I’ve seen just about every type of iPad case in the two years that the world’s best-selling tablet has been on the market, most of which are variations on the theme of protection.

Some of them act simply as cases, some are ultra-protective, and others add a keyboard. But the iMainGo XP (US$119.00 MSRP) case from Portable Sounds Labs is the first iPad case I’ve seen that includes a powerful set of stereo speakers.

The case isn’t exactly skinny as it contains a 2100 mAh rechargeable battery to power those speakers. iMainGo recommends charging that battery for eight to ten hours to get full life out of the speakers when you’re watching movies or playing DJ at a party. In full use, the battery will last for about six hours of use. The case was designed to work with the original iPad, then came with a snap-in insert to work with the iPad 2 and the new iPad.

DJ’s are going to love this portable setup for small parties. It protects your iPad in transit and it can actually crank out some decent sound. The specs say that the iMainGo XP only puts out 5 watts per channel, but it sounds much louder than that. I found it to be quite loud for personal listening with the iPad’s volume control turned up only half way, and it was intolerable to my wife in the next room when I played some music at full blast.

At a lower volume, the iMainGo XP did a wonderful job while I was watching HDTV through the Xfinity AnyPlay box in our house or watching movies from iTunes. There was good stereo separation, and the tuned bass and additional tweeters made movie soundtracks come alive.

The case isn’t exactly lightweight — without the iPad inside, it weighs in at almost two pounds. The case provides an external on/off button for the iPad, access to the volume rocker and orientation/mute lock. The speakers have a sliding lock to hold everything together and closed, and there’s an external stand included in case you want to tilt the iPad back a bit for easier viewing.

To pass your music to the speakers, the iMainGo XP doesn’t use Bluetooth. Instead, there’s a standard plug that you plug into the iPad’s headphone jack. There are also a pair of headphone jacks on the case — one of those can be used to daisy-chain a second iMainGo XP to the first for even more sound.

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