First-order Ambisonics reproduction is restricted to three loudspeakers

Evidence

In principle, first-order Ambisonics could be used for any loudspeaker set-up, but unfortunately it has a very limited range of use. The broad first-order directional patterns make the listening area very small, extending the size of the head of the listener only at frequencies below about 700 Hz (Solvang, 2008). At higher frequencies, the high coherence between the loudspeaker signals leads to undesired effects, such as colouration and loss of spaciousness. The number of loudspeakers in a horizontal set-up should not exceed 2N + 1, where N is the order of the B-format microphone, to avoid too high a coherence between the loudspeaker signals. Thus, first-order microphones can be used only with three-loudspeaker set-ups, which is far too few to produce the perception of virtual sources between the loudspeakers. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1863

Categorization

• DEFINE: The 2N + 1 loudspeaker limit for a given microphone order N is a crisp quantitative rule worth remembering.