Re: [SoX-users] mcompand: getting stats for each band

[Eric W. <nor...@yh...>]

Ulrich Klauer <ul...@ch...> wrote:
> Eric Wong <nor...@yh...>:
> >>In principle, L-R is just two Butterworth filters in series, so you
> >>can get the lower part by "lowpass 800 lowpass 800" and the higher one
> >>by "highpass 800 highpass 800", for a crossover frequency of 800.
> >>However, I did a quick comparison between this and using mcompand to
> >>split audio into several bands, and the results matched only for
> >>*some* bands. I am not sure why that is.
> >If you figure it out, I'd be curious to know.
> 
> It is due to the "unbalanced" way in which mcompand chains the
> filters. A Linkwitz-Riley filter, by itself, only splits into two
> bands, so you need to cascade several filters to get more. There,
> you have a choice regarding the topology.

<snip>

> There is a difference in the total filter steepness, as shown in the
> attached gnuplot file. Also, adding more crossover frequencies
> changes different bands.

Thank you for the informative explanation and gnuplot.

I'm also curious what the audible difference would be and if one
topology is consistently "better" than the other.  I'm not sure if
my ears are sufficiently trained to tell the difference in any case.