Tone is so subjective, but if you're not happy, it could be down to one or more of many things Dave, some less likely than others. Why not post your setup details - what steel; amp/speaker; settings; bar weight; how old are the strings; E9/C6 or both, etc - as much as you can and there'll be loads of feedback!! It would be a good topic for a new thread.

PS many 15in speakers have been THE business over the years, EV, JBL, Black Widow etc. etc. The reasoning was that 15's responded better to the wide range of frequencies put out, especially the bottom end of C6th. But then, 2x12 was also "standard" at one time. Now a 1x12 seems to be accepted as "it", at least for E9th(?). You need to try things before coming to a conclusion as to what's best for you. If your band and the punters are happy you're probably on the right track?