A. Virtually every movie that has been produced so far using digital soundtrack formats has used the two surround channels to produce a "stereo" sound field between the left and right walls of the auditorium. This is achieved in exactly the same way as the stereo sound field between the left and right speakers of a CD recording and that is by a combination of "panning" sounds to different positions between the two speakers, using stereo recording techniques to capture real world stereo sound fields. In many cases using electronic techniques such as reverb can add artificial stereo effects. The directional localization of sounds placed in the center of the stereo sound field can be greatly enhanced by using a separate center speaker which is fed via a steering matrix such as Circle Surround ™ ,Prologic.™ or other discreet matrix circuits This is clearly demonstrated by the almost universal use of a center (dialog) speaker for optical film soundtracks. The same applies to digital stereo surround channels in that a rear wall surround speaker array fed via a steering matrix greatly enhances the localization of sounds in the center of the stereo surround sound field which are intended to come from behind the audience rather than from both sides.

A. Encoding a stereo soundtrack for playback through more than two speakers has far more to do with the listening environment for the sound mixing engineer than with what actually goes onto the soundtrack. An "encoder" allows the mixing engineer to hear exactly what the soundtrack will sound like when played back though a matrix system. The encoder also ensures that sounds are positioned precisely in the sound field, which is very important for the optical stereo format to prevent crosstalk, particularly from the front channels to the surround channel, but largely unnecessary for the digital surround format. For the audience there is no discernible difference except that the use of the surround channels for sound effects is likely to be far more flamboyant with "encoded" soundtracks than with non-"encoded" soundtracks. A technique to phase shift a monaural signal to the surround channels may be employed in the encoding process. This process will destroy the steering capability and separation of ANY matrix during playback. Since digital soundtracks have stereo material is would be rare to see a mono signal used as a source. Since this process is in the encoding phase, the playback on all surround adapters should be about the same.

Q. Is the additional center surround signal a digital recording or analog?

A. The sound mixing studio places the center surround information equally on the left and right surround tracks. The original master recording is then sent to each of the 3 digital sound producers and digitized into their proprietary format. The three systems are DTS, SDDS, SRD. The tracks are stored digitally. The surround adapter in the theatre intercepts the surround channels after they are converted back to analog signals and sends the center information to a separate channel while removing the center channel sound from the left and right surround channels. All Surround adapters work this way.

A. No. You will hear the in-phase information equally from the left and right surround channels. This is commonly called a "Acoustic Phantom"

A. Dolby uses the Prologic™ matrix decoder chip in their product. This is the same chip used in home television sets. The surround channel is band restricted to 7 kHz. Also some chip makers have included a fixed 30 millisecond time delay and a modified type B noise reduction in the surround channel. This scheme is not conducive to producing a separate high quality channel for digital systems. The Circle Surround technology has a wide-band surround channel with no noise reduction or time delay.

A. This could be tricky and you may be disappointed. The general consumer version of the Prologic chip may not have the dynamic headroom to reproduce a digital signal without distortion. This is particularly true of the chips produced by foreign manufacturers. There is one American chip that has 10 dB more headroom than most of the others. Also a home decoder does not have the necessary equalizers, format switching capability, system interface, etc.

A. The simple process of extracting an existing center surround signal is not new, nor patentable. Three channel surround cinema systems were used as early as 1954. Martixed decoding of in-phase center material has been demonstrated publicly since digital systems were introduced a few years ago. Additional applications beyond the simple decoding may be patentable. SMART has applied for patent protection on the novel aspects of our product, but the additional features are already built into the product for future use.

A. You will hear virtually no difference because of the system you select. The movie studio delivers the same master to all three digital producers to be digitized into their proprietary process. The center surround information is embedded into the studio master and thus becomes part of the digital soundtrack.

A. The Dolby SA-10 will only go into the EX format mode of operation when is gets a digital "stamp" code from the SRD soundtrack. This command is issued by the CP500 when the processor is updated to version software. Without the software change the SA-10 will never come on.

The DTS-ES has recently introduced a digital surround adapter that features 4-channel one octave EQ and has a suggested net price of $1875. The DTS adapter uses DSP circuitry. A digital code on their time code track will actuate the adapter when encoded material is on the digital surround soundtracks. The time code reader feeds the DTS digital player and the adapter simultaneously. This allows additional functions to be performed, such as triggering special effects equipment in the auditorium, etc. The DTS-ES can also produce an overhead surround channel if desired by the producer.

The PANASTEREO SP23 Digital Surround Processors uses the same matrix and equalizer cards found in their CSP1200 stereo processor. The precision matrix reportedly does not produce sound artifacts that may be present in other systems. This is the only surround adapter that offers optional 1/3 octave EQ cards in the unit. The one octave model sells for $1795 and the 1/3 octave model is $2150.

The SMART Center Surround 3X has the ability to deliver up to 5 surround channels from a conventional 2 surround channel digital player if a film producer wishes to use this capability. The CS-3X is the lowest cost surround adapter in the industry.