The rotary speaker models are HX updates to rotary speaker pedals. So, they were originally designed to go before an amp. However, once they got in Helix, we realized that they are much more versatile. Let me explain what is going on in the effect.
The dry path is true stereo. The effected path is summed to mono.
The effected path goes through a simulated power amp. It’s nowhere near as accurate as the HX amp modeling. It was just to add some extra grit that one might find in a rotary speaker cab.
Then the signal splits and it gets the separate woofer and horn modeling. This includes filtering an EQ to model the speakers in the cabinet.
Now, how should it be used?
I would use it in one of two way: as a pre amplifier effect pedal, or as a post amplifier cab replacement.
If it’s being used before an amp mode, then there should definitely be a cab or IR model after the amp. The drive knob should be tweaked to the desired amount. I think the drive knob has enough range to distort with just a guitar level signal plugged in.
If it’s being used after an amp model, then the switch that turns on the rotary effect should also turn off the cab or IR block that is being used when the rotary effect is bypassed. Special care should be paid to the Dive knob in the rotary effect. Since it was originally designed to be an effect before an amp, the level coming out of an amp model can sometimes cause a lot of extra, unwanted distortion in the rotary effect. I’d start with the drive at zero and adjust up to taste in this instance.
Most people prefer to use the full amp models with the rotary effect. However, I’ve heard of some people liking to use the rotary effect after a preamp model, and then they will lean into the rotary’s drive knob. This is probably for a parallel path, or a patch where the rotary effect is never turned off.
Finally, I have to put out my standard disclaimer. There is no objectively wrong answer here. If it sounds good, then use it in that setting and enjoy. Users should use their ears and personal taste when setting this up. I’ve just outlined traditional settings for the rotary effects, but non-traditional tones can be exciting, groundbreaking, and inspiring. Dig in, folks!
— Ben Adrian