Time aligned, Phase coherent, Phase aligned, Transient accurate, What's up with that.
The figures above show the transient characteristics of the different crossover with differen driver alignments. However, we should look at the effect of driver alignment on the wingdings frequency response as well. Recall that for the standard crossovers the wingdings response will be flat when the driver's AACs are aligned (center baffle). But what is the effect of using the flat baffle, and what does the response of the last, non standard crossover look like? The figure to the left shows the response of the standard crossover with the drivers mounted on a flat baffle. As can be seen, the 1st and 3rd order Butterworth crossovers are subject to the most significant variation in frequency response due to driver missalignment. The 2nd and 4th order LR filters show relative insensitivity to the missalignment. This insensitivity to missalignment is one reason for the popularity of the LR crossovers.However, the reversed polarity null seen with these filters will move off axis as a result of the missalignment. The lower 3 curves show the response of the Bessel/1st order time aligned crossover for the three different baffles. Note that the response is quite acceptable when optimized with the drivers in the time aligned position.

Time aligned, Phase coherent, Phase aligned, Transient accurate, What's up with that.
Below are 3 different baffle layout that are typically used in convension loudspeakers. The first figure to the left shows a flat baffle. As is apparent, this layout generally results in a relative offset between the woofer an the tweeter in which the AC of the woofer is located behind that of the tweeter. This is a very common layout, but it will not allow time or phase alignments when using any of the standard crossovers (unless some other means is used to account for the non zero relative offset). The center figure represents a layout in which the ACs of the drivers lie in the same plane. There is no relative offset between the woofer and the tweeter in this case. Time aligned, phase coherent, phase aligned and true transient accurate crossovers can be developed with this configuration. Finally, the figure to the right shows a layout where the tweeter AC is located behind that of the woofer. This layout is typically used with non standard time aligned crossovers.

Time aligned, Phase coherent, Phase aligned, Transient accurate, What's up with that.
Below are 3 different baffle layout that are typically used in convension loudspeakers. The first figure to the left shows a flat baffle. As is apparent, this layout generally results in a relative offset between the woofer an the tweeter in which the AC of the woofer is located behind that of the tweeter. This is a very common layout, but it will not allow time or phase alignments when using any of the standard crossovers (unless some other means is used to account for the non zero relative offset). The center figure represents a layout in which the ACs of the drivers lie in the same plane. There is no relative offset between the woofer and the tweeter in this case. Time aligned, phase coherent, phase aligned and true transient accurate crossovers can be developed with this configuration. Finally, the figure to the right shows a layout where the tweeter AC is located behind that of the woofer. This layout is typically used with non standard time aligned crossovers.