Is it normal for the EQ on the head unit to effect all of the RCA preouts?

Should I use an external crossover?

Why should it not affect all outputs?

Why would anyone want sub frequencies in the mids or highs??

Well the sub has a filter that cuts off at 200hz anyway so it doesn't matter.

it would be pretty pointless if the EQ settings did not effect all of the RCA's, why would you just want to adjust freq on just one set of speakers, if that is what you need, then you will have to get a dedicated stand alone EQ.

however if it is crossover points that you are trying to adjust, then the HPF will do BOTH the front and rear and there is no seperate adjustments like other brands like alpine's and kenny's! however the SUB set of RCA's has its own separate crossover. if you really want different crossover points for the front and back set of speakers, (which i do think this radio should have because a lot of cars do not have the same size of speakers for the front and back)then you can and should just set your crossover points at the amp and not at the radio.

there should never be a need for a stand alone crossover.