ALLENTOWN, Pa. -

Downtown Allentown's new PPL Center is just weeks away from opening, but a big question remains: why is a new arena booking so many older music acts?

Classic rock legends The Eagles are set to officially open the facility on September 12. The show sold-out within 24 hours. Following close behind are Cher, Tom Petty, and other well-known stars.

"We feel really great," said PPL Center general manager Gunnar Fox. "We have a great diverse line-up of events."

But four of the five acts booked so far haven't had a hit since at least the late 90s. On our website and Facebook page, many of you are asking: why aren't today's hitmakers coming?

One commenter asked, "When will they book the first act under 60 years old?"

Fox said the arena isn't specifically targeting an older demographic. He blamed part of the problem on touring schedules.

"Some of those other acts will come; it just may not be when the schedules allow for the first part of our event calendar," said Fox.

Two music industry experts said a new venue, in an untested market like the Lehigh Valley, needs to prove to concert promoters it can draw in big crowds. Snagging several established names off-the-bat can put a venue on the map.

"The arena is relatively new, and so, what you might want to go for ... are tried-and-true artists that are going to have no difficulty whatsoever pulling in crowds," said Dan Greenhaus, a music industry analyst with BTIG Global Strategies Group in New York City. "Younger artists are a bit of a risk."

Greenhaus and others insisted, if the older acts sell, younger ones will follow.

"The Eagles, [Tom] Petty, and Cher generally are all playing buildings that are much bigger than 10,000 seats," said Gary Bongiovanni, editor-in-chief of Pollstar, a national concert industry publication. "I think it's a real win for the Allentown market to have a new building like that."

Fox noted the new PPL Center has another major advantage: arena operator Global Spectrum is well-established and backed by entertainment industry behemoth Comcast. He said the company's clout helped land such big names already.

"[Artists say] we've done shows with them before," said Fox. "They know what to expect when they come into a Spectrum facility, and that's a big part of acts coming to your building."

According to Greenhaus, many hot, up-and-coming acts actually perfer medium-sized venues because they don't have to sell as many seats.

"It's the younger acts that can't fill the Madison Square Gardens of the world," he said. "So presumedly, a 10,000 seat venue would be perfect for the younger acts."

Bongiovanni said the PPL Center's biggest challenge will be bands deciding whether they can sell enough tickets to play both Allentown and nearby Philadelphia. He predicted concert promoters will look carefully at where people are buying tickets from. He said if too many concertgoers come from the Philadelphia suburbs, bands may elect to simply play there instead.