Santa Rosa-based Internet service provider Sonic.net continues to grow, despite a drop in dial-up business.

Sonic, the largest independent ISP in Northern California, has expanded its coverage area and is adding subscribers for high-speed DSL service, according to Dane Jasper, Sonic's chief executive.

Sonic also is partnering with smaller Internet providers to offer broadband DSL to their customers, he said.

"That's really growing rapidly," Jasper said. "It's because we're building this large footprint."

In the past year, Sonic expanded to Monterey-Salinas, Davis-Sacramento-Lake Tahoe and Chico-Redding-Yreka.

The growth follows Sonic's entry into Southern California and parts of the San Joaquin Valley. The ISP now has about 47,000 subscribers from Los Angeles to the Oregon border.

But Sonic's dial-up business is declining as subscribers switch to DSL.

"The customer base for dial-up has been shrinking for five years," Jasper said. "We lost nearly 20 percent in 2005."

While some of Sonic's former dial-up customers have signed up for Sonic DSL, others went with rival DSL providers in locations where Sonic doesn't offer the service, Jasper said.

Today, about half of Sonic subscribers buy dial-up service, but dial-up generates only about 22 percent of the company's $13 million in annual sales.

The rest comes from home DSL services, Web site hosting, wireless access and business Internet connections. Sonic's broadband business grew by 50 percent in 2005 and now accounts for about two-thirds of the company's revenue, Jasper said.

Last year, Sonic began teaming with smaller ISPs to deliver DSL over Sonic's network. The local Internet providers were struggling to survive as their dial-up customers fled to DSL.

"We're throwing them a lifeline," Jasper said.

So far, Sonic has partnered with 58 small ISPs around the state. The company now is considering expanding into the San Diego and Fresno markets, Jasper said.

Sonic, which delivers DSL over AT&T lines, is AT&T's third-largest independent affiliate in the western U.S.

Sonic has about 70 employees at its headquarters in Santa Rosa. The business has its roots in an Internet project at Santa Rosa Junior College in 1991, when Jasper and Sonic technology chief Scott Doty worked together on a computer network to serve the campus.

Jasper and Doty founded Sonic in 1994, using two computers and eight phone lines. They are the company's majority owners.

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