Apex XTX50 and XTX40 - which first stage to choose?

[grf88]

It would also significantly reduce post service issues and unnecessary wear and tear.

 

[OMyMyOHellYes]

The MBS is a dumbed-down system that combines two completely separate functions: Venturi breathing assist and cracking effort.
It assumes divers are dumb and makes one knob an "easy/hard" adjustment.

Cracking effort is the amount of suck you have to apply to "crack" the valve open. It's a triggering force and is static.
Venturi flow assistance is a dynamic force that uses the Venturi principle to keep the valve open during a breath. This becomes important in two places: during the giant stride in, and when diving deep.

During the giant stride, if smacking the octo's reg face against the water triggers flow, having the Venturi adjustment in "Pre-dive" allows the valve to close unless the octo is sitting perfectly "mouthpiece up" in the water.
At depth, when air is "thicker" due to atmospheres of compression, the Venturi flow assist helps breathing by keeping the valve open wide.

The cracking effort function is one that very few divers ever adjust. In very cold water diving, it sometimes helps prevent freeflow to make your breathing resistance slightly harder. And some people erroneously believe that having too easy a breath "wastes gas". It does not.

So in my opinion, the Elite is to be preferred over the MBS. When you want your Venturi off during giant stride, turn it off. It won't affect the ease with which you breathe, because you haven't changed cracking effort. Don't mess with cracking effort, except to perhaps tighten it a hair if a reg (due for service) starts to dribble a little freeflow. You can often temporarily correct an old seat's leak by adding spring pressure with the resistance knob. Or tighten it a hair for cold water diving (along with having the first stage IP lowered).

Combining two different functions and claiming a new "Master Breathing System" is Marketing BS (MBS) .

But it's got a great first stage!

My 2 cents.

MBS sounds like putting an automatic transmission in a car. All "real" drivers know that clutch and stick are more betterer!

OMMOHY