-10 Celcius for me just reduces power and basically removes bass. I don't know enough to know if this type of thing is normal or not.I have this exact problem. In cold weather it doesn't work, just a loud hiss through the speakers, once everything warms up it gradually starts working, could be 15min could be an hour depending on temps. I chalked it up to a failed cold weld in the amp, but still trying to solve/fix.
Anyone have solutions?
I will say that I bought another Helix brand new and will be installing it in my partners car this summer. Might be a year from now but I'll eventually be able to compare.