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 frequency. 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 doing... 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? [http://www.soundonsound.com/sos/sep99/articles/synthsecrets.htm 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!