If you replace one 8ohm speaker with two 16ohm speakers in parallel then area will double but power to each speaker will half and SPL will stay the same.
Two 8ohm speakers in parallel will receive total of 2x power resulting in 3dB increase in SPL. It is the same as two exactly same subs, that Al mentioned, driven by separate identical amplifiers also resulting in 3dB increase.
It seems logical to me since adding more transducers (area) of the same efficiency without increase in power cannot improve overall efficiency. SPL is increased by 6dB only if power is doubled to each of two speakers (quadrupled power from the amp)
Two 8ohm speakers in parallel will receive total of 2x power resulting in 3dB increase in SPL. It is the same as two exactly same subs, that Al mentioned, driven by separate identical amplifiers also resulting in 3dB increase.
It seems logical to me since adding more transducers (area) of the same efficiency without increase in power cannot improve overall efficiency. SPL is increased by 6dB only if power is doubled to each of two speakers (quadrupled power from the amp)