DLK. I knew Don L. Kliewer and a bunch of guys who were friends who worked there. A Minneapolis company. I still own and use a pair of 1s and 3s and I have had the 4s and a modified pair of 4s.
I got all the parts for a pair of 4s from the company, built a pair of 1" wood cabinets, 14"x14" x4'? made some tubular stands, laid them on the side and put the little 5" mid-range in a very little box and the tweeter screwed to a board on top.
So they each consisted of 2-12" woofers, 5" mid and a tweeter. Now looking back I guess I sort of had a partial open baffle and I did not even know it! I do not know what I did with them, probably sold them!
Lots and still making great memories with DLKs!