Hi,
Trying to design speakers for mobile use in a car is a total nightmare. Think about it: In home speaker design, the engineer has control of the enclosure and knows roughly where the speaker will be set up for stereo and home theater applications in average rooms. And yes, every room is different, but not to the degree of car interiors!
In a car, every variable is different with each car and model: Where you can mount the speakers in the door, the air volume behind the woofers in the door, the amount of reflective glass, the dashboard area and material, the seat material, the fact that most listeners will be well off-axis to any installed tweeters. The list goes on.
The only positive thing about getting good sound in a car is the trunk, and subwoofer design. You can specify the box size, driver and crossover parameters, and stick the box in the trunk (or in the back of a hatchback), add a powerful dedicated amp for the sub (you have to overcome all that road, tire, and wind noise) and, because you're dealing with a relatively tiny enclosed space (roll up the windows, guys), a 12-inch or 10-inch driver in a sealed box can pressurize the interior so you can get response down to 20 Hz or lower for a modest amount of money (except for the amp, of course). But compared to trying to get 20 Hz low frequencies in a big living room, it's still relatively economical getting them in a car.
The best car systems are highly customized to a particular car's interior. JBL designers, along with the engineers at Ford, designed some excellent-sounding Ford/JBL systems for upscale Lincolns and the like. Paradoxically, Bose has produced better sounding car systems for Mercedes (albeit with rather peculiar imaging) than their home speakers. The Linn in the BMW left me underwhelmed, which doesn't surprise me because loudspeaker design has never been a strength of Linn's.
Regards,
