PA System Power RatingsOne of the values stated - and alas frequently misrepresented - in PA system specifications is the system's rated power. While we don't encourage you to compare systems on the basis of power alone (see below [1] and the System Design page for other important factors), the description of systems according to their output power is endemic in the live sound reinforcement business. For that reason, we have followed the same protocol. However, there are several different descriptions [2] of speaker and amplifier power in common use (AES, average, continuous, EIA, FTC, peak, PMPO, programme, RMS...), so comparing systems from different manufacturers or PA-hire companies may not be straightforward. There is a bit more information about what the words and numbers mean in our guide to loudspeaker and amplifier specifications. However, in using measurements to compare equipment, you should ensure that: • The measurement you use is meaningful and appropriate (PMPO is neither); • The measurement you use applies an accredited and replicable standard [3] (FTC amplifier ratings apply a defined standard of measurement, but "Watts RMS" does not); • Your comparisons all use the same scale (don't compare one system rated in "Watts, continuous average" with another rated in "Watts, peak"). Where we describe a system by power rating (e.g. 1.6 kW), we base this on the continuous average capacity (AES [4]) of the Front-of-House speakers in that system. This is the most conservative power rating we could use, and approximately corresponds with the "RMS" value more often - mistakenly - given. Other suppliers may use different ratings, and we have seen systems with less acoustic output than our 1.6 kW system advertised as "10k"! Some of the ratings in common use are described below, and the equivalent ratings of our own 1.6 kW & 3 kW systems are given for comparison.
1. We approach the question of how much output volume (dB SPL) is required by looking at the dimensions of the auditorium, and calculating the total acoustic output (dB SPL) of a system that will produce the required volume (dB SPL) in a given audience position. We then work out how many speakers of a given type will produce that overall output. As long as speakers can be well-positioned and correctly arrayed, this works well enough. However, where very high sound pressure levels are required (either because the auditorium is very large, or because the style of music is very loud), using different types of speaker and array may be a better solution than adding more boxes. We base this calculation on the measured acoustic output (AES) of the speakers we use in our systems. Because they are designed by professionals for professional use, other specifications that are useful for calculating system requirements are given by the manufacturers of the speakers (Martin Audio) and amplifiers (QSC) we use. There is more information about what the numbers mean in our guides to loudspeaker and amplifier specifications. 2. The fact that a description is in common use does not make it valid or useful. "Nervous Breakdown" is not a clinical or medical term (so a tabloid newspaper might use it, but a health professional wouldn't). "Watts RMS" isn't a valid technical term (so a high-street salesman might use it, but a qualified audio professional shouldn't). 3. A standard in measurement is one that has been agreed by consensus to provide the optimum replicability, consistency, and suitability. In PA systems, consensus on measurement is found among nationally and internationally recognised industry-wide professional organisations, as well as - in some cases - government legislation or official advisory bodies. Some of the principal relevant organisations are: • AES. Audio Engineering Society (USA/international). • ANSI. American National Standards Institution (USA). • BSI. British Standards Institution (UK). • EIA. Electronic Industries Alliance (USA). • FTC. Federal Trade Commission (USA). • IEC. International Electrotechnical Commission. • IEEE. Institute of Electrical and Electronic Engineers (international). • IET (formerly IEE). Institution of Engineering and Technology (UK). • ISO. International Standards Organisation. 4. The AES continuous power rating describes the average amount of power the speaker can handle over a long period (typical tests last two hours or more). 5. "Programme" power doesn't have any reliable definition, and our own advice is to view any description of equipment based upon it with that fact in mind. Typically, the "programme" power will be double the average continuous power (and we have given this value here for comparison, although there is no published "programme" power rating for Martin Audio speakers). 6. Peak power is not representative of overall speaker performance. It is the maximum power the speaker can handle for a few milliseconds at a time. Try it for a few milliseconds longer and Recones-Я-Us. The Martin Audio Wavefront systems are fully horn-loaded, and produce substantially higher sound pressure levels than front-loaded systems (e.g. our standard 1.6 kW and 3 kW systems). The acoustic output of the 2kW Wavefront system is equivalent to the output of six 1.6 kW F12 systems. Comparison of these on the basis of power handling is therefore inappropriate, although the same standards apply. All the amplifiers and speakers we supply will produce high levels of undistorted sound at full power over the system's whole frequency range, and will distribute the sound evenly. They will keep this up all night (i.e. indefinitely). Also, they sound great! If you think you have found something cheaper that is just as good or just as powerful, please call us to arrange a demonstration. [Site Map] [Top of page]
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