Justin Bieber enthralls the girls at AmericanAirlines Arena

What can a grownup possibly say about Justin Bieber? That hes cute and his songs are musically negligible? That hes only the latest in an endless series of teen heartthrobs? That were impressed hes got more Twitter followers than Lady Gaga? What does it matter what anyone over 15 thinks of Justin Bieber?

And so, to review Saturdays concert, the first of two by the Beeb, I brought along some experts; my 9-year old daughter Romina and two friends her age. Goldi, a veteran of the first tour, wore the Justin shirt she sleeps in. Molly, who knew all the songs and videos, was my back-up in case Bieber deviated from his set list. Romina put aside her indignation over Biebers split with Selena Gomez and her devotion to One Direction in the hysteria of her first pop concert.

They and their cohorts filled the AmericanAirlines Arena: girls from pre-school to teen, girls with smiling or grimacing mothers, girls in packs with matching Bieber T-shirts, girls who filled the arena with the glow of their phones. Ear-splitting gets thrown around a lot to describe fans reactions to their idols, but the phrases true meaning emerged Saturday in a way it never has in my almost 20 years of covering pop concerts. The sound whenever Bieber spoke, or stared soulfully without speaking, or when cameras filming the concert passed overhead, was like knives twisting in your inner ear. My daughter cowered and scrabbled for the ear plugs in my purse; but later she and Molly bounced up and down in unison shrieking while holding their hands over each others ears. Mom, my ears were bleeding! Romina said later. But it was worth it!

The source of all that pain and pleasure floated onstage on a pair of enormous wings, dressed in white and dark shades, singing All Around the World, the first of many songs (two-thirds of the set list) from his latest album, last years Believe. The 18-year-old superstar went confidently through a slick production, with 12 dancers, a giant tri-level! set and a phalanx of video screens that so filled the stage with Bieber images it was often hard to find the real thing.

His look was oddly suspended between tween heartthrob sweet and teen hip-hop hip: the moptop bangs curled back into an immobile 50s-ish pompadour, his pants (white, then black, then blue) hanging so low around his thighs they kept his dancing to a bent-kneed shuffle-bounce and his hand awkwardly holding up his crotch. He coyly hinted at seductiveness here and there, lifting his tank top (to hysteria), but stripping to bare chest only for the encore (indescribable). Which inspired the following exchange from my trio of experts:

Goldi: FYI guys, I really like the shirtless Justin Bieber. But he could have worked a little harder to be more buff.

Molly: What are you talking about?! He had a six-pack!

Goldi: Oh no he didnt!

Molly: Oh yes he did! The only six-pack boys our age have is a juice pack!

Did he lip synch? Maybe. Probably. But it doesnt matter. On power dance hits like Eenie Meenie or Beauty and a Beat, the dancing intensity and backing vocals and auto-tuning and general mass of sound were so overwhelming that it was impossible to tell the source of Biebers actual, original voice. Whether he can find a compelling way to sing now that hes aged out of his thrilling Baby falsetto is hard to say. His singing was pleasant, but not powerful on two nice enough ballads, Be Alright and Fall, for which he strummed acoustic guitar amidst gentle clouds of confetti. But their impact came because he performed them on a small platform on a crane that circled the arena, bringing him so close to the audience I thought the girls around me might pass out. Romina was sure he was staring right at her. So, no doubt, were thousands of other girls.

Whatever the haters and the music critics might say about Bieber, his power isnt the songs, its those gorgeous, fantastically soulful puppy dog eyes. So! metimes h! ed stop and stare at the crowd was there a hint of irony in that gaze? to enjoy the effect. In a video for She Dont Like the Lights that showed Bieber battling evil ninja-esque paparazzi, he stops to wink flirtatiously, which brought tears streaming to the teenage girl next to me. The girl plucked from the crowd for Bieber to hug, crown with flowers and sing Beautiful to looked as if she would explode.

So can he keep casting his spell as he and his audience grow up? His younger fans are a bit nostalgic for the days of 2009.

Molly: I kind of miss the old Justin Bieber, he was so sweet.

Romina: Yeah, the new one is kind of sexy and inappropriate.

Goldi: Well, keep in mind hes 18.

Molly: Yeah, hes not a little boy our age.

Thats for sure. How he does as a big boy remains to be seen.