John Atkinson made the point to Gordon Holt that the sound made by an electric guitar plugged into an amplifier was just as much an acoustic signal as is an acoustic instrument, and he was correct. But recorded sounds produced purely electronically is a different matter: that sound never traveled though air, from an instrument (whether acoustic or amplified) to the recording microphone. There are plenty of recordings in which the electric bass, electric guitar, and/or keyboard instrument/s was/were plugged into the recording console, not into an amplifier and then recorded with a mic.
I’ve watched and listened as a recording engineer played with the dial on a studio’s parametric equalizer (far different from a graphic equalizer), drastically changing the sound of the recording. For evaluating the timbral neutrality of loudspeakers, make and use your own recordings! Listening purely for pleasure is a different activity. "Turn off your mind, relax, and float downstream" as someone once sang. ;-)