SLS CS6600, User Manual, Page: 23 / 23

SLS™ CS6600 Line Array Module and CS6600RF Rigging Frame User’s Guide 15
Appendix B
Setting System Limiters
B.1 Setting up System Limiters
This documentation explains how to set up system limiters to protect your loudspeaker
and provide maximum performance when the digital signal processor (DSP), amplifier,
and loudspeaker hardware are all variables. The following procedure provides a limiter
setting threshold that can protect loudspeakers in a majority of use cases. However, the
speaker drivers may still be vulnerable to content issues, such as sustained feedback or
large, low ‐ frequency transients below box tuning. Good system design and common sense
should be the rule.
1. Obtain an audio source (to generate pink noise) and a true RMS voltage meter with a
bandwidth of at least 20 kHz that can average a reading over a period of at least 10
seconds.
2. Complete the room tuning and set the amplifier gain.
To prevent future user error, consider setting the amplifiers at full gain, unless the
amplifier gain setting is hardware or software protected. In such a case, you can
optimize the amplifier gain to achieve the best signal ‐ to ‐ noise ratio.
3. After completing the room tuning and setting the amplifier gain, bypass the limiter on
the DSP that you are using for protection, and leave all other DSP functions for that
output engaged. For example, the highpass filter, crossovers, equalization, and so on.
4. Mute all system outputs except the output that is currently being calibrated.
5. Place the voltage meter across the amplifier +/ ‐ output terminals and turn up the pink
noise source until the reading on the meter is slightly above the specified
Threshold/RMS voltage rating for that speaker driver and its recommended processor
settings (see Section 1.3 ).
6. Play the pink noise only long enough to obtain a stable RMS average voltage reading
For high ‐ frequency drivers, this is typically five seconds, and for full range
loudspeakers or subwoofers, it is typically ten seconds.
7. Set the limiter to a minimum ratio of 100:1, and then input the attack and release times
recommended by the speaker manufacturer.
8. Engage the limiter, and decrease the threshold until the voltage is lowered to the
specified rating, without changing the pink noise gain.
9. Repeat the above procedure for each driver and/or passive loudspeaker you are using.
10. If a predictive peak stop limiter is available on the DSP, engage it at 6 dB above the
RMS setting.
11. Monitor for amplifier clipping. If clipping occurs during system use, lower the
peak ‐ stop threshold until the amplifier clips slightly. Alternatively, you can engage
the self ‐ contained limiter circuit in the amplifier (if it has such a limiter circuit).
You need to perform this procedure only once, as long as the combined
amplifier ‐ limiter does not change. However, amplifier gain changes modify the limiter
action. If the amplifier gain is decreased, protection engages early, which limits driver
output. If the amplifier gain is increased, protection engages only after the driver
reading is above the safe RMS voltage.