XTA DP226 Operator's Manual

Also see for DP224: How-to

Contents

XTA DP226 Operator's Manual Manual pdf 42 page image

Page 42 DP224/6 Operators ManualSetting Accurate Limiter ThresholdsThe limiters built into the DP226 are intended to be used for for loudspeaker driverprotection, as opposed to amplifier protection. All modern professional poweramplifiers designed for live sound use have their own limiters which are tailored toprotecting the amplifier from clipping.The following section describes how to set up the DP226’s limiters to provideexceptional protection against driver overheating, and cone over-excursion.Most speaker systems are given a power rating in Watts RMS. This is the maximumcontinuous power that the system will handle and often appears very conservative. Inreality, as music program is far from continuous in nature, the peak power of thesystem is much higher – up to ten times the continuous figure. Any limiter, which isto protect the driver from damage, must be able to fulfil the following tasks.• Have an attack time which is calculated to allow transients through but keepthe RMS level below the speaker manufacturers specification;• Have a release time which is sufficiently long to avoid the limiter itselfmodulating the program ;• Be intelligent enough to adjust the envelope of the limiter according to thefrequency content of the program material.The DP226’s limiters are capable of performing all these tasks. The only parameterwhich the user must set manually is the threshold, and it is crucial that this is donecorrectly. Consider the table below.dB Ratio Vrms Pwr 8 Ω Pwr 4 Ω Pwr 2 Ω45 177.83 137.74 2371.71 4743.42 9486.8344 158.49 122.77 1883.91 3767.83 7535.6643 141.25 109.41 1496.45 2992.89 5985.7942 125.89 97.52 1188.67 2377.34 4754.6841 112.20 86.91 944.19 1888.39 3776.7840 100.00 77.46 750.00 1500.00 3000.0039 89.13 69.04 595.75 1191.49 2382.9838 79.43 61.53 473.22 946.44 1892.8737 70.79 54.84 375.89 751.78 1503.5636 63.10 48.87 298.58 597.16 1194.3235 56.23 43.56 237.17 474.34 948.6834 50.12 38.82 188.39 376.78 753.5733 44.67 34.60 149.64 299.29 598.5832 39.81 30.84 118.87 237.73 475.4731 35.48 27.48 94.42 188.84 377.6830 31.62 24.49 75.00 150.00 300.00Using this table it is a straightforward procedure to work out the required setting ofthe limiter thresholds for the system. Follow the steps described overleaf.