Crossovers are more than simply electrical filters. The individual loudspeaker drivers and their relative physical positioning in a cabinet are also a part of the complete electroacoustic crossover which, together, achieve the desired performance in terms of frequency response, timing, and directivity. There can also be purely mechanical crossovers within the moving parts of some loudspeaker drive units. Chapter 5 looks globally at the concept of crossovers, and discusses the ‘orders’, slopes, and turnover shapes typical in active and passive crossovers. The non-minimum-phase nature of most crossover reconstructions is treated in detail, along with the way in which some of these effects can be ameliorated with the use of digital processing.