Running Two Yamaha M-85's

Yes. But..I'm not sure about your pre-amp. I know a Yamaha C-80/85 or equivalent with a set of inverted outputs would make bridging whole lot easier. The M-85's are a common ground amplifier.
 
Is that amp bridgeable (I haven't seen info that confirms it IS)?
If not, then the speakers would have to be bi-amp-able to do what you want.
 
Is that amp bridgeable (I haven't seen info that confirms it IS)?
If not, then the speakers would have to be bi-amp-able to do what you want.

The amp is not internally bridgeable on its own. It is, as Avionic pointed out, a common ground amp so it CAN be bridged if you feed it an inverted signal on one channel. Yamaha built this feature into the pre-amp designed and sold with the M80/M-85 amps. This allows you to feed the Right channel to the Right input, feed the left channel the INVERTED input of the Right channel from the pre-amp. The R+ and L+ amp outputs are then used as input to a single speaker +/-.

BTW, most older JBL speakers, including the 250Ti are RED - and BLACK +, backwards from what you might expect. This generally only becomes an issue if you try to use them in an HT surround setup with other speakers as they will then be out of absolute phase. Modern HT PrePro and Receivers can detect this out of phase if they have auto calibration software like YPAO (Yamaha) or Audyssey.

The 250Ti is not factory bi-amp capable. Even if the speakers were bi-amp capable, you're talking about a vertical stereo bi-amp, not bridging the amps.
 
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