Filters

WR-914

The WR-914 - a fourteen-band fixed filter bank for formant sculpting and spectral colour.

The WR-914

The WR-914 is a fourteen-band fixed filter bank. Twelve band-pass filters at fixed frequencies (125, 175, 250, 350, 500, 700, 1000, 1400, 2000, 2800, 4000, 5600 Hz) sit alongside a four-pole LP shelf below 100 Hz and a four-pole HP shelf above 7.5 kHz. Each band has its own slider that scales its contribution to the summed output. There is no voltage control - cutoffs are fixed by design.

A fixed filter bank is essentially an analog equalizer reframed as an instrument. With fourteen sliders each controlling a separate band, the WR-914 carves formants (the resonant peaks that shape vowels), builds comb-filter textures (alternating sliders up and down), or shapes a noise source into something that sounds like wind, surf, or breath. Where a single voltage-controlled filter sweeps one moving cutoff, this module holds many cutoffs simultaneously - a chord of filters rather than a melody of filters.

Three outputs are exposed: a summed mix of all bands, plus isolated LP shelf and HP shelf outputs for routing the bass and treble shelves to separate destinations. The band-pass filters are biquads at Q ~ 2 (moderately overlapping), and both shelves are 4-pole cascades giving a 24 dB/oct slope. All sliders default to 0.5 so the module passes signal cleanly out of the box.

The WR-914

The WR-914 has fourteen vertical sliders (one LP shelf, twelve band-pass, one HP shelf), plus an IN input gain and OUT output gain knob. Band-pass filters are biquads at Q ~ 2. Shelves are 4-pole cascades at 100 Hz (LP) and 7.5 kHz (HP), each 24 dB/oct. All band sliders default to 0.5. Three outputs: a summed mix, an isolated LP shelf out, and an isolated HP shelf out. No voltage control - all cutoffs are fixed and only the sliders shape the output.

In a patch

The most musical WR-914 patch is the vocal formant. Open the 500 Hz, 700 Hz, and 2 kHz bands wide and close the rest. Send any rich audio source - a SAW from a WR-921, white noise from a WR-923, or a sustained note - through the bank, and the output sounds vowel-like. Different combinations give different vowels: ah is roughly 700 + 1000 + 2800 Hz, ee is 250 + 2800 + 4000 Hz, oh is 500 + 700.

For comb-filter and metallic textures, raise alternating sliders (125, 250, 500, 1000, 2000, 4000) and close the others. The result is a strong harmonic series filter that emphasizes one fundamental's overtones - feed any source through it and the source picks up a tonal centre. Useful for bell-like resonances on percussion, or for making white noise sound pitched.

For sweeping formants the WR-914 is the wrong tool - the cutoffs are fixed. Use a WR-904A (single voltage-controlled cutoff) or a WR-904C (band-pass with CV center) for moving filter motion. The WR-914 is for static spectral shapes set up once and used as a tone-colouring stage.

Inputs

IN (audio) — Audio input. Harmonically rich sources (saw, square, noise) show off the spectral sculpting most clearly.

Outputs

OUT (audio) — Summed output of all 14 bands after their slider scaling.
LP (audio) — Low-pass band output isolated (pre-slider). Use for sub-bass extraction.
HP (audio) — High-pass band output isolated (pre-slider). Use for treble extraction.

Controls

IN — Input gain 0-2x. Push into the filter bank harder for more pronounced band emphasis.
OUT — Output gain 0-2x. Compensate for overall level loss when most bands are closed.

Synths.pw and the Classic-series modules are not affiliated with, endorsed by, or sponsored by Moog Music Inc. Module numbers reference the late-1960s American modular tradition and are used in a historical sense.

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