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Product Review - Smart Theatre Systems Center Surround CS-3X Junior Processor for Digital Surround EX Decoding - March, 2000

Brian Florian

Smart Theatre Systems CS-3X Junior

Distortion: Less than 0.1% THD at maximum input level of +4dBV (1.6 V rms), 1 kHz input signal Typically less than 0.05% at nominal operating level of -10dBV (316 mV rms), 1kHz input signal

Noise On any channel, typically better than -70dB S/N ratio with -10dBV input signal reference and gains set for unity. Typically better than -80dBV absolute noise level at unity gain.

Dynamic Range Typically 85 dB At nominal operating level of -10 dBV, the headroom is typically 14 dB or better.

Subwoofer Crossover frequencies are 20 Hz and 125 Hz at -3dB down. Slope is 12 dB per octave.

MSRP: $299 USA     



Smart Theatre Systems, 5945 Peachtree Corners East, Norcross Georgia 30071; Phone (800) 45-SMART or (770) 449-6698; 
Fax (770) 449-6728; E-Mail; Web


As we strolled the isles of CES this last January, a quiet but prevalent buzz in home theater audio was that “EX is coming home”.  And why not?  Unlike most new ‘formats’, you don’t have to wait for EX encoded soundtracks to enjoy the benefits of a center-surround system.  Existing soundtracks with discrete surrounds stand to benefit from these new systems too.

But before we look at our first review of a center surround product, we should take a short side-trip into what I call . . .

A shallow dig into the third surround channel

Note:  As a prerequisite for this side trip, and in fact the whole article, you should already have a working knowledge of how the Pro Logic/Dolby Stereo system works.

It was early 1999, and the buzz over "The Phantom Menace" was in full swing.  Part and parcel of the hub-bub was that with the film would come Dolby’s next iteration into cinema sound, Dolby Surround EX.  Simply, it would add a new rear audio channel giving us Surround - Left, Center, and Right.  It took all of two seconds for the word to get out:  The new system did not add a seventh discrete channel but is essentially an application of the Dolby Stereo (A.k.a. Pro Logic) matrix system.  In the same way that the center channel is derived from Left and Right in a Pro Logic system, so too is the center surround channel derived from the left and right surrounds.  As such, it is not a discrete channel, and I discourage referring to the system as “6.1”.  Further, because it is analog, there is no reason why it could not be applied to DTS or even SDDS soundtracks in the future (though the tag line: “presented in DTS Digital Surround with Dolby Surround EX” might be a bit much).  The system was not created for pin-pointing sounds: the target playback chain is, as always, a cinema’s surround speaker arrays, only divided into three groups as oppose to two.  So now the sound engineer can give you a sense that a sound is to the right rear, left rear, or overall rear.  But before you run home, dust off your old Pro Logic gear and jerry-rig it into your digital system, there are a few things you should know.

When playing non-EX mixed soundtracks, there is a good chance of something documented as ‘center-pile-up’ occurring.  This is where in the Pro Logic system sound seems to come only from the center.  You may have witnessed it while playing some two channel music through Pro Logic.  If and when it happens in a movie, it’s not very objectionable because we are drawn to the mental reference of the video at the center anyway.  In contrast, if the two surround channels of a soundtrack were not mixed for EX playback, and things do pile-up into the center-surround,  it could produce a poor surround sound field.  In the commercial EX system, there is a flag in the digital bit stream that tells Dolby’s CP-500 to signal the EX add-on to “kick-in”.  In this way, only soundtracks mixed specifically for EX playback are presented as such.  (The home THX/EX system has a similar flag for DVDs.)  But, in the same way that a lot of 2 channel music “works” in Pro Logic, there is a host of 5.1 films that will do likewise in EX playback.  So, it becomes a guessing game as to whether you should use it or not.

Smart Theatre Systems’ Circle Surround 3X Jr. is an attempt at addressing these issues.  Lets take a look.

On with the review

Smart Theatre Systems has been making commercial theater products, including processors and speakers, since 1978.  Noteworthy is that they had a center surround system, the Circle Surround 3X, available to theaters in 1999, the same year Dolby Surround EX was becoming a reality.  The Circle Surround 3X Jr. represents the company’s first foray into the consumer market. 

It should come as no surprise that the Jr. has that hard, utilitarian look and feel of a commercial product.  No frills, no nonsense, just business.  That suits me fine. I’m not one for flashy appearances anyway.  The processing,  I understand, is identical to their commercial product, which adds only some EQ features and the requisite trigger hardware to interface with digital cinema processors.

The front panel has only three items.  A switch to select center surround or regular two speaker operation, a volume control for the center (relative to the left and right), and a power switch.  This doesn’t actually turn the Jr. off but rather shorts the left/right ins to the left/right outs, effectively taking the Jr. out of the signal path.  Its only real use is if there is something wrong with the unit, but you can’t be bothered unhooking it or rewiring. I suspect this is a carry over from Smart’s commercial applications, since, for cinema hardware, everything is done to ensure that a show will go on despite hardware failures.  Also on the front is a discrete ‘presence’ light.  Described by Smart as indicating the presence of center-surround information, it can be seen flickering on and off to varying degrees depending on the soundtrack.  Basically, it tells you when there is hard information being fed to the center-surround speaker.

The back is marginally more interesting with its gold plated I/O.  Input can be either the line level surround left and right from your processor or the corresponding speaker outputs from a receiver.  The Jr.’s outputs include line level left, center, and right surround, a simple summed subwoofer output and SP1 and 2 for “future use” (more on these later).  Also included are screw trim pots for the 6 output levels.  These come from the factory set for unity gain, which means that the same level that goes in goes out.  Most installations will not require any adjustment of these, but Smart does include a nice micro screwdriver should the need arise.  I found on my review sample that the center needed to be turned up quite a bit to bring it into balance with my other speakers.

Setup is simple.  After making the appropriate connections, you set the Jr. for two-speaker surround and set your processor’s levels as you normally would. (Note: you must make the left and right surround from your processor the same level.  If your room dictates they should be different, then you make that adjustment later on the Jr.)  Then place the unit in three-channel mode and use the built-in pink noise generator to match the surround center level to the surround left and right.  I found the built-in noise generator to be very loud when fed to my Rotel amplifier which has quite a high gain.  It takes more time, but I preferred to use Pro Logic test tones on a CD.  You wire the Jr. to the main outputs, balance the rears to each other, then rewire as normal and balance the rears to the fronts.

That done, I settled in for a listen or two.

You won't find the Dolby logo anywhere on the Jr.  Its matrix system works a little differently and has a chief feature:  Even with a hard-center signal, the left and rights are not fully muted.  Oh, I can hear the purist cursing under their breath at this.  Before you recoil from the page in disgust, consider this:  The surround sound field has different goals from the front.  Not to get onto a tangent here, but movies, even EX movies, are mixed for the expansive speaker arrays of theaters.   Far better be it that the two side speakers “blend” a little with the rear than have the center-rear drawing attention to itself.  Trust me.

As far as a piece of audio hardware goes, I could find little wrong with the Jr. in terms of sound quality.  It introduced a very faint buzz in the rear speakers that was inaudible from the seating position, but beyond that it performed rather transparently.

I will cut to the chase and say that a center surround is cool . . . when done right.  I began with a single speaker at center rear.  Even with Smart’s technique, the speaker called too much attention to itself and did not sound natural.  When a Jumbo jet is coming in from behind, it just won't sound correct if coming from a point source. We need the rear to be expansive, even the center-rear.  The first step to good performance is to use two speakers for the center-rear.

Once I got a pair of speakers wired for the center surround, the party started to really get going.  What became immediately apparent is that the three (rather four) speakers used in the rear must be identical or at least of the same family.  This has always been accepted as critical in the front and is equally so in the rear when using this system.  Any deviation from this results in the listener being able to tell where the sound is coming from based on tone rather than physical direction.

It goes without saying that "The Spy who Shagged Me" and "The Haunting" sound good using EX.  Though unaccredited, they are so far the only two EX soundtracks transposed to DVD.  What surprised me is how good some other stuff can sound.  Try the car chase from "The Fifth Element", anything from "Das Boot", or the rescue sequence from "The Matrix".

In a nutshell, this system let me get the best of two worlds. I could have the left and right surrounds in their EX text-book position (to the sides) and the center surround sounds in the rear.  Whereas the front three speakers wrap sound on a narrow visual, the three rears can now wrap sound on the wide surround field, which in principal starts to our left, carries on around the back, and stops only to our right.

Cool?  Definitely!

While I am not prepared to declare that everyone reading this must rush out and get a Jr., I will say that with appropriate supporting hardware, there are some rooms that could benefit greatly from this setup.  Long narrow rooms in particular stand to gain from this system.  And the Jr. is an excellent way to do it, requiring no sacrifice of existing processing hardware.  Only additional speakers and corresponding amplification are required.  The only thing on my wish list for maybe version 2 is a two-channel mode more like Smart’s commercial version.  With that unit, when you don’t want to use the three-channel mode, the 3X will pass the left signal to half of the rears in addition to the left array and likewise for the right (recreating the standard 5.1 environment).  In the meantime, I should point out that there were only a few soundtracks that the Jr. wasn’t welcome for, so leaving it on is a pretty safe bet.

Excuse me while I check out how "The Mummy" sounds . . . .

Notes on speaker placement

The diagram above shows how 5.1 EX would be laid out in a commercial theater. For the home, obviously you have to make a few changes. In my home theater (diagram shown below), the normal position for my direct radiating rears is B.  Given the room and its small capacity, this has worked the best.  I began by putting a matching center channel speaker at D and it proved to be a bad spot.  The guy in the prime seat (me), couldn’t tell whether a sound was coming from the center front or rear (some human hearing limitation I read about once).  For someone seated to the side (my wife) the center surround sounded more like it was off to one side and called a lot of attention to itself.  A better setup was two speakers at position C.  This worked great for me, and good for my wife.  A real aggressive move was to move the left and right surrounds to position A.  This absolutely required the centers to be at position C but was a wild, wide setup.  Although I did not have any dipole speakers on hand during the review, it is my strong suspicion that a pair at A, and either one at D or two at C would be an ‘ultimate’ scenario.

Post Script:  The SP1 and 2 outputs

Even though it is different enough not to need the Dolby logo on it, the Jr. is after all a matrix decoder.  Truth be told, the Jr.'s SP1 and 2 are what would ordinarily be the surround outputs if you were to use the Jr. as an everyday analog Pro Logic decoder.  While not conforming to the purist’s idea of such a decoder, the Jr. did nice things for music playback.  There have been sketchy rumors that the extra outputs could be used as a “ceiling-surround” channel down the road.  Heaven help us!

- Brian Florian -

© Copyright 2000 Secrets of Home Theater & High Fidelity
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