interesting comment from dive shop owner

[АлександрД]

Michael, I`d try to explain why old regs is better than new Is there really a difference?

A larger diaphragm probably won't make a reg easier to breath. Double hose Royal Aquamasters have a huge diaphragm and the same first and second stage as your Conshelf. They don't breath easier.

It is not a problem of big membrane, it is a problem of hoses:
Membrane of doublehose is plased not on the same level, as mouthpiece. And breathing difficulties has sources from column of water, between membrane and your mouth.

 

[Hickdive]

Provided you can parts for them there is no reason why an older regulator can't be used.

However, don't imagine that the older regulator will perform as well as a more modern one. The reason is that older designs from the eighties and earlier were never subject to work of breathing (WOB) tests. Only once the ANSTI test machine was invented could direct regulator v regulator comparisons be made. Some manufacturers and regulators didn't do particularly well in independent WOB tests on the ANSTI and I'm afraid US Divers models, part of the Aqualung group, was one of those poorer performers. In fact, when the EU introduced a minimum standard for regulators (EN250), US Divers disappeared from the European market.

 

[runsongas]

en250 only came out in 2000. that was also around when aqualung renamed their reg lines and got rid of La Spirotechnique and US Divers to rename everything under the Aqualung brand. The Titan and the Conshelf are virtually the same regulator, using the same service kit, and a large number of the same parts. The titan is en250 rated. The discontinuation of US Divers had more to do with rebranding than en250 requirements.

 

[GJC]

Michael, I`d try to explain why old regs is better than new Is there really a difference?

It is not a problem of big membrane, it is a problem of hoses:
Membrane of doublehose is plased not on the same level, as mouthpiece. And breathing difficulties has sources from column of water, between membrane and your mouth.
View attachment 549141

Excellent point and one of the factors I failed to remember that affect ease of breathing.

Back to the OPs question:

-The size of the diaphragm is only one factor that could determine breathing effort. A larger diaphragm (on a Royal Aquamaster vs Conshelf XIV) does not make breathing easier in my experience when the regulators are serviced and adjusted correctly. Other factors (mentioned above) have a greater effect on effort of breathing.

 

[BRT]

A larger surface area is more sensitive to pressure influences (a big button is easier to push than a small one kind of thing)
so yes a large diagram will respond quicker to inhalation effort due to the influence of ambient pressure on the large diagram.

I still use Scubapro MK5's and 156's converted from 109's and sold in the 1970's. All my years diving I've yet to find a better reg set. I've found plenty just as good and some not so good, but better no.

It will take less vacuum to move the larger diaphragm but will require more volume to produce that vacuum.

 

[GJC]

It will take less vacuum to move the larger diaphragm but will require more volume to produce that vacuum.

This is true. But when a dive regulator is designed, the amount of vacuum to move the diaphragm is also affected by the length of the lever on the diaphragm and the strength of the spring on the lever. You can't just say if it has a bigger diaphragm, it must be easier to move it. You need to consider all the other components. A regulator with a larger diaphragm and a short lever and stiff spring can make it very hard to breath from.

 

[AfterDark]

This is true. But when a dive regulator is designed, the amount of vacuum to move the diaphragm is also affected by the length of the lever on the diaphragm and the strength of the spring on the lever. You can't just say if it has a bigger diaphragm, it must be easier to move it. You need to consider all the other components. A regulator with a larger diaphragm and a short lever and stiff spring can make it very hard to breath from.

yeah but that ain't what he's got.

The op's reg is a time proven designed winner, because of that it benefits from the larger diagram.
Same for your post @BRT volume isn't an issue with the OP's reg. The question was about the OP's reg, not a general statement.

 

[AfterDark]

Michael, I`d try to explain why old regs is better than new Is there really a difference?

It is not a problem of big membrane, it is a problem of hoses:
Membrane of doublehose is plased not on the same level, as mouthpiece. And breathing difficulties has sources from column of water, between membrane and your mouth.

Good post same thought came to me when I read that post. That's what a crouth strap is for, to kept the tank and therefore the reg can in the right spot.

 

[Michael Jastrzebski]

In fact, when the EU introduced a minimum standard for regulators (EN250), US Divers disappeared from the European market.

This is super interesting and insightful however the disappearance of the US Diver brand occurred per my understanding from purely marketing/business reasons when french La Spirotechnique changed its name to Aqua Lung in 2003. If there is any concrete data that would suggest the regulators weren’t meeting the new standards I would like to see that. (Sorry, I just realized someone before me wrote essentially the same thing)

 

[Hickdive]

en250 only came out in 2000. that was also around when aqualung renamed their reg lines and got rid of La Spirotechnique and US Divers to rename everything under the Aqualung brand. The Titan and the Conshelf are virtually the same regulator, using the same service kit, and a large number of the same parts. The titan is en250 rated. The discontinuation of US Divers had more to do with rebranding than en250 requirements.

Diver magazine ran many popular regulators through an ANSTI machine. US Divers and certain Aqualung models failed to meet EN250,