SiriusXM reports revenue for the second quarter was $838 million — up 13% over the same period in 2011.

Net income for the second quarter 2012 and 2011 was $3.1 billion and $173 million, respectively. Adjusted earnings before interest, taxes, depreciation, and amortization for the second quarter of 2012 was $237 million, up 28% from $185 million in Q2 2011.

Strong auto sales helped the satcaster add more than 600,000 subscribers in the quarter, for a total of 22.9 million paying customers.

SiriusXM CEO Mel Karmazin called the subscriber numbers a “post-merger record,” and credited higher revenue and “tightly controlled expenses” with helping to produce adjusted EBITDA as well as free cash flow, which was $230 million in the quarter. That’s a 39% improvement over the same period a year ago, and a record for free cash flow generated in a single quarter for the company’s history, according to Karmazin.

The company announced its SiriusXM On-Demand service to its online subscribers via the Internet and smartphones, and the satcaster’s plans to launch a personalized music feature by the end of the year.