There's really no such thing as a first order electrical crossover; in theory a single cap or coil will give you a first order electrical crossover, but the variable impedance of the drivers in question will not result in a first order acoustic response. Outside of esoteric trash you're not going to see that approach.
If you want a first order acoustic response, which is a pretty outdated idea frankly, you actually need very special drivers and a fairly complex crossover, since you need to shape the response over many octaves instead of like one and a half. Dynaudio makes very damped woofers and robust tweeters, which helps a lot, but you sacrifice a few things.