Correct....
Basically what I'm getting at is that even though there are many drivers out there, (commercial, pro audio, car audio) design, attention to detail, build quality specs of these drivers is what will determine the final response and how they measure in the end....
Before Ilkka starting doing his measurements at HTS, many HT sub manufacturers distortion issues went unchecked as they really didn't post measurements of such details.... LOUD doesn't always mean good sound. Ultimately I'm sure all this kind of discussion was going on long before I started looking into HT subs, but things really have gotten better for the consumer in the last few years with people posting measurements of all sorts of products avail, to kinda weed out the bad and bring light to some of the best...
There are many designs of driver construction, XBL^2, underhung, overhung, LMT... heck even more then I know but the internet has lots of info you can read about on stuff like this.
SVSound from what I remember was getting drivers from TC-Sounds at one point and time, then later hired on
Stephen Ponte from TC-Sounds when they went under a few years back, so he has a great background of driver design, and was an amazing addition to SVS.