Audio processing with USRP2 and LFRX

Hi, I am attempting to use the Ettus USRP2 and LFRX daughterboard to
process a low-frequency audio signal (between DC and 1 KHz). I have had
no success so far in getting the uhd waterfall sink to display a
spectrogram of this frequency range at sufficient frequency resolution.
There seems to be no way to adjust the frequency scale, only the time
scale and sampling rate. Is there any way to do this or is it just not
possible with the USRP? The LFRX board is supposed to work down to DC.

I had read in other posts that the USRP firmware’s DC offset correction
had to be disable, but using the uhd_usrp_sink_sptr.set_dc_offset()
function in python did not seem to make a difference.