What did they do to the first stage? They used to have a non-replaceable filter in the piston.Then moved to a replaceable (but not cleanable) filter in the body. Then I noticed they have something called a laser cut filter that supposedly can be cleaned. Are they still using a flow-by piston or have they switched to a flow-through one?
Though I don't dive them often, Sherwood has several very interesting engineering features not common in other brands. It results in performance which they have reason to be proud of. The first feature, which is not new, is in the use of a floating HP orifice. The reg responds to decreasing tank pressure by using a series of spring washers to move the orifice away from the seat, maintaining IP despite a decreasing tank pressure. It is very stable.
In the SR1 and SR2 first stage, the reg stays dry inside through the use of an external diaphragm to sense seawater pressure. Yes, a diaphragm. This connects to the back of the piston to transfer increasing sea water pressure through the use of low friction heavy plastic legs. The diaphragm is part #19 on the exploded view, the pressure transfer device is parts #18 and #6. This was last used decades ago in a brand that I cannot recall. But the advantage of keeping your internals dry and free of floating sand and salt are obvious.
In the newer Brut models, the way they keep the reg dry inside is also through the use of a diaphragm, which in this case presses against the back of an old fashioned Schrader valve. This allows the IP to remain at the tuned gradient over sea water pressure. The parts in question here are #'s 31 and 18.
As I said, very different from the approach of other manufacturers. The SR series retains the huge flow of a flow-through piston, while the flow-by Brut stays dry inside, and yet with the spring washers, retains a stable IP with decreasing tank pressure.
For piston lovers, this is engineering worth appreciating. If, like me, you hate the damage to the piston land that occurs with the entry of floating grit into the environmental chamber behind the piston, these regs are sweet.
They don't command the cachet of the sealed piston Atomics, but even Scubapro Mk25 EVO has a wet environmental chamber in its piston series since it gave up the SPEC boot of the Mk 10. Sad.