You know your product's good when people start copying it. We had a go with the X-mini II and MAX II to find out how good they are at blastin'.
First of all, both of them get a battery that's rated for twelve hours. Realistically speaking, if you regularly use either speaker outdoors at higher volumes, the battery life does drop to about ten, but that's way longer than your average picnic.
What differentiates them however is that the X-mini II is purely a monaural speaker, whereas the Max II is a stereo variant. Both of them feature the BXS (Bass Xpansion System)-- twist the speakers and it “pops” out, revealing an accordion-like plastic tube that acts as a “bass chamber” in larger speakers. You could still use these speakers in the compact mode, but we wouldn't recommend it as you'll be reducing the bass response.
They sound similar too, with adequate bass performance for a small speaker and pronounced mids to highs. Going past the mid volume level, is when distortion rears its ugly head. The higher frequencies got too piercing and edgy, but that's partially why these speakers seem so loud. Cables on the other hand, are much neater for the X-mini II, but it's very short to keep things neat. It can be stowed away under the base of the speaker, whereas the Max II has a longer cable without any cable management.
Both of them are conveniently recharged via a standard mini USB port. Like the original X-mini, both of them feature a "buddy-jack" port, for you to daisy chain as many speakers as your want for extra volume that's going to wake the neighbours. At the end of the day, considering that many manufacturers offer compact portable speakers that are similarly priced, none of them come close to achieving the volume levels and the battery life of these X-minis.