Servus, first of all I wish you all a healthy new year 2006!! So I decided now for the Hertz ES-250. It comes now in a closed housing, what I would like to build myself. On this link:http://www.bigdogaudio.de/pd1007884974.htm?categoryId=43 you can find below all the data for the housing calculation. But there you can find, still a little further up, under technical details, data which do not match. At the one comes: VAS: 65,25 QTS: 0,4 4 FS: 23,3 = 41,24 L at the other: VAS: 55,40 QTS: 0,37 FS: 27 = 20,89 L there is already a huge difference or? Which should I use now or does someone happen to also have this sub? Another small question, there are two models once with 4 ohms and once 4+4 ohms. What is the difference and which is better, there are sound differences? Sorry but I don’t know myself at all from beautiful greetings, Serkan