L8400P (serv.man12) - JBL Audio Service Manual (repair manual). Page 8

Move the Master Power switch
¢ to the “On” position to use
the L8400P subwoofer.

If you will be away from home
for an extended period of time,
or if the subwoofer will not be

used, switch the Master
Power switch 

¢ to the “Off”

position.

The subwoofer Level Control
• adjusts the volume of the
subwoofer relative to the rest
of the system. Proper level

adjustment depends on sev-
eral variables such as room
size, subwoofer placement,
type of main speakers and

position. Adjust the subwoofer
level so that the volume of the
bass information is pleasing 
to you.

The Crossover Frequency
Control 

¶ determines the

highest frequency at which the
subwoofer reproduces sounds.
If your main speakers can
comfortably reproduce some
low-frequency sounds, set this
control to a lower frequency
setting, between 50Hz and
100Hz. This will concentrate
the subwoofer’s efforts on 
the ultradeep bass sounds
required by today’s films and
music. If you are using smaller
bookshelf speakers that do not
extend to the lower bass fre-
quencies, set the low-pass
crossover control to a higher
setting, between 120Hz and
150Hz. This control is not used
when the LFE switch 

∞ is in

the “LFE” position.

L8400P OM   6/8/05  4:10 PM  Page 8

L8400P 

 

L 

series 

       

 

 

7