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

I thought that I'd stop speculating and look these up:

Here are the spec's from the Stereophile review:
Description: Five-way, two-chassis, dynamic, floorstanding loudspeaker system with four EMIT ribbon tweeters, seven EMIM ribbon midrange units, and six servo-controlled polyproylene-cone woofers. Electronic crossover frequencies: 125Hz, 700Hz, 3kHz, and 8kHz.
Dimensions: LF section: 60" H by 14" W by 15" D. HF section. 60" H by 22" by 13" D.
Price: $5295/system (1985); no longer available (2006).

Read more at http://www.stereophile.com/content/infinity-reference-standard-1b-loudspeaker-specifications#3FRfKtT...

and here is the owners manual: 
   http://www.davidsaudio.com/rs1b-manual.pdf

Hi timlib
The Richter scale crossover is changeable through a chip. I have lots of values for it. You can even make your own crossover point, they give a formula in the manual. The other audio control is not an epicenter, I made a mistake but it uses the same crossover as the richter so using the two I can get a 3 way at any point I want. I am glad you have some respect for the Nakamichi, I wasn't sure what you would think about mixing car audio .I haven't tried using 4 amps at the factory crossover points. If I do I will let you know. Setting levels isn't a problem as I have an Audio Control 3050A spectrum analyzer. I am still not sure using so much electronics in the signal path is the best route to go. I really appreciate your help.
Marc

Not sure If I can add much to this discussion but active crossovers would have been more expensive at the time. The system was already expensive when you add the amp and other requirements. I own two sets of the RS1B woofer towers and the servo controller. These parts are getting old and my servo now has a low level hum that it didn't have before. I now use an active crossover without the servo system and get very satisfactory results. The RS1B was a great system but after listening to the Infinity Emits and Emims for the last 4 decades I have moved on.  

One of my best friends on the planet is an old timer very respected figure in the audio world.  He uses a 12v crossover with a passive sub, of course, he modded it with some nice parts and built a fully regulated 12v supply, but it does a great job.  Years gone by, I worked for Orion. I've heard of few of their amps in home use and at one time I owned a stereo store,  we did 12v to high end...and there,  we tried a soundstream amp with some home gear... I've seen very respectable results mixing.... Never true hard core audiophile with the amps, but some truly respectable results.