In the chart below, with bass extension controls set to Low Music, the response is 3 db down at 18Hz. The red and blue lines are the amplitude and phase response, respectively. The phase shift as only 120 degrees. But in reality the microphone itself has 18 degrees of phase shift at 20hz. Therefore L12 only has 102 degrees phase at 20hz.

L12 features bass extension switch allowing users to select among 3 different modes: Low Music (Q=0.5), Low HT (with a 18db/oct rumble filter at 20hz), and High (with 18db/oct bass extension at 28hz). Below is the frequency and phase response of Low HT mode. Note that the phase response (blue line) below 10hz is noisy because the response level is significantly down below 10hz.

The comparison of all 3 modes with LINE-IN is shown below

L12 accepts a pair of LINE-IN and one LFE IN. The LFE input mode extends the upper end response to 200hz.

Integration

L12 provides a 12/24 db/oct switchable low pass filter to so that it can easily integrate with any front speakers.

Another aspect of getting a correct integration is phase alignment between the front speakers and the sub. We have written a guide on how to achieve a phase aligned subwoofer. L12 has a phase/delay adjustment knob. More

Output, extension and user preferences

The bass extension switch allows the user to customize the deep bass extension and the rumble filter to control cone excursion. For HT application, one can set the extension to Low-HT or High for higher SPL output. For music one may prefer a lower cut off such as Low-Music setting. Changing the settings can also result in a better integration with the acoustic gain of the room.