The most obvious difference between conventional two-way loudspeaker design and Tetrad Technology, is our use of four low-frequency drivers instead of the usual single 15" woofer. Our 8" LF drivers respond to transient attacks much faster than a 15" and since four of them have a larger surface area than a 15", they also move a larger column of air. Bigger air column = more bass. The 8" drivers are also more consistent at delivering the upper end response of the woofer system. This is critical to creating a smooth transition at the crossover point in a two-way system.

Why such a big horn? Sure, it looks cool—but there's more to it than meets the eye. Traditional, smaller horn assemblies become extremely unstable at the lower end of their response curve, causing all sorts of noticeable audio anomalies—usually right at the crossover point. By using a larger horn, we are able to better control these midrange signals, which stabilizes them through the crossover point, presenting a superior sonic image.

Note that the 15" driver generates a rather sloppy rendition of the reference signal. All the peaks and valleys of the input tone have been rounded off, due to the relatively slow movement of the speaker basket. With its light-weight basket, and more efficient design, an 8" speaker can respond faster to the variations of the input signal, creating a tighter, punchier sound. All things being equal, smaller drivers will always be more efficient than their larger counterparts—and four S400 Series 8" speakers, with a combined surface area of 201 square inches, move a substantially larger column of air than a single fifteen (177 square inches). (see Fig. A)

Our LF driver placement is anything but random—they are strategically arranged to maximize their unified coverage, and to create the largest low-end wave-front possible. This translates into a bigger, more accurate, punchier sound. This precise spatial arrangement of the S408's LF drivers focuses their output to match the coverage pattern of the HF horn. And the use of multiple, smaller transducers allows for a substantially larger horn versus conventional 2-way, 15-inch designs. (see Fig. B)

By employing a larger than typical high-frequency horn, Tetrad™ Technology makes the S408's crossover transition much smoother and with much less distortion versus conventional two-way, 15-inch enclosures with smaller horns. (see Fig. C)

By positioning the high-frequency horn in the center and strategically arraying the low-frequency drivers around it, the S408 has both horizontal and vertical output symmetry, with a central point of origin for both the low- and high-frequency sounds. Two-way, 15" designs can only claim vertical symmetry, resulting in spatially separate high-and low-frequency sound origins. (see Fig. D)

In designing the Mackie S408, we've constructed a loudspeaker system that focuses LF and HF content into a vertically and horizontally symmetrical pattern—with a single, common psychoacoustic point of origin. The result; Tetrad Driver Alignment Technology yields consistent response throughout its entire 75°-coverage pattern. (see Fig. E)

Patented Tetrad™ Driver Alignment Technology delivers full, accurate, punchy sound to the entire audience, not just to those fortunate enough to sit in the center.