Edward M. Long
E. M. Long Assoc., 4107 Oakmore Rd., Oakland, CA 94602
A Time Align(registered) loudspeaker system must produce an acoustical output at the listening position such that the fundamental and overtones of a complex, transient signal have the same relationships that they have at the electrical input to the system. To qualify for the use of the Time Align(registered) trademark, the natural time offset between the acoustical outputs of the loudspeaker drivers must be corrected. This time offset is caused by the natural low-pass filter characteristics of the drivers and the electrical crossover filters. The time offsets between the acoustical output of each of the drivers must be corrected and the electrical crossover filters must be designed to produce an acoustical output from adjacent drivers that is 6 dB down from its passband level. When the coherent acoustical outputs of adjacent drivers are combined, the result is a uniform acoustical output. The polarity of the acoustical outputs is also affected by the crossovers; this is also a major consideration in the design of a Time Align(registered) crossover. A Time Align(registered) loudspeaker system must be able to produce acoustical square waves and have a short impulse response. Time Align(registered) design techniques are shown by practical examples.