On Mon, Jun 13, 2011 at 11:17:51PM +0200, Franck M. wrote:
 
> But back to that Massive Attack bass line: if we use something like E=1
> (full regularization, which means no XTC) in the low frequencies, when you
> pan a mono bass sound to the center, both loudspeakers will emit the same
> signal = (h1 + h2) (*) bass = (hi - hc) (*) bass = ..... = 0 (*) bass.

As you say the matrix inversion amounts to

H1 =  Hi / D       (1)
H2 = -Hc / D       (2)

with D = Hi^2 - Hc^2

What you write makes me think you are trying to regularise
this by replacing D by something like

  E + (1 - E) * D

??

Then setting E = 1 would mean

H1 =  Hi
H2 = -Hc

and since Hi ~= Hc at VLF, H1 + H2 will be near zero,
removing the mono bass.

But this is the wrong way to regularise such an inversion.
The Hi,Hc matrix is very ill-conditioned at VLF, but it
still has rank 1, not 0. So you need to regularise only
in one dimension.

Starting from (1),(2) we have

H1 + H2 = (Hi - Hc) / D = 1 / (Hi + Hc)   (3)
H1 - H2 = (Hi + Hc) / D = 1 / (Hi - Hc)   (4)

There is no problem with (3) when Hi ~= Hc, only
with (4), so only that one needs regularisation.

Which means that H1 + H2 (the mono response) can just
be (3), with no loss of bass at all.

Ciao,

-- 
FA


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