by Michael GallucciThe best of the late-'90s R&B crooning quartets ups the musical ante on their sophomore album, lacing the silky-smooth grooves with splashes of street-tough shouts that are meant to antagonize as much as they are to seduce. And for a good deal of Enter the Dru, the formula works. There's a gutsy edge to the songs here (especially the hard-knocking "How Deep Is Your Love") that make one-time peers like Boyz II Men sound like the soulless R&B robots they are. Even when they get all warm and cozy with Babyface on the potentially mushy "These Are the Times" (in spite the absurdity of the straight-faced line "Tear you up in little pieces/Swallow you like Reese's Pieces"), Dru Hill slice into the section of '90s soul music that crosses bedroom come-ons with classic street savvy (and nervy beats) without sounding at all whipped.