How much power is getting to this sub??

My friend has a 400 watt 4 channel amp. He has got the sub hooked up directly to one of the speaker terminals, he isnt running anything else off the amp. So is he getting 400 watts of power to the sub or just 100 watts?

 

Its 400 watts total, i just know the basics about this, and was just wonderin

 

on the connectors on the amp were all the different channel hook ups are. their should be one that surrounds them all that says BRIDGE the one of the line will be pointing to a negative(-) and the other a positive(+). hook it up to those to get the 400 watt max

 

alirght thank you for the help, those pics help out a lot

 

Can you bridge any amp?

 

No, I don't think you can bridge ANY amp. When you bridge one, you end up with 1/2 as many outputs, hence you will have 2 on a bridged 4channel amp (as seen in pics above). He can run another sub off the other output if he has the room OR....

He can get a dual voice coil sub and wire each bridged output to one side (voice coil) of the sub. In this way he will get full output from the amp. As things stand now he is using 25% of what's available, and even using one bridged output on a single channel sub he will only be getting 1/2 of what's available.