First stage
The compact first-stage body is crafted from forged marine-quality brass with a polished chrome-plate finish. The internal working system uses an environmentally sealed balanced diaphragm, and the sealing gives this model a coldwater rating.
Externally, there are two high-pressure and four lp ports, two of which are angled at 30° to enhance hose-routeing. The first stage is available with either 232bar International or
DIN tank-valve connections, the latter having a rubberised wheel to aid grip and weighing 850g.

Second stage
Both the second stage and dedicated octo bodies are made from technopolymer and elastomer plastics. The second stage features a locking diaphragm system and a dive/pre-dive control lever.
The demand valve is an asymmetric design, and Seac claims that this allows maximum valve opening to improve performance at depth.
There is a large elastomer front cover to allow simple manual purging, and the cover-plates are locked in place with Seac’s membrane block system. There is also a large surface exhaust valve and an ergonomic exhaust port with a built-in chin-rest.
The octo has a yellow front cover for instant identification, and both second stages are fitted with rubber low-pressure hoses and ergonomic mouthpieces.

The Test
I cheated a little with the real-world tests, and asked DIVER Test team-member Yvonne Tatchley if she would use the regulators in her daily workplace at Wraysbury dive centre. She agreed to dive with them over a fortnight of teaching, guiding and general underwater maintenance work before reporting her findings.
I also took them to Stoney Cove for several dives on the infamous Hydrobox, and on the wreck of the Stanegarth.
The first stage is very compact, especially with the DIN connection on the models we were given. The rubberised grip around the DIN wheel was a nice touch, and made disconnecting the valve a doddle, even with wet hands.
Hose-routeing was an easy affair, because the ports are laid out in a classic three-per-side configuration with the front two lp ports angled towards the wearer. These brought the primary second stage and BC inflator-hoses neatly over the shoulders with no undue snagging points.
The second stage felt light, especially at the surface, and stayed in place without either of us having to bite down hard on the mouthpiece. There is a small concave section on the exhaust port that seemed to enhance the comfort as it sat neatly across the chin.
Under water, the regulator behaved impeccably, delivering a smooth airflow even when we tried to turn the thing inside out by “hoofing” as much gas as we could possibly get.
The regulator remained dry no matter what our orientation, and refused to freeflow when spat out at depth. The dive/pre-dive knob was easily accessed, and successfully prevented any freeflows from the octo when entering the water.
There were a couple of minor niggles. We both agreed that the purge-cover was a bit misleading – the large rubber face looks to be depressible anywhere on its surface to actuate the purge mechanism, but in fact you have to be quite accurate, and press it as centrally as possible.
That done, the valve released air progressively until the purge was fully depressed, but didn’t over-deliver.
The other niggle was that the second-stage demand valve was noisy at the surface, although this stopped as soon as we were immersed, seemingly because the water was lubricating
its parts.

Conclusion
When I first became involved in regulator testing the units didn’t require a certificate of approval, but this all changed when European CE certification became mandatory for life-support equipment sold in the UK.
There used to be regulator sets that were seriously under-gunned when it came to performance, to the point of being downright dangerous, but nowadays we can enjoy our underwater breathing apparatus without fear of failure.
Standards are high, and I defy most divers to distinguish the performance between a set costing a few hundred pounds and one that will set you back four figures.
These Seac D-Synchros are a fine example of today’s state of play. They performed brilliantly under water, were compact, lightweight, comfortable and easy to get on with.
Yvonne certainly enjoyed them, and I wasn’t surprised to see that after a month she was still choosing to dive with these “entry-level” regulators. In that time she took them to dive with Lundy’s seals as well as on a wreck-diving trip out of Weymouth.
Her more expensive regulators seem to have been temporarily retired and are currently gathering dust on a shelf - high praise indeed for these Italian budget-busters.

SPECS
PRICES: First and second stages £169. Octo £81
FIRST STAGE: Environmentally sealed balanced diaphragm
CONNECTION: 232 bar A-clamp or DIN
PORTS: 2 hp, 4 lp, two angled at 30°
COLDWATER RATED: Yes
CONTROLS: Dive / pre-dive
CONTACT: www.seacsub.com
DIVER GUIDE: 9/10