Without a limiter, large transients in audio signals could generate dangerous SPLs in headphones, although the average volume might be set at an acceptable level. Because the ambient noise on stage can be fairly high, performers are tempted to steadily increase the volume of their personal monitors in order to hear the mix.
Limiters can ensure that headphone volume never exceeds a pre-determined threshold.
Because a limiter is actually a specialized form of audio compressor, the circuitry of audio limiters can vary tremendously in complexity from a pair of diodes to multi-stage voltage controlled amplifiers with split frequency bands. Diode-based limiters are instanteous, simpler in design and have a more accurate loudness response, but suffer from distortion in the clipping region. VCA-type limiters have low distortion, but can exhibit breathing or pumping effects from poor gain control. This article takes especial note of design principles for diode-based limiters and the wide range of clipping characteristics. For more information about limiters and compressors, see Signal Processing Fundamentals .