Driver matching vs break in period


I installed a new mid range driver for my B&W 803 SII and noticed that the image shifted to the speaker with the older driver. I got out my radio shack SLP meter and found that the new mid range driver was about 2-3 DB lower than the old driver in the other speaker. I ended up reinstalling the old driver and putting the new one back in the box. The question is: Is this a matter of matching drivers, or is a matter of allowing the new driver to break in, or is a bad driver? Any thoughts?
koryodell
I did switch the "new quiet" driver to the other cabinet and it was still "quieter", so it was not the crossover. I also might have over emphasized image shifting issue, while the image did shift a it was the additional "loudness" that was the main issue. at times, it was almost like having one speaker in the room, especially on vocals. My guess is that the driver might have been well matched with my cross over. Maybe I'll email the B&W representative and ask them what the issue is.
That sounds like a good move.I've had hard,or a little brighter on a couple mids in the past.On woofers,I've had boominess until it broke in.I can't ever remember a quieter one.At least they will know of the problem so you don't get stuck with an unusable driver.
Here is B&W's response:

"The speakers are all calibrated to a specific spec. Please check the capacitors and resistors on your crossover network. Too often I have seen this open."

Maybe I'll check the crossover values, but I'm not sure why it would be the cross over when the problems follows the driver when I change it to the other speaker.
It sounds like a typical I don't want to be bothered answer.Just give me my paycheck.They used to work with a customer from what I remember.
To check the crossover, do I need to actually get to the resistors, capacitors, etc? Or can I measure the value at the speaker leads and compare it with a new crossover?