Dynacord Stereo System manual Appendix a Distributed Audio Systems a Primer

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Appendix A: Distributed Audio Systems – A Primer

The technique of constant-voltage (CV) loudspeaker distribution has been a standard audio practice since the earliest days of sound contracting.

Why Is It Called “Constant Voltage”?

You may have heard a distributed speaker system referred to as a “70-volt constant voltage system.” Does this mean that there is a constant AC or DC voltage of 70 volts always going through the speaker line? No, it doesn't.

I've heard that the term goes back to early telephone systems. Audio engineers of that time were concerned with how the voltage arriving at the receiving device varied from the voltage sent out by the sending device, and how the voltage transfer would vary in conjunction with changes in the impedance of the receiving device. In distributed speaker systems, where the impedance of the receiving device (in this case, the transformer) is very high relative to the impedance of the sending device (in this case, the power amplifier), then the receiving device receives the same voltage regardless of the impedance of the receiving device (within reason). For example, if the amplifier is putting out a sine wave of 70 volts RMS, then the full 70 volts goes across the primary of the transformer whether you've connected to a 5-watt tap (which is 1,000 ohms) or to a 50-watt tap (which is 100 ohms). So there is “constant voltage” transfer regardless of the impedance.

Does this mean that multiple low-impedance speakers (8 ohms) driven by an amplifier is not a “constant voltage” system? Driving a low-impedance speaker system (16 ohms, 8 ohms, 4 ohms) with a power amplifier is also a “constant voltage” system until you have too low of an impedance for the amplifier to drive. For example, a 10-volt sine wave from the amplifier driving a 16-ohm speaker will continue to be a 10-volt sine wave if you connect an 8-ohm speaker instead. The 8- ohm speaker will simply draw more current from the 10-volt signal, resulting in more power draw. The voltage stays the same but the current draw varies, which results in different power taps.

Developed specifically for distributed paging and public address systems, and adopted by the EIA, the CV method relies upon standardizing the RMS voltage level of distribution lines. The common CV voltage standards are 70-volt (technically 70.7-volt, selected because of electrical, insurance and/or building code regulations limiting the maximum voltage in unprotected speaker lines) and 25-volt.

What Are the Advantages to Constant Voltage Systems?

CV systems permit flexible connection of loudspeakers across the distribution line, much like connecting a light bulb across a power line. Transformers are utilized at each loudspeaker to regulate the proportion of the total amplifier power that the speaker “sees” (which determines the maximum sound pressure level in the corresponding zone). This results in a very reliable system, as long as the net power demanded by each branch does not exceed the rated power of the driving amplifier. Even if one or more speakers become disconnected or fail, the power applied to the others remains the same.

Constant-voltage distribution greatly simplifies the calculations involved in designing a background music or paging system. Within the amplifier’s power limit, speakers can be freely added to (or subtracted from) the system without the relatively tedious recalculation of total load impedance. Moreover, the CV method allows a single amplifier to drive many speakers without resorting to series/parallel connection techniques: all connections are made in parallel with the line.

CV systems require that the output voltage be constant over a relatively wide range of load impedances, to a practical minimum limited by the output capability of the amplifier. Early direct- coupled tube amplifiers rarely met this requirement (or had output voltages that were far too high), and so tube amplifiers for CV systems once employed integral output transformers. Virtually all modem professional transistor amplifiers deliver an output voltage that is essentially independent of load, however, making contemporary CV systems much easier to implement.

ElectroVoice/Dynacord BGM Guide

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Contents Paging/Background Music Systems Disclaimer & Copyright Table Of Contents Analyzing the Application When To Specify Mixer/Amplifiers EV has ALL the Perfectly Positioned Products Business Audio BusinessElectroVoice/Dynacord BGM Guide Evid Surface Mount Speaker Systems EV Business Audio Product GuideEvid Ceiling Mount Speaker Systems Evid Ceiling Speaker Solution Why is it Different?Outdoor Ready Construction Evid 4.2, 8.2 and 8.2L Full Range Models with Punch EV Raw Frame Ceiling Speakers10.1 Finally a Compact True Ceiling Subwoofer MA Series Mixer Amplifiers EV Amplification ProductsCPS Series Power Amplifiers EV Commercial Power AmplifiersPrimary Features ProAnnounce Digital Routing System Key CPS Amplifier Product FeaturesOverview Basic System Components ProAnnounce DP Series Power AmplifiersAudio Routing Made Easy What to Recommend? Basic Business Audio System Design GuideConduct a Preliminary Layout and Walk Through Determine the Acoustic RequirementsExpect The Unexpected Assemble the Equipment ListStandardizing for Profitability Speaker SelectionCeiling vs. Surface Mount Systems Selecting & Positioning Ceiling LoudspeakersCeiling Speaker Coverage An Example of Coverage Pattern vs. Speaker Size Converting Coverage Specs to a LayoutUse of Subwoofers When Controlled Coverage is NeededPositioning Subwoofer Components Choosing the Best Mixer/AmplifierAnalyzing the Application When To Specify Mixer/Amplifiers DRM4000 vs. the DPM4000 When the Job Calls For ProAnnounceDPM4000 4x4 Matrix Router DRM 4000 MixerSignal Generators / Voice Message Memory Volume And Tone Controls / DelaysControl Inputs And Outputs Monitoring Clock / CalendarMacros InterfacesUnderstanding DCS Expansion Options Station Control ConsolesDCS 400 Expansion Chassis BGM and Paging System DesignsRetail Store Single Zone BGM Installations System ExamplesLayout Overview Office Building 5 Zone Simplified systemQuipment List Bar-Restaurant 2 ZoneSpeaker Systems Health Club 4 ZoneProannounce Equipment Retail Clothing Store -2 ZoneRetail Bookstore Equipment List Retail Book/Record Store -3 ZoneLarge Department Store 6 Zone Basic Warehouse 5 Zone Speaker Systems Proannounce Equipment Multi-Use Warehouse, Factory & Office Facility 15 ZoneAppendix a Distributed Audio Systems a Primer Why Is It Called Constant Voltage?What Are the Advantages to Constant Voltage Systems? Single-Channel Direct Drive Amplifier BridgingUse of Autotransformers

Stereo System specifications

The Dynacord Stereo System is a remarkable audio solution designed for audiophiles and professionals seeking superior sound quality and versatility. Renowned for its exceptional engineering, Dynacord emphasizes clarity, power, and precision in all of its products, and this stereo system is no exception.

One of the standout features of the Dynacord Stereo System is its advanced digital signal processing technology. This allows for precise tuning of audio output, ensuring that users experience optimal sound quality regardless of the input source. The system includes various presets tailored for different environments, whether it’s a small room or a large auditorium. This flexibility makes it ideal for both personal and professional settings.

Another significant characteristic of the Dynacord Stereo System is its robust build quality. Constructed from durable materials, the system is designed to withstand rigorous usage, making it a reliable choice for mobile DJs, event organizers, or even studio applications. Additionally, the aesthetics of the system are both modern and stylish, fitting seamlessly into any décor.

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In addition to its audio performance, the Dynacord Stereo System includes user-friendly controls and settings. The intuitive interface allows for easy adjustment of volume, tone, and effects, making it accessible for users of all experience levels. Whether you’re a casual listener or a seasoned sound engineer, the Dynacord system caters to all.

In conclusion, the Dynacord Stereo System stands out with its exceptional sound quality, durable construction, versatile connectivity options, and user-friendly features. This system is not only designed to meet the needs of audio professionals but also aims to enhance the listening experience for everyone. Whether at home, a concert venue, or on the go, the Dynacord Stereo System delivers a powerful performance that truly elevates audio enjoyment.
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