I want to make at least a small attempt to support having high slew rates in audio systems. I look at this from a slightly different perspective. I come from the ultrafast optical laser community where we make 10 femtosecond or shorter pulses routinely. To do this we need two important ingredients: Bandwidth (spectral width) is required to make a short pulse in the fourier limit (eg 30 nm coherent bandwidth at 800 nm makes a 35 or so femtosecond pulse). This is easy in a gain media like Ti:Sapphire that can support 100 nm of bandwidth. However, if the pulse is chirped meaning the colors are separated in time (dispersed), the optical pulse can be any length in time in theory. This chirp is used in chirped pulse amplification (that won a Nobel prize recently but was invented for radar decades earlier) with so we can reduce the peak intensity of laser pulse by making it longer in time as it gets more energy and then compressing the pulse by de-chirping it to put the colors back to the same phase or time. The phase of the various colors in the pulse needs to be flat (all colors come at the same time) ideally to make the shortest laser pulse. Thus, to make a short pulse at need control of bandwidth and phase.
A system that has a high slew rate in general can produce and preserve an impulse which similarly means it should preserve the phase of the spectral components of a signal. In other words, if properly designed, a high slew rate system will preserve the spectrum vs time of a signal as it propagates. Why does this matter for audio? Dispersion causes the sizzle of sharp transient peaks like a snare drum or cymbal crash or the initial strike of a piano wire to smear out in time. Does this say anything about distortion? No. Does it means is has to sound better? No. I just think this is not really appreciated widely and I do know from the optical world that dispersion can lead to a loss of fidelity and information. There may well be some Faustian bargains to make a circuit with a crazy slew rate and bandwidths but given the choice between two systems I know nothing about I would be more tempted to try the one with the wider bandwidth and higher slew rate. My $0.02.
This is also incidentally why I am horrified to design speaker crossovers. Putting poles on purpose near frequencies that have signal power will naturally cause dispersion if left uncompensated.
A system that has a high slew rate in general can produce and preserve an impulse which similarly means it should preserve the phase of the spectral components of a signal. In other words, if properly designed, a high slew rate system will preserve the spectrum vs time of a signal as it propagates. Why does this matter for audio? Dispersion causes the sizzle of sharp transient peaks like a snare drum or cymbal crash or the initial strike of a piano wire to smear out in time. Does this say anything about distortion? No. Does it means is has to sound better? No. I just think this is not really appreciated widely and I do know from the optical world that dispersion can lead to a loss of fidelity and information. There may well be some Faustian bargains to make a circuit with a crazy slew rate and bandwidths but given the choice between two systems I know nothing about I would be more tempted to try the one with the wider bandwidth and higher slew rate. My $0.02.
This is also incidentally why I am horrified to design speaker crossovers. Putting poles on purpose near frequencies that have signal power will naturally cause dispersion if left uncompensated.
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This bandwidth triggered phase error is negligible compared with what crossovers and drivers will do
Fair enough, but then you have to design for a flat frequency response and a flat group delay, both measures of the small-signal behaviour. The slew rate limit just needs to be high enough to process the steepest signals without internal clipping or excessive distortion.