Pandora’s number of premium subscribers grew to 2.5 million after the company acquired 700,000 new subscribers in Q1 of 2013, according to a recent press release, giving Pandora the largest US subscriber base of any online music subscription service.

The subscription numbers  also allowed the company to garner $20.4 million in subscription revenues in the first quarter alone, a 100% increase over the $10.2 million made in subscription revenue in Q1 of 2012.

CEO Joe Kennedy attributed part of the revenue increase to the company’s decision to create a cap on mobile listening: “During the quarter, we successfully implemented a mobile listening limit, enabling us to manage our content acquisition costs with minimal impact on listener-ship or revenue growth.”

Free subscribers not ready to sign up for Pandora One were given the option of signing up for a $1 trial through the end of the month. While we agree that the $1 trial is a best practice for getting qualified leads, Pandora might want to consider shortening their trial term — too long a trial, and consumers forget that they’re expected to pay.

Pandora’s overall revenue clocked in at $125.5 million, a 55% growth over the previous year. Notable other statistics include the fact that the company is spending nearly $83 million on content acquisition costs, $7 million on product development, and $40 million on marketing and sales.