WileEDiver:
FWIW, the Northern California ScubaPro rep, Joe Geiss, says that the S600 is set to be used in the openmost position Turning it at all from there is simply de-tuning the reg and he recommends not doing that at all. He says he'd like to do away with the adjustable knob completely.
Well...not really...It depends on how the second stage is tuned.
If the tech detunes the reg initially so that even with the adjustment knob all the way out you have a cracking effort of about 1.4" of water, there will never be a need to adjust the reg as it will not freeflow in a mild current or when you are in a face down position. In that sense Joe would be correct, any further adjustment of the reg would just further detune it and would not be required under normal circumstances. However a tech who tunes an adjustable second stage in this manner is already guilty of excessively detuning the reg and is preventing you from taking advantage of the higher performance capabilities of the second stage in the orientations that allow it.
When the diver is looking straight down, the reg is in a worst case postion and the cracking effort needs to be a little higher to prevent a slight freeflow (about 1.2 to 1.4 " of water) as the center of the diaphragm is deeper than the top of the exhaust valve. However in a normal swimming position, a head up (looking horizontal) position or when looking upward, the cracking effort can be progressively decreased to as low as .6 or.7" of water. In those cases, if the diver prefers they can turn the knob out until the reg is just short of freeflowing and enjoy minimum breathing effort. Most divers who adjust the reg will probably spend most of the dive with a cracking effort around .8 to 1.0" of water, significantly better performance than a reg detuned to 1.4 inches of water.
For divers who prefer not to mess with the adjustment, they can adjust it so it does not freeflow when looking straight down, and leave it there for the entire dive. However even those divers may desire the ability to adjust it for a slightly harder breathing if they ever use a scooter or if they find themselves holding positon in a strong current as both situations can cause the reg to freeflow due to the increased pressure on the diapgragm.
Personally, I like the adjust the orifice in SP adjustable second stages so that they are just short of a freeflow with the knob all the way out. This allows a cracking effort adjustement range of about .6 to 2.5 inches of water. It allows adequate adjustment for any condition and puts less pressure on the soft seat during storage. (the knob should always be all the way out when the reg is not in use.)
As for Mr. Geiss saying he'd prefer they do away with the S600's adjustment knob completely, SP already offers that option in the S550 which is an S600 without an adjutment knob. So in essence, what Joe is saying is that since he does not like adjustment knobs, no one else should be allowed to have them either. That's a pretty self centered point of view. God help us if he ever gets elected to public office.
