There is a very informative document on the speaker crossovers on the π Speakers website at www.PiSpeakers.com/Speaker_Crossover.doc. Also available online is a circuit evaluation tool called Spice, which contains the circuit models used in the crossover document just mentioned. This includes all crossovers used in every model of π Speakers available. The Spice software distribution for these crossover models is at www.PiSpeakers.com/Pi_Crossover_Spice.zip.The crossover document is 2.2Mb and the Spice distribution is 1.9Mb, so expect these files to take several seconds to load.