THE FIRST FOUR albums by the L.A. rock quartet X have sold only modestly, but they have had an impact far beyond the scope of their sales. Through hard work, inherent talent and uncompromising integrity, X has become the most important punk band in America -- this country's equivalent of the Clash.

The group has proven that subtlety, wit, sympathy and harmony can be worked into punk without blunting the genre's ferocious staccato attack.

With its fifth album, "Ain't Love Grand," X is making a bold bid to bust out of the cult artist ghetto and bring its message to a broader audience. It's the group's first album without producer Ray Manzarek of the Doors. In his place is Michael Wagener, best known for producing the heavy metal bands Dokken and Accept.

Wagener gives X a bigger guitar sound and a harder beat than before. The artistic nuances and self references of past albums are sacrificed for a streamlined clarity that makes the band's basic assets more obvious than ever.

It's no more a sellout than was Dylan's 1965 conversion to mainstream rock. The irresistibly anthemic "Around My Heart" may have the makings of a hit single, but it also captures the anguish of having an ex- lover who refuses to come back and refuses to go away. It's typical of the album's songs, which transform the pain of crumbling romance into unsparing rock'n'roll catharsis.

X -- "Ain't Love Grand" (Elektra, 9 60430); appearing at the Warner Theater Friday night.