How do you bridge two ampplifiers?

Um, usually when people use "bridging" with amplifiers, they're talking about combining two amplifier channels to produce one amplified signal -- for example, a 2-channel, 100 watt/channel amplifier bridged into a 1-channel amplifier, somewhere close to 200watts.

I'm curious as to how you mean 10.2.  Do you mean sort of "double decoding" to take a 5.1 signal and generate a 10.2 signal?

This would be similar to taking each "stereo pair" and running it through a Dolby ProLogic decoder.  With the way films are currently being made, I wouldn't recommend doing it to the front/center pairings -- there's too much difference there for a clean separation (since often times ONLY the voices are in the center.)  And doing the front mains to produce a "center" for the front soundfield is, well, possible, but...

Likewise, my understanding is that so-called 7.1 systems are already doing something like this for the rear pairing. 

You could, in theory, also do a front-left and rear-left, to simulate a side-left, and likewise on the right.  And, for insanity, the "surround" bring on the right (for the lefts.)  But this works on the assumption that the sound engineers and designers were doing any phase-encoding between the various pairings.  They might, but probably "not really."

Also, from what I recall, running a DPL-type decoding, one looses a tremendous amount of seperation between channels.  My recollection of the numbers was that at-best, a ProLogic "center" or "surround" was only about 30dB off of the mains it came from, meaning quite a lot of correlation, and a general "blurring" of the existing soundfield.  With conventional stereo, this wasn't always a bad thing, particularly if you had more than one person, and/or not sitting in the "sweet-spot."  

In other words, while what I think you're talking about is possible, I can't say it's likely to be successful.  

Of course, I could have entirely misinterpreted what you're asking, in which case...

Leo Kerr

I think we need a definition of "all the audio in my room".

This really isn't the way people usually go about adding more volume.  That is usually done with more power and speakers that can handle it.  Unless you have a stadium (large area) that you are trying to fill with sound, more speakers isn't really the way to go about it.

By adding a second amplifier in-line, you won't end up with twice the power.  It just doesn't work that way.

Exactly doubling the amplifiers and speakers won't make it twice as loud - it will only go 3 decibels louder, which is like "one or two notches" on a normal volume control.

You just need one much larger amp, and a set of much larger speakers.

Why would anyone want to listen to a 2.0 stereo source through 10 speakers?  It seems like we get a request like this every couple of months and it still baffles me.

Jonathan, adding more speakers will not make your system louder, and it certainly will not make it sound better.  In fact, depending on the mismatched brands and models of speakers you use, it could make it sound like a disaster.  You are much better off with a quality 7/5.1 setup than trying to squeeze your sound into 10 speakers, 3 to 5 of which were never meant to be heard.

PS - As a note, most music aficionados play their stereo music sources through 2.0 or 2.1 speakers.  More is not necessarily better, and quite often it is worse.  Go for quality, not quantity.