Dual 18" sub idea

I am toying with an idea about a low profiled dual 18" ported sub.

But i am a bit in the woods about how i should sim it.

Please have a look at the pictures...

Is it a bandpass type or just straight-up ported box?

I am also thinking of ditchin´the outside port and go for a slot port that ends behind the woofers instead of infront of the woofers.

The ported chamber will have around 360 liters internal volume.  

Not sure what about it you would sim as a horn, the only significantly tapered section feeds into the rear chamber so would just act as rear chamber volume and isn’t long enough on the “outside” to provide any real horn loading effect

Why would it need to be tapered to act like a horn? Its easier (and probably more truthfull to practise) to simulate it as a 2 segment ODH. You will definately see gain from it (being usable is another story). 

By just looking at you drawing and doing some gueswork I simmed the following:

And simmed as a standard BR:

While tuning is really low due to the small port area and relative long lenght, I can say that the real life response of the cab is more in line with the first sim. It acts like a large resonator (comparable to the paraflex high tuned resonator) and adds quite some gain higher up. How would you sim it as a 6th order bandpass? How would you specify that chamber?

I would say in real life its a bit between the two sims eventually, the gain from the cavity is imho not small enough to just ignore it.

Because that is fundamentally the difference between a horn and a port? Without providing any actual horn loading it is just a resonator.

Did you model the front chamber area on that BR plot?

It’s too short and the CSA too large for the drivers being mounted flat to effect it beyond the margin of error of a HR sim 

One thing you might consider to protect the drivers from drinks, etc. it to mount them the other way up, at that point the floor may cause a boundary effect that you need to consider in conjunction with the little chamber as the boundary will artificially increase the size of that chamber. Likewise boundary and inter-box coupling of the slot ports may be something to consider, depending on how anal you intend to get with this design.