2 - 10's in a sealed enclosure will give me the best sound

Will you put both 10's into a common enclosure, or separate them with a sealed bulkhead so they are in separate enclosures (even if it is all one box)?

There are several things to consider about this. If you are going to run the two subs in stereo (that is, one left channel, one right channel) you must separate them, otherwise you will get phase cancellation because they will be playing different signals in the same enclosure.

If you are going to run them bridged mono, then you have a choice. Run them in a common enclosure (this is called acoustic coupling) and you lose efficiency (that is, the maximum decibels you can produce) but you gain lower frequencies because the lowest frequency the speaker can produce is determined not by the size of the speakers, but by the total combined cone area within the enclosure.

There is another school of thought that says it doesn't matter because you are already getting acoustic coupling whether the two speakers are sealed individually or combined in a single enclosure, because they are playing into a sealed enclosure, that is, the cabin of the car.

When I build my ShoWagon stereo, I plan on building the sub box with a divider between the subs that has a port in it that I can open or close and I'll just determine empirically which way I like the best.

tanstaafl.