tuning 6X9 speakers

No, prodigal, in no "theory" does a 6 X 9 sound better than any similar-sized driver.  And at no time would you have had speakers "powered by only an equalizer".  An equalizer is not an amplifier.

You are confusing the benefit of point source speakers as replacement for a subwoofer.  Point source is (or could be) a benefit for use as front soundstage mid-bass/mid/tweeter components, not the subwoofer.  Use quality point source for your front soundstage, as their benefit will not be appreciated in the rear.  And use a sub;  there is no replacement for that.

Theory aside..as far as what "sounds" better is always a subjective issue.

Now IMO since most 6x9s are used full range and mounted either on a rear deck or in some case's a door...point source if anything is hurt..after all what kind of a decent sound stage can come from the rear or pointing at your feet or ribs?

In other words I do not believe you can compare an actual subwoofer setup to a 6x9 or any full range speaker.

As azn states subwoofer frequencies are "omni-directional" but still..in reality we all know you can tell it is coming from the rear in most cases... but,I have built as well as judged many sq vehicles that either have actual subs up front...or enough midbass up front to where the bass truly is in the front stage..or at least has the "illusion" which makes no difference because it sounds incredible. This can be done only with proper placement and cross over setup and adjustment.

However..if a particular person is happy with the bass produced by 6x9's alone, then thats fine for them..I have heard some produce very loud and deep bass...but regardless...this has nothing to do with point source or comparing a full range to a sub. if you want alot of sub bass...use a sub in an enclosure. If you want good point source use any speaker setup that places the mids/highs at the same physical point. But..if the speaker is not physically positioned to give as close to perfect as possible imaging, it won't matter what kind or size speaker it is.

I can tell you one thing I know for sure..and you all can verify this as well. Take a crappy set of speakers, either self enclosed or installed into an enclosure.   Position them so they are equal distant from both your ears and see how good it sounds..well if any of you have speakers at your PC you already experinced this. If you take much better speakers and place one right next to your left leg..and another one 3 or 4 feet away point at you right leg you will see what I mean. The overall quality might sound better with the beter speaker in some cases..but the imaging will be much better with the cheaper speakers properly placed to reproduce the stereo.

But since it is not feasible in all but the most extreme custom vehicle to be seated with the speakers at ear level and equidistant from each ear..the best we can do is floor pods aiming up and towards the listener..this is where point source helps IMO. You can also use processors like the audiocontrol ESP with a center channel speaker which helps to create the illiusion of perfect imaging in a much less then perfect environment.

oh..to your question...lol

well if you are going to put the 6x9 into enclosure and tune them for the best possible bass response you should be able to use a program if the T/S parameters of the woofer cone are accepted by the program. (and if you can get the parameters). It can be ported as well but don't expect to tune a 6 x 9 to 30hz. More realistic would be 45hz and to be safe I would want at least a 12db slope, 18 or 24 if possible, and to use an amp that has a subsonic filter..otherwise if you try to get too much bass..good bye speaker.

Now unless the 6x9 is "bi-ampable" all you can really do is set the amp for "high pass" and dial in the lower frequencies until you can hear the 6 x 9 distorting..at that point back it down a bit and it should be optimal.