Emu XL-7 & MP-7 User's Group

So, if you had managed to get past my first sentence, you'd have noticed the rest of my post which explained that.

From a mathematical sense, Z-plane = frequency domain instead of time domain.  It's as simple as that.  What E-mu *does* with those filters that are defined in the frequency domain is enable the morph between filter coefficient sets.

Your XL-7 (and any other H-chip based E-mu product) does do this morphing.  For most of the filters, Fc is accomplished by loading two sets of filter parameters, one corresponding to a low-pass filter with the Fc at a very low frequency and one with a similar filter with the Fc at a very high frequency.  If you used this approach and *didn't* use a frequency domain parametrized filter, fading between the two would simply turn down one peak and bring up the other.  Since the modulation actually affects all the parameters in the frequency domain, fading from one set to the other actually *moves the filter peak*.

Get it?

For the other filter types, you'll notice that Fc isn't necessarily a strict interpretation of cutoff frequency.  Filters other than the standard highpass/lowpass/bandpass work in somewhat mysterious ways in response to this parameter.  Since you're into reading the manual, check out page 202-204 where they explain what the parameters do for each filter.  An example:

AahAyEeh - 6th order - type: VOW
Vowel formant filter which sweeps from “Ah” sound, through “Ay” sound to “Ee” sound at maximum frequency setting.. Q varies the apparent size of the mouth cavity.

Still seem like a bold-faced lie?  Still seem irrelevant?

-Aaron



----- Original Message ----
From: innovine1 <innovine1@...>
To: xl7@yahoogroups..com
Sent: Tuesday, January 13, 2009 10:00:38 AM
Subject: [xl7] Re: z-plane - is it "all that"?

--- In xl7@yahoogroups.com, Aaron Eppolito <synthesis77@...> wrote:
>
> Z-plane doesn't actually have anything to do with "morphing" or
interpolation.  

So, when the manual says this.. 

"Changing a single parameter, the Morph, changes many complex filter
parameters simultaneously. Following along the Morph axis you can see
that the filter response smoothly interpolates between the two filters.
This is the essence of the Z-plane filter. Through the use of
interpolation, many complex parameters are condensed into one
manageable entity."

... it is simply a bold faced lie? Especially the 'condensed into one
manageable entity' phrase, considering, on my command station at
least, they seem to have condensed all this functionality into
absolutely nothing at all.


The manual section tries VERY hard to suggest that there are two
filters, that can be interpolated between using a Morph parameter. It
even cites a lot of (entirely irrelevant) mumbo jumbo about how the
human vocal tract morphs between vowels. Was this function dropped at
the last minute, or did Emu deliberatly intend to mislead its customers?