Page 70 DPA Series — DPA80/DPA100 Operating InstructionstaxSetting Accurate Limiter Thresholds — Program LimiterIntroductionThe limiters built into your amplifier are intended to be used for loudspeaker driverprotection, as opposed to amplifier protection. The amplifier has additional limiters whichcan adapt automatically to both temperature and incoming mains conditions to stayoperational and playing music for as long as possible. The following section describes how toset up the units’ limiters to provide exceptional protection against driver overheating andcone over-excursion. Most speaker systems are given a power rating in Watts RMS. This isthe maximum continuous power that the system will handle and often appears veryconservative. In reality, as music program is far from continuous in nature, the peak power ofthe system is much higher — up to ten times the continuous figure. Any limiter, which is toprotect the driver from damage, must be able to fulfil the following tasks:- Have an attack time which is calculated to allow transients through but keep the RMSlevel below the speaker manufacturers specification;- Have a release time which is sufficiently long to avoid the limiter itself modulating theprogram;- Be intelligent enough to adjust the envelope of the limiter according to the frequencycontent of the program material.The RMS limiters are capable of performing all these tasks. The only parameter that the usermust set manually is the threshold, and it is crucial that this is done correctly.
