I'm a bit of a beginner, and I just purchased an M-Audio Axiom 25, and I also updated to the Lion OSX on my Mac Pro desktop prior to purchasing the Axiom 25. I'm a little confused by the M-Audio website. Part of it looks like the drivers are just already within Lion, and on the same page it sounds like the Axiom 25 just might not be compatible with Lion as they haven't released the drivers for it yet.
I tried to use the driver for Snow Leopard because that one is available on the M-audio website, but then it says not to use it, so I uninstalled it. I got the same results with using the Snow Leopard drivers as without, which was seeing the MIDI data recording in Logic, but no sound during play or playback.
I have the Firestudio Project as my audio interface, but I started by using only the USB from Axiom to Mac Pro, as it recommends in the start up guide. There is no USB port on the Firestudio Project. The MIDI data is getting through to Logic, it's just that I don't hear any sound while playing in real time or during playback. I also had a MIDI cable running from Axiom to Firestudio at the same time as the USB was running from Axiom to Mac Pro. I'm not sure if I messed anything up by doing this. I also have no other way of powering the Axiom right now other than USB, as I don't have a power adapter for it yet.
Is the problem ultimately that there are no present drivers for Lion OSX at the moment? Should I downgrade back to Snow Leopard?
Processor 2.66 GHz Quad-Core Intel Xeon
Memory 3 GB 1066 MHz DDR3 ECC
Graphics NVIDIA GeForce GT 120 512MB
Software Mac OS X Lion 10.7.3 (11D50)
M-Audio Axiom 25 (2nd gen?)
Firestudio Project Firewire
Logic 9.1.7 64-bit
M-Audio BX5 D2 monitors