Ok, I don't get it. Serious amplifier question

[Maximo]

I am in the hunt for an IB sub amp. I have seen several that are rated in stereo for both 4 ohms and 8ohms. But when bridged they are only rated at 8 ohms.

Why?

 

[Towen7]

When bridged the power is doubled. If run to a 4 ohm load the current draw would also be doubled and apparently those amps can't handle outputting that much current.

 

[Flint]

When bridged mono, the load presented to the output circuit for each channel is halfed. So, if you have an 8 Ohm speaker wired to a single channel, the load on the amp is 8 ohms. If you take that same speaker and connect it to a bridged amp, the load to each channel of the amp is 4 ohms. So, if you put a 4 ohm speaker on a bridged amp, each output section sees a 2 ohm load and you have problems.

It really is that simple in practice, though the physics is more complicated.

 

[Maximo]

I got ya. I get it now, thank you!