Apeks US4 vs DS4

[mayastig]

Looking at purchasing my regs, but im stumped between these two. I know the ds4 has the diagphragm which automatically controls the flow of air at depth while the us4 is manually tuned to set a constant flow, setting those two aside any pros and cons between these two? currently at rec but i plan to go doubles in the future.

also...just as a side question, is the diagphragm supposed to give the diver a more "comfortable" dive at depth? i was wondering why you needed one as you can tune your reg (us4) at a constant flow anyways, irregardless of depth.

 

[StSomewhere]

Phil Ellis at DiveSports has a good webpage up that describes the differences between the Apeks first stages, including the DS4 and US4:

http://www.divesports.com/articles/apeksregsexplained.htm

Its basically a matter of the DS4 being environmentally sealed.

 

[H2Andy]

basically, the us4 is a balanced diaphragm reg and not environmentally sealed.

the ds4 is essentially the same with the addition that it is environmentally sealed

i own both (just got them recently). my primary is the ds4-ATX50, with
the us4-ATX40 as secondary.

i can't tell any difference between the two. they both breathe beautifully.

 

[mayastig]

US4 exceprt -"is not environmentally sealed to prevent water intrusion into the ambient pressure chamber." I assume this is the case when taking off the reg from the tank?

 

[StSomewhere]

US4 exceprt -"is not environmentally sealed to prevent water intrusion into the ambient pressure chamber." I assume this is the case when taking off the reg from the tank?

No. This has to do with how the reg "knows" how much pressure you are currently under so it "knows" how much additional intermediate pressure to add so you can still breathe at depth.

In the US4 and a lot of piston first stages, thats though direct contact with the water. With the DS4 and really any diaphragm reg with an environmental seal, its done with air pressure and the second diaphragm is only there to keep that dry. It has a lot to do with preventing freeflows in really, really cold water.

http://apeks.co.uk/technical/technical-apo525.asp

 

[H2Andy]

US4 exceprt -"is not environmentally sealed to prevent water intrusion into the ambient pressure chamber." I assume this is the case when taking off the reg from the tank?

i'm not sure i understand... but basically, sealed regs don't let water into the
first stage, whereas non-sealed regs do

this will happen upon inmersion