Integrated Controller Circuitry; Input Circuit; Filter Functions; Limiter - HK Audio SL 218 A Manual Del Usuario

SL 218 A Manual 1.0
Figure 1: View of the SL 218 A's control elements.
3. Integrated Controller
Circuitry
The SL 218 A is equipped with an active controller
providing crossover and limiter functions.

3.1 Input Circuit

The SL 218 A's audio input is electronically balanced.
Input impedance is greater than 22 kOhms.
The nominal input level is +4 dBu with the knob set
to 12 o'clock, or -2 dBu with the knob set to maximum
(clockwise). The maximum input level is 22 dBu.
The audio input is furnished with a high-frequency
filter protecting it against pick-up of stray high-
frequency noise.

3.2 Filter Functions

The integrated crossover function comprises a low-
pass filter with a 12-dB-per-octave slope and a variable
upper frequency limit that is adjustable within the
range of 60-100 Hertz. In addition, the audio signal's
polarity can be inverted by 180 degrees to match the
polarity of the PA requiring sub-bass reinforcement.
The SL 218 A's integrated crossover function is not
required when an external active controller (for
example, the DFC) is used to drive the SL 218 A.
In this case, you can circumvent the SL 218 A's
crossover by flipping the Bypass switch.
A 20-Hz electronic high-pass filter labeled Subsonic
Filter cuts extremely low frequencies. Although
hardly audible, these ultra-low frequencies could
push the 18" woofers unnecessarily hard. The speaker
membranes could be destroyed when subjected to
excessive travel.
Note:
The Subsonic Filter and the SL 218 A's Polarity switch
remain in the signal path when the crossover is
bypassed.

3.3 Limiter

The SL 218 A's integrated controller circuitry is equipped
with a peak limiter for each of the two channels.
They protect the power amps and connected speakers
against excessive signal levels.
4 Displays and Controls
Displays and controls are mounted out of harm's
way on a recessed panel on the rear of the SL 218 A.
Mains Power Switch
OFF or 0: The SL 218 A is powered down.
ON or 1: The SL 218 A is powered up.
Amp On Mains LEDs
Dedicated LEDs for the A and B power amp channels
light up blue to indicate the SL 218 A is switched on
and ready to operate.
Protect LEDs
Dedicated LEDs for the A and B power amp channels
light up red to indicate the SL 218 has switched to
Protect mode due to power overload, overheating
or an internal problem. When in Protect mode, the
given power amp channel is muted.
Gain
Twist this knob to adjust the level of the two 18"
woofers in the SL 218 A. The standard setting is 0 dB.
Signal and Clip LEDs
Dedicated LEDs for the A and B power amp channels
indicate incoming audio signal levels.
X-Over
Twist this knob to dial in the integrated crossover's
upper frequency limit, which can be set between
60 Hz and 100 Hz. Where it should be set depends
on the response of the sound reinforcement system
connected to the SL 218 A. (Refer to the section
entitled Applications).
Phase
Use this switch to determine the SL 218 A's polarity.
The setting depends on the sound reinforcement
system connected to the SL 218 A. (Refer to the
section entitled Applications).
0°: The SL 218 A's polarity is positive (in phase).
180°: The SL 218 A's polarity is negative (out of phase).
Bypass
Use the Bypass switch to remove the SL 218 A's
integrated crossover from the signal path. This is
necessary whenever you use an external active con-
troller (for example, the DFC) to drive the SL 218 A.