Semi-supergroup alert: Sad Planets co-stars Black Keys drummer Patrick Carney and indie-rock singer-guitarist MVP John Petkovic of Cobra Verde, Guided By Voices, Sweet Apple and assorted other bands. So you’d expect them to be able to put together a decently sweaty, gritty indie-rock and garage-blues gem. But for the most part, you’d be wrong. Supposedly, their debut album Akron, Ohio — named for their shared hometown — was the result of the duo hanging out in the studio and winging it. Too often, that laissez-faire attitude manifests itself in underwritten songs with meandering arrangements and a decided lack of hooks. When they do hit the mark, the scrappy power-poppy results sound more like Big Star or John Lennon knockoffs than anything that reminds you of their previous bands. It’s not exactly a total failure, but for much of its 35-minute running time, the sadly disappointing Sad Planets proves that two heads are not always better than one.