XM Satellite Radio said July 1 it added more than 640,000 new net subscribers during the second quarter of 2005, bringing its total number of subscribers to more than 4.4 million. The gain represents a 53 percent increase in new net subscribers compared to the second quarter of 2004 and an 18 percent increase compared to the new net additions from the first quarter of 2005.

“This was the best second quarter in the history of XM,” company CEO Hugh Panero said in a statement. “The momentum behind XM’s subscriber growth is undeniable. In just one year, XM has more than doubled its subscriber base.”