Do servo subs need a Linkwitz Transform?
Servo subs in general do not need Linkwitz Transform circuits. Our Direct servo subs don’t. The Direct servo subs are closed loop systems where a servo signal that monitors the movement of driver’s cone is fed back to the amplifier to achieve lower distortion, as well as a more coherent sound over a wide range of working conditions. LT-based subs are open loop systems. Flat response is achieved by predicting the transfer function between the amplifier output and the speaker output and pre-equalizing the amplifier output with the inverse of that transfer function. However, as the driver parameters change due to signal level, break-in, and fluctuating voice coil temperature, the actual transfer function between amplifier output and speaker output would also change. When that occurs, the output from the subwoofer will no longer be flat.
