Shielding help with eletrical interference but does not protect against low frequency AC magnetic fields, that is one aspect where balanced, differential circuits combined with twisted pairs can help significantly. Even better, use twisted pair conductors for both the
power and audio signals, thus reducing both the magnetic field emitted and the susceptibility to it.
Getting back to the original topic, Prodium Pro seems to offer both powered and unpowered mains as well as 10", 12" and 15"
subwoofer drivers, but the the only
subwoofer boxes and the only 18"
driver product they seem to offer is a powered
subwoofer box.
I'm guessing he has a limited budget, which is common, but also common is getting so spending everything you have on gear that won't do the job or is unreliable. It usually makes little sense to try to put a
system together based solely on a budget unless that budget just happens to be realistic for the application, so it usually helps in terms of recommending what to do or any alternatives, to identify the intended use, the budget, the goals/expectations and so on. For example, what kind of bands and inputs/sources might need to be supported? What size and type of venues? Is transportation, storage,
etc. of the
system a consideration?
I don't know what type of gigs he plans to do but how many times do the bands he works with actually need to provide their own
system or is what they would provide better than what the
venue or customer could provide? Might he be better to focus on some specific components such as microphones, maybe some processing,
etc. that could be used in conjunction with
house, production or rental systems and maybe later form the basis for a higher quality
system if their needing to provide a
system does become common?