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Subwoofers get active room equalization

Houston (October 17, 2005) –Velodyne Acoustics the leading supplier of high performance subwoofers has selected Texas Instruments Incorporated's TMS320C2000 platform of digital signal controllers across all new subwoofers – including the latest Small, Precise, Loud (SPL-R) Series. Velodyne’s subwoofers cover the full range of capabilities with prices from $399 to $14,999.

The Digital Drive (DD) Series and Distortion Limiting Series (DLS-R) subwoofers introduced in 2004 already feature C2000 controller technology. The latest subwoofer series, the SPL-R, features a small cabinet size of just 10 x 10 x 12 inches yet delivers 2000 watts of dynamic power with one-sixth the amount of distortion level of competitive systems.

Digital Technology Provides High Precision Audio Reproduction
Velodyne’s digital High Gain Servo technology is used in all Digital Drive subwoofers. This patented technology uses a sealed digital accelerometer to measure the actual movement of the subwoofer cone. The C2000 controller then compares the cone movement to the input signal at a rate of 15,800 times per second and controls the 1250 watt amplifier to modify its signal, keeping the cone’s motion under control. This system provides the industry’s highest definition and lowest distortion subwoofers available. Typical distortion rates at normal listening levels are more in line with usual mind range distortion of good quality amplifiers. The Velodyne subwoofers have distortion levels well below 0.5% compared to the typical 10% and higher found most other products.

Room Correction and Main Speaker Interface
A subwoofer faces two main challenges when integrated with a home theater or music system. First, it must integrate with the main speakers, which is achieved through adjustments to volume, crossover and phase adjustments as well as subwoofer placement in the room. Velodyne uses TI digital signal controllers and a real-time video display the controllers generate to demonstrate the effects of changing adjustments, enabling a perfect match with subwoofer and the main speakers every time. Secondly, a subwoofer must overcome acoustic room anomalies. Some rooms may accentuate certain bass frequencies and diminish others, while other rooms can have the opposite effect. TI’s digital signal controllers enable automatic digital equalization to adjust 6 and 8 band EQs in the SPL-R and Digital Drive series, respectively. The subwoofer generates a sweep tone that the included microphone detects. The microphone then “listens” to the sweep tone and automatically adjusts the digital EQ in order to minimize the effects of room modes. This process is totally automated and provides cost-effective, dramatically improved room equalization and adaptation to bass room anomalies than previously available.

“By integrating TI’s C2000 controllers into all new subwoofers we make, we’ve taken a big step forward in bass reproduction. We can leverage the feature set and integration capabilities of the C2000 line into digital calibration and setup options that allow our subwoofers to perform unlike any other subwoofer,” said Bruce Hall, president, Velodyne Acoustics, Inc. “We quickly realized that all subwoofers would eventually be digitally controlled. The benefits over conventional analog control are too great to ignore.”

Embedded Control Technology from TI
TI C2000 controllers combine the real-time performance of digital signal processors (DSP) with the peripheral integration, C-language efficiency and ease of use of a microcontroller. C2000 controllers integrate up to 265KB of flash memory for simple reprogramming during development and in-field software updates. Optimized control peripherals include PWM generators, programmable general-purpose timers, capture modules for time stamping and glueless quadrature encoder interfaces. The C2000 platform also features up to 12-bit analog-to-digital converters that provide fast conversions – up to 12.5 MSPS – for tight control loops. Up to five different on-chip standard communication ports, including CAN, provide simple communication interfaces to hosts, test equipment, displays and other components or networks.

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