Is this a good idea?

I just bought a 2 ohm amp and im thinking i can still use to run 4 ohm speakers?

Or, can i run a 4 ohm 12inch subwoofer?

Its 280 brigded.

 

yea - but if given the choice, purchase speakers that can be run @ 2 ohms

 

Well, if it's 2 ohm stable normally, then it's only 4 ohm stable bridged. I assume this is for a subwoofer, unless it's a 4ch amp, because otherwise you wouldn't bridge it.

 

No, any amp can handle greater impedance than spec. Increased impedance reduces current flow so there's no worry of burning out the output stage (you can run 18-ohm headphones off any amp as long as you don't turn it up enough to blow the headphones). Of course that means reduced output power as well so it's not the optimal solution but it will work.

The reverse is not true - you can't run lower impedance than what the amp is rated stable for (i.e. don't run a 1-ohm load on a 2-ohm stable amp). Lower impedance increases current flow causing more heat and damaging the amp (except for the protection circuit built-in to many amps).