I emailed a friend, who is a well know writer for some stereo magaznes.
His response:
Generally speaking if you measure a full-range speaker system that is perfectly flat in a perfectly anechoic environment you'll find that when you place that system in a space @ a reasonable listeninf distance you'll find that it exhibits a natural roll-off as frequency increases. The degree of fall-off is dependent on the size of the space.
For a car, where there is no 'near-field', a natural sounding curve has a reduction of approximately 3 dB per octave between 20 Hz and 20 kHz. In a listening room that falls to approximately 1.5 dB per octave.
However the fall-off also has a shape to it that includes a flattening in the middle. I'm surprised that there hasn't been more said about this in the literatue. One place where you might find some history is in the literature about movie theater house curves.
Another important factor with car audio systems that has been completely ignored in the popular press is that you really need a different EQ curve when the car is being driven. Many people just EQ the car in the bay and leave it at that but a car in motion is a completely different acoustical environment that the same car sitting in the bay with the engine off.
His response:
Generally speaking if you measure a full-range speaker system that is perfectly flat in a perfectly anechoic environment you'll find that when you place that system in a space @ a reasonable listeninf distance you'll find that it exhibits a natural roll-off as frequency increases. The degree of fall-off is dependent on the size of the space.
For a car, where there is no 'near-field', a natural sounding curve has a reduction of approximately 3 dB per octave between 20 Hz and 20 kHz. In a listening room that falls to approximately 1.5 dB per octave.
However the fall-off also has a shape to it that includes a flattening in the middle. I'm surprised that there hasn't been more said about this in the literatue. One place where you might find some history is in the literature about movie theater house curves.
Another important factor with car audio systems that has been completely ignored in the popular press is that you really need a different EQ curve when the car is being driven. Many people just EQ the car in the bay and leave it at that but a car in motion is a completely different acoustical environment that the same car sitting in the bay with the engine off.
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