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7.0 Crossover Shapes and Frequencies
It is not possible to provide one loudspeaker driver to cover all audible frequencies.
Even if the frequency response could be achieved,
the large size of the driver required to shift enough air at low frequencies
would offer an impossibly directional beam at high frequencies because at small wavelengths,
the differing path lengths from the extremities of the diaphragm to the listener would cause cancellations off-axis.
Therefore, it is necessary to use more than one driver and to split the bands with an electrical filter or crossover.
This filtering can be done by passive, active or digital means, external to or within the loudspeaker cabinet.
Ideally, the filtering is done so that when acoustically combined,
the drivers produce a constant output across the required range of frequencies.
Additionally, the signal phase behavior with frequency should offer smooth transitions across all the drivers to achieve a constant group delay.
Another important consideration is that the crossover should control the beaming properties, also known as the polar response,
so that listeners off-axis do not hear anomalies in the sound range.
Many crossover filter designs do not achieve these goals.
Finally, the signal should be quickly attenuated outside the optimum band of operation for each driver to avoid driver anomalies
such as resonance and over-excursion distortion at low frequencies. In these instances some crossover shapes have limitations.
The FDS-366T allows full control over each high and low pass filter of a crossover segment in shape,
slope and frequency. Graphically these parameters are labelled as below.
