Research & Development: Phase Coherence
The natural acoustic characteristics of all drivers limit their use to specific frequency ranges. Two or more drivers are required to cover the complete audible range. The speaker’s crossover divides the input signal so that each driver only receives frequencies that it can reproduce. Since drivers are physically separated from each other, there will be phase (or timing) differences between their outputs (Fig. 1). These differences must be addressed to ensure the faithful recreation of the original sound.
Achieving accurate phase alignment between drivers can be accomplished in a number of ways. Methods used over the years include: physical alignment, placing drivers on stepped baffles or sloped baffles; mounting tweeters coaxially or coincidentally; or electrical alignment through various crossover design techniques.
While each of these has its supporters and detractors, none are perfect, and some methods may even produce other more serious sonic anomalies. Paradigm speakers have phase coherent crossovers designed so that the summed output of the drivers is completely and accurately rejoined.
The resulting phase coherence (Fig. 2) faithfully preserves the sonic integrity of the original sound with tremendous clarity and resolution throughout a very large listening area. This phase coherence can be easily seen in measurements where the speaker’s frequency response shows a completely seamless transition from driver to driver, both on- and off-axis.
Fig. 1) Typical Phase Coherence: The large notch in both on- and off-axis response curves shows a lack of phase coherence between drive units.
Fig. 2) Paradigm speakers have outstanding phase coherence between drive units for superb seamless sonic integration.