The cutoff frequencies for the built-in high pass crossover. Crossovers are characterized by their frequency (Hz or kHz), and by the steepness of their roll-off slopes (the rate of attenuation outside their pass bands) as measured in decibels per interval (dB/octave). A high-pass crossover allows frequencies above the crossover point to pass, while frequencies below the crossover point are gently or harshly rolled-off, depending on the slope.