The all-metal second stage is built to withstand the slings and arrows of misfortune handed out to diving gear that stays rigged for action for 10 days or more, with never so much as a refreshing rinse in fresh water.

Second Stage
The second stage doesn’t go out of tune and need tweaking at the breathing resistance knob, because the designers at Mares designed out the need for such a gizmo long ago.
It uses a patented inhalation by-pass tube that routes the gas you breathe well away from the pressure-sensing diaphragm, and feeds it direct to the mouthpiece.
The remaining pressure of gas within the body of the second stage takes care of matching the gas pressure delivered to that of the surrounding water.
Without any air flowing fast across the back of the diaphragm, there’s no localised drop in pressure to allow the diaphragm to pull in, opening the valve further and causing that freeflow effect encountered with so many conventionally designed regulators at the surface, at the cusp between air and water.
You simply put the Mares Abyss second stage in your mouth and breathe.
The pressure-sensing diaphragm is covered in such a way that, when a diver is hooked in and facing into a strong current, there is no tendency for the regulator to purge involuntarily. That’s because water access through the front part is nicely diffused.

First Stage
The MR52 first stage has been rethought with cold freshwater divers in mind. It’s a diaphragm-type design with four medium-pressure and two high-pressure ports placed and angled so that there was no problem fitting a pressure-sensor for an air-integrated computer, even with a full complement of hoses.
Either side of the first stage there are large metal heat-sinks shaped to reduce the chance of ice-creep, should the water you are diving in be cold enough to freeze around it.

In The Water
Gas was delivered into my mouth in a comfortably diffused way, and there was always plenty down to the maximum depth of 50m at which I tried this regulator. The purge button was easy to locate, and although it worked well enough, there was never any feeling that it was going to blow my tonsils down my throat.
The medium-pressure hose is of the modern super-flexible woven type, so routeing was never a problem, and I never encountered that nagging feeling that if I turned my head suddenly to the left, the mouthpiece might get dragged from my grasp.

Conclusion
Overall, I enjoyed using the Mares Abyss for a week’s repetitive diving, and encountered no snags. Its bomb-proof design has evolved over all the years
in which I have worked in the diving industry, and its most recent incarnation merely reveals recent developments of what was already a first-class design.

COMPARABLE BALANCED DIAPHRAGM REGULATORS TO CONSIDER:
Cressi MC9 XG Compact, £209
Hollis 212 DC1, £350
Subgear SG1000, £349

SPECS
PRICE £360
FIRST STAGE Balanced diaphragm-type
PORTS 4mp, 2hp
SECOND STAGE Vortex bi-pass tube means no diver adjustments required
WEIGHT 925g
CONTACT www.mares.com
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