Is it possible to do 2.1 or 2.2 audio with 2 stereo sound cards (e.g. 2 Xonar Essance STXs with no external DACs) with JRMC18 or do you need a multi-channel card like a Lynx AES16e?
If so, how do you assign specific channels to specific cards in JRMC18?
I am looking to add low and high pass XO's as well as equalization.
TIA
The short answer is that you need a card with as many channels as you plan to use for output at any one time. Two STX's probably won't work, but you could get an Asus ST with the H6 daughterboard (which would give you 8 channels for less than the cost of two STXs). JRiver has the capability to route outputs like you're describing, and it will play to both at once,
but there's a large and (as far as I know) unresolvable problem with using two DACs.
The basic problem with simultaneous playback to two DACs is that (unless they're synced to the same word clock, or master/slaved, neither of which the STX supports) they won't be synchronized in their playback. Some people will tell you that non-asynchronous DACs will sync to the motherboard clock and so should play at the same rate. But it isn't that simple, as almost all non-asynchronous DACs do some slight time-shifting to account for jitter, and they do it on their own schedule.
I tried an experiment with two identical non-asynchronous DACs (admittedly not STXs) hoping to do exactly what you're describing (I have bi-amped main speakers and use JRiver as my crossover), and they would start out loosely synced, but then would just gradually drift farther and farther apart in time, and there was no way to correct it because each DAC was playing data at it's own rate.
I currently use an Asus ST/H-6 combo and can recommend it highly with JRiver for multichannel audio. If you happen to already have two STXs sitting on your desk and want to try and repeat my experiment with them, let me know and I'll talk you through the configuration steps, but I wouldn't recommend buying two for this purpose as it almost certainly won't work.