I challenge anyone to give me some scientific reasoning to show that Mares regs are not suited to "extreme" diving. First, I have hundreds of such dives using Mares MR12 regs. They are very well built and offer the benefits of being a robust design that delivers very high gas flow. The first stage utilizes very few O-rings and due to the design is not affected as much by adiabatic heating as many other models on the market. The first stage also used the dynamic flow control feature which boosts the pressure to the preferential port. This has been validated by independent testing on an ANSTI simulator.
The second stages offer simplicity that hinges on the effectiveness of the VAD design. This vortex-assisted-design creates a venturi action that assists in keeping the diaphragm depressed after the air flow has begun. This allows Mares regs to not be dependent upon adjustable venturi levers and inhalation effort controls.
I have first hand experience with the testing of Mares regs on an ANSTI breathing simulator. I was the Science Editor for Rodale's Scuba Diving Magazine for two years, and was blessed to work with the late Jon Hardy of ScubaLab. All of Mares's regs meet the EN250 standards by a wide margin. Even the R2 piston design does. The diaphragm designs, 12, 16, & 22, all MEET or EXCEED the US Navy class "A" standards also. In fact, my favorite reg, the MR12 Akros had a simulator score of 1.1 joules/liter, while the Navy standard is 1.4 j/l.
As far as the Abyss goes, I don't use them due to the fact that I can't field strip it under water. It is a great design for cold water, as the metal second stage does withstand the chilling effects of such conditions. Plus, it only has 3 O-rings in the whole second stage. Talk about durability and simplicity!
Jon Hardy did many "blind" tests with regs. His extensive data shows that divers cannot differentiate regs until the breathing effort exceeds 0.4 j/l. This means that you can't credibly tell the difference between a reg that has a 0.9 and a 1.2.
I have serviced many different brands of regs, and have had many different models stripped down to their individual components. THERE ARE NOT POOR PERFORMING REGS produced by the major manufacturers on the market.
I can honestly say that many divers choose a particular brand or model only by what other divers tell them. Just because a "tech guru" uses a certain brand doesn't mean that it is substantially better than others.
Now, I will make a few general remarks on regs. High pressure is a killer on HP valves. The life expectancy of the polymer compound takes a real beating from pressures in excess of 3,000psi. Mares valves do not hold up as long as I like when the pressures of 3,400 and higher are consistently used. When I say consistently, I should clarify that I've personally seen them fail and begin leaking enough to causes second stages to begin "burping" from the excess intermediate pressure. Not catastrophically leaking, but a slow bubbling I might add. But.....This is a very common problem for almost all models and lines. Many tout the virtues of ScubaPro regs, but they, too, have this very same problem. In fact there are some individuals that have a steady job of producing more robust seats custom made for technical divers. It is true that Apeks first stage seats hold up to such high pressures for generally a long time. Apeks uses a polymer compound that seems almost impervious to such tasks. Mares has begun producing seats that have a compound that "looks" very much like the Apeks material. Before anyone jumps on the "copy" bandwagon, I will add that the Mares dynamic flow control feature is now a common one of other lines. They usually call it an overbalanced first stage. Hey, if something works then why not use it?
As far as the comment about free flowing...I adjust all of the Mares regs that I service to have a cracking effort of 1.25" rather than the typical setting of 1.0". After rebuilding at least 50 to this standard, I've only been made aware of one that free flowed. When this is a problem, I make an adjustment that takes all but two minutes of time.
I honestly tire of the debates over regs. Many of these come from the same mindset that auto manufacturer fans have. Let's be quite frank, can someone specifically point out problems with Mares regs? My breath great at 130' on EAN or air, and easier flowing helium based mixes should be used beyond that point anyway.
One more big plus for Mares and ScubaPro is that you can go to virtually anywhere in the world and find a dealer and more importantly, parts.
I don't want to be argumentative, but let's hear some real facts to prove my points wrong. Subjective opinions are merely based upon perceptions. Real testing by a simulator is the ONLY viable result when it comes to breathing effort.
After 28 years of using regs, I am still amazed that the modern designs are still so similar to those of yesterday. Evolved, yes, revolutionary, no.
Greg Barlow