What I meant when I explained how I derived my crossover frequencies, was that 
I used actual, typical program audio and **its own inherent spectral energy 
density distribution** to determine empirically (over many months work) 
generally where to set the frequencies.

Much typical full-frequency-range music tends to have equal amounts of RMS 
energy above and below a dividing point in the range of roughly 500-600Hz. 
Further splitting those two bands into four equal-program-energy bands resulted 
experientially in the 150 and 1800 splits.

This determination is approximate; these frequencies are not hard and fast, 
never mind “magic,” and there will be exceptions, but the product I designed 
was known for its natural-ness on all music types: classical, pop, jazz, etc., 
and also worked well on voice. The fact that single-pole subtractive filters 
are extremely broad AND sum back to the original with extremely low transient 
distortion, was also helpful.

If what you do involves material with an unusual spectral balance, and/or if 
you use aggressive filter roll offs and/or you use something other than RMS 
detection, then my assumptions may not be useful.

David Reaves

Sent from my iPad

On Tue, 27 Mar 2018 15:10:12 +0200, gm <g...@voxangelica.net> wrote:
> i keep dividing into equal bands on a log2 scale,
> I believe thats equal energy on a -6dB/octave spectrum and gives figures 
> very close
> to what David Reaves suggested the other day for 4 bands when you set 
> 6300 Hz as the upper limit
> and 150 Hz corner frequency for the bass band (or 45 Hz for the lower limit)

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