In the pursuit of great sound it is essential to consider all aspects of audio reproduction. JL Audio, Audison and others make tremendous speakers which have been carefully designed for accurate music reproduction, unfortunately we have to fit them into less than perfect environments!
The average car door is an acoustic nightmare. A thin, unsealed metal enclosure fronted with hard plastic fittings, often with a loose polythene moisture barrier as well.Crucially, we want the full, uncoloured response from the speaker we are installing. Unfortunately the design of the door is working against us. Fundamentally, a speaker is a transducer converting electrical signals into pressure waves. Sound is generated from the front of the speaker and from the back.
This is important as the sound from the back of the speaker is playing into the car door. Some will be reflected back into the speaker cone causing distortion of the front signal. Some will be reflected into the door card creating unwanted resonance and annoying vibrations. The louder you want to play it, the worse it will be.
Some car manufacturers do apply a token amount of damping but this is just to prevent the panel from rattling, we want to optimise the enclosure for sound reproduction.
The answer is sound deadening. Quite different from sound proofing, sound deadening is about the control of pressure waves inside the door. By applying special materials we can eliminate unwanted resonances and reflections.
There are lots of different products out there but by far the best are Dynamat and Skinz. Dynamat Xtreme is the lightest and most efficient panel treatment I have ever used. It’s damping properties are second to none meaning less needs to be applied. All sound being radiated from the back of the speaker is absorbed and converted into low level heat. This of course stops unwanted vibrations and ensures that you only hear the sound from the front. A liberal application of Dynamat behind the speaker prevents reflections.
I believe that it is essential to consider sound deadening whenever a speaker upgrade is installed. Otherwise you will never achieve the full benefit.