Wayne Parham Messages: 18793 Registered: January 2001
Illuminati (33rd Degree)
Elliot is talking about keeping sound sources within 1/4λ, not zero phase offset. There's a big difference. As an example, the distance equivalent to 1/4λ at 100Hz is 3 feet, so you can have that much physical offset between sound sources at 100Hz and still be "time aligned" within 1/4λ. On the other hand, to achieve true time alignment - zero phase offset - you couldn't have any reactive components in the system, the loudspeaker drivers and cabinet would have to provide a purely resistive acoustic load and the voice coils would have to be motionless. Clearly these are physical impossibilities. But to keep sound sources within 1/4λ for proper summing is a worthy goal.