Audioman58,
I've never listened to a Coda amp but would love to!
Ralph,
I should say the main reason I want to use two midrange drivers is to match their output level to the tweeter for the same given power input. But I'm going by the notion that two drivers in parallel will result in a 6db boost in output. That is 3db from the doubling of drivers and 3db from the doubling of power. From my understanding two drivers in series will result in the same output as one because voltage for each will be cut in half (-3db) and the doubling of drivers will bring it back up again by 3db. I also don't know the exact explanation between efficiency and sensitivity other than one is expressed in percentage and the other in SPL/power/distance.
Either way, last night I modeled the drivers in a typical parallel crossover and it turns out the lowest they dip is 3 ohms. Not as bad as I thought.