Velodyne Acoustics DF-12sc, DF-10sc Servo Technology, Practice Safe Sound, Decibel Level Example

Servo Technology

Velodyne pioneered the use of servo-control technology as a means of reducing distortion over a decade ago. Now, we are the first to offer this revolutionary technology for use in the automobile.

In normal music listening, we are exposed to many forms of distortion. Every component in the signal path adds it's own char- acteristic distortion to the signal. Since most high quality electronics available now have distortion levels far lower than we are able to hear, that leaves your speakers as the worst offenders. While we scrutinize distortion specifications before we buy an electronic component, we rarely see anyone list distortion on loudspeakers. That is because traditional subwoofers (even high quality types) can produce distortion levels around 25% at typical levels. Even at only one watt input power, many subwoofers produce from 8-10% distortion.

Traditional speakers produce sound by using a cone which is forced to move by an electromagnetic motor. The motor is connected directly to an amplifier, which provides the necessary increase in power to drive the speaker. If a speaker was functionally "perfect", this method would work fine. The problem arises when the fast moving speaker cone is called upon to stop & change direction quickly. The speaker cone may continue to move, resulting in muddy bass with an increased amount of harmonic distortion. Unfortunately there is no way for this traditional system to "control" distortion. Until now.

Velodyne's patented servo-control system uses a "motional feed- back loop", which corrects for any distortion. Here's how it works. The music signal that normally goes to your amp is re-routed to our control unit. This unit monitors the music signal, which should be reproduced exactly without distortion. We then mount two acceler- ometers on the speaker. One accelerometer monitors cone motion, while the other accounts for motion of the vehicle. Now that we can monitor the actual motion of the cone, we can instantaneously compare how well the acoustic output of the speaker matches the music signal. If & when the output from the speaker starts to deviate from the music signal, the servo circuitry modifies the drive signal

Practice Safe Sound

WE WANT YOU LISTENING FOR A LIFETIME!

Used wisely your new sound reproduction equipment will provide you with a lifetime of listening pleasure. Unfortunately, hearing damage from exposure to loud noise is often undetectable until it is too late. Since it is all too easy to keep "turning up the volume" so you can overcome road noise, we would like to issue this word of caution. Velodyne recommends that you avoid prolonged exposure to excessive sound pressure levels. The following list is included for your protection.

Decibel Level	Example
40 dB	Quiet library, soft whispers
50 dB	Typical quiet room
60 dB	Office equipment, background noise
70 dB	Vacuum, hair dryer, restaurant
80 dB	Average city traffic

Sustained exposure to levels of noise higher than this can be dangerous to your hearing.

90 dB	Subway, motorcycle, lawn mower
100 dB	Garbage truck, power tools
120 dB	Live rock concert
140 dB	Gunshot (close range), jet plane
180 dB	Rocket launching pad

Information courtesy of Deafness Research Foundation.

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