Before using the SRM550, I was using the Fender Acoustasonic 150. This is a very good unit for one vocal mic and one guitar. Still, it was a tad under powered for the large venues I was using. Plus, I don't believe it was giving me clear enough vocals. For the guitar, its wonderful. So, I was looking to upgrade my entire system. My gigs are just one vocal and one guitar. After researching several items, I settled on a Mackie ProFX8v2 mixer and the Mackie SRM550 powered speaker. On occasion I will also use a TC Helicon VoiceTone Harmony GXT. After some limited use with the SRM550, I have two observations. First, using the speaker by itself and plugging in one vocal mic and one guitar, it does not seem as loud as I was hoping for a medium to large venue. Its excellent this way in a smaller setting. Still, even though its not as loud as I had hoped, the voice clarity is superb. It far exceeds the Acoustasonic. Second, when used with the Mackie mixer described above, the volume at just the 9 o'clock setting will virtually rattle the windows by using the mixer adjustments. Also, by using a Shure SM58, which tends to be bass heavy, I can adjust the EQ on the mixer and still get extremely loud volume without sacrificing vocal clarity.
I would highly recommend this speaker. Its not so heavy that a 70 yr old cogger can't pick it up. I am certainly more than happy with this speakers performance.