Measuring 10.3 by 5.3 by 1 inches, the folded-up inMotion is roughly the size of a slim hardcover book, and at 28 ounces, it's a little heavier than other portable speakers in its class. The twin speakers swing open in a smooth, firm motion, and you can tilt them at any angle, up to 180 degrees from the base. The power switch and the volume slider sit on the curved front section, while behind the base, you'll find an AC input, a minijack port, and a minijack plug on a retractable cable. There isn't a custom dock for an iPod, but our 20GB model sat comfortably atop the rubberized base. You can also plug the iM4 into your laptop with the included minijack-to-minijack cable. All that's missing is a remote control--a disappointing omission, given that the iM3 comes with a nice, wafer-thin remote that slid right into the assembly.
We were pleasantly surprised by the Altec Lansing inMotion iM4's full-bodied sound. In our experience, fold-up, portable speakers usually can't hack it when it comes to bass (the iM3 comes to mind, actually), but the iM4 delivered rumbling lows and crystal-clear high notes--impressive, considering the speakers' small size. We dialed up Led Zeppelin's Physical Graffiti, and the iM4 cranked out the thumping bass and soaring strings of "Kashmir" without skipping a beat, even when we turned up the volume to ear-splitting levels (very nice). The iM4 can also power from four AA batteries for a promised 18 hours of sound.