Multiple coaxial's in doors?

[FlexinHZ 3]

I am just curious on this topic, why does no one ever run multiple coaxial's in their door? Would kind of troubles would you run into doing this?

[lithium 358]

Google constructive and destructive interference. 

[jcarter1885 994]

There are people who do it but there are also better ways to achieve better sound. 

I think in general coaxials arent as popular anymore due to more common knowledge, more offerings of stand alone mids or tweets and the emergence of pro audio. Just my .02

[Tirefryr 1,742]

About 15-20 years ago, I was building door panels this way.  Not for myself, but I had many people that wanted a number of 6x9s or 6.5s in the door just blaring right in their ears.  It was horrible, but made me some cash.