You can "eq" the speakers through component selection in the crossover (even if unintentionally) and this is probably why some people prefer passive crossovers to active crossovers.
Case in point. All the values in the crossover have an "ideal" combination, but the combination can be tweaked to produce a hump or a dip in an area of the band that is pleasing to the listener.
The 5.8 mH choke with an 8 ohm load would actually like to "see" a 44 mfd cap to ground. A larger cap (e.g., 47 mfd) will create a greater roll-off, but it will also create a hump just below the crossover frequency. The larger the change from "ideal", the larger/broader the hump. So if you set the crossover to the "right" frequency and you "over-capacitor" it, you can add a "hump of bass" just below this frequency (which I have at 310 Hz).
Similarly, the combination of C2, C3, and C4 if "over-capacitored" will increase the roll-off, but create a hump below the crossover frequency, which puts it at ~1kHz where the ear is most sensitive. This takes a bit of the high end hash out of the 2251 while giving voices a warmer, more pleasant tone.
