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

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.

Hi Marc,
   Ok, I'm familiar with most of what you have... The Richter Scale is not really adjustable enough, I was made for a fairly low crossover point for a 2 way with an eq on top.  The Epicenter and the Nakamichi are 12v products...  The Nak would probably work fairly well. It one of the better units for car audio.  As much as I'd like to see you use the Audio Research the 6db slopes on top will not work well with the ribbons.  
There are more slopes than besel, butterworth and linkwitz riley, but these are the main 3 used today. The act differently with how linear they are and how they handle phase. Depending on frequency, 1 can cause smearing, another will bring a rise at the crossover point and another will be flat at the crossover...
Being able to mix slope, we can correct some errors... Mix as in 12 up and 18 down... Although most electronic crossovers today are linkwitz riley 24/24 and that is always a good choice... even though you may like the sound of another slope, when in doubt, Linkwitz Riley is the go to...
So the Nak is 18db per octave and I don't know what type of slope it uses.... but you can't make any changes, so it is what it is.  The Nak will allow you to experiment, but if you ever want to get the most that you can from these beautiful speakers, you'll need something more versatile.
What does it sound like using the published crossover points of 700 & 8k?  and of course you realize the real problem comes in level matching.