I can't figure this one out, so I thought I would try the forum. I have a Gallien Krueger Backline 600 I have been playing through for 8 months that I got used. Recently my twin 15" Vega EM158s tinsel wires disintegrated in my West bottom (I was told that happens with age), so I went to Guitar Center and bot the Acoustic B-410 bottom to use with the GK. The first bottom started making loud "crack" sounds within the first 10 minutes of playing, and after 2 hours it had a blown speaker. I exchanged it for another and this one made the same "crack" sound when I played a low "A". Now I am playing with the bass turned down to get through the job tonight. Is it my amp, my cord to the speaker, or what? The Guitar Center guy said I might be underpowering the bottom, but my Vegas handle more than 400W and didn't have that issue? Any ideas out there? Is it because the bottom is 8 ohms and the head is 4 or 8? I think the head puts out 180W @ 8 ohms.