Fig. 7 Highmid attenuation jumper socket.
3.1.5 MONO-Bass option
If you intend to use a system with a single bass speaker cabinet, use the SP2’s MONO-Bass
function. To this end you have to latch the two blue wire breakers which are labeled ‘Mono-Bass’.
The effect is an identical bass signal at the woofer output connectors.
3.2 Limiter operation
The SP2 incorporates 4 independent limiters ( HighMid CH. A and CH. B, Bass CH. A and CH. B).
For each of these you can preset one of 3 different attack/release time constants as well as the
maximum allowable speaker output power.
For proper limiter operation it is mandatory to connect the speakers to the ‘output to speaker’-
speakon connectors, and not directly to the power amp outputs. Those must be connected to the
‘power connection from amp’-inputs. By passing the power amp signal through the unit it is
possible to detect the actual power delivered to the speakers. This power detection is
indispensable for proper limiter operation (see also fig. 1).
The time constants are set by placement of the blue jumpers in the limiter section. The jumper
sockets are labeled A, B and C corresponding to fast, medium and slow attack/release times. The
actual time constants are different for the two signal paths:
Bass:
A = 20ms,
B = 100ms,
C = 200ms
HighMid:
A = 10ms,
B = 40 ms,
C = 100ms
The maximum allowable power is adjusted via the four 5-switch DIP-arrays. Table 2 in the
appendix shows the power amp thresholds for various speaker cabinet impedances. Limiter
operation is visible on the front panel by two red LEDs. The limiting characteristic of the SP2 is
shown in fig. 8: the diagram shows a dynamic characteristic curve where the signal is not abruptly
limited above a certain threshold, but rather compressed with a compression ratio
2
that increases
with increasing power.
2
see glossary in the appendix
