The mean 0.5–2.2 keV spectra of a) seven starbursts; b) five Compton-thick AGN; and c) five non X-ray AGN but with [Ne v]λ14.3   μm detection. The energy scale is in the rest frame. The individual spectra have been corrected for Galactic absorption and the detector effective area and then normalized to the 0.8–1 keV intensity before averaging within each sample. These mean spectra are constructed in order to facilitate comparison of the strength of Si xiii at 1.84 keV relative to the 0.8–1 keV band where Fe L emission dominates between the different classes of objects (see text for detail).