Well, I gave them a couple of days to jump in here...
So I'll just pass along what Brent told me;
(Sorry Brent if this is out of line!)
Below is my question to him, and his response;

TjB; "So, Are you guys all sitting around trying to decide what you are going to tell us about the change in drivers in the EP350, or are you coming up with a new name for a new sub?"
Brent; "You are an astute man.
The driver is a temporary replacement and will not be ongoing in the EP350. Essentially it is the same driver without the dust cap."

Pay particular attention to the part that says this is temporary, and will not be an ongoing replacement.

My guess is that they ran out of the 350 drivers, and decided it was better to ship subs with the 500 drivers rather than enduring a long out of stock, and possibly losing some orders. Perhaps they are/were going to be out of the correct drivers for quite some time?

And, I also do not really buy the "Essentially it is the same driver without the dust cap." thing.
If it were "essentially" the same driver, then why would they bother buying both?
I simply cannot imagine Axiom undertaking a project like the EP500/600, with all of the technilogical innovations that it included, and then just using the same driver from the previous generation subs. From what I have able to glean from the several months of research I put into buying these speakers, and the short, but involved time I have spent on these forums, this just does not seem like something that Axiom would do. Does it?
I certainly do not want to put words in anyone's mouth at Axiom but I think they simply ran out of the 350 drivers, and thought, "Hey, the 500/600 driver will fit, and some guys will get a little bit of a bonus, even if they don't notice! No harm, No Foul..."
What they might not have counted on (which I would have thought they would have seen coming from a mile away, considering these threads, and the folks who post here)was someone noticing, and then posting that observation, with the predictable results of those who got the 500 driver Crowing over their unexpected windfall (Guilty as Charged - Sorry!)and leaving those who did not get the new driver wondering if they got gyped - when they actually got exactly what they had ordered.
In the end I think that Axiom, being the great company that they are, with, (in my experience, and by EVERYONE'S accounts here), a tremendous record of customer service, came up with the best and quickest solution to see that their customers got their precious new subs in a timely fashion, and like so many other Good Deeds, it has come around to bite them in the behind!
Personaly I kind of feel bad that they are in this sticky little situation, cause they all seem like such nice folks, and certainly do not deserve ANY bad Karma in any form what-so-ever. And I kind of feel guilty about being a part of it all...
But I sure Ain't sending my "Experimental EP400" back!

This has resolved for me the question of whether to upgrade from my 350 (w/500/600 driver) to a 500. I did SPL readings down to 16 Hz and it was actually a little above the flatline (which I set at 80 dB). It's pushing well!

Seems to me you’re making this all much worst than it really is. So Axiom decided to improve one of its product lines; what’s the big deal? We all should be glad for, don’t we? You brought the point of the people who recently bought the ep350 and got V1.0. Well, they got what they paid for. So, why is this a ‘sticky little situation’?

~Jaime

No, no, no. I'm not trying to put a negative spin on this at all.
And I do not in any way think that it negatively reflects on Axiom.
I just think that it is a shame that there is now the "What If-itis" that some owners of the regular 350 are feeling (as expressed by some of the posts above), when, by all appearances, all Axiom did was make a quick change of an out of stock component in order to get product to eager customers.
I was not trying to be negative towards Axiom in any way at all. Not my intention.

It would also have been nice if they (Axiom) had of addrressed this on the board when it was first raised.

While Alan does post his experiences and advice, there seems to be a great delay in anything official when an issue is raised. Not that I am singling out Alan, but it would be nice to see more participation from Axiom in general.

Without the fancy-shmancy "digital amp" (which I suspect is using some EQ-ing to achieve it's amazing performance!), the driver itself probably doesn't make a lot of difference.

In this case, I wouldn't think that anybody has been ripped off or give a free bonus, other than the cool aesthetics of the capless driver.

In reply to:

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In this case, I wouldn't think that anybody has been ripped off or give a free bonus, other than the cool aesthetics of the capless driver.

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I dunno, I think it looks nicer.

I was able to fix that with my older driver, though, with silver spray paint from Home Depot.

I was going to use a can of paint and a brush, but I decided that the spray can would give a more professional look without those "brush lines" and everything. Since it's a metal driver, I sprang for the extra buck and used Rustoleum. They say aluminum doesn't rust, but why take the chance?

Now, for those of you that are taking this serious, I say: "Smarten Up! Everybody knows that you shouldn't do something like this without priming first!"

Great idea Mark!! Just curious though...what's the recommended break-in period for Rustoleum?

Mark,

On my drivers, I first..CAREFULLY smashed in the black center caps....and THEN painted them with the "correct" aluminum silver roofing paint.
With this method, they look ALMOST like the new drivers.

LT

This is what I love about this forum: all the smart people.

I never even thought of the roofing paint in terms of waterproofing the sub!

Excellent idea!