Probably a stupid idea .. but no question is stupid if you learn from it so here goes.

I have a 2 channel amp that can be switched to produce a stereo or mono signal (ie .. left/right signals as per channel or mono signal on each channel).
The amp can push at 4 ohms per channel or 2 ohm per channel and bridged at 4 ohms.

I am wondering what would happen, electronically, if I set the amp to push a mono signal from both channels and then combined the left and right signal and the ground wires and hooked them into my sub box. The box is an 8 ohm system.

Would this feedback into the amp and possibly blow it?
Does it do anything to the impedence matching of the system?

 

Probably not a good idea the way you are thinking (wiring wise) but you are have the right idea, You can combine the channels so to speak, usually requires a positive from one side and a negative from the other side, no grounding required. I haven't seen an amp yet that didn't recommend connecting L+ to R- for bridging. You can do this safely, yet still be at half of your max output due to the high impedance of your box. But this way is better than just hooking it to one channel.

 

So, basically, I should just bridge it for the 160watts @ 4 ohms and hook it to the box. I'll just get 80 watts across the two speakers (40 watts each?) ?

 

Yup! -that is assuming on my end that you have only one connection to your box - and it reads 8 Ohms. Then everything you said is correct.

 

What kind of box do you have? Does it have 1 woofer or 2? You might be able to rewire the sub(s) to work better with the amp.

 

2 ohms would be about the only option to rewire if he pulled them out of the box.

If they are wired together for 8 ohms, its either gonna be two svc 4 ohm subs series wired, which could be parallel wired for 2 ohm.
OR
two dvc 2 ohm subs, each sub wired in series, then series wired together for 8 ohm.
Again they could be rewired for 2 or .5 ohm.

but since he has a 2 channel amp its a very small posibility that it can handle a 2 ohm load bridged.

 

Most Amps will handle a 2 ohm load, but not bridged. Bridged watts are almost always 4 ohm. Check your Amp specs, you could fry it, and that would be bad.....no thump =

 

It's 2 4 ohm svc subs .. We decided to tear the box open, rip out the wiring and wire the subs seperately (with two inputs to the box). The Amp has a mono/stereo input switch so both channels should be putting out the same signal when we put it on mono. The amp isn't very powerful. Not sure what my brother was thinking when he bought this thing. But he's an old geezer (*chuckle* 40 in a couple of weeks) and he says that he doesn't need tons of power and that everything he's read about the JBL P80.2 sub says it puts out a lot more power than it's rated for. We'll see.

Thanks for the replies everyone.

 

Yeah, those JBL Power series amps are underrated. My 600.1 is more like 700 watts.
Cheap price, reliable, and built pretty good, cant beat them for the money.