Toe-in loudspeaker aiming failed to stabilize phantom center imagery off-axis

Evidence

In the early days of stereo Hugh Brittain, recognized for introducing metal cone loudspeakers while he was at GEC in England, promoted the idea of aiming the loudspeakers so that their axes crossed in front of the listener. His name became associated with that arrangement. Knowing that loudspeakers are somewhat directional, especially at high frequencies, the idea was that as one moved away from center the more distant loudspeaker would get louder and the nearer one would be reduced in level, thereby achieving a crude amplitude panning to compensate for the delay error (time/intensity trading); the phantom image would be perceived to move less. Obviously, with typical cone/dome loudspeakers it only works at mid-to-high frequencies and the off-axis behavior of loudspeakers is unpredictable; sound quality is at risk. Added to this, the time/amplitude trading ratio is different for sounds of different spectral and temporal structure and images tend to break up. So, it is not a solution. — Toole, Floyd E, Sound reproduction- the acoustics and…, 428

Categorization

• DEFINE: Explains the Brittain toe-in arrangement and why time/intensity trading makes it only partially work, then fail entirely due to image breakup.
• XREF: Connects to time/intensity trading (a core psychoacoustic principle) and its dependence on signal spectral and temporal structure.