Telex DN9848 Loudspeaker Processor Application Notes, Advantage of DN9848 Look-Ahead Limiters

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Application Notes

10.APPLICATION NOTES

10.1. The Advantage of DN9848 Look-Ahead Limiters

The limiter in a loudspeaker processor is the last line of defence in protecting the speaker drivers from damage, and as such it has a very specific and critical job to do. One of the chief modes of loudspeaker failure is driver over-excursion, and unless the limiter is designed to act instantly in response to sudden increases in level, it will allow through brief transients that can cause damage through over-excursion. All dynamics processors take a finite amount of time to respond to a change in input level, and unless additional steps are taken the result is that the input signal is initially let through at anything up to its full level, until the gain element in the limiter can act in response to the increase in signal level.

The DN9848 exploits the fact that digital signal processing works on a sample-by-sample basis (the signal data samples are clocked through the unit at the sample rate of 48 kHz) and that there is a small delay through each processing block, and literally ‘looks-ahead’ further back in the signal chain to sample the data for the limiter side chain, so that the limiter can apply the required gain reduction on an instantaneous sample-by-sample basis, so that the limiter never lets through any dangerous transients.

In the example below a 10 kHz tone burst of 10 ms duration has been used as the input signal and the output of both a DN9848 and a leading competitor are shown. Note the very large transient of the competitor unit which does not have a look-ahead limiter.

Signal source: Audio Precision System One

Settings: Waveform: Burst – Normal. Frequency: 10.0 kHz. Burst: 10 ms. Interval: 100 ms. High Level: +10.0 dBu Low level: - 40.0 dBu

DN9848 settings: HPF: 1.25kHz Lnk-Ril 24dB/Oct. LPF: 20kHz Lnk-Ril 24dB/Oct. Limiter Threshold: 0.0dBu Release: 50ms

Response: Hard Knee

Competitor settings: HPF: 1.26kHz Lnk-Ril 24dB/Oct. LPF: 22kHz Lnk-Ril 24dB/Oct. Limiter Threshold: 0.0dBu Attack &

Release: Automatic

All other settings are default on both units.

As with all units that use sigma-delta ADC and DAC converters, there is a propagation delay from input to output, 3.2 ms for the DN9848 and 2.1 ms for the competitor unit, the additional delay in

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Contents Page Page Important Safety Instructions Page Declaration of Conformity Page Contents Technical Specification After Unpacking Safety WarningInstallation Considerations Page Introducing the DN9848 DN9848 Key FeaturesFront Panel Controls, Connectors, IndicatorsRear Panel Navigating the DN9848 Menus Programming SettingsDN9848 Menu System DN9848 Programming PanelHome Set Up MenuStore and Recall DN9848 Menu Map Input Channels Setting Input ParametersInput Channels Brief Technical OverviewParametric Equalisation Pages 2 to Gain and DelayTo set the delay To adjust the gainTo set the compressor parameters Monitoring the Input SignalTo switch the compressor out of the circuit CompressionOutput Channels Output ChannelsRouting Setting Output ParametersTo access the Output menu pages for a particular channel Naming the Output ChannelTo set a precise phase shift at a reference frequency Signal Invert, Delay and Output LevelPhase Adjustment Pages 4 To invert the output signalTo bypass the high/low pass filter processing To apply a ‘shaped’ phase transition at a chosen frequencyHigh Pass and Low Pass Filters Pages 6 To add a high/low pass filter to output processingParametric Equalisation Pages 2 to To set the limiter parameters Monitoring the Output SignalTo switch the limiter out of the circuit Output LimiterOutput Gain and Mute Front Panel Control Remote Comms Channel Security and other Set Up OptionsSecurity Settings Pages 2 GeneralTo remove the Panel Lock When System Protect is onSystem Protect To set a Panel LockLCD Lighting To switch System Protect onTo switch System Protect off To adjust the lightingTo change the units of measurement Delay OptionsPower Up Options To lock the system memories, refer to .3 Security Settings Using the DN9848 MemoriesStoring and Recalling Settings To store settingsPress the black Recall button to access the Recall menu To recall stored settings from memoryDN9848 Remote Control Setup Remote Control SetupRS-485 input to rear panel To disable remote controlDN9848 Connection Laptop/PC Cable /Converter Required Application Notes Application NotesAdvantage of DN9848 Look-Ahead Limiters Application Notes Audio Precision Deg phase shift @ 20, 300, 1K, 20K 01/19/01 Phase-adjustment with the DN9848Audio Precision 1st order allpass @ 300, 1K, 10K 01/19/01 Technical Specification Technical SpecificationPower Requirements Factory Presets for X-Array Series Memory Out Identification P08 XI1122/85 4MIX R1-2 Memory Out Identification Factory Presets for X-Line Series Memory Out Identification

DOC02-DN9848, DN9848 Loudspeaker Processor specifications

The Telex DOC02-DN9848, commonly referred to as the DN9848 Loudspeaker Processor, is an advanced audio processing device designed to enhance sound quality in both live and recorded environments. With a sleek and modern design, the DN9848 is engineered to meet the demanding needs of professional audio applications, be it in concert venues, theaters, or broadcast studios.

One of the key features of the DN9848 is its comprehensive processing capabilities. Equipped with a powerful DSP (digital signal processing) engine, it offers extensive equalization options, dynamic range control, and advanced crossover functionality. The device utilizes up to 48 input and output channels, allowing for unparalleled flexibility in routing audio signals. This makes it ideal for installations that require precise control over multiple loudspeakers.

The DN9848 also boasts an intuitive user interface, which facilitates straightforward navigation through its various functions. The front panel features a large LCD display that provides clear visibility of parameters, and a selection of knobs and buttons enables easy adjustments. For remote operation, the device can be controlled via Ethernet, allowing technicians to make changes from virtually any location.

Another standout aspect of the DN9848 is its customizable algorithms that accommodate different speaker systems and acoustical environments. Users can fine-tune the processor to optimize performance for specific venues or loudspeakers. The device supports both FIR (finite impulse response) and IIR (infinite impulse response) filters, providing users with the flexibility to deploy advanced filtering techniques according to their needs.

The DN9848’s robust connectivity options further enhance its utility. It features standard analog XLR connectors, as well as digital interfaces that include AES/EBU and Dante. This multi-format compatibility ensures seamless integration into existing audio setups, making it a versatile choice for audio professionals.

In terms of reliability and durability, the DN9848 is built to withstand the rigors of the professional audio world. Its rugged chassis and high-quality components ensure that it can perform consistently in various conditions, making it a trusted partner for sound engineers.

In summary, the Telex DOC02-DN9848 Loudspeaker Processor combines sophisticated audio processing capabilities with user-friendly features and robust connectivity. Its advanced technology and flexible options make it an indispensable tool for achieving optimal sound in a variety of professional audio environments.
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