Why are the Infinity IRS, Reference 1b, Beta ect speakers passive on the mids and highs?

I can only change frequency. Slope is 18db/octave. I don't know Bessel, ect... You are correct on the crossover frequencies except I thought it was 140hz not 125hz.

I'm going by memory, I could be wrong... What crossover are you using, I'll look it up.

meaning which electronic crossover are you using?

I have a couple. I have 2 audio control units from a Richter scale and an Epicenter. I can swap crossover frequencies easily. I also have an Audio Research tube crossover  ec-4 which is hard to change. I think it is 12db on bass and 6db on mid and high. I am using that on a set of Tympani 1D but would swap it out if it was a better choice. And lastly I have a Nakamichi ec-302 which is a 12 volt unit on a power supply. The Nak can select 10hz steps so it is great to experiment with.
Marc

140Hz does seem a little low for the EMIM’s to go down to , my epsilons L-EMIM goes down to 140Hz but it is a large driver, would be nice if the woofers were able to go a little higher.