Parametric EQ controls
The toggle switch on the top can switch the single band of parametric EQ on or off. Below this is the gain setting on the left. The gain level is from 3 dB to -12 dB. The bandwidth controls how wide the notch/peak is. The frequency knob on the right controls the centre frequency. It can be set from 20 Hz to 80 Hz with each dot position representing a 10 Hz increment. Boost below 40 Hz is not recommended. Above this point, our subwoofers have greater headroom.
Crossover controls include phase control on the left, then crossover setting in the middle and gain on the right.
The phase control has been improved in resolution and labels have been adjusted to be more accurate. The circuit is a simple RC all pass filter. A similar circuit is used for adding delay time (such as those in Linkwitz's all active speakers). While the circuit does provide delay, it is limited to 180 degrees. Theoretically, given a fixed delay, the phase shift should be proportional to frequency. However, this RC circuit will not go beyond 180 degrees.
Bass extension and management controls
The two switches on the left control bass management and the rumble filter. The two switches on the right are our bass extension controls which are standard on all our amplifiers, and control how low the bass response will extend.
For users with a home theatre receiver using the receiver for bass management: select 12 db/EXT (middle position). EXT means the main crossover is external. In this case, the crossover control knob is mainly for fine tuning.
For users not using bass management: select either 50hz/24 or 80hz/24. 50hz/24 means the plate amp implement a low pass filter with a fixed 12db at 50hz, plus the 12db adjustable knob to make up a 24db total slope. Similarly for 80hz/24. The following shows the frequency response of this 50hz and 80hz fixed filter.
In either case, one should always use the crossover knob in the middle to fine tune the overlap between subwoofer and front speakers. It is more important to combine this control and phase control to achieve the best results.
The rumble filter is useful in particular for vinyl use and in home theatre applications where high output is desired. The driver is protected from over excursion resulting from high amplitude subsonic content.
The settings on our studio balanced version are the same except for the inputs.
Single subwoofer use: Connect input to "source in" and set mode to master.
Multiple subwoofer use: Connect the master subwoofer with master mode selected. The controls on that amplifier will be used for the other slave subwoofers. Connect the master out to the slave input of the other slave subwoofers. Set slave subwoofers to slave mode. All other settings on the slave amplifiers will be by passed.