What is a correct loudspeaker connecting scheme and why? Thinking of "what would be best shape for a subwoofer box?" i came to idea of a barrel, with its sides (or covers) "replaced" with speakers:

I have stereo bass amplifier which is fed from single signal source. So there are 2 possible ways to connect a terminals to an amplifier channels:



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*With zero phase offset: this would double the pressure inside (lower or higher than air), if is compared than a single speaker in a barrel






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*With inverse phase offset: this would cancel out internal pressure. When front speaker's diaphragm would be pushed forward, back would be also pushed forward.




I am interested what scheme is used and why - what consequences inner pressure would introduce to bass sound, what effect would create those two schemes?
 A: Assuming that, when listening to the music, you are sitting at a point equidistant from the two bass drivers then the sound from them will travel an equal distance from each driver to reach you. If you wire the speakers in antiphase then the sound from the two drivers will be in antiphase when it reaches you and will interfere destructively. This will reduce the volume where you're sitting, which is almost certainly not what you want.
If you did the experiment in an anechoic chamber the sound intensity could in principle be reduced to zero. In practice in a normal room there will be lots of scatter from the walls of the room so the volume will be decreased a bit, but not to zero.
So, wire the two drivers in phase.
A: At $100\,\mathrm{Hz}$ the wavelength of sound is about $3.4\,\mathrm{m}$.  If your cabinet is substantially smaller than that, which it probably is, then it's well-modelled as a point source.  This means that you want the speakers in-phase, or you'll end up with very dramatic cancellation.
