Center Channel Speakers In A Movie Theater?

I used to be in charge of product for Cinema for JBL. Its the same speaker in the center as the left and the right-and that's how we did it at the Academy of Motion Pictures as well.

In a correct film mix, dialogue is the ONLY thing supposed to come from the center speaker. However, I hear from my scoring mixer friends that there are a few [film] mixes out there with non dialogue showing up in the Center. I think its harder to give motion or position since center and left (or right) aren't so far apart.

In IMAX they use a lot more channels than typical film as they use a vertical component of audio to imply an up and down motion (most film only uses left to right).

Someday maybe we'll have 12.1- level one LCR front and LCR surround and level two LCR front and LCR back. Give me a few more overhead and they can do 360 steering!

BTW, center channel in 5.1 music mixes are another story. All bets are off, you can do anything you want.

The LCR set of speakers is behind the screen in all cinema systems except the non perforated Taurus screens that AMC uses (not sure if they still do) Non perforated screens require speakers be mounted above the screens, and you can tell that the sound is not from behind. Subs are typically below the screen in cinema systems.

Surrounds are strung along the sides, all from from one left and one right channel. There is no delay in use.

Different cinema chains supported different manufacturers. For example, Edwards, Harkins, Mann always bought JBL. AMC bought EV. I doubt there is an easy way to figure out who is who.

The era the theater was built in sort of determined the quality. In 1991 or so I attended Jurrasic Park premier with DTS (and JBL speakers), the first of the 5.1 cinema sound systems. At that time, 95% of the cinemas were mono with a few stereo ones out in LA. A huge wave of theater building came then, and THX was supported in one room of a big complex, mostly in major markets.

In the case of JBL, the behind the screen speakers never changed much. It was a dual 15 with a 4 inch driver on a professional horn. Theaters built after 1993 or 1994 or so had the better 8340 JBL surround, which offered wider HF dispersion and higher dynamics, to handle better surround tracks.

THX was about dynamic range, room design (speaker dispersion ) and room isolation (less leakage from the room next door), and max SPL. It really helped convince theater owners, who only made money selling popcorn and candy, to embrace better audio playback. The competitiveness of the industry problem did more to get it going, as one owner would not want to be outdone by a competitor. You really could not compete with a mono theater against the draw of a 5.1 film properly supported.

I always felt like Edwards on the west coast did the best job with audio, their theaters generally sounded the best to me. And the bigger ones closer to Hollywood WERE better, I guess due to industry clientele would be more aggressive with their complaining. Complaints do seems to drive theaters to make adjustments.

Brad

Well I think there are some valid points there, but I think its simpler than that. The sound needs to come from the action on the screen and the screen is higher. Secondly the floor is not flat, its "theater" seating with seats on steps up to the back row (for visibility originally) . You cannot put a limited vertical dispersion speaker down low and have it cover the last rows.

The surround design is what it is for a simpler reason-output and consistency of coverage. These surrounds cannot play loud like the LCR set, so you need a lot of them to get level from surround channels. Building/using a few higher power surrounds would create nasty hot spots that theater goers would complain about. Its a common technique in live, using multiple speakers at lower level works out when you have close listener proximity issues.
Brad