Logitechs’s Wireless Speaker Z515 is a relatively affordable, rechargeable, wireless speaker system. The unit’s black-plastic shell takes a rectangular shape with rounded edges and a large, metal speaker grille on the front. At 13.8 inches wide, 5.4 inches tall, and just 3.3 inches deep at its thickest point, the Z515 is small and slim enough to fit in a laptop bag or carry-on, and the system weighs barely more than 2 pounds. The included carrying pouch doesn’t offer much padding or protection, but the Z515 is portable with or without it.

On the right side of the unit’s face are two LEDs. One represents battery life; it glows solid green when the internal battery is at least 50 percent full, switches to orange when you go under that halfway point, and then red when you’re in the final 10 percent. The second light shows the Z515’s current wireless-pairing status.

The Z515 can pair with audio sources in two different ways. You can connect via Bluetooth—for example, to listen to iOS devices or to a Bluetooth-enabled computer. But included with the unit is a 2.4GHz, radio-frequency (RF) USB dongle; insert it into a free USB port on your Mac, and you’re paired almost instantly. (You choose the USB stick as your audio output in the Sound pane of System Preferences, which sends all audio to the Z515.) Note that you can connect wirelessly to the Z515 using either Bluetooth or the USB stick—the two pairing modes are mutually exclusive. So, for example, if you previously paired the Z515 with your iPhone using Bluetooth, you must disable that Bluetooth connection (via your phone) in order to connect to your Mac using the USB dongle (and vice-versa).

On the back of the Z515 is a hinged, plastic stand that, when opened, reveals a snug hiding place to tuck the USB stick when you’re not using it. Above the fold-out stand are the Z515’s sole hardware buttons—Power, Volume Up, and Volume Down. The buttons are shaped so that you can tell them apart by touch, which is helpful, since you can’t see them from the front. Not surprisingly, given the Z515’s price and wireless focus, Logitech doesn’t include a remote control.

When you pair with the Z515 via Bluetooth, you can adjust playback volume both from your paired device and on the speaker itself. Using a USB stick with a Mac, however, only the Z515’s controls work; the Z515’s USB stick is treated as a line-level audio output, so your Mac’s volume controls are disabled. While there are arguments to be made in favor of such an approach, I find it frustrating—I frequently adjust the volume, say, when I pause iTunes to answer a Skype call, and I disliked having to reach for the Z515 instead of using my keyboard’s dedicated volume keys.

On the system’s right-hand side is a 1/8-inch (3.5mm) stereo line-in jack for connecting a wired audio source. Doing so disables wireless audio streaming. Next to this audio jack is one for the included AC adapter. Fully charging the Z515’s internal battery takes about six hours, and Logitech says that one charge should get you 10 hours of listening time, which seemed to match with my experience.

I don’t know that you’d want to listen to the Z515 for ten hours straight, though, as the Z515 just doesn’t sound that great. Audio quality from the system’s dual two-inch drivers is mediocre at best—much like an amplified version of my laptop’s built-in speakers. Bass presence is negligible, and treble response sounds muddled and, and louder volumes, a bit distorted.

To coax the best sound from the Z515 that the device can offer, you must use AC power, rather than the internal battery, and connect to a computer using the USB dongle. When run off AC power, the Z515 uses all of its 3 watts; using battery power, the system uses less power in order to conserve battery life. (Logitech doesn’t say how much less power is used; the documentation simply says “less.”) Unfortunately, even when streaming from my Mac over the USB stick—which I’m guessing improves audio quality by using less compression than standard Bluetooth—intermittent stuttering and audio glitches still marred my listening experience.

Granted, the Z515 is the first wireless speaker system we’ve seen that connects via both Bluetooth and RF, and it’s got a built-in rechargeable battery, to boot. These are all features that add to the price of portable speakers. But it seems as though squeezing these features into a $100 package left little metaphorical room for audio performance.

Macworld’s buying advice

When using the Z515 off its built-in battery, I was reminded of listening to cassette-based stereos from the early 1990s—if you didn’t know any better, you’d think they sounded just fine, or even good. But if you told me that you had a $100 budget and wanted a wireless speaker, I’d insteand recommend the Yubz Magnum or Spracht Aura BluNote over the Z515. The Z515’s audio quality is disappointing, and those other similarly-priced models simply sound better. Even when run off AC power, the Z515’s sound quality doesn’t match its features and connection flexibility.