Vented enclosures: ports at the front or rear?

I have an MTM system (Focal 5-inch kevlar midbass and Accuton tweeter) which I drive with my DIY Aleph-30s.

I'm very satisfied with the sound, but I'd like to extend the bass. I have two 11-inch Focal woofers (model 11V7511) which I want to use. The plan was to build two separate vented enclosures with one 11V7511 in each enclosure, then move to a biamp setup with the Aleph 30s driving the MTM and a Rotel 100W A/B amp driving the 11V7511s.

The question is: should the port in the vented enclosure be at the front or the rear of the enclosure? What are the pros and cons of each?

Any comments welcome.
 
In general, it's usually better to have the port on the rear. Since the spacing between the vent and the driver is relatively small considering the wavelengths the vent is going to produce, you don't really have to worry it being too far away from the driver to sum coherently.

Having it on the rear gives the big advantage of attenuating any stray midrange/distortion output that may exit the enclosure through the port - which generally can make a speaker quite a bit better. It also reduces the audibility (and measurability, of course) of any pipe resonances, as they tend to be at higher frequencies and will again be lower in amplitude due to the port facing away from you.

Of course, this also obviates the ability to place the speakers directly against the wall, but this usually isn't a problem.