Perfect Timing

Let’s talk about sound and specifically how we perceive a sound’s location, (we’ll come back to the elephant in the room). To do this we need to understand what sound is and how it travels.

In its basic form sound is a compression wave propagating through a medium. Think of ripples in water travelling away from where the stone hit. The sound is exactly the same but travelling through air. Travelling very quickly by the way at over 700 miles an hour.

The defining characteristic of a wave is the fact that it has high and low points.

 

Points along this wave are known as the phase and describe whether the wave is positive or negative and by how much. Now for the clever bit. Consider a listener sat in a chair with their eyes shut, someone off to their left claps. Of course, he can tell it was to his left but how? We all have two ears so it might be true that we can detect the time difference between the sound reaching our left and right ears. But at 700 miles an hour this is a VERY short difference and if true it would mean that all frequencies could be located but as we know the lower the sound the harder it is for us to locate the source.

What we are predominantly detecting is the difference in the phase of the wave between our ears. By measuring the difference between the high and low points on the wave our brains can very accurately calculate sound location and create our spatial awareness. That is why we cannot locate very low (very long wave) sounds as the difference in the phase between our close set ears is minimal (think about thunder).

So now we know this how can we use it in the car audio environments?

One of the big problems in the car is that we are always sat closer to one speaker than the other, therefore the stereo effect is foreshortened to one side. A very crude way to combat this is to put the balance off to one side to compensate but that does not enhance the stereo performance. What we really need to do is place the speakers an equal distance from the listener. Difficult if you are not in a McLaren but we can fool our ears into thinking the sound is coming from somewhere else using phase.

By carefully manipulating the phase of the sound from the speakers we can create the effect that the close speaker is actually further away which leads to a much wider stereo field. This manipulation is very delicate as you can imagine but as a member of the FourMasters network, we are equipped with a sophisticated range of tools and software to achieve this.

The difference between a standard setup and a phase aligned one is astonishing. The whole soundstage comes alive with instruments and vocals spread across the car in a very lifelike and live performance. It is possible to compensate for difficult speaker positioning (BMW) or over separated speakers (VW).

Of course, you will need to have the products to permit this tuning and fortunately, there is a range of sophisticated processors from Audison and Hertz that offer these features. Products like the astonishing Bit family from Audison. These devices give me the capacity to completely shape the acoustic performance in your car which means you will have a completely bespoke sound that perfectly complements your car and your personal tastes.

We have a demonstration vehicle always available at our shop on Sunderland Street in Macclesfield. In this we can demonstrate the difference between a standard and phase aligned sound, we would love to show it off if you want to pop in for an audition.

Oh and the elephant? Elephants communicate their location by stamping on the hard ground. This creates a very low-frequency sound which can travel a great distance. You or I could not locate this low sound but elephants can, why? Because their ears are much further apart and can detect the phase differences!

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