I was looking at this website today and noticed a section on whats called a "transient perfect crossover". The design there is essentially a crossover with a final 2nd order response that sums flat and has no phase shift at all. This seems pretty interesting to me, and I've not seen any other sort of crossover that has no phase shift. No phase shift from the crossover would seem to be the ideal thing, so I'm wondering why it hasn't been used more widely. Its described as "The filters sum to a non-flat, minimum phase response which is then equalized, using a simple passive equalization network which is also a minimum phase network. The final response is flat with no phase shift".

The actual document for this can be found at http://www.geocities.com/kreskovs/CrossoverdocN.html

What are peoples opinions on this sort of crossover then? Its a pity its only 2nd order, I prefer higher order crossovers.

Adrian