There are a couple of thread on DLSs, but here's what I know. DLS stands for (ahem) "Dangerous LoudSpeaker". So much for british reticence. EMI used an elliptical woofer with an aluminum center and pulp outer part, which I think allowed the upper end to be better and extend higher than a uniform construction cone would, and the elliptical shape both spread resonances out so they were less noticeable, and allowed better dispersion (in one dimension) than a round driver would, while getting some of the low end that a large driver can provide. I agree with the previous poster that the tweeters on the DLSs don't sound particularly smooth or extended, but that may be a capacitor issue -- my earlier pair of EMIs with a single slighly larger coaxially mounted tweeter sounds much nicer.
Ellipticals have an unwarrented lousy reputation because of their use in car stereos in the 60s and 70s. The speakers used in cars back then were designed with no regard for their actual use, and efficency/loudness and durability were the only important criteria, apparently. And it was pretty obvious when you listened to them (of course the eighttrack may have not been the best source either).
But the EMI elliptical was a different beast, good enough that it has a following in the full range world, and in the 70s, Monitor Audio used them in their top model speaker (and, oddly enough, used them mounted at a 45 degree angle on the baffle).
