One of the 20 theaters in the AMC River Park Square 20 multiplex in downtown Spokane is being retrofitted with IMAX equipment and a larger screen, and could be ready to show IMAX movies by Thanksgiving, theater officials say.

The multiplex's owner, Kansas City, Mo.-based AMC Entertainment Inc., is working with IMAX Corp., of Toronto, to upgrade about 100 theaters across the country with IMAX digital projection systems and digital sound systems, the two companies say.

At River Park Square, the multiplex's auditorium 18 is getting a new, larger screen that will measure nearly 53 feet wide and 27 feet high, says Justin Scott, an AMC Entertainment spokesman in Kansas City. The previous screen in that auditorium was 45 feet wide and 21 feet high.

By comparison, the screen in the IMAX theater in nearby Riverfront park measures 70 feet wide and 55 feet high, says Pete Caruso, chief projectionist at the Riverfront Park IMAX Theatre.

Jackson Myers, a Toronto-based spokesman for IMAX, says auditorium 18 will be what's called a multiplex-design IMAX theater.

Scott says, "People are not going to be walking into what has traditionally been considered an IMAX theater. No walls will be moved here, and the ceiling is not going to be raised" in this project.

The larger screen in retrofitted auditorium 18 also will be slightly curved and positioned closer to the audience to maximize the field of view.

The first few rows of seats had to be removed to move the screen, Myers says. Scott says that auditorium now has about 350 seats, down from about 400 before the retrofitting.

He says the new IMAX projection system in auditorium 18 will use the power of two modified projectors equipped with IMAX's proprietary image enhancer to deliver clear images in 3-D. IMAX also installed an audio system that delivers what's called laser-aligned digital sound, Myers says.

"This system has 10 times more dynamic range than the system that was previously in this auditorium, cuts down on distortion and provides a sound quality that feels more immersive, especially with added acoustic paneling that absorbs sound to remove echo," Myers says.

Scott says the retrofitted auditorium could be ready by Thanksgiving for a "soft" opening, in which the first movie to be played there would be "A Christmas Carol." A grand opening is slated for Dec. 18, when the movie "Avatar" will open in the new IMAX theater, he says.

Scott declines to say how much the project will cost, but says IMAX and AMC are sharing in the costs and also will share in revenues generated from the conversion.

Myers says the IMAX projection system alone costs about $500,000.