[quote name='jockhater2']I thought there isn't much to tweak on subs since the signal is mono.
Hmmm. The HU being 3 way doesn't really mad anyways correct. Because once you run it active. Aren't you relying on the amplifiers crossovers then? The audison has an intense amount of crossovers.[/QUOTE]
Active vs. passive is concerning the crossovers. Active uses some sort of digital processing, passive is done mechanically with capacitors, resistors, etc. Almost all subs are crossed actively, don't think I have ever actually personally seen passive subs that actually use a crossover, though I'm sure it happens in home audio. Even though the sub signal is mono, you can still adjust a lot, such as levels, crossover points and slope, time alignment, things like that.
The HU being 4 way does matter very much. It allows you to set your crossover points and slopes very accurately on the HU, and doesn't require external processing. Using the crossovers on an amp, if they are there, is usually hard to do because they only have rotational knobs that aren't detented. To get 3 way fronts otherwise, you would need a processor that breaks that signal down and does the same thing. I guess you could run a full range signal out of any HU, split it to 3 channels of an amp, and use the crossovers there as well, but I don't think I have seen that.
When you use the crossovers on a HU, you generally don't use them on the amp, only to get a steeper rolloff at a certain frequency. Not sure how
@keep_hope_alive is going to have you set it up, but my guess is you will be using the crossovers on the HU and running the amp as full range. That's how my 80prs is set up at least.
And of course, he will most likely know much more than what I just wrote, and probably point out that I am incorrect somewhere. This stuff gets confusing sometimes, and I'll be the first to admit I don't know everything.