Ported is key. I've dealt with Eclipse before, and one thing I can tell you is that Eclipse tech support doesn't really "know" their sub lineup, nor do they really recommend the best applications for these subs. I know that line may sound a little crazy, but Eclipse subs are built by TC sounds. I have dealt with enough Tis and the older Aluminums, and I can promise you they do MUCH better ported. You can verify this just by plotting this in WinISD or more elaborate box building programs. They are heavily inclined to ported enclosures.
They perform well in small sealed boxes (pretty much any low Qts sub works well small sealed or ported), they just open up a LOT more ported. Much better low end out of the subs, combined with lower distortion.
A .707 q is usually recommended for sealed. Fsc (-3db point) typically occurs between 40-50hz for most examples of 12" subs, though it varies. 10s and 8s will be even higher. Fc is resonance, which will be at a higher frequency than F3. So, your sub will effectively be flat to Fc and will roll off at a rate of approximately 12db/oct past that. At and around resonance, a sealed sub sees its highest excursion, also the most distortion at that point. That's one thing I don't like about sealed at high volumes, since you're in the meat of the bass range.
A ported box will (should) give a flat response down to tuning. The difference between ported and sealed is that it allows a lower system resonance than sealed (say 30hz or whatever you tune to), thus giving you improved low frequency response. The port also gives more mechanical control over the driver at that point, lowering distortion in addition to the added output. Ported boxes are actually capable of being better damped at resonance than sealed boxes are. Remember, ported enclosures aren't actually 3db louder at all frequencies, they're considered 3db louder is because they are able to provide a flat response to a lower frequency. In a car, this can result in a peak due to transfer function (cabin gain). The only time you get a peaky anechoic output is when it is designed for that, or you are using a sub not well suited for a ported enclosure. Drawbacks of ported are that they lose power handling below tuning, and group delay is higher.
don't mean to hijack this thread but jonathan have you heard of a single reflex band pass box, i was reading about it in one of my carstereo books, its a seald box and a ported box in one, and i was wondering if you knew any information on it.