Editors' note (February 21, 2012): The speakers reviewed here have been replaced by the newer Audioengine 5+ speakers.
We've been a little tardy in reviewing Audioengine's PC speakers, but we're glad we finally got our hands on both the 5 series ($325) reviewed here and the step-down Audioengine 2 series ($199) because they really are quite impressive.
The key thing to note about both sets of speakers is that they are bookshelf-style speakers masquerading as PC or "multimedia" speakers (as these things are apt to be labeled). But unlike classic bookshelf speakers, these Audioengine models are powered (via a standard AC plug); there's no need for a separate receiver or amplifier, so you can use them with any audio source. The larger 5 series is the more industrial-looking (read: less stylish) of the two models and appears to share some heritage with monitor speakers you'd find in a recording studio. It's available in either black or white, as are the 2s. There's also a bamboo version of the 5 series that costs $449.
The Audioengine 5 speakers measure 10 inches high by 7 inches wide by 7.9 inches deep. They each have a 5-inch Kevlar woofer and a 20mm silk dome tweeter. Because the left speaker houses the amplifier (50 watts per channel), it's heavier than the right speaker. Unlike the 2s, which are ported on the front, the 5s are ported on the rear.
It's worth noting that both the 2 and 5 series Audioengine speakers come nicely packaged, with cloth covers over the speakers and cables. The left and right speakers connect to each other with "real" speaker wire (included) and you also get an input cable that allows you to connect your PC to the 3.5mm aux input on the back of the left speaker. The use of standard cables means that--unlike some speakers with proprietary connections and cables--you can invest in custom-length cables that are as long or as short as you'd like.
What's most unique about the Audioengine 5 speakers is the 3.5mm aux input on top of the left speaker that sits next to a USB port. To be clear, the USB port is only for power, not for reading audio files; it also doesn't allow pass-through syncing to PCs. But that combination of USB power-plus-audio input allows you to charge your iPod/iPhone with a USB cable while you're listening to your music. And though the cables make it a bit less appealing to the eye than a standard iPod dock, the combo is far more universal in its compatibility: you can charge 'n' play any USB-powered audio device, including a wide array of non-Apple music phones and media players.
It gets even better: the second 3.5mm input on the left speaker's backside is located near a full-on AC power jack. Audioengine touts the fact that you can plug an Apple AirPort Express directly into the outlet, turning the speakers into an iTunes streamer (via Apple's AirTunes functionality). Of course, that outlet can also power any other audio source--anything from a Sonos or Squeezebox streamer to a CD player.
Note that you can't toggle between inputs; both are always active. That's either going to be a feature (say, the ability to listen to music from an iPod while being able to hear the bleeping and blooping from your PC) or a bug (the constant need to mute one audio source while listening to the other), depending on your point of view.