Eric Alexander, designer/CEO of Tekton Design, has developed a reputation for being a brilliant inventor and builder of innovative speakers offering high-end performance at prices that the average, hard-working music/home theater fan can afford. His most highly acclaimed speaker, the Pendragon, was dubbed on the street as the “B&W/Wilson killer” because the Pendragon performed at the level of those highly regarded speakers, yet it cost thousands of dollars less than those very expensive models. Alexander’s speakers use high-quality parts and are extremely well built. However, they are not eye candy; the total cost of building his speakers goes toward excellent performance, not aesthetics.
For years, Alexander has been working on an open-baffle speaker. He wanted his design to have the sonic virtues of a planar/dipolar speaker or open-baffle design–i.e., a very natural type of soundstaging with space between the individual players, great transparency and micro-details, and a figure-eight sound dispersion pattern mimicking the sound of live music. Yet, at the same time, he worked on eliminating the disadvantages of these speaker designs, such as the need for large, space-consuming panels, poor power handling, active equalization/DSP processing, the need for very powerful or high current amplification, the exaggeration of the size of instruments, and the lack of bass extension/power.
This time-consuming research has finally led to Tekton Design’s unique Sigma OB speaker, retailing for $3,000/pair. To explain his design theory and the implementation of his strategy, Alexander states, “My open-baffle hybrid concept is easily visualized as the following…place and locate a speaker on a flat panel–a pure open-baffle dipole producing sound on both sides of the panel in equal and opposite pressure and polarities. Next, place a second speaker matching in size on the rear side of the open baffle, locate it within immediate proximity to the open-baffle speaker, and use it to create a short circuit nullification path for all low-frequency content radiating from the back side of the open-baffle speaker. Wire the open-baffle speaker and the nullifying speaker in tandem, so they are moving in the same direction to create an acoustical mass transformer. This process produces a monopole low-frequency radiation pattern that entirely emanates from the front panel, then smoothly transitions into an open-baffle dipole radiation pattern, the attribute of open-baffle/planar design that makes audiophiles drool, from the mid-bass frequencies going up. The standard (classical) embodiment of the invention/design is to dissipate the rear energy produced by the nullification (short circuit) speaker using a secondary enclosure of the infinite baffle or transmission line with long termination. Product development phases proved it was advantageous to incorporate a venting system that increased system efficiency and further extended low-frequency performance.”
Each Sigma OB speaker weighs 58 pounds and measures 48 inches high by 19.25 inches wide by 14.25 inches deep. Located in front of baffle are the one-inch tweeter and eight-inch midrange/bass driver. Below the two drivers are two small vent/ports that radiate low-frequency energy from the upward-firing eight-inch nullification driver of the speaker’s low-frequency back wave. All three drivers are high-quality SEAS transducers. You’ll find one pair of speaker-wire terminals on the back of the Sigma OB. My review samples had a nice satin-black finish with no speaker grilles for the front or back exposed speaker. I would describe the Sigma OB’s appearance as industrial or Spartan-looking. Its range is listed as 35 Hz to 30 kHz, and its sensitivity is 93 dB, offering a nominal impedance of four ohms.
I wanted to see how the Sigma OBs would perform in both a very large acoustic space and a smaller room that’s more typical of the size of most readers’ home theater or two-channel rooms. So, I first used the pair of the Sigma OB speakers with my large reference system, replacing the Lawrence Audio Cello Speakers. I then placed them into my smaller system, replacing the Aerial Acoustic 6T speakers. Both of these systems have top-notch upstream gear (Pass Labs, First Watt, Concert Fidelity, Perla Audio, Backert Labs, and Raven Audio). In both environments, Sigma OB Speakers proved to be great performers.
Click over to Page Two for Performance, The Downside, Comparison & Competition, and Conclusion…
My first selection to see what the Sigma OB speakers had to offer was Booker T.’s Potato Hole (Anti-Records–and yes, it’s the same Booker T. of the famous Stax/Soul group Booker T. and the M.G.’s). This well-recorded album of funky updated soul music was a good test to see if the low-frequency range and hard-hitting dynamics of his music would be rendered by the Sigma OB. The speakers reproduced the pop and power of this music at any sound level I wanted without any drawbacks like a lack of low-end dynamics or bottom-end clarity, typically experienced in planar speakers.
One of the most historically important jazz albums of all times is Duke Ellington’s Masterpieces by Ellington (Columbia). Besides the beauty of his arrangements and music, the album marked the first time in the history of jazz recordings that full-length arrangements were recorded with no time restrictions. This album’s tone/timbres, along with its spatial qualities, are a marvel, given that it was recorded in 1950. The Sigma OB speakers completely disappeared in a massive soundstage in both height and width. Unlike some planar/open-baffle dipole speakers that generate this type of soundstaging but distort the size of the instruments/singers, the Sigma OB produced accurately sized players spread across the soundstage in the recording studio.
I wanted to test the Sigma OB’s ability to reproduce acoustic space with accuracy. Many of the planar/open-baffle designs I have listened to impress you at first with big wall-to-wall soundstaging but do not do justice to smaller more intimate recordings. Count Basie’s Basie Jam #3 (Pablo) was recorded in a small studio on the West Coast with seven other players, not his usual big band. The Sigma OB speakers created the illusion that you were sitting in on the recording that day. I could easily tell where each player was sitting or standing when he performed individually or in a group. For overall tonality, the Sigma OBs are silky smooth with a touch of warmth, having a clean, pure high-frequency treble range.
My final selection was Albert King’s album Albert King with Stevie Ray Vaughan in Session (Stax). This studio recording has sizzling guitar work and emotional vocals. Through the Sigma OB speakers, both of their voices’ unique timbres and smallest nuances could be heard with total resolution. The Sigma OB is a fast speaker that presents the transients with great leading-edge definition and clarity but without etch or any unpleasant “in your face” qualities.
I find no real meaningful shortcomings regarding the beautiful musical performance of the Sigma OB speaker. The only concern I have is that some listeners will possibly find the physical appearance of this small but relatively wide speaker to be too industrial or Spartan, and it might not easily fit aesthetically with their room décor. Even in the Tekton lineup of speakers, there are better looking speakers and God knows there are plenty of fantastic looking, audiophile grade speakers out there. But for every lid there is a pot and when you close your eyes and listen, you will hear the magic.
Comparison and Competition
Based on price, two speakers that would compete with the Sigma OB would be the Dynaudio Excite X34, retailing for $3,400/pair and the Vandersteen 2Ce Signature II, retailing for $2,395/pair. The Dynaudio Excite X34 is a fast, dynamic, and detailed performer; however, it came nowhere close to the world-class soundstaging and disappearing act that the Sigma OB can produce in large and small spaces. The Vandersteen 2Ce Signature II came closer in comparison to some of the spatial qualities offered by the Sigma OB, but it could not really compete in the areas of transient speed and rendering of micro-details with great clarity. The Vandersteen 2Ce Signature II actually sounded somewhat veiled in comparison to the Sigma OB.
After almost two years of deep thought and many prototype experiments, Eric Alexander has come up with a hybrid open-baffle design that functions like a monopole in the low frequencies, which is great for bass extension and accuracy. Additionally, it functions in a dipole fashion in the midrange and high frequencies which is great for spatial qualities. He was able to pull this off without having to use active bass equalization or DSP processing. What does this really mean to the music lover looking for a relatively inexpensive speaker? It means that the Sigma OB can be driven with as little as eight watts, yet it can create soundstaging that rivals the best large planar or electrostatic panel speakers, but with much more accuracy in the location and size of players. It also has great lower-end bass extension; bass is tight and has great slam. Finally, these speakers render tonality and details of the music in a relaxing, natural way.
For over 15 years, I lived with and enjoyed Magnepan MG-20 speakers. These very large seven-foot-tall, hard-to-drive planar speakers were great performers in many ways. However, they struggled with low-end grunt; and, with some music, they made the players sound much larger than in real life. Also, they had volume limitations when it came to certain types of music. It is important to mention this because the whole time I spent reviewing the Sigma OB speakers, I kept thinking that these speakers have all the spatial virtues of big panels but add accurate sizing of players, along with chest-thumping bass and dynamics. If what I’ve shared in the review intrigues you enough to hear the Sigma OB speakers in your own system, I recommend you give Mr. Eric Alexander a call at Tekton Design to set up a home audition.
• Check out our Floorstanding Speakers category page to read similar reviews.
• Visit the Tekton Design website for more product information.
• Tekton Designs: Audiophile Success Despite All Odds at HomeTheaterReview.com.