[Elecraft] K3 Filters

[R March]

The K3 description mentions variable XTAL filters ("up to three") in the
front end, prior to the DSP. My question is: are these filters variable band
width (similar to the K2, which used a filter whose BW could be changed as a
function of voltage applied ) or are the filters variable in that multiple
filters are switched to track with the DSP setting.  IOW, if one has just
the 500 Hz filter for the front end, can the BW of that filter be narrowed
if one sets a tighter BW overall?  Or does one need a narrower roofing
filter to narrow the roofing filter stage BW?  Thanks,  Bob, N7UA