Quote Originally Posted by RGA
Not all speakers are matched to one another very closely - there could be a variety of reasons but why not take em back to the dealer and get a new set --- sometimes this just happens -- There could be a crossover problem or some internal problem.
Unmatched speakers really only suffer in the bottom end as most are crossed over well before they begin to roll off, well outside an even 20% tolernace range which the cheapest drivers surpass. Except in rare cases. The other area could be voice coil inductance and efficiency, though this would vary considerably less.

The benefits of closely matching drivers can't be overstated though, that bottom end extension of the driver can really skew things though. Especially when you level match your speakers at a higher frequency, and have say the right side roll-off earlier than the left. A total soundstage shift and possibly poor imaging.

In this case I wonder if there's an unusual defect in one of the drivers that didn't get detected earlier.
Could be any number of possibilities - over damping, a port blocked, faulty element in the crossover.

StateDJ85, could you explain for across which frequencies you hear the difference in sound? I'm sure you've checked to ensure the wires are connected in proper polarity. Did they sound fine with your old receiver/amp? Perhaps it's the receiver, not the speakers?
As RGA suggested, I'd contact your dealer before dragging this on much further.