MK Sound MX-150THX, V-125THX, Operation Manual

page 6

THX subwoofers

TESTING THE SUBWOOFER (THX MODE)

Once all of the interconnect cables are in place, you are just about ready to plug in the subwoofer.

Set the "LOW PASS FILTER" toggle switch to the "THX" position and the "BASS LEVEL" toggle switch
to the "THX" position.

Set the "SUBWOOFER PHASE" switch to the "+" position.  If your THX controller has a

SUBWOOFER (OFF/ON) switch on its front panel, rear panel, or remote control, set it to ON.  (See
the controller's manual for details).

Plug the subwoofer's AC cord in.  The red LED on the back panel should illuminate.

Play some program material that has good bass content through your system.  Carefully advance

the system volume control.  You should hear the subwoofer operate.  If you think the subwoofer isn't
working, walk up to the speaker and listen to it from a distance of a foot or less.

If you confirm that it is not working, unplug the subwoofer and check all of your connections before

trying it again.  If you have a problem that you cannot solve, contact your dealer or the M&K factory.

When your system wiring is complete and the subwoofer is plugged into the wall, leave it plugged

in, even when the system is turned off.  The normal mode of operation for the subwoofer is to remain
plugged in 24 hours a day.  Among other things, this means that you don't have to walk over to the
subwoofer to turn it on every time you want to use the system.

DO NOT PLUG THE SUBWOOFER INTO A SWITCHED OUTLET ON ANOTHER COMPONENT. IT CAN DRAW UP

TO 400 WATTS FROM THE AC LINE.  IT MUST BE PLUGGED INTO A SOLID AC LINE.

5.  CALIBRATING THE SUBWOOFER (THX)

On the back panel of the subwoofer, three toggle switches allow you to select various modes of

operation.  Two are described here.   A description of the function of the third toggle switch can be
found in section 7, SATELLITE & SUBWOOFER PHASING TEST (page 11).

OPERATION OF THE "LOW PASS FILTER" SWITCH (THX)

When using the subwoofer with a THX controller, this switch should be set to the "THX" position.

When using the subwoofer with a standard stereo system or a surround sound processor that is not
THX-certified, this switch should be set to the "80 Hz 24 dB/OCTAVE" position.

The THX mode bypasses the internal crossover of the subwoofer and fixes its gain to a standard

setting.  The THX controller contains the crossover and sets the rolloff point of the signal fed to the
subwoofer to 80 Hz (with a Linkwitz-Riley characteristic).

OPERATION OF THE "BASS LEVEL" SWITCH (THX)

When using the subwoofer with a THX controller, this switch should be set to the "THX" position.  The

controller sets the output level of the subwoofer, so this switch disables the subwoofer's level control.
For the MX-150

THX

, this position provides the proper sensitivity for when one subwoofer is used in the

system.  For the V-125

THX

, this position is proper when two subwoofers are used in the system.

The "CALIBRATED" level control mark is referenced to the level set by the "THX" switch.  On the

MX-150

THX, 

both levels are identical.  If you set the MX-150

THX

 switch to "VARIABLE" and the level

control to "CALIBRATED," its output level is the same as when you set the switch to "THX."