JL Audio Fathom f212 - Manual (Page 17)

Page 17 | Fathom f212
E.L.F. Trim
Th e Extreme Low Frequency (“e.l.f. trim”) knob allows the user to apply
a certain amount of signal equalization at 25 Hertz (extremely low bass). At
full counterclockwise rotation, the signal at 25 Hz is cut by 12 dB. At “0” the
equalizer is set fl at for zero contribution to the signal. At full clockwise rotation,
the signal at 25 Hz is boosted by 3 dB.
Th e E.L.F. Trim feature is useful for tailoring the Fathom’s very low frequency
output for your particular room. Adding some boost can make certain material
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 fi nite
(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
Th e Polarity switch allows the user to select between normal (0 deg) and
reversed (180 deg) signal polarity. Th e Polarity switch will primarily aff ect the
small frequency range around the crossover point between your subwoofer and
satellite speakers.
Unlike the Phase control, which eff ectively 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 fl ipping the phase switch you instantly convert that peak into a trough
or amplitude dip. Because the eff ect of the Polarity switch is immediate, it
compliments the operation of the Phase control and cannot be replaced by it.
When placing your Fathom 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 Fathom subwoofer and the satellite
speakers. Use source material with good mid and upper bass content for evaluation.
Phase
Th e Phase control knob allows the user to adjust the “timing” of the
subwoofer output relative to the main speakers. Th e Phase control will primarily
aff ect the small frequency range around the crossover point between your
subwoofer and satellite speakers. Th
e Phase control’s labels are referenced to 80
Hz since this is the most common crossover point between satellite speakers and
a subwoofer. Phase settings between 0 degrees (full counter-clockwise rotation)
and 280 degrees (full clockwise rotation) are possible.
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 aff ects the perceived quality of sound output,
sometimes it is helpful to delay the subwoofer output. Th
is is exactly what occurs
when you turn the Phase control beyond 0 degrees.
Once your Fathom has been placed in your listening room to give you the
smoothest overall sound and aft er 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 defi ned 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.