HiFAL (High Frequency Acceleration Limiter, pronounced “High Fall”) brings a classic vinyl mastering technique into the modern era with the flexibility and precision only digital can offer. Designed for modern workflows, HiFAL lets you shape brightness, transient detail, and stereo image as subtly or aggressively as your mix needs.

Acceleration limiting was originally developed to manage high frequencies during vinyl cutting, keeping the stylus from overheating while preserving clarity and energy in the record.

HiFAL has two processing sections: the Main HiFAL and the Parallel Limiter. Each can be turned on or off using the power button in the bottom right corner of its section. 

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.

When switching processing modes, both the input meter and gain reduction meter update their labels between LR and MS.

In LR (Left/Right) mode, it’s common to keep thresholds linked since both channels usually share similar dynamics. Channel link settings can then be adjusted to control how much the channels influence each other. In MS (Mid/Side) mode, the Mid and Side signals often differ significantly in level, so unlinked thresholds are usually better for applying appropriate gain reduction to each.

HiFAL 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.

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

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.

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.

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 Spectral Balance Display is the opposite—I made it large and visually dominant on purpose.

It also ties directly into the name HiFAL (pronounced “High Fall”). The spectrum analyzer shows high frequencies falling down from the top of the interface, creating a visual metaphor for the plugin. I thought it was a fun play on words and a fitting visualization for a tool designed to shape high-end energy. I also had never seen a spectrum analyzer tied to the top and falling down, and I thought it created a nice user experience for frequency selection.

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 spacing.