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New! The T-Driver Subwoofer THE AMERICAN POWER AND LIGHT, INC., T-DRIVER SUBWOOFERDeep, articulate, bass extension has long been an elusive goal of subwoofer design. Often, the sonic characteristic of a subwoofer is out of character with the low midrange and bass information of the main loudspeakers, and thus adds a heaviness or slowness to the reproduced full range signal. The T-Driver uses four high flux density, very low free air resonant drivers in an extended double transmission line enclosure, where both sides of each cone are identically and critically damped. Thus, the electromagnetically driven mechanical cone treats both incoming waveform polarities, positive and negative, in an exactly identical way: there is no preferred direction of travel for the driver, as it has exactly the same acoustical, mechanical loading on either side of the diaphragm. Because the transmission lines are folded and long, at a one quarter wave tuning, there is no characteristic high Q low frequency reactive impedance rise, which effectively decouples the subwoofer from the driving amplifier, and which further modulates the output of the subwoofer above this high Q resonant point. The analogy would be to a typically high Q symphony tympany drum, which likes to respond at a given frequency, no matter what the nature and character of the mechanical input. Since the drivers in the T-DRIVER SUBWOOFER, are precisely and exactly terminated on either diaphragm side, asymmetrical energy storage in a trapped air volume is eliminated, through the smooth extension of the driver pressure wave through the coupled transmission line. All of the drivers in the subwoofer are internal, and motionally balanced. That is, two drivers complete an excursion in response to a given input polarity, while the other two drivers move in the other direction in response to the same input polarity. Thus the subwoofer system is dynamically balanced, and not subject to large magnitude Newton Third Law, action reaction forces: energy not lost in the reaction between the driver and the enclosure can appear in the air instead, as useful, low frequency output. THE AMERICAN POWER AND LIGHT, INC., T-DRIVER SUBWOOFER SPECIFICATIONS SIZE: 28 INCHES HIGH, 16 INCHES WIDE, AND DEEP. WEIGHT: 68 POUNDS. FINISH: AVAILABLE IN SELECTED NON-ENDANGERED AMERICAN HARDWOODS, OR WITH MARBLE, OR GRANITE TOPS AND ACCENTS. FREQUENCY RESPONSE: 15 HERTZ TO 120 HERTZ, PLUS OR MINUS 2 DECIBELS. ( NOTE: SUBWOOFER FREQUENCY RESPONSE IS UNUSUALLY DEPENDENT UPON ROOM PLACEMENT, AND UPON ROOM FREQUENCY CHARACTERISTICS. OUR MEASUREMENTS ARE DERIVED IN A VERY LARGE ROOM, 48 FEET LONG, 28 FEET WIDE, WITH AN OPEN CEILING AT 16 FEET, WITH THE WOOFER PLACED IN THE MIDDLE OF THE ROOM. ) CONVERSION SENSITIVITY: 91 DECIBELS AT ONE WATT, ONE METER ON AXIS. (NOTE: SINCE THE OUTPUT OF A SUBWOOFER IS OMNIDIRECTIONAL, IT IS DIFFICULT TO DERIVE OVERALL CONVERSION EFFICIENCY, ELECTRICAL WATTS TO ACOUSTICAL WATTS. THERE ARE MANY CONVENTIONS, ONE OF THE MOST HONEST SEEMS TO BE MEASURING THE OUTPUT OF THE SUBWOOFER IN A GREAT CIRCLE AROUND THE UNIT AND THE SUMMING THE MEASUREMENTS. POWER HANDLING: 200 WATTS RMS AT ANY FREQUENCY, OR COMBINATION OF FREQUENCIES, 15 TO 100 HERTZ. PERFORMANCE NOTE MANY SUBWOOFER SPECIFICATIONS FOCUS ON LOW FREQUENCY EXTENSION, OR ON SIMPLE AMPLITUDE. A MORE IMPORTANT CRITERIA IS RISE TIME, AND SETTLE TIME, IN OTHER WORDS, HOW FAST IS THE SUBWOOFER. ONE OF THE MOST SIGNIFICANT CAUSES OF APPARENT DISCONTINUITY AMONG THE MAIN SPEAKERS, AND THE SUBWOOFER IS PRECISELY THIS LACK OF DYNAMIC SPEED, OR RISE TIME. MANY SUBWOOFER DESIGNS ARE EQUIVALENTLY VERY RESONANT, WHERE THE MECHANICAL, ACOUSTICAL FORCES SURROUNDING THE DRIVEN CONE DOMINATE THE ELECTRICAL SIGNAL SENT BY THE AMPLIFIER.