There should be a warning label on the Bad Brains' new album: ''Caution: Contents are Volatile.'' The first album in five years from this hugely respected punk/dub band is explosive.

Produced by the Beastie Boys' Adam Yauch using analog tape and equipment, ''Build a Nation'' delivers a potent mix of speed, wicked riffs, and HR's powerful vocals. It's a full-frontal assault. Your ears may start ringing just by holding this CD in your hands.

Guitarist Dr. Know and bassist Darryl Jenifer are in top form with their deft, bewilderingly fast riffs, and drummer Earl Hudson holds it together for the wild range of vocals erupting from his brother, HR.

That is, when the Brain's have their switch turned to rock. On the other hand, ''Build a Nation'' is also a mellow dub reggae album built on a rich brew of textured rhythms and sounds.

While past Brains' albums have been largely hardcore (such as 1986's seminal ''I Against I'' which has one of the heaviest rock intros ever recorded) or intoxicatingly dub (2002's ''I And I Survived''), the 14 tracks on this collection swerve between the two genres, or weld the two into a wicked creation, such as on the opening track ''Give Thanks and Praises.''

Be warned: You may be coming off a mellow groove like ''Jah Love,'' but if the track switches and you hear Hudson make a quick, sharp click with his sticks, you better either turn the volume down fast or be prepared to thrash your head.

CHECK THIS TRACK OUT: The album's dub cuts are each exquisite, but you'll be playing ''Natty Dreadlocks 'pon the Mountain Top'' over and over as you sing along with HR's vibalicious vocals.

By MICHELLE MORGANTE Associated Press Writer

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