Composite LBT zJ spectra for N and W + w quasars. Top panel: Median LBT zJ spectra for the X-ray normal (N, in blue) and the X-ray weak (W+w, in red) subsamples. The gold spectrum is the average quasar spectrum from Vanden Berk (2001). Fluxes are normalised by their value at 3000 Å. The continuum power laws are the extrapolation of those found at UV wavelengths (i.e. SDSS). Middle panel: Number of spectra contributing to each spectral channel, following to the same colour-coding. Bottom panel: Ratio of the N spectrum to the W+w spectrum.