Low Sound Output from Front 6.5"'s

I am getting barely any sound output from my front 6.5" speakers when I tune the balance on my head unit all the way to the front (which actually says it's the rear). Sound output from the rears is fine and the head unit powers the amp for the sub in the trunk with no problems but the fronts give me nothing. The previous owner told me someone broke into the car and stole the subs and amp and he had to get the audio rewired so I guess that's where the front and rear wiring got switched but I don't know why I'm getting so little sound from my front speakers.

The front speakers might be crossed over high or something in the hu settings.

Care to elaborate a little for me, new to most of the terminology here.
And regardless of what I do in the head unit settings I get nothing from the fronts.

Radios, esp the high end ones provide filters. a HPF or high pass filter allows only higher frequencies to pass through the speaker. IE so your front speakers dont play bass and the sub will have a LPF or low pass filter allowing only low frequencies to play so your sub doesnt play your highs, just the lows. if its set wrong it will play only the highest highs and not the midbass youre looking for. if youre wanting them to play bass then youre expecting too much out of the system. it could be 1 of 1000 things though. It could also be set correctly and the speaker is mounted wrong. say a 6.5 in a 6x8 hole or something to that effect. also if your doors are not sealed (most doors have huge holes in them from the factory so you can repair them) then the midbass wont be there (the door needs to act like a giant box similar to the way your subs have a box) .