What Watt is What for Car Audio?

What Watt is What for Car Audio?

Car Speakers and Amplifiers are rated in Watts just like home audio. However, the world of home hi-fi has enjoyed far more discipline than car audio when it comes to technical specifications. Power rating is very important when matching an amplifier to a set of speakers. If the amplifier pumps out more power than the speakers can use then they (the speakers) won’t last very long. Conversely, if you drive powerful speakers with a light-weight amplifier you will never get them to work to their true potential.

One would think that this is all very simple stuff. Simply match the output of the amplifier to the input of the speaker and everyone is happy. However, due to a very crowded market place, bright sparks of marketing decided to create a power ratings war by finding different ways of expressing the rating of their amplifiers and speakers under the premise that a bigger number is always more attractive to a consumer (see page 3, The Sun). This has been taken to dangerous extremes and a certain far eastern manufacturer I know of expresses the rating of its speakers as the maximum amount of power which can be sustained for no longer than 400 microseconds. This rating is pretty unhelpful at best and the fact that they keep the details of the rating a secret make it potentially dangerous. Any excess power delivered to a speaker is turned into heat and in extreme cases, light, which is how electric fires and incandescent light bulbs work! They of course call their rating Maximum Power but even this term is extremely loose!

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However, help is at hand by way of RMS power ratings……. or is it? The problem is that even RMS ratings can be manipulated and you need to be quite a scientist to be absolutely certain that you are not comparing apples with bicycles! RMS stands for Root Mean Squared which in itself, is quite scary. Once you start to think about the rest of the measurement parameters though it gets even scarier. 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 it needs to be stated at a certain frequency. The same is true of speakers which will reproduce certain frequencies more efficiently than others (tiny speakers don’t handle bass very well!) Then, there is distortion to take into account. A speaker may be able to “take” a 100 Watt RMS signal but if this makes it distort horribly then it is not a very desirable or meaningful measurement. An amplifier that produces huge amounts of distortion in order 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 which stands for Total Harmonic Distortion but again, not always! In the case of the aforementioned far Eastern manufacturer you actually have to divide it’s maximum power rating by seven to get close to the continuous RMS rating!

If this information is not helping, I am truly sorry and I really do wish that there was an easy way to navigate this particular minefield. If there was, then people would be able to safely buy quality equipment in the knowledge that they are not being hoodwinked. FOUR MASTERS regularly come across “victims” who have purchased (usually online) a 1000 Watt amplifier only to find that only 10 of those Watts is of any use and the rest are strangled out of a non-scientific approach to power measurement.  They see just as many “victims” who have fallen for a pair of speakers because they boast a huge power rating but who do not have the vital piece of knowledge; you can only ever get out what you put in minus some inevitable inefficiencies somewhere along the line. If you drive a 1000 Watt subwoofer with a 1 Watt amplifier then you are not going to get much noise out of it unless it has an as of yet unseen efficiency rating – and therein, lies an entirely new article!

Taking the above into account enables you to make slightly better informed decisions but there is never any substitute for taking the advice of an expert. This is why we always end by advising you visit your local FOUR MASTER who is a trained expert in this area. A FOUR MASTER will recommend product matches based on their own experience. I know we live in a cynical world but you are not necessarily being pushed toward a product they have too much of – FOUR MASTERS don’t work this way – They simply know which products work together to give you excellent, trouble-free performance for as long as you need it!


Call 0800 652 5125 or visit www.fourmasterscaraudio.co.uk to find your nearest expert.

(Content supplied by Driving Sounds – www.drivingsounds.co.uk)