Spectral irradiances (in photon flux units) within the SEM 1 bandpass for two dates (during maximum in 2001 and minimum activity in 2010) based on the SOHO CDS NIS + DEM approach are compared to those estimated by FISM, by SOLERS22, and for the 2010 case to those observed by SDO/EVE MEGS. When used as reference spectra for determining irradiance from the SEM 1 observed count rates, the CDS NIS + DEM, FISM, and SDO/EVE spectra yield similar results, whereas SOLERS22 produces SEM irradiances that are systematically higher.