The iMainGo X is the latest in Portable Sound Laboratories’ line of "speaker cases" for the iPhone and iPod. The iMainGo X is more versatile than the company's iMainGo 2, ( ) while offering a similar combination of protection and good sound.

Since the original iMainGo, released back in 2007, Portable Sound Laboratories hasn’t strayed much from the initial design of its product. The iMainGo X still uses a two-part, clamshell case that zips closed. One half houses the amplifier, speakers, and battery, while the other half holds your device. (You connect the iMainGo X's audio cable to your iPod or iPhone's headphone jack, adjusting volume with your player's own volume control.) When closed, the iMainGo X measures 5.7 inches long, 3.8 inches across, and 2.4 inches thick; it weighs 1.5 pounds.

The biggest difference between the iMainGo X and its predecessors is that the iMainGo X uses a rechargeable, Lithium-ion battery instead of four AA batteries. Portable Sound Laboratories says the battery can last up to 12 hours; in my testing, the battery lasted 11 hours, 40 minutes with my MacBook Pro's volume set halfway between minimum and maximum. The iMainGo X's battery powers only the speakers—unlike docking speaker systems, the iMainGo does not charge your iPod or iPhone's battery.

The iMainGo X's two speakers are slightly bigger than those in its predecessor—37mm compared to 32 mm. Fortunately, the larger speakers maintain the audio quality of the iMainGo 2. Bass response is surprisingly—and pleasantly—full, and midrange tones have good warmth. (Compared to the iMainGo 2, the iMainGo X has more warmth, but it's not significantly better sounding.) On the downside, the iMainGo suffers from common drawbacks of compact speaker systems: If you turn up the volume all the way, audio is badly distorted, and since the speakers are close together, it's difficult to notice any stereo separation, so you're not going to get "real" stereo sound.

With the iMainGo 2, you had to remove your device from case if you wanted to use headphones instead of the speakers. The iMainGo X, on the other hand, features not one but two pass-through headphones jacks on the outside, as well as a 3.5mm audio-in jack that lets you use the speakers with other audio sources. You can even combine these input and output jacks to daisy-chain multiple iMainGo X’s together, though if you want to connect a device other than an iMainGo to the audio-in jack, you’ll have to provide your own 3.5mm audio cable.

Portable Sound Laboratories also redesigned the device compartment in the iMainGo X to be more secure. The iMainGo 2 used a plastic panel and a Velcro strap to hold down your device; the iMainGo X use a larger plastic panel that snaps into place. The panel is also backed with foam, so your device fits snugly, and the clear, vinyl panel that lets you to see and control your device when in the case is now sewn into place, so you don’t have to worry about it falling off.

At $70, the iMainGo X is $30 more than the iMainGo 2, which is still available. While that may seem like a big price difference, once you factor in the cost of replacement—or rechargeable—batteries for the iMainGo 2, the difference in cost isn't nearly as significant.

Macworld’s buying advice

The iMainGo X takes what worked in previous iMainGo products—a protective, zippered speaker case with good sound quality—and makes it better with a rechargeable battery, and headphone and audio-in jacks. It’s an excellent portable audio solution for your iPhone or iPod touch.