To make up for not having the AC power jack, the speaker does have a second pair of composite (red/white) input jacks, cables included, as well as a set of outputs for connecting a subwoofer.
Note that you can't toggle between inputs; both are always active. That's either going to be a feature--say, if you want to listen to music from an iPod while being able to hear the bleeping and blooping from your PC--or a bug, in which you constantly need to mute one audio source while listening to the other, depending on your point of view.
The Audioengine 5 series did not come with a remote, but the 5+ series does include one, which controls volume, puts the speaker to sleep, and can mute it. The 5+ retains the volume control button on the front of the left speaker. Unlike with the 2 series, that volume knob doesn't double as the power switch; there's a separate power toggle on the back of the speaker. However, Audioengine has equipped the 5 and 5+ series with an autosleep power-save mode that kicks in after about 10 minutes when no audio passes through the speakers. (With the 5 series, some people complained that the speakers make a sound when the power-save mode kicks in--and it can be fairly loud if you have your volume up high--which you may find annoying).
Also of note: though the Audioengines aren't technically "certified for iPhone," they are magnetically shielded. We didn't experience any GSM interference from the iPhone (those annoying clicks and buzzes that can afflict nonshielded speakers), even when we left it directly on top.
Audioengine sells some accessories, including the S8 subwoofer ($350) and the W3 wireless adapter ($149, available in March). The subwoofer connects via the red/white RCA stereo outputs on the back of the left speaker. It would obviously allow you to get more bass and even richer sound, but the appeal of these speakers is that you can really do without the sub.
The W3 is a pair of two USB-powered adapters--a receiver for the A5+, and a transmitter for a source PC/Mac--that allows easy wireless streaming. Audioengine says that the W3 delivers 16-bit audio over the 2.4GHz band, and it will be able to transmit to up to three receivers simultaneously. It's also designed to reduce interference from other Wi-Fi devices on the same band.
When we reviewed the Audioengine 5 series speakers, we said it was difficult to quantify how much better they sounded than the Audioengine 2s, but they definitely "delivered bigger, richer sound with deep, tight bass, and excellent clarity--and they played very loud." With higher-end PC speakers you just get fuller, smoother sound that has that much more detail, and when you listen to either the 5 series or 5+ speakers, you start to hear stuff (such as individual instruments) in your music that you weren't aware was there. They easily best more-expensive iPod speakers out there, including those from Bose and B&W, which in some cases retail for more.
In reviewing PC speakers, we like to throw an eclectic mix of music at them, as well as a couple of action movies and games, usually a first-person shooter or two. We also like to do a little jury testing, and for this review, as for the review of the 5 series, I pulled in Steve Guttenberg, who reviews home theater speakers for CNET and had previously praised the Audioengine 2s and the Audioengine P4s (unpowered, passive bookshelf speakers) in his Audiophiliac blog.
For the music test we put the Audioengine 5 series next to the 5+ and compared their sound using lossless tracks stored on an iPod. Quite simply, the 5+ series sounded like bigger speakers with more expansive sound.
As I said, the actual size difference of the speakers is relatively small, but you can definitely hear a difference in sound quality. We're always a little concerned that when companies change a speaker design the sound can get worse (while the price magically goes up). But in this case you get a nice bump in performance moving from the 5 to the 5+ models. It's not huge a bump, but it's certainly noticeable.
As I said in my review of the 5 series, this model will just seem too bulky to leave sitting on a desk. They truly are bookshelf speakers with a more industrial flair to them. However, despite the price bump, once again the bottom line here is that you're going to be hard-pressed to find a 2.0 system that sounds better for the money and has the 5+'s connectivity options.
Yes, we could quibble about there not being an integrated AC power outlet anymore, but the combination of the design improvements (USB port on back), feature tweaks (included remote), and the speakers' exceptional sound makes the Audioengine 5+ speakers worthy of an Editors' Choice Award.