JL Audio Gotham v2 Owner's Manual page 17

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E.L.F. Trim
The Extreme Low Frequency ("e.l.f. trim") knob allows the user to apply
a certain amount of signal equalization at 24 Hertz (extremely low bass). At
full counter-clockwise rotation, the signal at 24 Hz is cut by 12 dB. At "0" the
equalizer is set flat for zero contribution to the signal. At full clockwise rotation,
the signal at 24 Hz is boosted by 3 dB.
The e.l.f. trim feature is useful for tailoring the Gotham v2's very low
frequency output for your particular room. Adding some boost can make certain
material feel more exciting. Using the cut function can help to compensate for
room or boundary gain in the low frequencies. Room boundaries and the room's
finite (limited) size naturally cause very low frequencies to be boosted relative
to other parts of the signal. As such, using the e.l.f. trim feature to cut the lowest
frequencies can help to tame "bloat" or unnatural sounding low bass in small to
medium sized rooms (and can also reduce unwanted vibrations in the room or
throughout the house).
Polarity
The Polarity switch allows the user to select between normal (0 deg) and
reversed (180 deg) signal polarity. The Polarity switch will primarily affect the
small frequency range around the crossover point between your subwoofer and
satellite speakers.
Unlike the Phase control, which effectively adds time delay, the Polarity
switch produces an instantaneous reversal of the signal's amplitude peaks.
For example, if at a given reference point a sine wave has an amplitude peak,
by flipping the phase switch you instantly convert that peak into a trough
or amplitude dip. Because the effect of the Polarity switch is immediate, it
compliments the operation of the Phase control and cannot be replaced by it.
When placing your Gotham v2 in the room, experiment with the Polarity switch
before adjusting the "Phase" control. Either position of the Polarity switch may
provide a smoother transition between your Gotham v2 subwoofer and the satellite
speakers. Use source material with good mid and upper bass content for evaluation.
Phase
The Phase control knob allows the user to adjust the "timing" of the
subwoofer output relative to the main speakers. The Phase control will primarily
affect the small frequency range around the crossover point between your
subwoofer and satellite speakers. Phase settings between 0 degrees (full counter-
clockwise rotation) and 270 degrees (full clockwise rotation) are possible. The
Phase control's labels are referenced to a frequency of 80 Hz since this is the most
common crossover point between satellite speakers and a subwoofer.
Speaker, subwoofer, and listening seat positions vary greatly in home
theater installations. Since physical positioning of speakers relative to the room
boundaries, and each other, greatly affects the perceived quality of sound output,
sometimes it is helpful to delay the subwoofer output. This is exactly what occurs
when you turn the Phase control beyond 0 degrees.
Once your Gotham v2 has been placed in your listening room to give you the
smoothest overall sound and after you have determined the optimum "Polarity"
switch position (see preceding section), experiment with the position of the Phase
control. Using familiar source material with good mid and upper bass content,
adjust the Phase control and listen for better defined mid-bass and a smoother
transition between the subwoofer and satellite speaker systems. If no single
setting sounds better than another, leave the Phase control at 0 degrees.
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