It was a high quality programable electronic crossover. There were optional 14 and 28 band equilizers that could be installed giveing the ability to sit in the driver seat and adjust both crossover and eq settings. The user also had the ability to store mutiple sets of settings, making it easy to change them between RTA , SQ , and SPL sessions during competitions. Audio Control has some digital units available that are similar. A good used EXP2 would be cheaper. The Audio Control pieces are are a bit expensive and the dash mount controler is about a $200 option at retail prices.