Scubapro X650 vs newer SP regs

[HBO MD]

Hi all,
I own a SP X650 reg, and while there was a lot of unfortunate mis steps by SP at it's introduction,( appearance not withstanding), I can say that it's breathing characteristics have been superb. I'm not sure which aspects of the second stage contribute to this as I think it's one of the easiest breathing SP regs.
However, I was wondering how the new 600 series would compare, and the differences in basic mechanics of the 2 second stages.
Thanks.

 

[DA Aquamaster]

They use very similar poppets and performance is essentially identical. The X650 utilizes what amounts to an axial "flow vane" arrangement that in my opinion results in smoother air flow.

 

[HBO MD]

In the original blurb/comparison between the x650 and other regs, they refer to "super high flow" for the x650 vs only "high flow" for the other regs.
Is this real? Does this refer to the inhalational cycle?

 

[Hank658]

I agree with DA. While the specs are very similar the internal arrangement in the 650 creates a very smooth WOB. The A700, which I have been using for about a year, has similar internals to the X650 and breathes, IMHO, equal to or easier than the 650. When tuned the 700 is almost effortless on both inhalation and exhalation. Easier han either a 555 or 600.

 

[DA Aquamaster]

High flow versus super high flow is just marketing BS. All of the Scubapro balanced regs use the same basic poppet design (the X650 poppet is slightly shorter than the others, but that makes no difference in performance) and they use the same orifice design, so the flow rate is the same.

As noted above the A700 shares the same air barrel / axial flow control design and I am glad SP incorporated that into the A700.

The X650 was supposed to replace the D400 and shared a similar angled diaphragm configuration. In the D400 (and earlier D350 and D300) this angled diaphragm was combined with a coaxial exhaust valve to create a regulator that breathed equally well in any position. However in the X650 they went with a conventional exhaust valve and that made absolutely no sense.

The angle of the diaphragm in the D400 placed the diaphragm level in the water in a normal swimming position so that there was no difference between the height of the highest point of the exhaust valve and the center of the diaphragm. And it meant that the worst case positions (where the differnece in height in the water column between the highest point of the exhaust valve and the center of the diaphragm occurred in positions divers are not normally in. And in any case with the co-axial valve this difference is only .5" anyway. The end result was that you could tune the D400 for an inhalation effort of perhaps .6 or .7 inches of water and have it be both stable and freeflow free.

In a normal design this case geometry fault mans their is usually about 1" difference between the top fo the exhaust valve and the center of the diaphragm. Air dribbles out the exhaust valve until the pressure is equalized and this preloads the diaphragm and lever by about 1" of water in the worst case position (facing straight down). So the reg has to be detuned for an inhalation effort of around 1.0 to 1.1" of water to prevent freeflow in this postion.

So...in the X650 the angled diaphragm does not help as it does not have the co-axial exhaust valve. In fact this actually moves the worst case position to the normal swiming position, so it breathes slightly harder looking up, etc. I am unsure if the angle was kept as a marketing thing, in total ignorance of the engineering, or if the engineers were totally ignorant of case geometry issues or whether the intent was to give it a coaxial exhaust valve, but they were unable to solve the lever problems that woudl result when trying to blend that with a conventional air barrel design.

In any case, the X650 is still the equal of the S600, and is much better in cold water as it does not share the S600's tendency to develop a slight freeeflow, but it was dissapointing as it had a great deal of unrealized potential and never really lived up to the performance of the D400.

 

[Puffer Fish]

Well I had a 650, and is the only reg I have ever given away. breathing was ok (the 250V is as good or better), but the thing leaked if you were upside down (something I do from time to time).

My understanding is that the large exhaust diaphram is the cause of this, and that at the point I complained it was a known issue...don't go inverted, and you don't have the issue..

 

[DA Aquamaster]

Overly large exhaust valves are an artifact of too much emphasis by everyone on Work of Breathing machine testing. One of the easier ways to decrease the total WOB is to have a really large exhaust valve with low exhalation effort.

The downside is of course the tendency to breathe wet when inverted.

Personally, I think WOB testing is a load of crap that overshadows and demphasizes many more important but subjective aspects of regular breathing performance.

 

[Texfrazer]

Realistically, the best place to tell how a reg breathes is underwater. Wouldn't it be fun to assemble a whole string of 1st/2nd stages onto a string of tanks and drop down to 100 feet or so and take turns breathing off of them. Then you'd know which ones rock, which ones stink, and which ones you wouldn't give an enemy in a pool.

 

[HBO MD]

That would be cool. Like REI or other outdoor companies provide days to trial their kayaks etc.
Just imagine : a weekend of equipment try outs held by Scubapro, Aqualung, etc in some of the major cities, or down by the beach somewhere.
Do you hear that equipment manufacturers?:banana:

 

[Greg Barlow]

Personally, I think WOB testing is a load of crap that overshadows and demphasizes many more important but subjective aspects of regular breathing performance.

DAAM,

We don't disagree on much about regs, but I do beg to differ on this point. The EU standards might not be to your liking (nor mine), but the testing data is very important. The ANSTI simulator has forced manufacturers to design high quality products.

Subjective "reviews" of reg performance are not reliable at all. USN and independent testing has clearly demonstrated that a person cannot reliably tell the difference in WOB until the difference exceeds 0.4j/l.

To judge a reg's performance by "testing" it at the surface is like determining how quick a car is from 0-100mph, by counting 1 Mississippi, 2 Mississippi, etc. Reminds me of a HS buddy who told me that his 1975 Chevy Nova with a standard 2 barrel 305 could run a 13 second quarter. He must have been stuttering when he was countin'...

Greg