If you put only six of these woofers in a 72 inch line array, they are going to be 12 center to center inches apart. This means that to avoid serious and very audible comb filter distortion, you will need to cross to your tweeters at about 1130hz.I couldn't find any specs on them but i guess its within the realm of possibility that they do go down that low since the B&G ribbon lines go to 600hz.
How much is the total cost for this monster?
Marlboro