Powder diffractometers are naturally suited for short-pulse spallation sources, as they optimally exploit the brilliance from the sharp neutron pulses, with a relative time-resolution constant over a broad wavelength range. Their design has considerably progressed over the last three decades, in particular due to advances in detector technology. In the 80s, the first instruments such as HRPD at Argonne and HRPD at ISIS employed backscattering geometry, where the instruments are naturally focussed, and have long primary flight-paths in order to acquire high-resolution data. To improve count rates, large solid angles could be covered but detectors were positioned on a locus that allowed geometrical focusing, where time-of-flight (TOF) histograms produced by individual detector elements have equal resolution and can be directly grouped into a single diffraction pattern.