09) Crossover Flags & Momentary Solo

HiFALHiFAL Guide

Jul 23

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 to isolate the selected frequency range with mastering-grade accuracy. The half-octave buffer between crossover flags prevents overlap and maintains clean, phase-coherent processing.

In Practice:
II typically use HiFAL in Split Band mode, which most closely mirrors the behavior of the hardware counterpart and is HiFAL’s default state. For a more surgical approach, I define the bandwidth with both crossover flags, then right-click between them to solo the process band and search for the exact frequencies I want to control.

Solo & Momentary Solo

The crossover flags offer soloing options 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.

Key Commands

Right Click or Control-drag (Ctrl-drag) the flagpole to momentarily solo the band.
Right Click or Control-drag (Ctrl-drag) between the Crossover flags to momentarily solo and move the band up or down while keeping its width unchanged.

In Practice:
I do not recommend mixing or mastering in solo, but HiFAL’s momentary solo feature helps me move fast without getting stuck there. Right-click or Control-drag to quickly isolate what matters, then release it to hear everything back in context. The fixed Solo buttons are there when you need them, but I almost always prefer working momentarily.

Be well,

Ryan Schwabe

Grammy-nominated and multi-platinum mixing & mastering engineer

Founder of Schwabe Digital

Blog

01) High Frequency Control for the Modern Age

HiFAL 2 (High Frequency Acceleration Limiter, pronounced “High Fall”) brings a classic vinyl mastering technique into the modern era. Using an often overlooked approach to high-frequency processing, HiFAL 2 lets you shape brightness, transient detail, and stereo image as subtly or aggressively as your mix needs. Designed for the mix bus, HiFAL 2 is jsut as useful anywhere in your mix where high frequencies need attention.

02) Overview of HiFAL

HiFAL 2 has two processing sections: the Main high-frequency acceleration limiter and the Parallel Limiter, called PARALIMIT. The Main processor includes a Dry/Wet control in the footer for blending the processed and unprocessed signals. PARALIMIT operates as a separate parallel processing path alongside the Main processor. Each section can be turned on or off using the power button in the bottom-right corner of its section.

03) PARALIMIT: A New Dimension in High-End Processing

The idea was partly inspired by an old parallel compression technique. One version of the classic Motown vocal trick was to duplicate a vocal, high-pass it, compress it heavily, and blend it back underneath the original.

The original vocal maintains its dynamics, while the compressed high-frequency layer adds clarity, presence, and density. Here is a quick video explaining the Motown approach and how it inspired PARALIMIT.

04) Understanding Metering & Ceiling Threshold Needle

The input meter in HiFAL shows the level of the filtered input signal. For example, if the Low Frequency Crossover Flag is set to 2.5kHz and the High Frequency Crossover Flag is bypassed, the meter only reflects the amplitude of frequencies above 2.5kHz.

As you raise the Low Frequency Crossover Flag, you’ll likely see a drop in the meter reading, since higher frequencies usually have lower amplitude. While it’s uncommon for an input meter to reflect a filtered signal, it makes sense here because HiFAL applies dynamic processing to an isolated frequency band.

05) Channel Select and Linking Techniques

HiFAL can operate in either LR (Left/Right) or MS (Mid/Side) mode, giving you different ways to control high-frequency dynamics across the stereo image. When switching modes, both the input and gain reduction meters update between LR and MS.

06) Attack & Release of an Acceleration Limiter

HiFAL 2 uses a sophisticated, sample-by-sample approach to compression that dynamically adjusts attack and release times based on the amount of gain reduction. While computationally intensive, this process results in exceptionally smooth and transparent high-frequency limiting. As gain reduction increases, the attack and release accelerate in response to the signal. This dynamic movement is the core idea behind HiFAL: a high frequency limiter that doesn’t just react, but adapts in real time.

Because the timing constantly changes in response to the input signal and threshold, HiFAL does not offer user-definable attack and release controls. Fixed values wouldn’t behave meaningfully in this context. Instead, HiFAL delivers natural-sounding dynamic control without too much manual adjustment.

07) Gain Reduction Meter & Delta

Visualizing gain reduction can strongly influence how we make decisions while listening. Because visual perception often takes precedence over auditory perception, the way an effect looks on meters can shape how we hear it and how we use it in a mix or master. This mismatch is similar to the McGurk effect, where what we see can actually overrides what we hear.

08) Using Trim as Balance Control

Trim applies up to +6dB or -6dB of gain to the HiFAL process band. While simple, this control is essential for rightsizing high frequencies within a mix or sound. When using high frequency acceleration limiting, two key factors come into play:

HF Dynamics – set by how much limiting occurs
HF Loudness – the level of the high band relative to the rest of the mix.

09) Crossover Flags & Momentary Solo

10) Using HiFAL’s Tuned Tonal Balance Display

This is one of my favorite additions to HiFAL. I was initially worried that big gain reduction meters might influence how I compress, so I kept them minimal. The Tonal Balance Display is the opposite—I made it large and visually dominant on purpose.

11) Shaping the High End with PARALIMIT

We have already looked at the idea behind PARALIMIT and its M, LR, and S channel modes. Now I want to get into how the processor actually works and how I use its controls.

PARALIMIT isolates a mid or high-frequency band, applies acceleration limiting, and blends that processed signal back in parallel with the Main HiFAL processor.

12) Better Stem Printing with HiFAL 2

HiFAL includes an external sidechain input, labeled EXT at the top of the plugin. This lets you patch in an external signal to control the key input of both the main and parallel limiter.

When active, the EXT side-chain replaces the input as the trigger for compression. Gain reduction follows the filter settings and is applied in response to the external signal. This lets you use techniques like instrument ducking to unmask one track, apply frequency-based shaping, or create side-chain-driven midrange s

Ryan Schwabe

https://www.RyanSchwabe.com