Headphones, lateralisation and crosstalk

The same stereo recording sounds very different on headphones and on loudspeakers. The reason lies in how our hearing assigns positions in both cases.

Localisation and lateralisation

• Localisation is perceiving a source in the space around you, at some direction and distance.
• Lateralisation is perceiving a position inside the head, along the line between the ears, which is what typically happens on headphones.

Headphones feed each ear with only one channel. There is no acoustic crosstalk, and no effect of the head and the outer ear on the sound (or only the one the headphone itself creates). The brain interprets the level and time differences as a position on the line between the ears, and the image often appears inside the head.

Crosstalk on loudspeakers

With two loudspeakers, each ear hears both channels. The signal from the far loudspeaker arrives about 0.2 to 0.3 ms later and is filtered by the head. This crosstalk is what makes phantom sources work, see Phantom sources. Remove it, as headphones do, and the sound stage collapses to a line between the ears.

Ways to improve headphone listening

• Crossfeed: mix a little of each channel, delayed by about 0.3 ms and low-pass filtered, into the other ear. This mimics the loudspeaker crosstalk and reduces the exaggerated separation.
• Binaural recording: microphones in the ears of a dummy head or a person capture the effect of the head and ears. Played back on headphones with a matching response, it can be very convincing, especially to front and sides.
• HRTF processing: filters that simulate the head response for a chosen direction. Works best when the filters match the listener.

The success varies by person, because pinna shapes differ.

Loudspeakers for binaural recordings

Binaural recordings played on two loudspeakers lose their effect due to the crosstalk. Transaural processing cancels it by adding a delayed, inverted signal to each channel. It works only for a listener at the exact sweet spot and with careful alignment of the loudspeakers.

Practical notes

1. Mix on loudspeakers when you can, and check on headphones.
2. A hard-panned instrument sits in one ear on headphones, which can be fatiguing. Loudspeakers avoid this.
3. Reverb and spaciousness are easier to judge on loudspeakers.
4. Mono check is the same on both, see Mono compatibility.

Draft: written by an AI assistant, awaiting technical review.