Earthquake Supernova MKVI 15" Subwoofer

The Design

The MKVI sports a 15" active driver on one side and a 15" passive radiator on the other.

The amplifier is rated at 600 watts RMS. The controls consist of an adjustable crossover (40 Hz - 200 Hz) that can be turned off, a subsonic filter, phase delay (0 - 20 ms), phase shift (00 - 1800), two sets of XLR and RCA input jacks, and three bands of EQ (20 Hz, 30 Hz, and 40 Hz).


The MKVI is unique in having three EQ bands. Usually there is only one. But, it is also unique in having adjustable phase shift. The way this is used is to play a 50 Hz tone through your entire home theater system, with the MKVI connected, and adjust the phase shift until the tone sounds the loudest. This occurs when the phase of the MKVI matches the phase of the other speakers that are also producing some sound at 50 Hz.

The way it works is as follows:
1. Set the 00/1800 switch to 00.
2. Set the delay to 0 ms.
3. Set an SPL meter on the sofa (or wherever your listening position is) with 50 Hz at about 90 dB playing in your system.
4. Rotate the delay knob while checking for the dB meter changes. As soon as you see the first peak, stop turning the delay know and document its setting. For example, say it peaks at 2 o'clock rotational position.
5. Now set the phase switch to 1800.
6. Redo the above by rotating the delay knob.
7. Once again look for the first peak. Document the delay knob position. If it is say 12 o'clock, which is lower than the 2 o'clock position by some 15 degrees, then this is the better phase adjustment, as it took less delay to achieve the same thing. This circuit is only available with the MKVI.

Shown below is a diagram of two different examples.