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...