08) Crossover Flags & Momentary Solo
The main HiFAL and Parallel Limiter modules include both Low Frequency and High Frequency Crossover Flags. These define the process band and are adjustable from 1 kHz to 20 kHz, with built-in logic that maintains at least half an octave of separation between them. If one flag moves too close to the other, the system automatically adjusts to preserve spacing.
Pushing the high-frequency flag beyond 20 kHz bypasses the crossover entirely and activates split-band mode. This mimics the behavior of the original hardware, which uses a fixed 2.5 kHz crossover.
HiFAL uses the custom Schwabe Digital Linear Phase Filterbank, which is maximally smooth, CPU-efficient, and perfectly phase-coherent. This filterbank isolates the selected frequency range with mastering-grade accuracy.
The 1/2-octave buffer between crossover flags ensures bands never overlap and maintains perfect phase alignment for clean, surgical acceleration limiting.
In Practice:
I typically use HiFAL in Split Band mode, which most closely mirrors the behavior of the hardware counterpart. This is also HiFAL’s default state. Split Band mode is engaged when the Low Frequency Crossover Flag is active and the High Frequency Crossover Flag is bypassed. In this mode, only the high frequencies are processed—everything below the LF crossover flag passes through unchanged. It’s a simple setup that ensures clean, controlled high-frequency processing. For a more surgical approach, I’ll pull the Low Frequency Crossover Flag down to define the desired bandwidth, then Right-click the space between the flags to solo the process band and search for the exact frequencies I want to control.
Solo & Momentary Solo
The crossover flags offer extensive soloing functionality to help you make fast, accurate decisions while mixing or mastering. Each flag includes a latch-able solo button and Momentary Solo key command:
The Low Frequency Crossover Flag solos the process band above it. If the HF Flag is bypassed, LF Flag solos everything above the selected frequency. If the HF Flag is active, the LF Flag solos the process band between the two flags.
The High Frequency Crossover Flag solos the passband above it—essentially previewing the high frequencies excluded from the process band.
This behavior is identical in both the main HiFAL processor and the Parallel Limiter.
In addition to latch-able solo buttons, both crossover flags support momentary soloing. Control-click or Right-Click a flag pole to temporarily solo the process or pass band, allowing you to quickly zero in on frequencies for acceleration limiting. This intuitive workflow makes precise adjustments fast and effortless with minimal mouse movement and maximum control. Simple, clean, and powerful inspection tools for a uniquely surgical dynamics processor.
Key Commands
Right Click or Control-drag the flagpole to momentarily solo the band.
Right Click or Control-drag between the Crossover flags to momentarily solo and move the band up or down while keeping its width unchanged.
In Practice:
I don’t recommend mixing or mastering in solo, but HiFAL’s momentary solo feature helps me move fast without getting stuck in solo. Right-click or control-dragging lets me quickly hear what HiFAL is doing without losing momentum. Fixed solos can mislead because you may spend too much time listening without context—but momentary solos are a powerful tool. The on/off solo buttons are there if you need them, but I prefer Control-dragging to quickly isolate what matters, then zooming back out to hear the big picture. Simple, elegant, and effective.
Be well,
Ryan Schwabe
Grammy-nominated and multi-platinum mixing & mastering engineer
Founder of Schwabe Digital
