I want to say 30... Why do that though. Anything above 0 hurts my ears in this car. To say that I'm unimpressed is an understatement. If you guys were to actually see the Bose sub you'd laugh. It's a 5.25" "sub"woofer in a thin plastic waveguide (1/4 wavelength transmission line) enclosure. That thin plastic picks up resonance like crazy. Not to mention, it's smaller than the door drivers. The upper midrange sounds like ass because they didn't put any filters on the midwoofers. They're just relying on the woofer's natural rolloff. What would two small inductors have cost mazda/bose? A dollar? It has the harshest midrange of any stereo I've owned.
One positive, the imaging and stage height are good.
All the factory stuff, except for headunit are out of my GT. Still working on my alternative.