Over Sensitive About Car Audio? – Speaker Sensitivity Explored

Over Sensitive About Car Audio? – Speaker Sensitivity Explored

Continuing our journey into specification-land, we chance upon speaker sensitivity. We can see it is measured in Decibels (dB), but what is it? what kind of figure is good – is it simply that the higher the number is, the better a speaker is? What do we do with this information when designing a car audio system? – Well, let’s have a little look.

A speaker is essentially a linear motor (it moves forward and backwards rather than round and round) attached to a cone which pushes and pulls air. The cone is fastened to a supporting structure (basket) by its surround. The surround is usually made of a supple material such as rubber. At the base of the cone is the voice coil which is connected to another suspension device known as a spider (it looks nothing like a spider by the way; has no legs and doesn’t generate halloween decorations!) that is also anchored to the basket. The coil itself, presents an amplifier with a load, known as impedance and measured in Ohms. Effectively this as an electrical resistance to the output of an amplifier and is quoted as a nominal figure as it changes dynamically as the coil receives greater or lesser electrical impetus from the amplifier. The surround and spider add mechanical resistance to speaker movement which also has an affect on the efficiency of the amplifier/speaker combination.

These things plus other factors such as the resistance of any connecting wires add a load to an audio system that needs to be “carried” by the amplifier’s output. It is therefore desirable that the speaker reacts efficiently to the input provided at its coil. The efficiency of the speaker is its sensitivity.

Is speaker sensitivity important? 

It could be argued that a sensitivity figure is of greater importance than a power rating when selecting speakers to match a chosen amplifier. If you have plenty of clean Watts available from your amplifier then a low sensitivity figure is perfectly fine. Many very loud speakers have a comparatively low sensitivity figure due to the robust nature of the cone suspension system. A speaker with a large cone area may also be less sensitive and require more power because of the volume of air it has to push therefore, one would expect the sensitivity to be higher than that of a small-coned speaker. In conclusion, a greater sensitivity means you will get more absolute level (volume, loudness, grunt) from an amplifier than a speaker with a lower sensitivity. If you are planning to run a pair of speakers directly from your head unit then a high sensitivity figure is essential as many head units suffer from far lower power output than they claim!

How is sensitivity of a speaker measured?

Unlike power, there is generally only one accepted and credible method for measuring speaker sensitivity. Many marketing departments have tried to distort this as with Watts, but the measurement criteria remain the same now as they always have done despite these efforts. Essentially, a speaker is presented with 1 Watt at its input and the resulting level or output is measured by an SPL meter placed 1 Meter away – This measurement is only really valid when tested at a specific frequency (usually 1kHz) in an anechoic environment otherwise the space in which it is measured may affect the reading due to reflected sound waves (room gain).

Any Examples?

                                      

This fresh range of speakers from Italian Manufacturer Hertz boasts high sensitivity. It is a brand we know a lot about and have absolute trust in their specification listings. The Cento CPK 165 2-way components pictured above have a reported sensitivity of 92.5 dB which is right up there. You would get plenty of level from these with a modest amplifier with an RMS rating of 30 Watts or above – The Hertz HCP range would be a perfect partner for instance. The combination of these two products properly installed with the requisite amount of Skinz sound deadening would transform your in car listening and take your driving pleasure to new levels!

 

We would always recommend that you put your equipment choices in the hands of a specialist expert like a FOUR MASTER. Their hands on knowledge is extremely powerful and can help to avoid you being drawn into a poor purchase based on misquoted figures. As always, the proof of the pudding is in the eating and your local FOUR MASTER will have eaten many different types of pudding!

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