The ProAcs are British loudspeakers. These particular ones were, IIRC, were considered as among the best around of their type when new. One of the best speakers I ever heard were the big ProAcs (I don't remember the model number) but they ran around $15k a pair a dozen years ago. ProAc still has a website so you might check out some info there or try a British audiophile forum. As for the external crossover, there was a belief (don't know if it's still current) that having the crossover in proximity to the speakers negatively affected performance. There were several speakers at that time with external crossovers. ProAc seems to still make a version of the Response 1s, though it doesn't appear to have an external crossover. www.proac-loudspeakers.com is the company website.