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SP1 Circle Surround Sound Processor
Sid Vanderpool- Contributing Writer Pro Audio Review Magaizne


For over 40 years, electronic engineers have searched for ways to make the sound of a recorded performance or movie come to life, to give listeners a multi-dimensional perception of being "right there" when it was performed or recorded. In the early 1960's, David Hafler developed one of the original matrix systems.  His system was designed as a passive decoder that would split a stereo signal into four channels. In the late 1960's, Peter Scheiber filed a US Patent for an encoder/decoder matrix system that would turn out to be a major competing format for quadraphonic sound in the early 1970's. Later, Dolby Laboratories cited many of Scheiber's patents in the creation of the Dolby Surround system. This brings to light that the original concepts of what has become known as "Dolby Surround" was based on the efforts of Peter Scheiber.  In the 1990's Rocktron created Circle Surround, a new spin on the surround world that could produce front channel stereo, true rear channel stereo with 30dB separation, and a phantom center channel- all from a regular stereo input. SRS Labs of Santa Ana, California later purchased the Circle Surround technology.


To look at the unit, it appears to be just another sound processor. The case is one standard rackspace high in silver with large control knobs in pink brushed aluminum (don't ask) to the left that control the main volume and effects, and five smaller more precise thumb knobs to the right that individually control each of the five outputs. A base enhancer switch and "test" switch can also be seen on the front. On the back of the unit, we have XLR balanced inputs for right and left and five XLR balanced outputs, right front, left front, right rear, left rear, and subwoofer.

When designing their first surround unit the engineers at Gemini Sound Products were so impressed with the SRS Labs' Circle Surround technology, they licensed the chipset. These components let the SP-1 to not only decode regular surround sound, but to work with the standard analog stereo output signal produced by most traditional DJ systems and club PAs to produce awesome realism in the music.

In Use

Setting this up for a demo was a breeze. Balanced main out of the mixer to the unit and balanced outputs to three amplifiers (Crown), a child could have done it. Our speakers were Cerwin Vega V-37Ds on the front right and left, Cerwin Vega V-12s on tripods in the back of the dance floor and a JBL dual 15" ported sub on the floor. The music of choice for the test was Glenn Miller, In the Digital Mood a digitally remastered and digitally recorded cd.  Also, for the digital PC DJ's benefit, I used an MP3 file recorded at the low 128-bit rate, patched in from my computer.


After the SP-1 was hooked up, I calibrated it with the on board white noise generator, tweaking each channel until I was satisfied. The SP-1 gave me four effect choices. The Two Channel Stereo and Two Channel Four Speaker Stereo settings are pretty much self-explanatory. The third choice was Two Channel Four Speaker Stereo Diagonal. It stated in the owner's manual that this setting was useful for large rooms and club environments. I could see how this would accent a venue like a large gymnasium or club, but it was still just stereo with a different twist.

With a flip of the knob, I was in Circle Surround heaven and standing in the middle of the Glenn Miller orchestra. I could literally close my eyes and see ol' Glenn directing the band; I was blown away! I experienced this type of sound in our local movie theater, but never at a dance or musical event. Unlike the surround sound I had listened to before, the SP-1 gave me full separation of the rear channels, which added more depth to the music. The processing made the music as crisp if not crisper than running it in regular stereo, while the sub pumped out hard-hitting bass. Reaching over and pulling the plug on the sub, I noticed a slight loss in sound pressure but with just the four speakers, I still had full range sound and plenty of bass.

Next up was the 128-bit MP3 file. Since the encoding of this file was not the best, I used it as a reference to see if the SP-1 could make up for the deficiencies found in some MP3s. With a little help from the subwoofer enhancer, the MP3 file rocked in all modes and was greatly enhanced by the Circle Surround setting.

In a "live" test at a wedding later in the day, the crowd concurred with my original findings, the music sounded terrific. Suddenly they were dancing in the center of the mix. Synths are whirling around their heads, yet the vocals are coming only from the front speakers. The sound was truly spectacular. The other interesting thing is that the sound pressure (SPL) on the dance floor was really loud, yet when you walk to the sides of the room you could converse at normal levels. It was weird, people are always telling me I play good music, but with the SP-1, it wasn't what I was playing as much as how I was making it sound so good.


Over the 23 years I have been a DJ, I have tried a number of processors that can enhance recorded music. The SP-1 surprised me in many ways. The unit itself is solid and in this time of most all DJ equipment having unbalanced hookups, I was impressed that Gemini went the extra mile with balanced connections. The effect it produced was way beyond what I had expected and I might say, it was quite the experience to go through my music library and discover a whole new sound coming from my cds. I found the initial effect it had on me was carried over to the dance floor full of guests. Which was way cool. If you have room in your rack and the support equipment to hook it up, the SP-1 will make a great enhancement to your system.   

Key Features:

SRS Circle Surround chipset

XLR Balanced connectors

Bass enhancer




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