SPC Plugins

ArcSyn User Manual: Filter Types

ArcSyn Synthesizer Filter Types

Notes


1. OFF

No filtering. Note that DRIVE and all the filter routing, panning and level controls will still work.


•The next 15 filters have output stages modelled on an Oberheim Matrix 12 or Xpander VCF. They will self-oscillate when the resonance is increased past about 90%, even if no input signal is present. There are 15 different frequency responses available which try to cover the most useful or interesting responses. These filters are designed to be driven with the oscillators set to about 50% level. Greater oscillator level will increase the slight 'overdrive' produced by these filter's resonance code. It's worth experimenting with oscillator level in relation to filter resonance level.

2. LP 1 POLE*

One pole (-6dB per octave) lowpass filter. A one pole lowpass filter which still has strong resonance is very useful for general sound design.

3. LP 2 POLE*

Two pole (-12dB per octave) lowpass filter. The same cutoff slope as an ARP Odyssey or Korg MS-20 LP VCF.

4. LP 3 POLE*

Three pole (-18dB per octave) lowpass filter.

5. LP 4 POLE*

Four pole (-24dB per octave) lowpass filter. The same cutoff slope as a Moog Minimoog

6. HP 1 POLE*

One pole (+6dB per octave) highpass filter.

7. HP 2 POLE*

Two pole (+12dB per octave) highpass filter.

8. HP 3 POLE*

Three pole (+18dB per octave) highpass filter.

9. HP 4 POLE*

Four pole (+24dB per octave) highpass filter.

10. BP 2 POLE*

Two pole (+6dB / -6dB per octave) bandpass filter.

11. BP 4 POLE*

Four pole (+12dB / -12dB per octave) bandpass filter. Not many hardware analogue synthesizers ever included a 4 pole bandpass filter!

12. SINGLE NOTCH*

Two pole (-6dB / +6dB per octave) notch filter.

13. DOUBLE NOTCH*

Filter with two notches. Useful for emulating a vintage phasing effect.

14. DEEP NOTCH*

Filter with very deep notch. This filter won't resonate due to the depth of the notch.

15. WIDE NOTCH*

Filter with very wide but shallow notch. This filter's frequency response is similar to an old "bass and treble" tone control with both controls turned up.

16. LP NOTCH*

Filter with an overall lowpass frequency response but with a notch above the cutoff frequency. This has an interesting sound which is like a cross between a filter and a phaser.


•The following 5 filters are based on the type of filter (State Variable Filter. or SVF) used in an early ARP Odyssey. They won't oscillate when the resonance is turned up high but have a clean and pure character with relatively low CPU usage which is very useful for general sound design. If you want to modify a sound but don't want the 'warm' character of the first 15 filters, these filter would be a good choice.

17. LP SVF*

A -12dB per octave lowpass (LP) filter.

18. HP SVF*

A +12dB per octave highpass (HP) filter.

19. BP SVF*

A +6dB / -6dB per octave bandpass (BP) filter.

20. PEAK SVF*

A +6dB / -6dB per octave peaking filter.

21. NOTCH SVF*

A -6dB / +6dB per octave notch filter. Increasing the resonance on this filter will have the effect of flattening-out the notch and causing it to 'disappear'.


•The next 4 filters are phase shifters (phasers) with varying numbers of stages. One stage equals two poles.

22. PHASER 4 POLE*

A phase shifter with 2 stages.

23. PHASER 8 POLE*

A phase shifter with 4 stages.

24. PHASER 12 POLE*

A phase shifter with 6 stages.

25. PHASER 16 POLE*

A phase shifter with 8 stages.


•The next 2 filters are comb filters or varying time delays. The maximum delay time is equal to the duration of one cycle at the lowest filter frequency of 16.3Hz which is about 61ms. As the resonance on these filters increases, the direct (dry) signal level is reduced to achieve a smoother effect. These comb filters use extremely high-quality interpolation and oversampling to achieve very high sound quality.

26. COMB POS*

A comb filter with positive feedback.

27. COMB NEG*

A comb filter with negative feedback.


28. VOCAL*

A filter which tries to impart a voice-like quality to input signals by combining the outputs of 3 resonant bandpass filters tuned to the main resonant (formant) frequencies of different human vowel sounds. With this filter, the CUTOFF control crossfades between the vowel sounds instead of changing the filter's frequency, the RES control works normally. A fairly high resonance setting will improve the realism of the resulting sound.


•The next 3 filters are frequency shifters which means they change the frequencies of all the individual harmonic components of an input sound by the same amount in Hz. This changes the harmonics in such a way that they are no longer related to each other which produces a discordant, bell-like quality.

29. FREQUENCY SHIFT UP

A filter which shifts (offsets) input frequencies up. The RES control has no affect in this mode.

30. FREQUENCY SHIFT DOWN

A filter which shifts (offsets) input frequencies down. If shifted below 0Hz, harmonics will 'wrap around' and start to move upward. The RES control has no affect in this mode.

31. FREQUENCY SQUASH

A novel filter which 'squashes' (or 'folds?) input frequencies up from the low-frequency end. It consists of a downward frequency shifter followed by an upward frequency shifter. Both frequency shifters are set to the same frequency. The RES control has no affect in this mode.

32. RING MOD

A ring modulator multiples the input signal with a sine wave set to the filter's frequency. This results in a discordant, bell-like sound which is technically identical to combined up and down frequency shifting, so sounds more discordant than either alone. The RES control has no affect in this mode.


•The remaining filters use variations on sample rate reduction. The audible effect of these filters is often rough and intentionally introduces aliasing and inharmonic components.

33. ALIAS

A filter which reduces the sample rate of the input signal. This is sometimes called a sample-and-hold effect. The RES control has no affect in this mode.

34. MULTI ALIAS

A filter which consists of eight copies of the ALIAS filter (above) which run in parallel at different but closely-spaced rates. The audible effect of this is a shimmering fuzzy effect. The RES control has no affect in this mode.

35. LINEAR

A filter which reduces the sample rate of the input signal, like the ALIAS filter (33) but which then smooths the resulting signal by joining the steps with straight lines. The audible effect of this is a sort of crude, buzzy LP filtering. The RES control has no effect in this mode.

36. MULTISTAGE ALIAS

A filter which consists of eight copies of the ALIAS filter (above) connected in series, so each stage samples the output of the previous stage. The audible effect of this is a sort-of cross between flanging and aliasing. The RES control has no affect in this mode.

37. SCRAMBLE*

A filter which uses a short delay, like the COMB filters (26 and 27) which 'scrambles' the input signal by reading the sound out of the delay line in the 'wrong' order. The RES control selects which ordering is used. There are 64 different orderings.

38. RETRIGGER*

A filter which uses a short delay, like the COMB filters (26 and 27) which repeats or loops short segments of the input signal. The CUTOFF control sets the length of the repeated segments, the RES control sets the number of repeats from 1 to 128. The audible effect of this filter is a (difficult to describe!) buzzy, sometimes pitched, near-destruction of the input signal.

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