The K3S's DSP Brick-Wall filters are cascaded after the crystal filters. After about -30 dB down from the peak of the crystal filter response curve, the DSP handles the remaining signal rejection for very strong signals (more than S9+25, attenuator off) that are inside the filter response curve, effectively sharpening the remaining filter response and limiting the b/w to that point.
For signals less than S9+25 that are inside of the -30 dBc crystal filter bandwidth, the DSP can handle all of the filtering without blanking and provides the final bandwidth, adjustable down to 50 Hz.
Note: Different kHz per division scale on each plot. Top top reference levels will also differ depending upon test setup at time of test (sig gen level etc.) Use relative attenuation values from filter peak response for comparison.