Millenium subwoofer of Jurassic Park / Muhammad Faridzman Mansor and Mohd Rofaizal Ahmad

The subwoofer circuit comprises of a few basic building blocks. Most of the electronic circuitry is built around a TL072 dual op amp IC, which functions as an input buffer and a variable low past filter. The input circuitry consists of a mixer and voltage dividers formed by two pairs of 200 ohm and 10K ohm potentiometer / volume control connected to a unity gain op amp buffer. The input signals to the subwoofer circuitry are the same as those from the output of the power amplifier. A simple reason for doing so is to have the volume loudness of the subwoofer vary accordingly with the output level of the existing set of speakers.
The second TL 072 op amp is configured as a 12dB per octave low pass filter with the help of two 47K ohm resistors , a 100K ohm potentiometer and 0.012p F capacitor each . The cut off frequency to between 50 Hz and 150Hz . The frequency value is determined by the equation 1 / 2 p RC.
The low frequency signal is then sent to a power amplifier. In this design, we have opted for the use of an off the shelf power amplifier module available in the market, from either Farnell or R.S Components. This is a standard power amplifier with very robust characteristics and requires minimum additional external components. As quoted the HY series of power amplifier modules are a versatile range of building block for the construction of high quality audio amplifiers. ‘ The power amplifier modules can of course be replace by any other standard amplifier without problem, though for good performance , only an amplifier having an output power of no less than 30 watts is recommended