My wife surprised me with a new S1 Pro for our anniversary after seeing how well our L1 M2 performs. My application for this was intended as a practice amp and portable PA for my Roland RD 700, portable PA for my singer-songwriter son, and Bluetooth background music.
After trying this unit, I am disappointed in its performance. The piano sounds (which are great on my JBL monitors and L1) sounded compressed and lifeless. In addition, keyboard splits were distorted with rattling bass. The unit performed well for prerecorded music especially in the country and pop genres (vocals were well represented) however jazz and classical were not reproduced faithfully.
I think that the S1 can be successfully used for guitar/voice or background music applications but as a practice amp or PA for keyboards, it does not meet my expectations. It does not have the dynamic range to faithfully reproduce piano sounds.
Unfortunately, I will be returning it to Bose and hopefully waiting for a new and improved version.