Routing to a multi channels audio bus

If I do like you just said : I route (by using outputs instead of sends) all my tracks to a track of an aux → I won't be able to decide in which output (of my sound card) it will sounds because all my tracks have ONE output which will be the bus and which will be assigned to ONE output.

I do not know how else I can explain it to you, but, as I mentioned above a few times, for a multichannel bus setup with eight different submixes you have to use eight Aux channels (and not one, as you describe above).

Alternatively, join your eight submix elements into stacks and send each stack's output to a SEPARATE bus (e.g. stack one goes to Bus 100, stack two goes to Bus 101, and so on). These Buses serve as inputs for 8 SEPARATE Aux channels to which you assign eight SEPARATE outputs on your audio interface.

Get it now?

If I understand you correctly, you just have to set up 8 Aux channels in Mixer and assign a separate output channel on your audio interface to each of them. Set up a separate Bus (say, Bus 1 to Bus 8) as input on each of them. You'll also have to set these buses as outputs for the tracks in Mixer that you want to send to a particular speaker. Here's your basic multichannel output setup (see screenshot): 8 Aux channels with Bus 1-8 assigned as inputs, no output so far (as I don't have my multichannel interface connected, you can label the channels according to the speakers they output signal to (here it's Sp 1-8).

Hope that helps. Cheers!

Well, you are limited to 8 send slots per track, but that doesn't mean that you have to use sends to OUTPUT audio from the track. There are 256 buses, right? So, first you route all the audio from a particular track or submix (including Aux channels responsible for send effects in that track or submix) to one of the free bus channels. That bus channel is set as an input on one of Aux channels, which in turn is set to output audio to one of the separate outputs on your audio interface. Is that clear now? I hope it is.

Btw, as a note, IT IS possible to save the multichannel bus setup (as I described above) as a user patch in the Library. That would preserve the all channel routings, so you can recall it any time.

Unfortunately, your screenshot doesn't tell me anything without further comments. As for your question, it has evolved a bit far from the original one, I must say. Not sure I clearly understand what are you trying to do here. First it was about routing the sound to your sound system. Now it's about automation and exporting tracks as audio.

Just FYI, Logic does not encode multichannel audio files. Do do so, you'll have to export a multitrack and use either the Compressor app (sold separately) or some other 3rd party software to encode it further into a broadcast format you prefer (if that's what you want, of course).

You don't necessarily need to route tracks to your sound system for Logic to be able to export the audio. Say, you have just 8 audio tracks in your arrangement and you're satisfied with how each of them sounds when you monitor the song through the sound system. Also, you've automated their respective playback parameters (volume, pan, etc.) to your liking. At this point you may use File -> Export -> "All Tracks as Audio Files" to create a multitrack for further encoding into a multichannel audio file.

It may be a bit more complicated if you have numerous tracks that you want to be grouped into eight submixes corresponding to the sound system outputs. To be able to export these as separate audio files with playback automation (as you describe it), I'd suggest you use 8 summing track stacks. Again, once the song sounds to your liking, you can export these 8 summing stacks as a multitrack using the command described above.

You can definitely recreate this bus functionality of Pro Tools with a bit of creative routing in Logic's Mixer.

Aux channels, that you can assign separate inputs (summing stacks / buses) and outputs (speakers in your sound system) to, can also be grouped in a summing stack. You can then save this stack as a channel strip setting and name it something like "Multichannel Bus". Viola! Now you have this option in Logic.

Not exactly what I meant. To create that multichannel bus, you have to route audio from your tracks (or track stacks, groups, submixes, or whatever is producing audio in your project and is supposed to go to the eight audio outputs) to Aux channels via Buses 1-8, with these buses serving as inputs for Aux channels and as outputs for the 8 audio-producing elements in your project (like I pointed out in my initial reply). That's the first step. Next, you assign multiple outputs, according to your sound system, to these Aux channels. That's the second step. The final step is to select these Aux channels in Mixer and join them in a stack.

I think I might not be quite right about saving the Aux channel stack as a channel strip setting that would recall the bus audio routings later on. However, there's always a possibility to recreate the audio routing in an empty project and save it. In Logic you can import Environment layers from other projects, so you'll be able to recall this bus setting at any time.

Here's a starting point for setting up surround in Logic: https://help.apple.com/logicpro/mac/10.4/#/lgcp57f6cc60

If anything isn't clear above, check out these user guide sections:

Stacks: https://help.apple.com/logicpro/mac/10.4/#/lgcp9bc4b63d

Signal flow / Aux tracks: https://help.apple.com/logicpro/mac/10.4/#/lgcp8e7db552

Saving custom Library patches: https://help.apple.com/logicpro/mac/10.4/#/lgcpe0e71c76