Satellite radio investors, troubled by weak signals from Sirius (SIRI) - Get Report Wednesday, will set the dial to rival XM's (XMSR) second-quarter report Thursday morning in hopes of hearing a happier tune.

Sirius took a 12% flogging Wednesday after delivering a weak subscriber-growth figure. The company also posted a loss that was a penny wider than expected, along with a sharp dip in revenue per user numbers.

But XM, which is a bit further along on the pay-radio trajectory, is set to dazzle Wall Street with a soundly better performance, say fans. Its shares, which have more than tripled this year, fell 78 cents Wednesday to $13.27. Sirius dropped 24 cents to $1.71.

Both companies have captured investors' fancy of late by promising to take subscription radio service to the masses. As one of the few high-growth plays in tech these days, the two-horse premium radio field has found no shortage of players willing to speculate on a possibly rosy future.

Wall Street is expecting XM to post a net loss of $1.25 per share on $18.8 million in revenues. That's a penny better than the previous quarter on a 40% top-line improvement.

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The most-watched numbers at this early stage, though, are the subscriber figures. XM said last month that it had hit its second-quarter target of adding 209,000 new subscribers. Optimists will be looking for the company to better that number slightly tomorrow.

Spiking
XM (top) and Sirius over a year

For its part, Sirius posted a second-quarter loss of 12 cents a share on sales of $2.1 million. Analysts had sought an 11-cent loss. The New York broadcaster said it had added 105,000 subscribers, but again, Wall Street expected slightly more.

Another big troubling development for Sirius was its sudden drop in average revenue per subscriber figure. So-called ARPU dropped below $8 from $10.80 previously, due largely to one-time promotion giveaways, the company said.

XM bears expect some of the same pressure, but say the larger subscriber base will help spread the per-user revenue slide more painlessly than Sirius managed to pull off. Some suggest that XM's promotions may be more than offset by higher revenues from its new premium channel offerings.

XM will report earnings before the market opens Thursday and is expected to discuss the results and business outlook on a 10 a.m. EDT conference call.