Funny I bought a new 75w creamback to use in an extension cab for my ac15 so I could run 2-12's.. (internal speaker and extension cab) Funny thing is: I tried it for first time this morning and the extension cab sounds louder than the internal greenback. I think it's because it's 1. Fresh out of the box new. 2. Could be the difference in impedance. (30watt greenback vs. 75watt creamback.) Thoughts? Probably just needs to get broken in.