After I made the discovery, I took a closer look at the specs on Sony's website and saw that indeed it has two output ratings:
- Output : 5 W x 2 + 10 W (AC power), 1 W x 2 + 6 W (battery power)
You can look at this one of two ways: it's either a flaw in the speaker (after all, it should sound the same when it's running on battery power), or it's a plus that you can plug it in and get even better sound out of it. I'm on the fence on whether to knock it for this issue, or to give it a pass. I'll leave it a draw for now.
Since it has some bass ports on the back (there's one full-range driver along with two subwoofers), it helps to place the speaker near a wall to get some reflection. I thought it sounded really good in a smaller room, but it didn't do quite as well when I took it into our large video studio.
Pressing the "audio" button on top allows you to enter a ClearAudio+ mode that seems to widen the soundstage a bit, but stereo separation is clearly lacking (that's almost always the case with these types of small speakers where the drivers are so close together).
I put a lot of different kinds of music through the X5 and overall found it to be pretty well balanced, with a warm, clean midrange that made vocals sound crisp and present (it excelled with Michael Jackson's a cappella version of "Never Can Say Goodbye" and Sam Smith's acoustic version of "Latch"). Treble detail was good and not over-accentuated (for instance, when I listened to Spoon's "You Got Yr. Cherry Bomb," the tambourine that runs through it didn't overpower the rest of the song).
As I said, for a small speaker, it delivers a lot of bass, but it doesn't quite play quite as loud or deliver quite as much bass the Bose SoundLink Bluetooth III. But plugged into its AC adapter, it isn't far off. And while the SRS-X7 is a larger speaker, it arguably doesn't sound as good. That seems weird, but it's the impression I got.
In the end, there's a case to be made that this is a better buy than the Bose SoundLink Mini. It may not be as compact (the Bose Mini weighs significantly less) or have quite as sturdy a design, but it sounds as good or better (as I said, it helps to have the speaker plugged in), it adds speakerphone functionality, and it costs slightly less online.
Either way, it's one of the best sounding compact Bluetooth wireless speakers in the $150-to-$200 price range, and it's definitely recommendable if you're looking for a wireless speaker that you plan on using mainly indoors.