The Thermals’ consistency is both a blessing and a curse. On the one hand, the Portland trio’s records deliver a reliable combination of pogo-worthy punk, garage-rock fuzzbombs, and snaky lo-fi production. But after a decade in existence, the band is starting to suffer from the law of diminishing returns: The more a new Thermals album treads similar ground as previous records, the less essential this new music feels. That’s the case with the raw, distortion-scratched Desperate Ground, the band’s sixth record and first for Saddle Creek. Energy-wise, the John Agnello-produced album is a marked improvement over 2010’s Personal Life; “The Sword By My Side” and “You Will Be Free” are sharp bursts of aggression, while vocalist Hutch Harris’ strident yelps (think a feistier Mac McCaughan) brim with urgency.