Sure, JH; without the room gain(below the frequency of the longest room dimension)to increase the bottom end extension the lower limits of the sub will be essentially the same as when measured anechoically. At the 6-8' distance the sound level will fall off more quickly than it would inside, since there'd only be ground reflections to add to it, but it wouldn't disappear, and if you can solve the other problems mentioned with a sub outside, the effect should be satisfactory.

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Enjoy the music, not the equipment.