HK Audio L SUB 1500 A, Manual

LINEAR SUB   1.5

6

12 Status LED  

(L SUB 1500 A, L SUB 1800 A)

This LED lights up green when the Power button is set to On and the unit is 
getting mains power.
This LED lights up red when the power amp’s input signal is too high or a 
fault has been detected. The LED briefl y fl ashes red to tell you the limiters 
are responding to signal peaks.

Heads up! If the Limit LED stays red while the unit is up and running, it 
is being overloaded. Turn down the signal level! If you are not routing a 
signal in and the Limit LED stays red, the system has detected a fault. 

13 Power

This is the on/off  button for the LINEAR active sub. Its status LED lights up 
green when it is engaged.

14 Mains

Use the factory-included mains cord to connect this socket to a wall outlet.

Note: All LINEAR SUBs are equipped with V-Lock mains sockets. If you 
use a VOLEX locking mains cord or another optionally available brand 
with the same design, you can fi x the mains cord in place to prevent 
accidental disconnection.

15 Speaker Out  

(L SUB 1200 A only)

This port serves to connect a passive L SUB 1200.

Heads up: Do not connect any other device. If you do, it may be destroyed 
along with L SUB 1200 A.

2 Connecting Cords

Use a microphone cord equipped with XLR connectors or 6.3 mm (1/4”) jack 
plugs to send the signal from the audio source (master, monitor, line, or a 
similar output) to the balanced L/R Inputs. Connect the active mid/ high 
units to the XLR outputs labeled Line Out Mid/High. Use the two Thru L/R 
ports to route the fullrange signal to other speakers. 

3 Operating the Sub

• Ensure the LINEAR active sub’s Power switch is set to off . 

Caution! Always make sure the local mains voltage matches the voltage 
specifi ed on the LINEAR SUB. You may destroy its electronic components 
if you connect it to the wrong mains voltage.

•  Turn the Gain Bass knob to the 12 o’clock position (0 dB/ center-notched).

•  Set the Confi guration switch accordingly to match the number of LINEAR 

active subs you are using.

•  Ensure all connected line sources are switched on before powering up. 

First, switch on the connected mixer and all signal sources connected to 
it, for example, keyboards, amps, eff ects, and so forth. LINEAR active 
speakers should always be connected to the Line Out Mid/high ports and 
switched on after all other components are up and running. When you’re 
ready to tear the rig down, please turn the LINEAR active speaker down by 
rotating the Input A/B Gain knobs counterclockwise as far as they will go 
and switch them off  before powering down all other connected devices.

•  When you fl ip the Power switch, the fan will briefl y start up (system 

check) and stop after about fi ve seconds. The fan is temperature-
controlled. It kicks on only at very high volume levels and runs according 
to the given temperature. The Status LED (L SUB 1200 A, L SUB 2000 A, 
L SUB 4000 A) lights up red during the system check and will extinguish 
unless a fault is detected.
L SUB 1500 A, L SUB 1800 A: The Status LED lights up red during the 
system check, and then green if there is no malfunction and the unit is 
getting mains power.

4 Settings

• Adjusting Volume Levels with the Gain Bass Knob

Use the Gain Bass knob to adjust the active subwoofer’s volume to suit the 
venue and situation. If you want to increase or decrease the subwoofer’s 
volume, simply turn this knob to the left or right (control range +/-6 dB). 
If you hear distortion or the signal sounds saturated, fi rst check the signal 
sources and, if possible, reduce the output signal level there.

•  Adjusting the Corner Frequency: 

With the X-Over Bass Switch

You can use this switch to adjust the LINEAR active sub’s frequency range 
to match the signal you wish to render and/or the surroundings. The Line 
Out Mid/High Left/Right outputs are not aff ected by this setting.

With the Mode Switch  

(L SUB 4000 A only)

Use this switch to adjust the frequency response of the active LINEAR 
subwoofer to the audio signal and the surroundings. The Line Out Mid/High 
Left/Right outputs are not aff ected by Mode changes.
If you add the L SUB 4000 A to an existing PA system as a deep bass 
extension, Sub Low is the recommended setting. The LINEAR range’s 
acoustic and phase-corrected tuning ensure that the L SUB 4000 A works 
with every model available.

• Adjusting the Phase Position with the Phase Switch

You can use the Phase switch to adjust the LINEAR active sub’s phase 
position to match that of the connected mid/ high unit (for more on this, 
see section 1.7)