On 2026-07-04 1:04 PM, Fons Adriaensen wrote:
On Fri, Jul 03, 2026 at 07:32:13PM +0200, Robin Gareus wrote:While I tend to avoid linear phase EQs due to pre-ringing artifactsLinear phase for audio is one of those subjects that seem to generate a lot of hype.
I expect it's still the fallout from the days when it first became possible to actually build a linear phase EQ, which is not possible in the analog world where all EQs are "just short delays".
[..]
LP filtering has its place in domains where the time-domain interpretation or perception (rather than the spectrum) of a signal matters most. This include things like video, radar, sonar, seismology, etc. In audio it doesn't matter at all except maybe in some very rare corner cases - those where very steep filtering is done in the region where human hearing transitions between T-domain and F-domain perception and things can become ambiguous. In particular the association of LP filtering with mastering is suspect. Any EQ done there tends to be quite subtle, and when it is not it is probably being done in the wrong place. Human hearing is to some extent optimised for minimum phase waveforms. Also all natural or physical processes that shape or modify sound seem to be of the minimum phase type. If you know of any linear-phase process that occurs naturally please let me know.
Thank you for sharing your thoughts and insights. I always like reading those.
On a more philosophical note: almost all the math theory that describes physical processes (e.g. differential equations) requires complex numbers. In other words, numbers that combine amplitude and phase into a single concept. There is in general no reason to assume that any process would modify only one of them and leave the other alone when not unnaturally contrived to do so.
Except the human ear is does not perceive phase. Radio stations use[d] all-pass filters to shift peaks so they could add more gain before clipping. A few years ago I wrote a phase-rotate plugin [1] to experiment with this. I found if fascinating to rotate the phase of a square-wave, which results in vastly different waveform shapes without my ear being able to hear any difference whatsoever.
greetings from Crete, robin [1] https://x42-plugins.com/x42/x42-phaserotate
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