I'm sure that Dan Wiggins would be more than willing to supply you with his DUMAX test results and any other paperwork you need. As a subwoofer designer, I'm sure he is intimately aware of correct testing procedures. Now, one thing about the DIY market, is there is no such thing as marketing, it is marketed by word of mouth and personal experiences. If you market a product that doesn't reach its specs, you will eaten alive. Consider this, how many Car Audio "experts" know much more than basic installation principles? The answer is probably less than 5%. The number of car audio buyers that know the tech side is probably well under 1%. Now, it's easy for car audio companies to deceive their customers (No, i don't think JL does this) because they have a relatively unknowledgeable market.
Now, let's look at the DIY market. I am probably the least knowledgeable customer that Adire has sold a product to. I have been doing this for almost a decade and every day, i'm in awe of how much more everyone seems to know. The guys I deal with in my daily interactions are every bit as knowledgeable as Richard Clark and all the other mobile gurus. If Adire sold them junk, adire would cease to exist.
You were correct on a couple of issues. The T/S parameters, well one anyway (qts) will change one using only one coil of a DVC woofer, but this can be counter acted by shorting the other coil. The Xmax will remain the same unless their is some inherent problem in the design of the speaker. And again, using one VC will not damage a well made DVC speaker, it will perform very well, but less effeciently. And again, I go back to my original stance, if there is a SVC woofer made for the application, don't get a DVC and use one coil. But if you had a DVC woofer, don't be afraid that the speaker will self destruct by using one coil.
