MOTM

I was looking through some old synth
schematics and became very misty-eyed
and nostaligic over a very useful item-
A Fixed filter bank would be great.
I have seen some out there , one is an
8 band unit and I think the other is 14
with overlap frequencies.

A 10 or 12 band unit with high boost
deep rejection : par. output ,of course.MOTM-450?

part of the soundtrack for Eraser-head I suspect
has some white noise going through some
fixed filter banks ? can anybody confirm this
or even know what I'm talking about here?
well, Eraser-head aside what does everybody think?
MOTM-450 Filter Bank ! Weeee!.. more knobs to tweak!
-
I have gotten some cool/awsome and also very
esoteric effects by ring-mod outputs being fed
into fixed filter banks and phasing one of the
X/Y Ring mod. inputs. 
Thank You for reading, all.......Bill.


=====

Sure, I like 'em. Parametrics, too.

Not to be a stick in the mud, but what are the advantages of say the Moog
filter bank
over a $99 Rane 18 band Graphic EQ?

Paul S.

-----Original Message-----
From: william Hanson <williamneumann@...>
To: motm@onelist.com <motm@onelist.com>
Date: Sunday, October 03, 1999 3:01 AM

Subject: Re: [motm] Anybody like Fixed filter banks?(new mod)


>From: william Hanson <williamneumann@...>
>
>I was looking through some old synth
>schematics and became very misty-eyed
>and nostaligic over a very useful item-
>A Fixed filter bank would be great.
>I have seen some out there , one is an
>8 band unit and I think the other is 14
>with overlap frequencies.
>
>A 10 or 12 band unit with high boost
>deep rejection : par. output ,of course.MOTM-450?
>
>part of the soundtrack for Eraser-head I suspect
>has some white noise going through some
>fixed filter banks ? can anybody confirm this
>or even know what I'm talking about here?
>well, Eraser-head aside what does everybody think?
>MOTM-450 Filter Bank ! Weeee!.. more knobs to tweak!
>-
>I have gotten some cool/awsome and also very
>esoteric effects by ring-mod outputs being fed
>into fixed filter banks and phasing one of the
>X/Y Ring mod. inputs.
>Thank You for reading, all.......Bill.
>
>
>=====
>
>>

Where do you find $99 18 band graphic Rane EQs?
LH

----------

> From: Paul Schreiber <synth1@...>
> To: motm@onelist.com
> Subject: Re: [motm] Anybody like Fixed filter banks?(new mod)
> Date: Sunday, October 03, 1999 5:58 PM
> 
> From: "Paul Schreiber" <synth1@...>
> 
> Not to be a stick in the mud, but what are the advantages of say the Moog
> filter bank
> over a $99 Rane 18 band Graphic EQ?
> 
> Paul S.

Hi All !

Graphic eq has only gain control .  Fixed Q and frequency .

In the Elektor formantfilter 3 parallel state variable BP filters, 
with variable Q, freq and gain boost .

Digisound has a dual resonant filter : twin state variable bp, based 
on CEM3350, same controls as above plus vc freq amount .

Intresting stuff, can be done with a parametric eq, but as with all 
filters, the sound will depend on the actual circuit used and there 
are plenty of variables here :)

I am not too familiar with these other "fixed filter banks" .  What 
are the controls per section/band, if freq is fixed, what center 
frequencies are used ?

Bye for now .


Keep 'em oscillating :)


Hugo
=

> From: "Hugo Haesaert" <hugo.haesaert@...>
>
> Hi All !
>
> Graphic eq has only gain control .  Fixed Q and frequency .
>
> In the Elektor formantfilter 3 parallel state variable BP filters,
> with variable Q, freq and gain boost .
>
> Digisound has a dual resonant filter : twin state variable bp, based
> on CEM3350, same controls as above plus vc freq amount .
>
> Intresting stuff, can be done with a parametric eq, but as with all
> filters, the sound will depend on the actual circuit used and there
> are plenty of variables here :)

The MOTM 420 is 3 resonant bandpass filters. Fixed resonance, but
individually tuneable filters so you can do similar interesting things. I
plan to use mine a lot for formant types of things, not just swooshing
around with the LFOs.

> I am not too familiar with these other "fixed filter banks" .  What
> are the controls per section/band, if freq is fixed, what center
> frequencies are used ?
>

The Moog fixed filter banks are fixed frequency AND resonance, so no better
than a common graphic eq. Just a gain control for each band. If I remember
right, there is an 8 band and a 12 band version, each with an additional low
and high shelving control.

Dave

Dave Bradley (09:42 AM 10/5/1999) wrote:

 >> Intresting stuff, can be done with a parametric eq, but as with all
 >> filters, the sound will depend on the actual circuit used and there
 >> are plenty of variables here :)
 >
 >The MOTM 420 is 3 resonant bandpass filters. Fixed resonance, but
 >individually tuneable filters so you can do similar interesting things. I
 >plan to use mine a lot for formant types of things, not just swooshing
 >around with the LFOs.

Is someone was gonna go nuts on a filter bank, my vote is for a full 
Formant filter. I have a custom 4-band in my Moog modular, and it's awesome.

(I know you know this Dave, but...)

A Formant filter is basically a number of bands (4 is common, I've seen 
overkill at 8) where each band has a variable center freq, a cut/boost 
control, and a fine control for resonance - usually a 10 turn pot.

The point is to mimic the nasal sounds of the oral cavity. The 10-turn pot 
on resonance is required in order to be able to hang the filter stage 
*right* on the edge of feedback - RIGHT on the edge.


 >> I am not too familiar with these other "fixed filter banks" .  What
 >> are the controls per section/band, if freq is fixed, what center
 >> frequencies are used ?
 >
 >The Moog fixed filter banks are fixed frequency AND resonance, so no better
 >than a common graphic eq. Just a gain control for each band. If I remember
 >right, there is an 8 band and a 12 band version, each with an additional low
 >and high shelving control.

I remember the Moog filter bank being only cut, no boost. Sweet sounding 
stages though. :)


Mark

Months ago when the list was smaller, we talked about Paul doing a real
formant filter. I was all for separate voltage control of each band, so you
could morph between vowels with a sequencer or something. Paul's take on it
was that you needed fixed bands, VERY accurately tuned, and would switch
them on and off to obtain different vowel sounds. I believe 15 bands was
mentioned as the number necessary to cover the known vowel sounds in various
languages.

I don't remember particularly why we were talking mostly about vocal
formants instead of acoustic instrument formants - maybe the discussion grew
out of another thread about vocoders.

I hope that Paul will get around to a some kind of formant module
eventually.

Dave

> Is someone was gonna go nuts on a filter bank, my vote is for a full
> Formant filter. I have a custom 4-band in my Moog modular, and
> it's awesome.
>
> (I know you know this Dave, but...)
>
> A Formant filter is basically a number of bands (4 is common, I've seen
> overkill at 8) where each band has a variable center freq, a cut/boost
> control, and a fine control for resonance - usually a 10 turn pot.
>
> The point is to mimic the nasal sounds of the oral cavity. The
> 10-turn pot
> on resonance is required in order to be able to hang the filter stage
> *right* on the edge of feedback - RIGHT on the edge.

I used the Moog (8 band as I recall) and I liked it. It may have just been 
passive as Mark (?) said, but I seem to recall that it had a nice 
distribution of bands -- was it musical 7ths or 9ths? (It might not be very 
exotic nowadays when compared to all the EQs available) Does anybody know how 
the bands were arranged? 

JB

In a message dated 10/5/99 7:46:22 AM, daveb@... writes:

>The Moog fixed filter banks are fixed frequency AND resonance, so no better
>than a common graphic eq. Just a gain control for each band. If I remember
>right, there is an 8 band and a 12 band version, each with an additional
>low
>and high shelving control.

Okay, here's the story (I've got the schematic right in front of me):

The Moog 907 Fixed Filter Bank had ten controls. The first knob was a
shelving filter marked "Low Pass" and the last "High Pass." In between, the
resonant frequencies of the bandpass filters were labeled: 250Hz, 350Hz,
500Hz, 700Hz, 1Hz, 2 KHz, 2.8KHz, 14KHz. Some of those seem strange, but
that's what the schematic says.

The input stage has a one-transistor amplifier, and the output stage was a
two-transistor deal. The filter stages were all
poteniometer/2-inductors/3-capacitors/3-resistor deals.

Two of these ten-band (sic) filter banks were the core of Wendy Carlos'
ten-band vocoder as first used ion her Beethoven's Ninth Symphony, and soon
after in Timesteps, as heard in "A Clockwork Orange." She had Moog give her
jack-access to the filters so that she could run the first bank of separated
signals into envelope followers, and the ten from the second FFB into VCAs.
When the former controlled the latter, she had a simple vocoder.

Later, Moog produced the Model 914 FFB. The design was very similar to the
former, but with 14 bands of resolution. Only "Lo Pass" and "Hi Pass" are
marked on the schematic. I'm too tired to do the math to figure out the
center frequencies of the bands.

Hope this helps.

		-----Original Message-----
		From:	JWBarlow@... [mailto:JWBarlow@...]
		Sent:	Tuesday, October 05, 1999 10:04 PM
		To:	motm@onelist.com
		Subject:	Re: RE: [motm] Anybody like Fixed filter
banks?(new mod)

		From: JWBarlow@...

		I used the Moog (8 band as I recall) and I liked it. It may
have just been 
		passive as Mark (?) said, but I seem to recall that it had a
nice 
		distribution of bands -- was it musical 7ths or 9ths? (It
might not be very 
		exotic nowadays when compared to all the EQs available) Does
anybody know how 
		the bands were arranged? 

		JB

		In a message dated 10/5/99 7:46:22 AM, daveb@... writes:

		>The Moog fixed filter banks are fixed frequency AND
resonance, so no better
		>than a common graphic eq. Just a gain control for each
band. If I remember
		>right, there is an 8 band and a 12 band version, each with
an additional
		>low
		>and high shelving control.

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Many thanks for this Ken. It clears up my misunderstanding (misremembering) 
of the module as not having octave related bands (250, 500, 1K, 2K and 350, 
700, 2.8K and both groups related to 14K) , and having some strict 
relationship between bands like 1/3 octave or 1/7 octave. Strange indeed.

JB

In a message dated 10/6/99 5:23:52 AM, Ken.Tkacs@... writes:

>The Moog 907 Fixed Filter Bank had ten controls. The first knob was a
>
>shelving filter marked "Low Pass" and the last "High Pass." In between,
>the
>
>resonant frequencies of the bandpass filters were labeled: 250Hz, 350Hz,
>
>500Hz, 700Hz, 1Hz, 2 KHz, 2.8KHz, 14KHz. Some of those seem strange, but
>
>that's what the schematic says.
>
>
>
>The input stage has a one-transistor amplifier, and the output stage was
>a
>
>two-transistor deal. The filter stages were all
>
>poteniometer/2-inductors/3-capacitors/3-resistor deals.
>
>