Limiter
Canonical Definition
A limiter is a dynamics processor designed to restrict signal level above a defined region using a very high ratio or limiting transfer curve. Its achieved ceiling is determined by detector behavior, attack or lookahead, hold and release, sample- or true-peak target, channel linking, processing placement, and downstream analog limits.
Threshold Is Not The Measured Ceiling
The displayed threshold or curve defines the gain rule. The final peak can still exceed it because of:
- detector timing and attack
- lack of lookahead
- sample timing and reconstruction
- release interaction and repeated transients
- gain or EQ after the limiter
- DAC, line-stage, or amplifier behavior
Measure the achieved ceiling at the signal point that matters.
Lookahead And Overshoot
A zero-lookahead limiter cannot reduce gain before the detector observes the event. It may allow an initial overshoot, especially with a slower detector or attack. Lookahead delays the audio path so the gain controller can react first, but it adds latency and remains limited by detector and implementation accuracy.
Digital And Analog Ceilings
| Ceiling | What it limits | What still needs verification |
|---|---|---|
| Digital sample or internal value | The numerical node where the block operates | Later gain, DAC, line output and analog overload |
| DSP analog output voltage | Line-stage capability | Amplifier input sensitivity and input-stage clipping |
| Amplifier output voltage | Voltage under one supply and load condition | Frequency-dependent impedance, sag, clipping, heating and protection |
| Driver thermal goal | Energy over time | Program spectrum, duty cycle, cooling and voice-coil state |
| Driver excursion goal | Frequency-dependent mechanical demand | Enclosure, high-pass filter, voltage, frequency and nonlinear behavior |
Voltage-Limiter Calibration
- Establish clean source, DSP and amplifier gain structure.
- Define the exact amplifier channel, gain, bridge mode, load, supply voltage and crossover state.
- Apply a suitable test signal and measure amplifier output voltage and waveform.
- Adjust the limiter until the measured output meets the intended condition.
- Test multiple frequencies, bursts and sustained signals.
- Repeat under realistic voltage, temperature and load conditions.
- Lock or document every downstream control that can defeat the calibration.
Why One Limiter Cannot Solve Every Driver Limit
Thermal limits depend on energy and time. Excursion limits depend strongly on frequency, enclosure loading and voltage. A single full-band voltage threshold can be useful, but it cannot simultaneously model every thermal and mechanical condition without additional frequency-selective filtering, multiband control, or a validated driver model.
Release And Repeated Program
A release that is too fast can pump or distort; a release that is too slow can hold the system down and change crossover balance. Repeated bass bursts can accumulate heat even when each peak is limited. Measure gain reduction and recovery over the expected program duty cycle.
Verification Record
- detector and sidechain source
- threshold or curve, attack or lookahead, hold and release
- linked-channel behavior
- block location and every downstream gain stage
- measured digital and analog peak and RMS level
- amplifier gain, supply, load, temperature and bridge mode
- frequencies, burst lengths, program material and stop conditions