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The Roxy's sound system

In November of 2005, our 10-year-old stereo processor started giving us trouble. The dialogue channel (the middle speaker) cut out right in the middle of a Harry Potter movie, leading us to give the entire audience free tickets for another showing. Over the next few weeks, various channels began dropping out seemingly at random. We starting diagnosing the problem over the phone with our technician, and he started sending us replacement parts. The problem would disappear for a week or two, only to resurface unexpectedly.

While this was going on, two of our amplifiers decided to quit working, so we pressed our spare unit into service. We finally decided it was time to replace some of the key components in our system before we started losing more shows.  Looking into the future, we chose equipment that was compatible with digital cinema technology, knowing that it was coming fairly soon.

In our time-honored tradition of always trying to give our moviegoers the very best, we decided to install Dolby Digital Sound and a complete new amplification system.

Here's an in-depth look at the Roxy's sound system. As always, if you have any questions, just hit the "Contact Us" button at the top of each page.


Feb. 22, 2006: Here's a shot of part of our previous sound system before it was removed. The DTS unit will find a new home in Wyoming. The top unit is the Ultra Stereo processor.



The new system will bi-amp our speakers, so that means a new set of wires needs to run from the booth to the stage.

Intrepid explorer Scott Lee ventures into the Roxy's attic to run the new speaker cables to the stage.


Technician Mark Gulbrandsen of CLACO Equipment & Service begins removing the previous system.


It takes a lot of wires to get six channels of sound off of the film and out to our 15 speakers (plus two subwoofers). All our stage speakers are bi-amped, meaning each woofer and tweeter has its own amplifier, resulting in better overall sound.



The complete system. From the top: QSC booth monitor and crossover. Next comes the Dolby CP650 digital sound processor, followed by five QSC amplifiers. At the bottom (not visible) is our spare amplifier. In late 2012 we added a sixth amplifier to this group, giving the balcony surrounds their own amplifier. That way we can control the balcony's sound independently from the main auditorium.

Dolby Digital Sound is printed on the film. This device, mounted on top of the projector, reads the sound data from the film using a miniature video camera.


After the system is installed, Mark calibrates it using a series of microphones placed in the auditorium. The mics are connected to an analyzer, which is connected to the Dolby processor through a computer.

So how does film sound work? The picture at the left shows a typical piece of film. The picture above shows a close-up of the soundtrack area.

The two jagged white lines on the right are the stereo analog soundtrack. We can use this track as a backup, if necessary. The gray areas between the sprocket holes are the data blocks containing the Dolby Digital soundtrack. During the show, a miniature camera reads those data blocks. The data is sent to the processor where it is converted to the sound you hear.


Here's a diagram of our sound system. This diagram doesn't include one critical element -- our wood floor. Thanks to the good old-fashioned wood floor in the Roxy, you feel the reverberations from the bass. Our floor is part of what makes the Roxy's sound what it is.

In 2010, we switched to Digital Cinema, so the sound-on-film process is a thing of the past. Ojm 2013 we switched to all-new QSC amplifiers and installed a full baffle wall behind the screen, and in late 2019 we replaced our Dolby sound processor with a new Trinnov Ovation 2 processor.  This new machine eleminates the separate D/A converter between the Dolby unit and the amplifiers, giving us sound that's now clearer and sharper than ever.  Watch for an update on that new system coming soon.


Thanks for taking this tour of the Roxy's sound system!