A wireless cable shorts. A wedge mic gets too close to its own speaker. A patchbay routes the wrong signal to the IEM bus. In any of those cases, the volume in a sealed earphone can hit 130 dB SPL in under a hundred milliseconds — and you only get to make that mistake once. Limiters are the load-bearing safety device on every IEM rig. Here’s where they go and how to tune them.

How loud is too loud, exactly

85 dB SPL — the OSHA exposure threshold for an 8-hour shift.
100 dB SPL — your IEM mix on a reasonable show.
110 dB SPL — uncomfortable, but survivable for short periods.
130 dB SPL — instant pain. Permanent damage in under a minute.
140+ dB SPL — the level a feedback squeal through a fresh-battery IEM bodypack in a sealed ear can reach. Permanent damage in seconds.

A brick-wall limiter caps the bus level so even if something catastrophic happens upstream, the output to the IEM transmitter can’t exceed your threshold.

Where in the chain the limiter goes

Three reasonable positions, each with tradeoffs:

On the IEM mix bus (most common)

The limiter sits on each IEM bus, just before the bus output routes to the IEM transmitter. Catches anything that comes through any input channel.

Best for: most rigs. Console-built-in limiters at the bus level are universal.

On the physical output

A hardware limiter sits between the console output and the IEM transmitter input. Same as bus-level but external.

Best for: rigs where you don’t trust the console’s software limiter, or live broadcasts where you want a second-stage hardware backstop.

In the IEM transmitter itself

Many wireless IEM transmitters (Shure PSM1000, Sennheiser EW IEM G4) have their own limiter at the input stage.

Best for: belt-and-suspenders alongside a bus limiter. Don’t rely on the transmitter alone — its threshold is usually fixed and may be set above safe levels.

Threshold settings

The threshold is the audio level above which the limiter kicks in. Aggressive thresholds clip more often but protect more; conservative thresholds preserve dynamics but only catch the truly catastrophic events.

-3 dBFS — almost no compression unless something’s wrong. The limiter is purely a safety backstop. Recommended for most rigs.
-6 dBFS — limiter catches occasional peaks. Light compression effect on the mix.
-10 dBFS — limiter shapes the mix. Aggressive but very safe.

Setting too aggressive a threshold means the limiter is engaged on every loud note, which can flatten the mix and tire the listener. Setting too conservative means the limiter might not catch a fast transient.

Attack, ratio, knee

Ratio: ∞:1 (brick wall). A limiter is a compressor with infinite ratio. Anything above the threshold doesn’t pass.
Attack: as fast as the gear allows (usually 0.1 ms or lookahead-style). Slow attack means the first millisecond of the transient gets through.
Release: ~50-100 ms. Faster release means the limiter recovers between transients; slower release means it stays engaged after a peak, which ducks the surrounding music.
Knee: hard. Soft knee bleeds before hitting the threshold, which we don’t want from a safety limiter.

Multi-band vs single-band

A multi-band limiter splits the bus into 2–4 frequency bands and limits each independently. Advantage: a loud bass note doesn’t duck the vocal. Disadvantage: complexity, and possibility for mis-tuning.

For most rigs, single-band brick-wall is fine. Multi- band is worth considering only on broadcast rigs or large worship environments where the IEM mix needs to survive sustained loud sections without pumping.

A daily soundcheck habit

A limiter you can’t verify is the same as a limiter you don’t have. Build a 30-second habit:

Pre-show, scream into any open vocal mic.
Watch the IEM bus output meter — it should slam into the threshold and stay flat.
If the meter blows past the threshold, the limiter is bypassed, broken, or mis-routed. Fix it before going to stage.

Also: every band rehearsal, briefly unplug one performer’s wireless cable while their pack is on. Feed a known test tone through their bus and confirm the limiter holds. The 30 seconds is paid back the first time a flaky cable arc-shorts mid-show.

Earphone choice matters too

The limiter caps the signal level into the transmitter, but the perceived SPL in your ear also depends on:

Earphone sensitivity. A higher sensitivity earphone produces more SPL per dB of input. Two 110 dB SPL earphones at the same input level can differ by 6 dB or more.
Bodypack volume. The performer can turn it up after your limiter. Cap the maximum bodypack volume if possible (some packs allow it via menu).
Custom vs universal molds. A better seal means lower volume is acceptable. Custom molds let performers run at lower SPLs and still hear everything.

A limiter isn’t a substitute for the rest

Routing discipline. The limiter shouldn’t be the thing protecting you from a wrong patchbay assignment. Get the routing right first.
Earphone seal. Loose earphones leak and feedback. Foam tips or custom molds.
Sensible mix levels. If musicians consistently dial their packs to max because the mix is too quiet, the system is wrong. Raise the bus level (with limiter intact) so they’re not chasing.

IEM Limiters and Hearing Protection: Settings That Actually Save Ears