So I asked Line 6 about this, they recommended that we go into the spider editor app, create a pass through plug-in where the amp and cab are turned off, and the signal is sent to the modeler of choice.
Line 6 said, I would suggest setting it up as such:
Amp: No amp or L6 preamp
Cab: No cab
Mic: No mic
Cab enable: Off
Speaker (firmware >2.00): try either mode, I'm not sure though it will make difference without a cab enabled.
Other than using the aux in, this is the best suggestion I can come up with. Beyond this, you might have better results splitting the amp/cab model within Neural and send the preamp only and use the Spider cabinet modelling.
