Some car and equipment manufacturers' desperation to compete when faced with genuine quality products often results in gross exaggeration based on the bending of science. In this article, we look at the humble watt as a power measurement.
Power rating is essential when matching an amplifier to a set of speakers. If an amplifier pumps out more power than the speakers can use, the speakers won’t last very long, converting excess energy to heat and, ultimately, light, resulting in permanent damage to the speaker’s voice. Conversely, driving powerful speakers with a lightweight amplifier will never get them to work to their full potential.
Unfortunately, companies have exploited a perceived direct correlation between watts and output level for years. The mistaken belief is that the more power a product has, the louder it will be. While under some circumstances, this is true, many other criteria are required when making such a comparison.
Unfortunately for the ordinary consumer, power measurement is complex. Many factors will affect the measurement. Even more confusing is that watts can be stated in differing forms.
Most marketing departments exploit this when quoting sometimes crazy figures. Most good-quality manufacturers will quote amplifier output power as an RMS figure.
RMS stands for Root Mean Squared, a scary mathematical concept. However, it gets even more frightening once you start to think about the rest of the measurement parameters. For instance, an amplifier will need to use more power to produce a low frequency at the same level (or volume) as a high frequency, and so when comparing RMS ratings, they need to be stated at a specific frequency.
An amplifier that produces vast amounts of distortion to reach an output power figure is also undesirable, as distortion damages speakers and ears. So, once again, when comparing ratings, distortion has to be quoted—usually stated as THD (Total Harmonic Distortion), but again, not always.
However, a standard of measurement for amplifiers does exist, which, if it were to be adopted by all manufacturers and policed comprehensively, would diminish the risk. Previously known as CEA2006, this standard was devised by the Consumer Electronics Association to promote good practice on behalf of over 2000 companies working in the Consumer Electronics industry. The standard itself is rigorous, and CEA member companies displaying the logo have all gone to the trouble of ensuring that quoted figures comply with this standard. CEA changed its name to the Consumer Technology Association (CTA) in 2014, which has muddied the water, and the membership changes frequently.
Those who do not subscribe to CTA or are running scared of better quality competitor products in the same marketplace continue to state power as Maximum Power (roughly RMS X 2), Peak to Peak power (roughly RMS X 4) or worse. These are all valid ratings, but comparisons between the measurements cannot be made. It is, therefore, vital that when choosing an amplifier, RMS is compared to RMS at the same frequency and distortion figure, not peak or peak to peak, which is vastly different.
The temptation is to go for the biggest number, but this would be a mistake unless you are certain that the measurements have been taken precisely the same way.
Speaker power is beset with the same issues. Generally, speaker power is quoted as “continuous”. A time element has to be included. We have seen in the past figures quoted that are measured for just 400 microseconds. This is the speaker's minimum time to survive at the quoted power.
Speaker power measurement can be even more complex than amplifier measurement. Parameters such as impedance, for instance, vary depending on the frequency and amplitude of the input signal and temperature.
In many ways, a speaker’s power rating is more safety-critical than amplifier power. However, the very best option is to match both the amplifier and speaker power, or if not, ensure your speakers can handle more power than the amplifier can produce.
Driving Sounds always recommends that you consult a specialist installer when choosing equipment for your car. They work with different product combinations daily and know from experience which amplifiers and speakers will work best together.
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