Q & A


Can someone list the synths that the filters are designed from. i.e 
Lowpass_mg 4 pole is a moog emulation right?

Can someone also explain what a pole is???

I've listed the filters below to save time in answering this post.

Lowpass_ob_2 pole...
Lowpass_mg_3 pole...
Lowpass_rp_4 pole...
Lowpass_jp_4 pole...
Lowpass_at_4 pole...
Bandpass_ab_2 pole..
Bandpass_al_6 pole.. 


Lowpass_ob_2 pole...
Oberheim. Up for some debate whether it's the SEM modules or later Oberheim filters, though. Same for the ob high and bandpass
Lowpass_mg_3 pole...
Is actually mg 4 pole. Moog filter, famously in a Minimoog, but in pretty much all of them, actually
Lowpass_rp_4 pole...
ARP 2600
Lowpass_jp_4 pole...
Roland Jupiter 8
Lowpass_at_4 pole...
Bandpass_ab_2 pole..
Bandpass_al_6 pole..
Not sure what you mean by at, ab and al filters
There's also:
TB 3 pole, which emulates a TB303.
The rest are Ion only and not modelled on any vintage synth


Ob stands for Oberheim Xpander
Mg stands for Moog Minimoog
rp stands Arp 2600
jp stands for Roland Jupiter
tb stands for Roland TB303
and al filters were designed by Alesis (and apparently al stands for
the initial of the filter designer)


When talking about filters, the number of poles tells
you how steep the cutoff is.  This is usually in terms
of dB per octaves.  Therefore, a 2-pole would be a
much gentler (closer to a tone control on a home
stereo) roll-off than a 4-pole (which is more like the
the filtering in most 'classic' analog synths).

Thinking of it in these terms, it is easy to confuse
poles with resonance or quality (Q).  With any filter,
a higher resonance makes the effect of the filter more
pronounced.  Think of a lowpass filter curve with a
cutoff around 2k.  Higher resonance adds energy in a
little bump amplifying 2k and the adjacent
frequencies.  This has the effect of emphasizing the
energy around 2k.  If this energy is emphasized
enough, it will feed back and the filter will
self-oscillate producing a sine tone at the cutoff

A higher pole filter increases how sharply immediately
after 2k the net energy is diminished. In other words
- how much energy do we want to  allow to 'sneak out'
after our cutoff frequency?

In practical use, this type of thoery is nice to know,
but not as important as knowing what the differnt
filters' characteristics are.  This is a little like
knowing the mechanics of harmonic thoery versus
knowing how a particular chord or chord sequence will
make the listener feel.

In the end, your ears will tell you what the poles are

I would suggest doing this:

Take a patch... maybe a pad or comp/keys kind of
patch.  Zero out anything that will change the
harmonic content (ie, bypass filter 2, effects, and
any FM modulation or PW modulation).  Remove any
modulation, envelope, or velocity orkey tracking from
filter 1.  Assign X to filter 1 cutoff and Y to filter
1 resonance.  Now spend some quality time with each of
the filter models, experimenting with how they react
with different cutoff and resonance values.

A two-pole design results in a 12dB/octave (two-pole Oberheim-type).
A four-pole design results in a 24dB per octave cut-off slope(classic 24dB/octave (four-pole) so loved by Minimoog).
Further reading? [ SYNTH SECRETS Part 5: Further With Filters] Here you will find what the term "Pole" means.

Types of Filters

How to use Filters

Using OP filter to boost bass

The idea is to add a self-oscillating OP filter to an existing bass 
patch for extra punch. Several ways to do this; here's one.  

Make a bass patch that uses one filter(this must be filter 2). Select "OP" 
filter for filter 1; set freq to 129.82hz; rez 100%; keytrack 100%; 
env amnt 0. 

Post filter mix: filter 1 level, 0. Filter 2 level, 100%. 

Prefilter mix: set all osc balances 50%flt1/50%flt2. 

Now slowly increase filter1-to-filter2 amount while playing test notes; you 
should hear a boost in bass. Adjust filter 1 freq to tune the "4th osc". 

Caution: Watch your speakers! You'll probably need to reduce 
output level once OP filter is added. Keep in mind that a bass patch 
is only as good as the speakers reproducing it- lowest key on a piano 
is 27.5hz!

Tricks, unique items to ION/Micron and other general info