The selected speakers Line6 has choosen for the DT50, gives you a wide sound variety to cover the whole bandwith of the amp models and cab/mics sims you can choose. There is no explicitely need to use cab/mic sims. Some users prefer pre amp models and cab/mics sims off. I personally meinly use the standard cab/mics sims on. It is a matter of taste.
The series wiring is in my opinion no specificly designed for the cabinet emulations.
Being honest: I am not a specialist on the technical aspects of guitar cab wiring and their potenial impact on the guitar sound.
So before I am telling you something wrong, I like to refer to more knowledgable users in this forum in that case to chime in.
What I personally can tell you is:
I have never made myself too much headache whether my cabs are wired seriell or parallel as long as they sound good to me.
There could a be a couple of reasons...
The main one is that there isn't a 16 ohm GH90...You could certainly run the stock 8 ohm GH90 and V30 in parallel and use the 4 ohm tap...but then you have some problems adding an outboard cabinet...
Series or Parallel really makes no difference other than trying to get a load that matches the amplifier...
FYI: Series wiring carries a marginal risk...If any of the speakers fail open in a series circuit, then the entire circuit fails to a no load condition which is not generally a good idea for a tube amp...If you wire parallel, then you have redundancy built into the circuit...Example: A mono parallel 412 cab is triple redundant...3 speakers can fail and you will still have a load...
I didn't want to make a new topic, so i'll ask my question in here:
Do you know, if DT-Amps has Pre-Amp + Cab sim on, as default?
I played with my DT50 combo yesterday. I first played with the DT50 alone and then connected my POD HD500 in. I wanted to dial the same Rectifier sound to HD500 + DT50 setup, that i manage to get with using DT50 alone.
I manage to do it, but i had to dial Treadplate-PRE + CAB sim, to get that exact sound. This is why i'm asking.