Australia is a difficult place build good subs mostly because of driver availability. You cant air freight an 18 inch driver from Europe because of the magnetic content. Sea freight is very expensive and takes upwards of 10 weeks. 

Most DIY designs out there require 18 inch drivers. 1850 horn, g sub, sbh, most scoops, x1 ... the list goes on. There is the Punisher that uses a 12 but getting the 12.00sw right now is very difficult, especially from Aus. There is also the LAB horn but that isn't free of issues either. (build cost, build difficulty, size, weight, need group of 4 to work properly, cost to amp properly with 2 drivers per cab)

With all this in mind iv decided i'm going take the initiative and design a 2x15 cab for Australians and anyone else who struggles to get larger drivers. With enough support/help from people on here I will design build and test/measure a cab and make the plans publicly available. 

My design goals are:

->130db spl from 2x15 cab

-tight sound, focus is on dance music like house, tech, disco etc.

-f3 between 35 and 40hz. Probably closer to 40hz as the 8 punishers I have go plenty deep enough.

-light weight drivers to make shipping easier

-Sound takes priority over building a compact light weight cab. 

First step is to find some suitable drivers. After looking at t/s paramaters for a bunch of drivers iv narrowed it down to three. 

PDN.15BR40 - http://www.precision-devices.com/Product-Details/PDN15BR40

15NLW9500 - http://www.eighteensound.it/PRODUCTS456/Products123/CatID/8/ProdID/56#.V7MpLZh96DM

Colossus 15XBN - http://www.fane-international.com/prod_details.aspx?pid=515

Here are some sims in a 2x15 300L cab tuned to 39hz of the 3 drivers. pink is the 15XBN, White is the 15NLW9500, Purple is the PDN.15BR40.

The xbn is a clear looser from what I can see. Highest group delay, loses spl down low. According to the graphs it looks like the PDN.15BR40 is the winner by a smidge, lowest group delay, flattest frequency response. Also has the largest xmax but looking at the t/s parameters the 18sound is a tighter driver which will help meet my goal of a tight sound. (higher BL, lower qts) 

Any advice will be greatly appreciated. 

If you're looking for a fairly tight, punchy sound and are happy with a cut-off at about 40Hz, then I would suggest looking at drivers with slightly lighter cones and you shouldn't need a cab bigger than 200-250L.  My single 15" design is only about 80L!  Most drivers will have the excursion and power handling available to be able to EQ the low end up slightly, so don't worry too much about getting the natural response flat to 40Hz.

2200 usd. For a 20ft container. And 980 usd of that amount is the truck transport from here to the Greek port.

Tbh, the best way is set up a supply channel with distributor on here; Paulie Paul, Bee, Marjan etc. This means access to better prices (Thomann is relatively expensive), advice, reliability, group buys, helps others in the future etc. 

Get in touch with John at Global Freight Network and say hello to the international market. We're not at all limited over here, we're just not experienced in the global market. For e.g. Most younger builders from Oz will let the costs of overseas shipping from various web-shops be a major influence in their component selection processes. However, at the end of a worthwhile build, the $400aud / pallet costs of private sea freight become negligible in the overall budget and the networks established are very valuable too. 

It's worthwhile considering anyway.

Also, take your time with the design process and ask lots of questions.

I just shipped a cnc machine of 450kg from China for 335us$. So sea fright is not expensive.

If anyone is going to put the time into designing something worthwhile, don't start the design process from the position of 'this is what's available to me, let me get the best possible from this'. It's very fun and satisfying to do this if you've got bits and pieces lying around the place to make use of, but if starting fresh, it makes no sense to begin from this limited position. 

So many compromises have to be made along the way to a successful design that you need all the help you can get, to begin with. 

Citizen - I'd start again, considering 15's, 18's, 21's - whatever you want. You can have any driver you want at the same price anyone else around the world is paying for it. Worry less about the driver and more about how you're going to get that driver to do what you want, i.e. worry about the enclosure. Focus on this and you'll end up with the right driver in the right design. 

Something along BMS 15N850 or Faital 15XL1400. Those are the drivers that in a 2x15 box will get close to an average 2x18 box in performance.

For all the rest, you better use 18 inch drivers because most of the average 18 inch drivers like P-audio Challenger 18 will piss all over any other 2x15 box made with the components you are considering.

Just my 2 cents.

By performance do you mean SPL? or do you mean in sound quality to? Id expect a 15inch reflex to sound tighter then an 18 but the 18 to be louder and deeper (depending on tuning).

Also is there something up with the T/S parameters of this  http://www.bmsspeakers.com/fileadmin/bms-data/product_data_2011/cones_neodymium/bms_15n850v2_2011-04_neodymium_woofer.pdf" rel="nofollow - http://www.bmsspeakers.com/fileadmin/bms-data/product_data_2011/cones_neodymium/bms_15n850v2_2011-04_neodymium_woofer.pdf

I think the CMS is wrong? or the Vas? I'm not really sure but bass box pro does not like it.

I did actually start by deciding what kind of box I wanted to make. Thats why I simmed them all in a 39hz 300 liter box. I wan an f3 of a little bit below 40, tight sound and im not concerned about size. Im thinking now that 300 liter is a little big so it will probs end up about 200-250. 

I didn't just choose those drivers because they were on thomann, i looked at a lot of other drivers too but they seemed to best fit the idea I have in my head of a good reflex driver. If you have better ideas for drivers let me know, im here to learn. 

I think 15 is suitable for this project because i'm after a tight sound but maybe its a misconception that a 15 is better for this?

Lastly I think Thomann is fine for small orders. I challenge any of the people you have named to ship 4 drivers to Australia from europe for under $300. Thomann can do it for $70. I can see sea freight being good if I wanted 100 drivers but I don't. I also dont want to wait 10 weeks for an order. 

I will ask for a quote. But 70us$ is quite unrealistic. They want 50 to ship 4 18 inch drivers to me. And i am in Europe.

Distributor = better prices so it equals out though. 

This is the lesser point also. Main point being the design process. You want this to be a worthwhile job, not just another 215 reflex. Otherwise just get some drivers and chuck em in the recommended enclosure from the manufacturer, job done. 

Maybe buy one driver from thomann and experiment with it, in different boxes. Large reflex, bp6, push-pull (2 drivers), Q15 type design from Tony Wilkes (RIP) etc. There's heaps you can do, and try, and learn and end up with something really good. I know it is what you're doing anyway, but I'm just suggesting don't rush into it. 

It's ideas like 'high BL and low qt's = punchy sound' that need a bit more investigating. There's a lot more to it and the design is just as important if not more imp than the driver.

10 weeks is nothing, it takes 10 weeks to understand 1 of the many types of reflex designs to consider and sim etc.

And go with 18's for sure