::And what is the effect or purpose of the front chamber and what would be the effect of eliminating it? In other words, what purpose does it serve?
It acts a a low pass filter. So eliminating it would let higher freq. pass.

::I know it will increase pressure, but what is the advantage of that? And the disadvantage?
Horn gain-over a narrower bandwidth, disadvantage-less efficent horn.

::Would you loose efficiency, but gain bandwidth by removing it?
Yes.

HTH
Bill W.