The Es 15 I modded down to fit squarely on the cubo 15 so it's about 610x610 , remember my project has always been about a balanced small system not a super system so spl and getting the most out of each cabinet has never been what I'm looking for . I have looked at the SMT and the single version some have built and then factored in costs of extra amps etc as bi amping the tops and extra x-over channels that are going to be needed , I am now thinking a passive mid top may be a better solution for my application. I know there are many here who believe passive crossovers rape your amps power but as I said spl is not really my thing, just a balanced system that covers all freq ranges in the right places at an affordable cost to the DIY population.