One speaker putting out -3db less?

One of my speakers is playing around -3db less than the other. I switched the speaker cables to make sure it wasn't a channel in my amp. This just recently started. I also turned my sub off when I checked it. I used a spl meter to do so. My amp is a B&K reference 200.2 and my speakers are Paradigm Studio 40 v4. Any ideas what can be causing this? My speaks are only 2 years old and I do occasionally crank them, but never all the up.
You need to use white noise to test and mono if playing music.

Look for a tweeter that is not working.

Make sure the connectors are all clean and tight.

Use contact cleaner and clean the volume and balance controls. Shut off power and twist knobs multiple times.
If you've had "terrible static", definately unplug all of your equipment, wait a minute, and plug it back in. You might be quite pleased with the result.
04-13-10: Audiofeil
The speaker cable length, if different, is inconsequential.
Audiofeil (Threads | Answers)

Likely right, but there could be a difference, if slight, depending on the length discrepancy and cable specs. Being a forum and asking for advice, I'll chalk it up to 'covering all the bases'.
My speaker cables are the same length. And as far as room boundaries, these speakers, and everything else, have been in the same spot for almost 2 years. I used a Blue Sky calibration disc.

40-80hz I'm almost dead even.
500-2.5hz there's a huge difference.

I hope I haven't huffed a tweeter. My local Paradigm dealer quit carrying them a couple of months ago. Any ideas where to get parts? This is a very unwelcome developement.
Thanks again for everyones help.