The A4 is a speaker that plugs into the wall -- this isn't battery operated. It has that kind of super-shiny finish that finds fingerprints in the air and attracts them (<-- hyperbole).
You _can_ use it by connecting to it wire-fully, or through Bluetooth, but that's not why I bought it. I bought it because it will also do AirPlay if connected through a LAN. Since we're very Apple centric, and T. likes to control what happens on the TV through the Apple TV, I was betting that he'd be happy to play music from his iPad on the speaker. And indeed, he is.
It sounds nice. We stuck it on a bookshelf, which is suboptimal from an audio perspective, but it has a nice range and relatively precise bass.
If you are have an Apple centric batch of devices, and would like to share your music, not just listen to it yourself through earbuds or headphones, think about this when you are shopping for a speaker. I'm sure there are other options out there. But I bought this one based on the WireCutter review.
When I bought it on Amazon in September, it was $179.
R. is not overjoyed about the lack of an internet radio on this device. I do not care one tiny little bit.