Hi Sugarspice, the RC does not limit the frequency range to the speaker, a characteristic of a dipole loudspeaker is that below the cancellation frequency, determined by the size of the speaker, the output will decrease with 6dB/octave. The series resistor of 1.5 Ohm compensates this effect that by increasing the Q factor. In parallel is a 220uF capacitor for bypassing the mid/high frequencies. So it would not warrant an external crossover/filter unless you were using a subwoofer. Removing the RC in the speaker would present the amp with a dead short if the protection circuit shut down the speaker. So I believe this is best dealt with at the speaker level, especially given the significant improvement with the changing out the parts as noted.