Distorted Car Audio Signals Aint What They Used To Be

Distorted Car Audio Signals Aint What They Used To Be


Car audio components are prone to overheating when exposed to certain forms of Distortion

Why Car Audio Components Fry!

Audio distortion can be defined as any attribute which changes an input signal when it is passed through any form of processing, hence the lame joke in the title! If you consider this for a moment it suggests that not all distortion is bad and in fact some distortion of an input signal may even be deliberately introduced for effect! One such form is equalisation or tone adjustment. By shaping an audio signal to emphasise certain frequencies you are effectively distorting the input signal. In this case it is generally a user action taken in order to compensate for a system deficiency or simply because you want more bass in your life for example. Some (well, most these days) electric guitar players add many different forms of distortion to create their own signature sound or in an attempt to replicate the sound of their hero. The use of “soft clipping” devices is widespread in these circles!

Distortion maker, not for use in car audio systems

Typical Guitar Distortion Pedal With Comedy Name

However, some forms of distortion can be extremely damaging to the equipment that has to reproduce it. Probably the most dangerous is hard clipping. This happens when a solid state amplifier or other active device within the signal chain is fed a signal that is too big for it to cope with. Effectively, the signal is squeezed to fit the “headroom” available within the amplifying device. Headroom is generally limited by the maximum voltage handling capability and it cannot be exceeded. When I say squeezed, the top of the waveform being processed is cut off. If you look carefully at the image at the head of this article you will see a perfect example. There are two sinusoidal wave patterns depicting voltage against time. The top one flattens off when it reaches the limit of the amplifying devices capability. The lower one is just within limits and shows no distortion at all. The red shaded area is where the danger lies as this represents excess energy which is fed through all the devices creating heat and it is generally heat that does all of the damage. The most susceptible components to heat damage are speakers and crossover networks although amplifiers without sophisticated electronic safeguards built-in can also be damaged often beyond repair due to this kind of distortion.

High-end car audio equipment distributor FOUR only occasionally sees products being returned faulty and a quick look under the cover of a crossover network or a quick manual compression of a speaker diaphragm is often all it takes to discover that heat damage has caused the component to fail. In most cases, products will be exchanged with a warning but for high-cost items, products may be returned to the customer with a note explaining that the damage was caused by poor set up. Fortunately, products fitted by a FOUR MASTER installer very, very rarely get damaged in this way as professional installers know how to set the levels at the inputs of all connected devices to ensure hard clipping doesn’t occur and as long as occasional “health checks” are carried out, all installed equipment will last a very long time.

All audio components induce varying levels of distortion. A good manufacturer will come clean about the levels of distortion a listener can expect expressing it as THD. This stands for Total Harmonic Distortion. As with our earlier article on Watts though, it is important to ensure you are comparing like for like measurements when looking at equipment specifications. THD will change at different frequencies (measured in Hertz or Hz) and at different levels (expressed either in Volts, Decibels or dB or Watts). As with power ratings, their is pretty heavy science behind both THD measurement and its effect. The difference from a consumer point of view is that whereas manufacturers have manipulated power ratings to give a high number for market appeal, they have manipulated THD figures to appear smaller to the same end. Once again, however unpalatable it may seem to those wishing to make the right choices, you are often faced with taking a punt on the specified ratings or far more sensibly, taking the guidance of a professional who has hands-on experience with a wide-range of products.

Those who are very into their subject will pontificate and cogitate on the benefits of amazingly small differences in the physics of good sound. The only real way to select the right product for you is to listen to as many as you can in the same environment using the same source equipment. For car audio, this is not that easy so even more trust has to be placed in your chosen advisor – A FOUR MASTER will work with you to ensure that in the end you go away perfectly happy with the results of their endeavours and if you don’t they will make changes until you are.


FOUR MASTERS is a network of independent car audio specialists

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

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