Altec Lansing Technologies is showing its latest inMotion iM portable audio speaker system for music players, including iPods at Macworld Expo, San Francisco.

The inMotion iM4 Portable Speaker System has a stand-up rubber platform measuring 10.25-inches-x-5.3-inches-x-1-inch (26.03cms-x-13.46cms-x-2.54 cms), with speakers on either side. When the system is in use, the middle of the platform can fold down to hold a portable audio player while the speakers remain standing. The iM4 can deliver 18 hours of audio playback on its four AA batteries. It weighs 1.75 pounds (0.79 kg) without the batteries.

The speaker system uses a 4-watt digital amplifier and has technology to produce deep bass without a subwoofer. A retractable cable connects the system to the portable audio player, and a second audio source, such as a PC, can be connected to the speaker system with an auxiliary input jack.

Available in several colours, including iPod white, the $130 system ships in the US in February.