The Philips BT2500B is one among many inexpensive micro Bluetooth speakers to hit the market in the last couple of years. A lot of speakers of this type have more of a canister design to them, but what helps set this one apart is its relatively flat design, which makes it easy to slip into a bag or even a pocket. It's also modestly priced at around $45 online.
Though you can sit the speaker up vertically, it's really meant to be laid down flat with the driver firing upward. In that sense, it looks like a portable speakerphone and happens to offer that feature as well. I can't say the build quality or all-plastic design are all that swanky, but the speaker looks fairly attractive and has enough heft to it -- it weighs 7.7 ounces -- to steer it away from feeling cheap.
Like a lot of these little speakers, the 3.9x3.9x1.3-inch BT2500B plays louder than its size would indicate, and I liked the analog volume knob, which gives the speaker a slightly retro look and, more importantly, makes it easy to raise and lower the speaker's volume.
That same volume knob can be found on the step-up BT3500, which costs around $30 more and is essentially a double-wide version of the BT2500B. It adds NFC tap-to-pair technology for devices that support it, but otherwise the two speakers have identical feature sets and include the standard audio input for non-Bluetooth devices.
It's hard to say which speaker I like better. I thought they both sounded pretty good for their size, though as you'd expect, the larger BT3500 does sound a bit fuller and plays louder; it's clearly the better performer. However, I like the design of the smaller BT2500B. It's literally pocket-size.