There is no sign pointing to the Signal 66 gallery. To find it, one must leave N Street and walk down Blagden Alley past a row of garages. A single mailbox on the red brick wall bears the correct number, 926, but there's no door--it's hidden around the corner. One couple, however, clearly knows the trick. The buzzer is a little hard to see, but the man fingers it without a second guess. When the door swings wide, they are welcomed with a smile and a wave.

Inside, several hundred other in-the-know art lovers are pressed shoulder to shoulder. They've gathered via word-of-mouth, mostly, though some have been lured by postcards passed by friends. The crowd includes respected local artists, members of the music scene, curators and those faces that are familiar from other art-scene gatherings. From the far corner, a band in garish outfits fills the room with its ruckus. Video imagery streams overhead on a huge screen.

As visitors mill about, beverages in hand, some break away from chatting to peer at the artworks. Above the entrance hang images from old engravings, blown up and colored in neon pop-art style, by the married artist duo known as Clark-Hogan. Stretching upward for yards, Manon Cleary's comical series of nude photographs covers an entire wall. On the adjoining wall, Ken Ashton's "Megalopolis" photos document the sprawl of the I-95 corridor. They are balanced by John Figura's painting of Icarus plunging into the sea, just opposite. The selection of artworks is as eclectic as the crowd, which has deserted the Dupont gallery walks and the Seventh Street arts district to trek to a lonely ex-warehouse in Shaw. What's all the buzz about?

"Every city has interesting alternative spaces," says Signal 66 co-owner Stephen Lewis, "but those are mostly run by hired arts administrators. That's a very different philosophy. They see themselves as bastions of culture, and everyone else has to step up. We're populists. We know there's a large segment of the population that's smart and will tune in."

No doubt the music, the videos, the party atmosphere and the thrill of the inside scoop don't hurt the gallery's draw. Not to mention the bohemian feel of this converted industrial structure, which is unique among Washington's gallery spaces.

Signal 66 is the brainchild of three area figurative painters--Lewis, Figura and Pat Rogan--plus video artist and former Betapunk Eric Gravley. The four have long maintained studios on the second floor of the building, a pre-Civil War livery stable-turned-warehouse, where they occasionally held one-night shows. A permanent gallery space, however, eluded them. After the previous tenant vacated the first floor, the artists found an investor and approached their landlord, Giorgio Furioso, a former painter turned developer (and board member of the planned Washington Arts Museum). Furioso accepted and even helped underwrite the cost of improvements.

Unlike row houses or storefronts, which are common to D.C.'s art scene, this building is wide and tall, with few interior walls and supported by thick, unfinished beams. The loading dock, with its enormous door, allows entry for oversize paintings and sculptures without dismantling them. The space can be tailored to the vision of the artists and curators.

While common in other cities, such former industrial structures are rare in Washington. It's a space like one might encounter in Brooklyn or Philadelphia.

So far, Signal 66 has relied on recognized area artists, though future shows will include larger names (Pin Morales, local curator Ramon Osuna). Submissions are also being accepted through July 12 for the gallery's first juried show, opening late this month. With bigger names and increasing visibility, the four partners foresee more lucrative sales.

"We're targeting a different demographic, not just lawyers and accountants," says Lewis. "This area has a lot of young people. Plus some who are 35 and multimillionaires, now that they've gotten out of school, worked and made money. We're offering good art they can see, plus good bands they wouldn't otherwise see."

For the time being, postcards announcing upcoming Signal 66 events still get passed hand-to-hand. There's no Web site as yet. There's not even a sign pointing down the alley. Yet Lewis doesn't seem concerned. "The whole idea is grass-roots," he says. "What has to happen is there needs to be like five of these spaces, and then the whole art scene in D.C. would change."

Signal 66 is located at 926 N St. NW (rear), in Blagden Alley. For information, call 202-842-3436. Gallery hours are Thursday from 1 to 5 p.m., Friday from 5 to 8:30 p.m., and Saturday from noon to 6.

CAPTION: Signal 66 stands apart from other D.C. galleries. It's in a converted warehouse in Shaw.