Crossover is suggested no lower than 1500 Hz. A "K" crossover in very good operating condition works pretty good with the 704.

I agree - the 704 "likes" a little more power to get the low end working well, but mostly, I think, in order to handle transients in the modern digital media. They're the most efficient 2-way ever built in the Altec tradition, perhaps by anyone else, too, but they do like to have a big box and extra amplifier headroom.

As for box tuning, Jerry Hubbard tuned the Iconic Stonehenge V System we demonstrated at the GPAF at 40 Hz using a horizontal slot of 11" H x 2.5" v x .75" D.

• Iconic's Stonehenge Systems Page