Diffusing Waves In Cars

Skinz Wave Diffuser is a fascinating product. Looking more like a sound absorber than a diffuser, in practice it performs both jobs to an extent. But how does it save us from poor sound?

A speaker produces sound by moving air. A cone vibrates at various frequencies and throws air forward………and backwards. Herein lies the problem that led to the development of Skinz Wave Diffuser.

The issue is that the sound or air movement produced from the rear of a speaker can reflect from solid surfaces behind and affect the movement of the air from the front as well as distorting the cone shape. In a car, speakers are generally mounted in the doors. The rear of the speaker sits very close to the metal door panel and so reflections are strong and prevalent. Such reflections can cause many problems with the resultant sound in the vehicle interior. Frequencies will literally bounce back from the door panels and hit the rear of the speaker cone compromising the frequencies being sent out from the front. In real audio terms the effects are many and varied as there is no coherent correlation between the reflections and the new sound emanating at the time they reach the cone. They include phase issues and frequency colouration and probably most discernibly, level.

No one wants to get less out of their speakers than they put in and so it makes perfect sense to take measures to reduce the effects mentioned. Wave Diffuser is a most effective way of doing this. Looking more like a sound absorber than a diffuser, the foam is sculpted into an egg box profile and actually does both jobs to an extent. The soft open cell foam will invariably absorb some of the sound from the rear of the speaker but the main job is to break up the wave pattern to disperse its energy and scatter it. A firm coating is added to the undulating face of the foam. This helps to protect the foam from water ingress but also breaks up sound waves that are fired directly at it.

The metal in the door will already be sound proofed using Skinz Sound Deadening. This actually makes the problem with reflections worse, as it adds much needed rigidity to the metal. However, sound deadening is there for a different yet equally important reason. Sound deadening reduces the noise passing through the door offering the double benefit of reducing outside noise and protecting the neighbours from the music inside the vehicle when you arrive home!

Home hi-fi speaker boffins will advise caution when stuffing enclosures with different materials. Most limit themselves to a small amount of lightweight material. This tends to calm some issues in the mid/high frequencies whereas adding something heavier will reduce bass performance. This is not the case in car doors as these can rarely be described as tuned enclosures. Arguably, in a standard installation, car speakers run free air and therefore the volume of the cabinet is irrelevant. We know through measurement that wave diffuser helps speakers to project more of their output into the vehicle while the reduction in reflected “back waves” reduces any degradation of all important mid-range frequencies. If bass is a big aim, then we would always recommend some kind of subwoofer. This will help protect against swamping where heavy bass reduces clarity in the lower mid-range. While on this subject, wave diffuser will have less of an effect on low bass as those frequencies tend to pass straight through most substances rather than being reflected anyway.

Although no scientific data is currently available, we have tested cars with and without Wave Diffuser and always find better clarity, accuracy and projection is discernible in cars with it fitted.

Visit your local FOUR MASTER for more information.

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