Can anyone explain this bass drum configuration?

[tedanderson]

I've only seen this doubled bass drum configuration one other time in my life. I didn't quite understand it then and now that I saw it again, I figured that I'd ask someone. (see pic) This leads me to a few questions:

1. What is the purpose of this configuration? Does it enhance the sound of what the audience hears or is it just more comfortable sounding for the drummer?

2. Are the bass drums interconnected? Do they both have heads on both sides of each drum or is there one big opening between both drums? Or is there a smaller opening that the air passes through where the two drums meet?

3. Is this something that is pieced together using two standard drums or is this a special pair that only work together with specialized hardware?

4. How do you mic it?

[cmchamp]

1: augmentation of the fundamentals of the kick, the second drum may be tuned identically to the first, or lower, to provide a deeper, darker and fuller tone.
2: only acoustically coupled, and they are probably set up identically accept the "live" drum may have a whole for a mic.
3: yup, in my experience, standard kicks.
4: Possibly a Beta91 on a pillow in both for better isolation (if that's possible) from non-kick noise.