If my 4 channel amp puts out 150w @4ohms and my speaks have 100w rms, why would I bridge the amp?

 

Speaker ratings aren't carved in stone and many can reliably handle much more than RMS power. More importantly, many perform better with more kick behind them.

On the amp side one reason to bridge is to get the additional power needed for a given speaker, another is to give the amp more headroom. If your speakers sound good at 150W but sound great at 200W and can handle that power that's a no brainer (i.e. moto 602). Bridging the arc and setting gains to limit power to 200W does wonders for the speaker performance and gives the amp plenty of reserve power - it's working well under it's limit/capacity which should be good for longevity.

 

Industry standard headroom for speakers are generally 150% RMS thus u are golden with 100W RMS speaks.

Headroom is good to a point then u cross over into reliability issues. Many folks say the the Moto 602 or the XYZ or the ABC speakers sound awesome at ridiculous watts and I'm sure they do but running the red line on anything has consequences. Watts won't fix inefficient speaker issues long term.

T.