Shermanik Filterbank

Updated on 11 December 2024.

I really like my Sherman Filterbank 2 (SFb2), but since you can't save presets with hardware, I thought I would try my hand at building something similar in Bitwig. Here is a preset I've just finished putting together in the fxGrid that makes some very fun sounds. Please feel free to play about with it. Shermanik Filterbank v1.2.9 (Bitwig v5.2+ fxGrid Preset). 

Warning: Deactivating the final limiter and EQ Post FX can generate extreme low and high frequencies which may damage audio gear and speaker coils.

How to work with it? Simple. Download the preset from the link above and load it onto a track in Bitwig. I suggest saving it into your own preset library for easy access. When you load it into Bitwig, you'll see the modulator layout shown below. I've placed two devices on the Post FX bus: a basic EQ to limit extreme low and high frequencies and a Limiter to prevent clipping. The controls may seem daunting at first, but if you take some time to play around with what everything does, you'll find that there is a wealth of sonically exciting sweetspots to be discovered.

Let's check out the controls. 

At top left is the Gain. This drives a saturation stage that increasingly adds distortion to the signal. I have this defaulted to a low level so you can hear immediate results. At top right is the Byp<>Eff (Bypass-Effect) control. This is a blend control between dry and fully wet signal. I have it defaulted to fully wet. 

Below the gain is the Hi Cut<> Bst (Boost). This is a >1kHz shelf that you can use to brighten or darken the incoming signal.

At the bottom left is the Sensetrig. This is a threshold control for the incoming signal and is part of an envelope follower which in turn drives the gate for the ADSR/AR envelopes. You can choose which envelope is used to offset the Filter 1 Resonance and Filter 2 Resonance levels. We'll come back to this shortly.

The AR envelope can be used to modulate the Gain. Activate the AR button on the Ext Trg/Gn (Gain) buttons modulator to automate the Gain. Adjust the AR Gain to control how much this is modulated by. The A and R envelope controls on the top row control the Attack and Release of both the Filter Cutoff modulation and opening and closing of the AR Gain. 

A, D, S/Sense, and R, control the Filter 1 & 2 Resonance modulation and this is offset and multiplied with the Amt (1 & 2) +/- attenuverters. In ADSR mode (default) the envelope is an typical ADSR envelope. In AR mode the envelope follower is multiplied by the S/Sense either positively or negatively. This has a much more lively and dynamic response as it is the incoming audio that modulates the sustain portion of the envelope. You can choose to modify the response by modifying the Rise (0.1ms) and Fall (5ms) of the Follower RF to smooth the response, and the amplify node can be used to attenuate the signal up or down. I've choses values that feel snappy and a bit edgy. 

Along the bottom row, you can see the two filter stages and their various controls. We have your usual Freq (1 & 2) cutoff frequency controls. The SFb2 does not offer precision in setting the cutoff frequency and this preset is the same - adjust these by ear to suit your needs. The Amt (1 & 2) +/- knobs are attenuverters for the ADSR/AR envelope and these, in turn, determine the offset modulation of the filter resonance. The filters self-oscillate above 49%. These filters are both SVF or State Variable Filter modules in the Grid (as they are on the physical SFb2). These filters are unique in that they can simultaneously output LP (Low Pass), BP (Band Pass), and HP (High Pass) signals. The LBH (1 & 2) controls allow you to blend between these outputs. Full left is LP, centre is BP, and full right is HP. Func (1 & 2) provides some additional signal processing.The default is set to 50% and this coupled with LBH at 50% (also default state) makes the filters behave much as an All Pass Filter at a slight signal reduction. You can place a Bitwig Tool Device ahead of the Shermanik Filterbank to make up for lost signal gain if you want.

If LBH (1 or 2) is set to 50%, then this corresponds to Bandpass (B). Func (1 & 2) subtracts B at 0%, and subtracts B from the sum of L+H at 100%. This means you can use the Func (1 or 2) as a form of independent volume control for each filter when LBH (1 or 2) is at 50% and the associated Func is attenuated from 0% to 50%.

Sync Filt2 will lock the cutoff frequency of Filter 2 to Filter 1, when activated (Freq 2 input is bypassed in this state). The Harmonics control is a frequency divider and will set the cutoff to a series of increasingly lower intervals (up to 4 octaves!). These can quite easily be below audio rate if the Freq1 is set below 50%. If you set the Freq 1 to 62.8% this will be near enough to be C4 when Res 1 is set to 49% and is just starting to self-oscillate. Higher resonance will detune as you raise it up to 100%. Res (1 & 2) control the resonance. Self Oscilation occurs at 50% and above.

LFO Speed and LFO Depth controls the modulation of the filter cutoff. As of v1.2.9 these have exponential response curves. LFO Depth is a bit special. Setting this above 50% modulates the cutoff of both filters positively. When adjusted below 50%, filter 2 cutoff is inverted and they move in opposition. This should be explored for some exciting sound design possibilities. See the graphics below for what this modulation signal can look like. The Saw/Sin button switches the LFO between Saw and Sine (default is Saw). The LFO Trig will use the AR envelope to modulate the LFO Depth. LFO Sync will reset the LFO on each incoming gate trigger.

Above are some screen shots of the LFO modes; these, based on the overall depth, modulate the Cutoff Frequencies of the two filters. The LFO runs from 0hz - 30kHz, so some fun audio rate things happen. The LFO Trig will multiply the LFO by the ADSR/AR to effectively gate the LFO, and you can sync the LFO to the gate pulse so that the LFO starts anew at each trigger.

Trig AR routes the final output through a mixer that uses the Attack and Release levels to open and close the output signal. The Attack and Release settings are separate from the ADSR/AR envelopes. Active the Trig button on the Ext Trg/Gn buttons modulator to use an incoming MIDI gate to drive the resonance ADSR/AR envelope and output AR envelope.

FM multiplies the incoming, unprocessed signal with itself. If you open the Grid for this device, you can select an external FM source. 

AM amplitude modulates the output of Filter 2 from 0-50% and ring-modulates this signal from 50% to 100%.  If you open the Grid for this device, you can select an external AM source. 

BonkWave adjusts many parameters at once to reveal much sonic weirdness. Perfect for making BonkWave, or NotBonkWave music.

Advanced Use:
Chain two or more Shermanik Filterbank presets in sequence on your track for even more extreme filtering. The SFb2 uses a special LINK cable to control the Freq 1 of all the linked SFb2 devices together. You can do something very similar by adding track level modulators and use one of these to control the Freq 1 of each device in your chain. I suggest deactivating the Post FX of all but the final Shermanik Filterbank.

Deep inside the fxGrid is a Harmonics Tuner section along with back up copies of the Harmonics Steps and Tuner Pitches. I've set up a small You could make your own musically configured harmonics should you wish and have the original settings to fall back on if you want them. Here we see the Steps and the Pitches used (these are deactivated in the preset).

The Steps match (as near as I can get) the pitch intervals that are documented in the Sherman Filterbank manual.