Filter slopes
> Every cascading filter type in Outboard-EQ has a per-band slope, from a single biquad (6 dB/oct) up to an eight-stage Butterworth cascade (96 dB/oct). Right-click the band disc → Slope to pick.
Every cascading filter type in Outboard-EQ has a per-band slope, from a single biquad (6 dB/oct) up to an eight-stage Butterworth cascade (96 dB/oct). Right-click the band disc → Slope to pick.
Available slopes
| Value | Stages | Practical use |
|---|---|---|
| 0 dB/oct | unity bypass | Disables the band's cascade. Useful on cut bands when you want the band engaged but inactive. |
| 6 dB/oct | 1 | Single biquad. Gentle vintage curve. |
| 12 dB/oct | 2 | The legacy default. Bit-identical to a Pro-Q-style "0.5 octave" cut. |
| 18 dB/oct | 3 | Slightly steeper without sounding clinical. |
| 24 dB/oct | 4 | Classic Linkwitz-Riley territory. Good for cuts that need to disappear without phase artefacts being obvious. |
| 36 dB/oct | 6 | Surgical. Use when 24 is leaking too much. |
| 48 dB/oct | 8-of-8 | Half of the maximum. Suitable for tight DJ-style low-end shaping. |
| 72 dB/oct | 8-of-8 (truncated cascade) | Near-brickwall. |
| 96 dB/oct | 8 | Maximum. Equivalent to the BrickwallLP/HP types. |
Which types respond
Slope is meaningful on every cascading type:
- LowCut / HighCut
- LowShelf / HighShelf
- Peak (cascades multiple peaks at the same f/Q for sharper bells)
- Notch (cascades narrow notches for a wider, deeper V)
- TiltShelf
- BandPass
- AllPassLow / AllPassHigh
Slope is ignored on:
- Air (the PurestAir slew-limiter doesn't cascade)
- AllPass (the centre-symmetric phase rotator)
- PultecShelf and the Pultec card (always bakes its own two stages)
- BrickwallLP / BrickwallHP (always 96 dB/oct regardless)
- Sword / FlatTilt / FlatTop (built-in topology)
Phase implications
Steeper slopes mean more biquads, which means more phase rotation around the cutoff. If transient integrity matters — mastering bus, drum bus, anywhere a snare needs to stay punchy — consider running the band in LinPhase or Hybrid mode (see Phase modes). Per-band linphase flags let you mix surgical FIR brickwalls with min-phase character bands in one chain.
CPU cost
A band's CPU cost scales linearly with its slope: 96 dB/oct costs about 8× a 12 dB/oct band. Spectral and Linear-Phase modes have their own (much larger) fixed overhead — slope inside those is essentially free once those engines are running.
Tips
- For mastering high-pass, 18 to 24 dB/oct is usually transparent enough. Don't reach for 96 dB/oct unless you have a specific reason (LFE management, brickwall protection).
- On a Peak band, a Q of 4 with slope 24 dB/oct gives a sharper bell than Q 8 with slope 12 dB/oct, and behaves more predictably under automation.
- The slope choice is preset-stored as a literal integer — moving a preset between projects always lands on the same dB/oct value, not "the 4th option in the list".
See also
Filter types
> Each band can take one of 18 filter shapes — from the classic mixing toolkit to specialty types built for mastering and resonance work. Right-click any band disc to choose.
Dynamic EQ
> Every band in Outboard-EQ can react to the audio passing through it. Set a threshold, and the band's gain bends only when the signal crosses it — a static cut that wakes up just for the loud notes,