Mo, John may have been referring to the acoustic power being twice as high, rather than the result actually being subjectively twice as loud(generally said to require a 10 dB increase, as you point out), although he did use the term "loud". The 3dB increase which two widely separated speakers playing the same sound produce does involve twice the acoustic power(and twice the total amplifier power)but the 3dB increase, while noticeable, is far from the subjective "twice as loud" standard.

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Enjoy the music, not the equipment.