Front and Rear Panel Descriptions
®
120A User Manual
2
Section 1
120A
J- Subwoofer Level Control
This control sets the level of the low frequency crossover signal (original program plus synthe-
sized harmonics) coming out of the SUBWOOFER jack.
K- LF Boost Control
This control is used to even out the total apparent Bass output of the 120A. Use the LF Boost
to gently boost the bass on each channel (after the harmonics are summed in) to fill in the
gap between the synthesized low bass (below 55 Hz) and the mid-bass of the original pro-
gram. Always be careful of using excessive boost, especially if the Subharmonics control is
past its midpoint, or if you are using a speaker equalizer, or any other bass tone control.
LF BOOST can be used with or without Subharmonic Synthesis.
L- Subharmonics Control
This control, along with the individual frequency controls, sets the amount of synthesized bass
that the 120A adds to the program. Its affect depends not only on where it is set between MIN
and MAX, but also on how much bass is present in the original signal to be augmented. Note
that the effect will be most apparent in systems with subwoofers or other speakers that effec-
tively reproduce very low bass tones.
M- 24Hz-36Hz and 36Hz-56Hz Level Controls
These controls individually let you customize the amount of the respective synthesized fre-
quencies to be added in, tuning the ultimate bass response of your system to taste. For
example, if the sound is too woofy or growly, try turning down the 36Hz-56Hz level. If your
woofers are bottoming out (making a ticking, popping sound), or fuses are blowing, or your
amp is clipping, try turning down the 24Hz-36Hz level. You may find that a setting produces
fine results in one room, but produces too much boominess in another. If this occurs, adjust
the controls as needed, (e.g., increase one or the other of the band levels). Experimentation
will pay off with smooth, full, deeply extended bass. Remember, you are not selecting a fre-
quency. You are controlling the overall level of each band.
Setting Levels
Do not use the 120A at its extreme settings with loud volume levels, especially with digitally-
produced audio.
Very low bass frequencies call for considerable amplifier power and for loudspeakers that can
take this considerable power. However, the 120A not only can boost the bass that is present
in the original program, but can simultaneously generate sizable amounts of new bass at even
lower frequencies. If not used with care, the 120A can damage system components (e.g.
woofers can be readily damaged by very loud bass, intentional or otherwise). dbx Professional
Products cannot take responsibility for any damage to the amplifier, loudspeakers, or other
stereo components that results from the 120A.
When using the 120A (or any other component in your system), reduce the system’s output
level. It is also recommended that all of the 120A front panel controls be set to fully counter-
clockwise to minimum (MIN). When installation is complete, carefully return the system to nor-
mal listening levels and adjust the 120A to taste.
If clipping occurs, lower the volume and decrease the 120A settings. Note: Never try to repro-
duce non-musical sounds like artillery explosions or gunfire with the 120A.
1.3 Operating Notes