The W is the famous sand filled double wall. It's a 2x15 cabinet and the best I've ever heard. It just sounds like the recording, never like a speaker. It is not based on the old Jensen designs, it's just a big bass reflex with too small ports of unequal size. An odd design, but it sure works.

The other Onkens are based on the Jensen Ultraflex. They are the multiple ports on the front. I've never seen one of the them with the sand filled walls, not sure how you'd do that. I like them very much, it's a great sounding bass box. I've spent time with the big Onken (Altec 416 15") the small Onken (Altec 414 12") and the mini Onken (Focal 10") as well as Planet 10's Fonkens which are small fullrange versions with Fostex drivers. There is something quite nice about all of these. I don't know if it's the port arrangement or just the construction technique, but they all sound very clean, very fast. Like they have very little overhang or resonance. To my ear, it's a lovely design.