Sony SRS-X33 review: A standout mini Bluetooth speaker - CNET
Sony SRS-X33 vs. JBL Charge 2+ (binaural soundcheck) - YouTube
JBL Charge 2+ review: A sweet-sounding Bluetooth speaker that can juice up your phone, too - CNET
Oluv's Gadgets: Review: JBL Charge 2 - the failed new benchmark!
Sony SRS-X33: A smaller but punchier Bluetooth speaker - YouTube
JBL Charge 2+ review: A sweet-sounding Bluetooth speaker that can juice up your phone, too - CNET
Amazon.com: Synergy Digital Speaker Battery, Compatible with Sony SRS-X33 Speaker, (Li-Pol, 7.4V, 1900mAh) Ultra High Capacity, Replacement for Sony ST-03 Battery : Electronics
Oluv's Gadgets: Review: JBL Charge 2 - the failed new benchmark!