We have been pairing two JBL Flip 3s via this app; both were purchased in December 2015. The first step was to update the software on both of them (one at a time) using this app and connecting the speaker to a power source. When paired with each other using this app it worked well enough (it even differentiated the speakers based on their actual color), though any kind of volume change would cause one speaker to cut in and out for 10 to 20 seconds until it "caught up." Im not sure if this is because the phone is connected to only one of the speakers and then that speaker is connected to the other speaker, or perhaps it could also be the phone is connected to both speakers at once and the bluetooth signal isnt quite strong enough. Either way, there is a lag time for any volume inputs that *would* be slightly annoying in a party setting. Once "caught up" though, it worked well. It seemed the max distance for the phone from the speakers was cut way down when paired with both. I would recommend having the phone somewhere between them. Worth a download, but will hopefully be updated to be even more seamless (if that lag is even fixable).
Gfthomas about JBL Portable