I am helping someone set up a 7.1 system. the room was prewired for 5.1 and the only way to get the back two is by using flat wire. the carpet is being replaced so I figured that would be perfect. Here is what we got..
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=100-040

The run will be about 15 feet to a 8 ohm tower and I was wondering if there would be any benefit to doubling the wire if we have enough. (I don't mean bi-amping)
Does 2 16ga make a right?

If you double it, it does increase the gauge; I'm not sure to what, but at least to 14 gauge, I would think. At least then it would be lower resistance, not that I think it's really a factor at that distance.

Chet, doubling up wire creates the equivalent of a a gauge three lower, e.g., doubling 16ga results in the equivalent of 13ga. No, there wouldn't be any significant benefit from this since 16ga is more than enough for a 15' run(see speaker wire table ). Also, unless the two doubled wires are in close contact, this increases the inductance of the wiring, with possible high frequency attenuation.

Right, they do have to be very close together. I forgot about that part.

Yes, running combined twisted pair does make a difference... you get rid of induction... in twisted pair. Doubled up loose wire you won't see that benefit:

http://www.hometheaterhifi.com/volume_10_2/ultralink-CL414-cable-5-2003.html

I can't take credit for that link. I got it from another thread on this board a long time ago.

According to the article above, using doubled 14g results in the current capacity/resistance of an 11g wire. I figured I didn't quite need that so I looked up the stats on 16g.

Twisted pair 14g:
- Conductor diameter close to 8g? Don't recall
- Resistance close to 11g
- no induction

Twisted pair 16g:
- Conductor diameter close to 10g
- Resistance of 13g
- no induction

Personally I'm getting my stuff at the end of this month and intend to go with 16g 4 conducter in wall, from monoprice.

Hope this helps:
snazzed