Back loaded horn bipoles? What? Why?

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hi all, I'm a newbie
a newbie to diy speakers, but not to diy in general. And since acoustics is kind of black magic, I have to consult the druids...

my goal: Long story short I want to start building a diy 5.1 HT speaker set using FR drivers.

Why? not so much to save a buck (I won't), but more for the fun of diy-ing, tweaking and enjoying my creation.

the project: I will begin with 2 bipole surround speakers, since, for the time being, I have 2 good front L and R. Center and sub will follow. Bipoles, I've heard, are excellent for surround.

the drivers: Fostex FE127E.
I chose them over the FE126 because, if the bipolar thing fails, then I will make two monopoles for the surround and the two remaining drivers will go into the center channel, where magnetic shielding counts. It seems like a tall order for my first project to be two bipoles, but read on; I 'll make it taller. After all, I mostly do it for the fun of it :)

the question: I've been reading for the past month and info is just starting to sink in. I have seen all kinds of designs and have become quite a fan of back loaded horns, mostly because they are interesting in both design and theory. However, not once have I seen a back loaded horn bipole. To get a picture of what I mean, imagine the PAWO design for example, but with two drivers back to back (and volumes adjusted accordingly). Can anyone enlighten me as to why this kind of design has never been implemented?

Bewildered noob...
Expense. Cabinet volume. Room placement. Most folk haven't heard bipole and there doesn't seem to be much of a cult following for it as there is for, say, dipole, OB, etc. (like me ;-p). I think that's mostly it.

Nothing wrong with bipole, IMO, and several things that are likely positive. I've seen alot of folks at least sketch up bipole versions of existing designs, most frequently, bipole BiB enclosures. Personally, having had experience with BiBs of that size (though not with those drivers) I'd say a bipole version would be pretty nice. What happens is that the volume of the cabinet and the area of the mouth opening would need to double. Then, with this fairly large cabinet, you'd have to have it out in the room, probably at least 2' from the wall, maybe more (won't know exactly till you build it and put it in your room and start tweaking). Expense doesn't seem to bother you and you're predisposed to the bipole, so if you can put up with pretty bulky cabinets out on your floor, I don't see why you wouldn't want to go for it.

Another noob chiming in, but...

...given the shallow design of the PAWO(I really like the look of it BTW), why not build four and slap them back-to-back? Mirror the one so they vent toward the same side and your done with no math involved. Use some sort of reversible way to mount them together so if it doesn't sound good that way, you can split them back apart and have four monopoles to play with.

Or am I completely in the wrong on this one?
thank you all for replying

@qurley123: I have also thought of that because it would make it easy to turn my 5.1 into a 7.1 ! But I know that it's much more of a hassle to finish (in some style) 4 small cabs rather than 2 larger ones. Let alone that BSC's would be needed for the monopoles, which kind of negates the benefit of bipoles. However it remains plausible...

@Scottmoose: I've heard that "motors coupled together" stuff before. Do you guys actually mean mechanical coupling of some sort or what? Oh, and I 'll also take it that wiring should be in series, right?
Just double the depth of the existing box & stick a second FE127E on the back, wired in phase, & the motors coupled together to get the maximum out of the configuration.

Well Scott my friend , at that point i would consider changing the throat area and that would change the expansion length as well as having to re-design for the added displacement/loading. It would be more akin to designing for a larger driver.

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