Eh hem!...Subwoofers... What do ya know?

Does anyone technically know what happens when you aim two subs at each other?  Say a foot or 2 feet apart .

What do you mean? In phase? Or out of phase?

Is there an ideal distance apart to do with frequency?

What do you mean? Are we still talking about pointed at each other? Why would you even want to do that?

Does it have an affect on the opposing woofer itself such as improving the rearward movement of each other? Would have to be a specific distance i assume . A possible equation ?

Only thing I can think you might possibly be trying to get at is what's been covered a zillion times, that waves propagate and bounce and reinforce and cancel, everywhere and all the time, and at all frequencies. And regardless of which direction they were pointed first.

@millercarbon Very well said
Emphasis on this

his one fault is being blessed with an overabundance of modesty

Duke has made available to audiophiles an integrated multi subwoofer system at a great price. Kudos to him. 
There are three considerations when it comes to accurate bass performance. The woofer itself by which I mean the driver and it's enclosure, the amp driving it and it's integration with the satellites including crossover cut off points, slopes, phase/ time alignment and room control. There are plenty of high powered amps capable of great bass. More electronics are including digital bass management and room control with delay capabilities which makes integration a snap TACT, Anthem and Trinnov come to mind. It turns out the most difficult part to do correctly is the subwoofer itself. Making an enclosure capable of perfectly isolating a high power, long excursion 12" driver is very difficult. Put you hand on your subwoofer while it is playing. Feel that vibration? That is distortion. Any flex or movement of the enclosure is distortion. The ideal enclosure would be infinitely heavy and infinitely stiff. It would be a concrete bunker. This of course is commercially impractical. Designing the internal dimensions of a sealed subwoofer enclosure is easy. Making it acoustically dead is another story altogether. This is where the home hobbyist has a great advantage. There are a slew of great drivers out there and you don't have to worry about shipping and labor costs. You can make an enclosure as heavy as you want as long as it does not fall through the floor. We made killer enclosures with a sandwich of Corian and 1" MDF  Corian/MDF/Corian 2" thick. They weighted 250 lb each and when you put your hand on them you felt nothing. 

davekayc, two drivers operating in phase with each other are acting acoustically as one driver if they are within 1/2 wave length of each other at their highest operational frequency. It does not matter where they are pointed. As an example if the woofers are crossed out at 100 Hz, 100 Hz has a wavelength of 10 feet. If the woofers are closer than 5 feet they are functionally one driver assuming they are operating in phase with each other. I have two 12" drivers pointed right at each other 3 feet apart right up against the middle of the front wall. There are two other identical woofers one in each front corner. They are placed so that the edge of the driver is right up against a wall. They are over twice as efficient this way. They are all acting as one driver, one wave front. Since the woofers are right up against the wall the first reflection off the front wall is exactly the same as the initial propagation so essentially there is no first or early reflection. Since the drivers form an infinite line source there is no reflection from the side walls either. 

I would think that within a certain distance . One opposing driver would either assist or hinder the other at a given frequency. Taking all walls and reflective surfaces out of the equation . Dead of space. Think about a truly tuned exhaust. It reflects a sound wave within to increase power . At some point i would assume the area of an 18” speaker would be affected by the other . In phase. Question is how.