A while back I stumbled across some information on the Audio Development MM 4" mid range driver. I was intrigued enough to buy a pair of them ( the fact I love the Vipera F6 drivers from AD also helped). Upon opening the box you notice the lack of a dust cap on the cone. Then you start noticing all of the machine work on the basket. Aesthetically, these really are beautiful pieces of workmanship. I then proceeded to install the drivers into my truck. I for the moment have a new favorite mid range driver, WOW! These drivers ( in my install anyway ) require very little eq to dial them in. I am currently running these from 200Hz to 6500Hz with LR 24db slopes. These drivers are simply amazing. I expected that they would be very good, I wasn't expecting them to be THIS GOOD. In my personal perspective these are the best mid ranges I have had to date. When one considers that I have had the Eton 3-400, Hybrid Audio Legatia L3v1 and the Sinfoni c89m all in the truck, the fact I feel that the mm4 out shines them all to me anyway is a mouth full. Admittedly, these are easily the most expensive mid range drivers I have tried to date, but, worth every single penny of what I spent. If your into sound quality, you simply can't go wrong with the mm4, I feel it is just that good.