Hi PKi

What you need to do is use reflex ports for your forced-air cooling. For example, one port near each speaker and a fan mounted internally in the centre, blowing air from one end to the other. You probably also want to make a circuit to mono-ise the low frequencies so the drivers aren't fighting each other down there (or get someone to add it to hijack).

I can calculate port lengths for you if you supply box dimensions (internal, minus space used up by amp etc) and driver specs. I've been known to dabble in speakers (deafened my first Broadcom colleague yesterday).

Cheers, John