Second Stage Question: Non-Balanced that breathes Like a Balanced?

[beanojones]

Second Stage Question: Is the a Non-Balanced second stage that breathes Like a Balanced Second Stage?

(Ignoring Omega, and Posiedon types for now.)

In other threads, I hear people saying that there are other ways of getting a smooth breather that do not involve a balance chamber design. Personally I have never used a reg that breathes like a balancing chamber design, except the balance chamber ones.

Is there such a beast?

Are there any makers whose top of the line is not a balance chamber second stage?

 

[herman]

It depends on what you mean. As long as the IP does not change and the 2 seconds are of similar design, there is no real difference in how a second stage will breath balanced or not. The purpose of balancing - regardless of 1st or 2nd stage- is to compensate for changing tank pressure. Changing tank pressure will result in a changing IP if the first stage is not balanced and as it changes the cracking pressure of a second stage will change accordingly. To compensate for changing tank pressure and it's resultant IP pressure you can either balance the first stage and keep the IP constant or you can balance the second stage and use the design of the stage to compensate for changing IP. Balancing both is redundant. As an example, you can upgrade a SP 109 to a balanced design by replacing it's internal parts. If you compare an upgraded one to a standard one, as long as you set them up the same and use the same IP, they will breath the same. The difference would come if you attach them to a unbalanced first stage, as tank pressure changes followed by the changing IP, the unbalanced one's cracking pressure will change, either up or down depending on the type of unbalanced first stage you use (some designs increase IP as tank pressure drops, other designs the IP drops as tank pressure drops). IMO, the big drawback to non balanced seconds is not that they breath worse but when hooked to a nonbalanced first stage they must be set a lot more conservatively to compensate for the changing IP. The tech really has no choice, the second must be set not to freeflow at the highest expected IP and when the IP is lower than that, the reg breaths poorly. By balancing either stage, the second can be set to perform a lot better.

 

[scubadiverchris]

My opinion is there is a lot more to a second stage than rather it is balanced or unbalanced. If you use an unbalanced second on an overbalanced first you will have problems at depth unless of course you set the wob harder. Key to a nice breathing reg is a properly paired first and second stage that is properly adjusted. Mares and AL both make non balanced that breath ok. Proton Ice by Mares received very good reviews and (dont quote me but) it is not a chamber design.

 

[DA Aquamaster]

I noticed early on in my diving career mid-80's) that if properly adjusted and placed on a balanced first stage, the low end unbalanced Scubapro R108 "High Performance" would breathe every bit as well as the high end balanced R156 Balanced Adjustable.

It makes sense when you consider that they share the same orifice and diaphragm and should deliver similar volumes of air as long as the working range of the valves are similar.

The difference was that if the IP was unstable (as is the case on an unbalanced first stage) the inhalation effort of the unbalanced second stage increases as it loses some of the downstream assist as the IP falls at lower tank pressures.

Scuba pro played to that by usually packaging the balanced second stages with balanced first stages to magnify the differences and to obscure the fact that a high quality unbalanced second stage will perform very well on a balanced first stage. That marketing/packaging approach continues today with more than one company.

The key to second stage performance on a balanced first stage is really the quality of the second stage not whether it is balanced or not. If you put a cheap second stage and/or use one with a small diaphragm or orifice, you may not get the flow rate or inhlation performance you could get with a better one.

 

[pescador775]

Beano, by omitting servo designs like Omega you are stacking the deck. Even so, Mares produces a popular line of "unbalanced" valves. Whether they breath the same is not necessarily relevant but a subjective value unless one is referring to ANSI tests. If one is referring to subjective impressions I believe that the balance valve breaths a little smoother than some others, possibly due to the damping effect of the internal piston/poppet arrangement in regs like the G250. It could also be due to case design or the so called linear flow arrangement.

I don't believe these mechanisms are actually balance valves because the actual amount of offset posed by the "balance" piston is too small to actually compensate for variations in IP. Moreover, the IP of most regulators is balanced out from the git-go. Although I feel that balance valves are smooth breathers others argue that unbalanced valves are equally smooth. As an experiment to test this idea, I fine tuned an old R109 and a G250HP. By comparison, any difference hardly seems significant. At depth, the unbalanced R109 seems to depend more on Venturi to produce high flow but one would have to be actively looking for a difference to detect it. It seems that control of air within the regulator case is responsible for any slight differences in "feel" when comparing two quality regulators. It may be that balance valve designs tweak the internal architecture in favor of smooth flow but that is speculation. In conclusion, I would have to defer to individual tastes.

 

[cerich]

I noticed early on in my diving career mid-80's) that if properly adjusted and placed on a balanced first stage, the low end unbalanced Scubapro R108 "High Performance" would breathe every bit as well as the high end balanced R156 Balanced Adjustable.

It makes sense when you consider that they share the same orifice and diaphragm and should deliver similar volumes of air as long as the working range of the valves are similar.

The difference was that if the IP was unstable (as is the case on an unbalanced first stage) the inhalation effort of the unbalanced second stage increases as it loses some of the downstream assist as the IP falls at lower tank pressures.

Scuba pro played to that by usually packaging the balanced second stages with balanced first stages to magnify the differences and to obscure the fact that a high quality unbalanced second stage will perform very well on a balanced first stage. That marketing/packaging approach continues today with more than one company.

The key to second stage performance on a balanced first stage is really the quality of the second stage not whether it is balanced or not. If you put a cheap second stage and/or use one with a small diaphragm or orifice, you may not get the flow rate or inhlation performance you could get with a better one.

well said, a excellent unbalanced second stage on an excellent balanced first stage that has not just god flow capacity but also excellent IP stability can easily do as well (sometimes better) as a balanced second stage.

 

[redacted]

Balancing a 2nd stage should have no direct effect on cracking pressure. It may effect it indirectly by having a somewhat reduced tendency to set a groove in the LP seat.

Once the gas starts flowing, the "air spring" in a balanced 2nd should be reduced a bit while the metal spring force must continue to be countered to keep the gas flowing. However, that small difference may be completely overridden by case geometry and the venturi effect.

I don't believe that Mares produces any balanced 2nds.

 

[Hallmac]

Breath an early model Conshelf or Calypso, especially the metal body ones, and you will never notice the difference.

Excellent breathability, even by today's standards.

 

[DA Aquamaster]

Today's standards is a key statement. The all metal SP R108 was a great second stage, even if it was entry level. The quality and materials were first rate.

Today, there is a substantial difference in the quality of an R190 or R295 and an upper end second stage like the S600 or G250V. Some of the current/recent R190's, R390's, R whatevers can be made to breathe very well while other cannot - unless you have a large supply of parts to mix and match to get a set that work well together (a process similar to putting togther a national match M1 or M14) as the quality control is more hit and miss at the low end of product line.

And not all of it is SP's fault either, nor are they the only company where the low end reg performance has actually fallen. EU standards in generally are biased in favor of freeflow resistance which basically means the reg has to be capable of being rendered able to breathe like a rock, so for a non adjustabel reg that means breathe like a rock all the time performance and a great deal of quality or quality control is required to hit a low standard of inhalation excellence.

 

[halocline]

I think what you're probably looking for is a barrel poppet 2nd stage with a decent quality lever/poppet/orifice set up. The SP G200 is a perfect example, if you can find one. Alternatively, you could buy a G250 or G200B and "unbalance" it by exchanging the balanced poppet and seat for the one in the G200 kit. These are in addition to the old 109, which you don't want because you found they wear out around the lever in the air barrel. (You can replace the air barrel in the others, and they're much newer)

I'm sure there are other manufacturers out there making decent barrel poppet unbalanced 2nds.