 hz increments.
 
A square wave (such as you might get from clipping the signal, either intentionally as an effect, or unintentionally due to poor gain structure), consists of the odd-order harmonics of the fundamental signal in the ration of 1/n, where n is the order of the harmonic. So a 60hz square wave could be constructed by summing a 60hz sine wave, a 180hz sine wave at 4.5dB down, a 300hz sine wave at 7dB down, and so forth. So the signal you've described as being at "base level at 60hz, then 180 and so on" could easily just be a clipped 60hz signal.
 
Harmonics (overtones) impact so many things - like why clarinets, flutes, oboes and saxophones sound quite different but all have a reed or two and lots of holes!
 
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