The four π loudspeaker asks a lot of its midwoofer, as does any two-way loudspeaker designed to provide uniform directivity. The crossover point has to be fairly high in order to match directivity of the midwoofer with the tweeter, because it requires the midwoofer's collapsing directivity to match the radiating angle of the tweeter. That doesn't happen until around 1kHz.As a result, midwoofer selection is critical. The quality of the midwoofer is extremely important, because it is what voices the speaker through the critical midrange.
Try to find a JBL 2226 if you can.