I am planning to build yet another extension speaker for my GK MB150E combo amp. The current design on my drawing board is expected to have the same low end frequency response curve as the combo, but with a 15" driver for higher efficiency plus greater power handling for future use with a more powerful amp head. I am aware that most URBists don't like the sound of 15's. But based on a fair amount of study, I expect the box design to overcome the typical "boomy" sound associated with commercial 1x15 cabs. Driver choice and box design play critical roles. Or, I could change the frequency response to give the speaker more "boom" than the MB150E. Or less. With a small box, those are the basic options, and therein lies my dilemma. I am happy with my overall sound, but would like to hear from other bassists whether you think the MB150 combo should have more or less low end for the best possible sound with URB. This is a chance for me to get a variety of opinions before I commit to cutting plywood. If and when I am successful, I will happily share my design.