The filming of country singer Johnny Cash biopic Walk the Line narrowly escaped tragedy after a speaker caught fire in the warehouse where his legendary 1968 Folsom Prison gig was being recreated.

The movie, which stars Gladiator actor Joaquin Phoenix in the lead role, was being filmed in Memphis, Tennessee, when the speaker exploded in front of hundreds of extras.

But 30-year-old Phoenix insists the accident made the scene a roaring success.

He says, "Everyone went nuts and we just started playing RING OF FIRE.

"That was one of the most fun segments to film. We were actually in the moment, feeding off the energy of those guys, it was really natural."