It may be better to leave them separated - IF you can maintain a separation distance of at least, say, 6-8" along their length. If not, then it may be better to twist them together. If you're still in any doubt, you can always try it one way awhile and then compare to the other. But, usually the full-range difference results in some change in openness in the upper mids or highs, although I would expect that difference to usually be slight, if at all. But, since you're dealing with woofers here, I would say there may not be normally much of anything amiss soundwise either way, really. Hope this helps.
