When I mentioned the compromise of an internal amp, I was referring to the known degradation of the sound of especially solid state circuits subjected to vibration. But the deleterious effects are mostly noticed in upper midrange and high freuqnecies, if they are noticed at all. I don't consider it a significant issue in the Zu sub imprementation. Offering a kit permitting removal of the internal amp and controls in exchange for easy connection of external sub amplification and a croosover or active low pass filter is essentially a way to revive the concept of the Definition 1.5-era Definition Pro, which had few takers. But in this case it can be done without having to ship a separate model.
At the time of the Def Pro, Definition 1.5 had only recently gotten a sub level control. (My original Def 1.5s in 2005 were delivered with no sub adjustment of any kind. My first feedback to Sean and Adam was to ask for a level control and suggested that all Definitions should be so built. Sean and Adam soon showed up at my house in Los Angeles to do a field upgrade and then they proceeded to visit every Definitions owner in the US to install level controls.)
So Def Pro was introduced in the context of Definitions only having simple level controls on the sub array. I think with the five-way sub control panel on Def 4 along with the big driver upgrade, downfiring, and the amp improvement inside, the difference externalizing the sub electronics will be so much smaller that it will be worth tangling up your room with more gear and cable in only the most demanding and extraordinary circumstances, like if you are trying to load a very large space and plan to use high power monoblocks on the main drivers/supertweet and need something mammoth for the sub. And if you were going to that trouble, a pair of Zu's new subs used in conjunction with the internal Def4 sub would be cleaner and likely more effective.
But it's the Zu way to accommodate downstream customization so takers there may be. Still, one of the chief appeals and value propositions of the Definition format is having everything for 16Hz - 25kHz objective presentation in a single simple column for regular 2.0 gear.
Phil
