I thought the way phatom powering worked was that the mics pulled from the power box, so that the mics would only pull the 9v it needed, not fry on the 15, but I obviously don't really know...
Okay, I'm going slightly OT here, but I'd like to test/sharpen my physics knowledge.
If you apply a voltage differential to something, it will pull the *current* it needs, based on the resistance the mics provide. However, the voltage drop is constant, unless there's some kind of regulator built into the mics. So the mics will "see" whatever voltage you apply to them, and presumably have a fixed resistance, so since V=IR, the current they draw will fry them.
It's been a while, so I could be off-base. Regardless, I'd call or email Sound Pros. They've always been incredibly nice and helpful in my dealings with them.
The at853r's have a power module built into the XLR connectors. Sound pro's version with the at853 capsules do not have that.
J