What is a free-air loud speaker?

[pixel01]

Hi all,

I am trying to upgrade my car's audio system. There are kinds of free air loud speakers. I am not what they are.
Anyone could explain and why they should be used in a car?

 

[Ranger Mike]

Wwwwwhhhaaaaatttttt?

 

[pallidin]

There are several references in Google.
Key term I used... free air loudspeakers

 

[dr dodge]

how about this
its as free air as you can get

http://www.eminent-tech.com/RWbrochure.htm

dr