Apeks uses a metal air barrel in the second stage. This is a BIG plus over the plastic air barrel that ScubaPro has gone to to make the bean counters happy. This is NO reason for ScubaPro to do so. There is a valid reason why Atomic and Apeks still use metal in this part, and that is its thermal benefits.
If ScubaPro really wants to build a cold water reg that can compete against Apeks then they should go back to the original design, along with the new sealed diaphragm first stage.
When I started diving back in the 70's with unsealed diaphragm first stages and all metal second stages, free flows were about as rare as hen's teeth. With my Mares and Apeks regs I have never had one hint of a free flow, and most of my dives are in water colder than 45 degrees. Heck, last week I dove in 38 degree water with my MR12 Akros regs (on doubles, and unsealed) and they worked great. Come to think of it....The only free flows that I have seen with my dive buddies are from those divers using "high performance" balanced piston first stages. When you move air volumes of that magnitude there is a lot of temperature drop in a first stage.
Me? I'll stick to the balanced diaprhragm with their lowly flow rates of 140-180 cubic feet per minute. Considering that second stages generally don't flow more than 70cfm, that is more than enough for me and a buddy.
Greg Barlow
Former Science Editor for Rodale's Scuba Diving Magazine
Oh, that's the reason, the metal air barrel contributed the thermal advantage....
Didn't really keep track, and not an expert at all, but I have an impression that, Scubapro always wanted to try different materials to lower the weight for people who prefers that, is that the reason? Al, then plastic etc...
Just if, hypothesis, if Mk17 is selling. Would Apeks try to lower the price, just for the sake of keeping the status of the number one sealed product?
To me, what I can see is that, the sealed feature is important, but something equally important could be the flexibiliity of just buying the 1st stage/2nd stage independently. Yes, I can do that online, I know. But price-wise, I can always get a set of Apeks 1st stage + 2nd stage with a lower price from certain LDS. Are there any reason for Apeks not to?
Then something very important is the maintainence (including convenience to get spare parts) availability over the world. Esp. imprtant for people who would dive at different sites around the world. Then of course, the cost.
