I was just looking at the DSP specs and was wondering...

What does the EQ in 9a currently have as the Q on each band in 4-channel mode vs 2-channel mode? And did this change since 8c? I know there was a brief problem with setting the bands properly between 9 and 9a.

The reason I ask is because I'm not sure of the results I'm getting when I adjust my 4-channel EQ to remove the bass from my front speakers. It seems that even when I crank down the low frequencies on the front speakers, some bass is still getting through. Am I getting frequencies that are "leaking" out from between the bands because of incorrect "Q" values, or is it something else I don't understand?

In a related question:

How exactly is the Loudness feature implemented? Since it's implemented in the DSP software, there's no description of it in the spec sheet. Is it a modification of the EQ parameters?


-- Tony Fabris -- Empeg #144 --
Caution: Do not look into laser with remaining good eye.

What does the EQ in 9a currently have as the Q on each band in 4-channel mode vs 2-channel mode? And did this change since 8c? I know there was a brief problem with setting the bands properly between 9 and 9a.

All versions from 7b should have the same Q coefficients calculated. The first beta 8 had problems with the band centres being incorrectly defaulted and not reading old presets, but there should be no behaviour changes in the current versions (hopefully).

Currently, Q adjusts automatically with gain so that lowering a band to -30dB (for example) doesn't take with it most of the rest of the spectrum. Unfortunately it means a lot of spectrum leaks through. However... I've been playing with making a UI for true parametric operation (modify gain/q/freq independently). If you really want some frequencies attenuated that far, I'd recommend using two bands at the same centre frequency (or slightly apart).

Full parametric operation should make it into the next release (but no promises - I haven't tested it much yet).

- John.

(The above may not represent the views of empeg :)

John, thanks very much for the detailed reply. That explains why I'm getting frequencies that leak through between the bands when I'm attenuating the front speakers in 4-channel mode. There's no rush on implementing parametric operation, it would just be kinda cool. Imagine how much extra it would cost for someone to add a physical 20-band 4-channel parametric EQ to their car, and here you are about to implement it in software. That's just insanely cool.

What about the loudness control? Is there anything you can tell me about how that's implemented? What frequencies does it boost, and how is it related to the EQ (if at all)?



-- Tony Fabris -- Empeg #144 --
Caution: Do not look into laser with remaining good eye.