Piston vs Diaphragm OR MK25 vs MK17

[ajduplessis]

Yes, they will also freeze up in space!

 

[Ozwald]

@travelrider The very same reason people say BMW is better than Merc. It's a matter of opinion. The 25 can be dived in ice (2 Celsius) with a G250 or A700, many divers here have done so without issues. SP launched the A700 on the 25 while ice diving.

The argument around the piston spring getting stuck in duty water is BS. Ask you dealer to give you a piston spring as see if you can compress it with your hands. Then tell what needs to be in the water to make it get stuck!! The 25’s also route very well on doubles.

I would like to hear from someone who has actually had their 25 freeze up.

 

[rhwestfall]

Tobomory has claimed a few.... 1st or 2nd stage, I know not which was the culprit.

 

[DA Aquamaster]

I would like to hear from someone who has actually had their 25 freeze up.

I have had buddies with Mk 25s freeze up in 150'-180' deep alpine lake dives where the freshwater temperature was in the 33-35 degree F range.

The usual pattern was a free flow starting just after reaching max depth (3-4 minutes into the dive), while using a high pressure tank (3000-3500 psi) with a drysuit. Any deviation from perfect cold water technique (pre-breathing the reg or inflating the wing or dry suit before fully submerging, overbreathing the reg or simultaneously inhaling and inflating the suit or wing was usually enough to push it over the endge into a freeze flow. That remained a constant through a series of incremental "improvements" in the TIS system (different piston head bushings, different piston stem bushings, a mirror polished piston stem, etc.)

During this period of time I was still diving older SPEC protected Mk 20s or eaerly production Mk 25s (where the Mk 20 SPEC boot would still fit) and I never had an issue. In fact I could inflate 200 pound lift bags in one continuous fill in 35 degree water at 100' plus depths with the SPEC protected Mk 20 and not freeze one up, suggesting the older SPEC system was vastly superior.

 

[Hard Suit Pilot]

Why doesn't Atomic get some of the "tech love"? They seem to build a great product as well.

 

[DA Aquamaster]

Why doesn't Atomic get some of the "tech love"? They seem to build a great product as well.

I enjoy working on Atomic First stages. The company was inhabited by disgruntled Scubapro engineers and the first stages reflect that. They are what a precision made, close toleranced, horrendously over engineered Scubapro piston first stage would look like - because that is basically what it is.

Their T1 and M1 first stages are things of beauty and I have no issues with them other than price - and that is a big issue when you own several regs for back gas stages, etc. I am less enamored with their second stages as they are also over engineered. but to no useful purpose.

I wish Scubapro had used the same Christolube approach with their older Mk 15/20 style SPEC boots rather than adopting the less than wonderful TIS system on the later Mk 20s and Mk 25s.

 

[ams511]

Sometimes I'm really surprised at the stupidity of some of these large companies, and I suspect this decision might go down as the 'netflix fiasco' of the scuba industry. First, in a highly competitive, leisure industry with a shrinking market, high sales margins, and an antiquated retail structure, you can't possibly predict a benefit from significantly lowering customer service AND screwing your dealers at the same time. Second, the 'free parts' program is practically cost free to SP, and one of the primary selling points for new, brick-and-mortar dealer sales. The mark up on rebuild kits, compared to the cost of production, is stunning, meaning that SP can give away an item with a perceived value of about $25 at a cost that surely must be lower than $1. Now, by charging that absurd price to loyal customers, they get an additional $10-15 (from the dealer) per reg per year, but lose whatever perceived edge they might have had over lower cost options such as internet sales of competitors' brands. They have abandoned a policy that had a much better perceived value than actual value in the first place, just to try to fleece customers a little bit more.

The only good news IMO is that this might signal the crumbling of the dumb policy that so much of the dive gear industry is clinging to; restricted sales on parts and reliance on dealer service.

Scubapro is a business and as such is looking to maximize profits by increasing revenues and cutting costs. Scubapro's revenue is equal to the wholesale price multiplied by the number of units sold. As such Scubapro makes the same amount of profit whether an LDS sells a reg at list or Leisurepro sells it at a discount. If they allow their retailers to discount the regs then more consumers will purchase them. The discount comes out of the dealer's margin so Scubapro should make more money. Parts for life was an unsuccessful selling tool, it hasn't impacted sales at Leisurepro or the used market on Ebay. I am sure being it was unsuccessful that the decision was made to turn it into a revenue source. Also if they want they can also bring it back for special purchases. My predictions for the future of Scubapro is that they will also increase the wholesale price and increase the yearly minimums to be a dealer. They will also start getting more aggressive with parts pricing with dealers. I also think they are probably looking to get rid of the bottom 10-25% of their dealers and use mailorder sales to replace them.

 

[DA Aquamaster]

Parts for life may or may not have impacted sales, but it was a justification for the comparatively high retail price. Consider Subgear - same Scubapro regs at lower prices with no FPFL. After the first of the year I'd expect both lines to have the same price for comparable regs, but I really doubt that will happen.

The change in marketing strategy and shift in the types of dealers who'll gain from it has the appearance of promoting short term profit over long term health of the company and dealer network, and when that happens you have to wonder about larger agendas. It makes you wonder if Johnson Worldwide Associates is looking to get out of the scuba business.

 

[halocline]

Scubapro is a business and as such is looking to maximize profits by increasing revenues and cutting costs.

Well, the revenues are generated by sales above all, and while you're charging high retail prices in a very highly competitive business that relies exclusively on leisure decisions made by consumers, doing anything that is perceived as lowering customer service or perceived value is going to lower sales; you'd have to be pretty blind not to assume that. The oddball thing is that I personally always considered the 'free' parts for life (as long as you spend money on annual service) program as a bit of a scam in the first place. But, that's certainly NOT how it's perceived in the general dive gear market. And, it was essentially cost-free to SP; that's the kicker. They're hardly lowering costs in this move. Now, when comparison shopping, new divers can see that most other premium brands of regulators offer a free parts program. Because the servicing benefits dealers by getting customers in the shop on an annual basis (and provides some revenue) which brands do you think the shops will now push?

Unless I'm missing something, it's a lose-lose for scubapro. I'd bet that this decision gets rescinded at some point, after SP takes enough of a beating from their dealers. It does make me wonder if it's SP's idea to basically abandon the retail dealer network and focus on web sales at lower prices.

 

[kadoe23]

There are pros and cons. An unbalanced second stage is perceived as being simpler and that is generally the case. However many of them are fairly low performance.

For example in the distant past Scubapro sold the 109 "Adjustable" second stage and it was unbalanced, and as the name suggests, had an inhalation adjustment knob. It was a high performance second stage in every sense of the word and was still not overly complex. The 108 "High Performance" second stage was an entry level second stage, using an even simpler downstream valve design - but it still offerred inhalation efforts that are hard to match today, and generally aren't in the "entry level" range.

When scubapro balanced the 109 to create the "Balanced Adjustable" it used a balanced poppet that theoretically performs better, but you'll only notice it on an unbalanced first stage. On a balanced first stage, I'd challenge anyone to tell the difference between the two.

The important thing is that all three second stages use the same diameter orifice and wer epowered by a full size diaphragm, and all three were built to very high standards of quality.

In some cases with an unbalanced design, there is a finite limit on the practical orifice size and that can limit performance by limiting flow rate. Also, in general, the working range on a standard downstream valve as used in the 108, R190, R390, etc. is potentially reduced and that again reduces flow rate.

A bigger issue with the less expensive unbalanced second stages (from any company) is that quality control os often less with more generous dimensional tolerances. That means you may get some that breathe very well and other that breathe only so-so.

The C200 and C300 use an approach to an unbalanced second stage that allows a full size orifice and also allows for a large working range for the valve, so flow rates are very good, and the design also appears to deliver very good inhalation efforts. ANd most inmportantly, the QA standards are very high (out of neccesity due to the lever design), so performance should be uniformly good.

Which is to say the answer to the advantages of balanced versus unbalanced seconds is "it depends".

It sounds like the free parts program is for all practical purposes dead at the end of the year, so I would not factor that into the equation.

Nearly all regs with a 2 year service interval require an annual inspection and going the second year without a service depends entirley on condition of the reg after the first year. In that regard you can do the same with the Mk 17 and with no free parts program to worry about, the condition of the reg is all that matters. Consequently, if you get it flow tested after 1 year and/or know how to monitor the IP and detect emerging problems, a two year service interval is no big deal with any reg. The Scubapro balanced second stages all demonstrate adequate seat life to go two years with no real issues.

In fact, with Scubapro moving away from the free parts program, I see the largest casualty being annual regulator service as the customers will now have no real incentive to bring the reg in every year for service as opposed to every two years, at least with new regs or with regs where they have missed a year already and lost the free parts program eligibility. The big losers will be shops and the revenue they earn off service work. It will save scubapro money, but it will again screw the local dive shops/dealers.

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I prefer the Mk 17 due to it's fully sealed performance and I do feel it is the best performing diaphragm reg available. But a diaphragm first stage from Apeks, Aqualung or Zeagle is also very good and if the Mk 17 were not available, I'd be diving something like the Aqualung Legend or the Apeks XTX200 and not feel too bad about it.

I have also been pleased with the Dive Rite 1205 and 1208 first stages and their recent balanced second stages and would not hesitate to use them as well. There are some clones out there, but in general I have not seem the same attention to detail in machining and finish so I won't recommend them even though they look generally similar.

In short, it is hard to go wrong with a quality balanced regulator package.

The exception here is the Sherwood SR1, which is overly complex and has a well deserved reputation for un reliability.

I would have to agree. The MK17 is the work horse of Scubapro and hands down the best cold water performer from them. I have done arctic dives on ice burgs with them and never had a free flow. They are tried tested and true. However, atomic aquatics m1 and t series are amazing sealed pistons as well. Tough choices. But u cannot go wrong with the MK17