Open baffle subwoofer question

Hello Ladies and gents.....
i have a question related where to start from when choosing my driver for lower frequencies... i need it to cover bottom to 150Hz max....
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thing is - my room is brick walls and concrete floor and ceiling (European homes).... 16m2 of area... not to big of a room.....
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so i have been changing my mind between 12inch or 15inch and i am worried then one 15inch per channel would be to much when put it in a H baffle without active crossover - all passive....
so i am kind of more for 12inch and if needed, i can always put two of them (one on top of the other)....
the downside of the 12inch driver is that it does not go as low as 15inch....
so...
i was checking SB Audience bianco 12OB150 and compared to Monacor SP-382PA..... (they seem to be nice options for Europe - any better suggestions?)
seems that 12inch Bianco has better "air moving capabilities" even when compared to 15inch Monacor.... higher sensitivity also ... and is also a little bit lighter in weight of the membrane....
Donwnside is that Fs for Bianco is 44Hz and for Monacor 25Hz..... also Qts is a bit lower then Monacor (0.63 for Bianco and 0.75 for Monacor).....
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Bianco 12OB150 looks better in some parameters but not so good in others - do i need my woofer to go lower then Bianco goes... do i need that much "air moving" in my brick/concrete room .....
if i go for Monacor, i will have it go low and with less SPL maybe it will do the job even better then 12inch Bianco in my room
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What to take and start playing with .... that is the question now....
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need to say also that i am listening to electronic music, blues, rock, experimental, acoustic, basically everything but classical......
 
to be honnest i am a bit affraid to go for 15inch Bianco... this is why i was surprised that Monacor has actually less "air moving capabilities" but offering lower frequency... sounded like a win win... i am affraid that i might end up having to much base and at the end that i will have to split the speakers and feeding them with 2 stereo power amps... which i would be happy to avoid in this stage........ohhh ohhh... decissions decissions....
 
The Monacor SP-382 PA has very limited Xmax (3.5mm) but it could work if you use a couple of them. As an example, a few years ago I built a pair of M-frames with each one having two Eminence Alpha 15A drivers. Even though those drivers have about the same amount of Xmax (e.g. not much) there was a surprising amount of bass down to about 35Hz. But I did use two per side and the M-frame was about 14 inches deep and 30 inches wide. A pic can be found at the link below.

M-frame subwoofers below nude dipole speakers
 
Here’s the thing that no one wants to admit……OB/Dipole bass is only efficiently effective to 80hz…..best to supplement 80hz on down with an enclosed sub or two or three with a fairly narrow Q boost. Only really well made drivers with high motor strength can be trusted down low OB……see Troels advice and experience with driver Q and OB bass.

The Bianco driver is the new Eminence Alpha now that Alpha is much pricier…..same cheap stamped steel frame and weak motor…..when a driver is asked to play below Fs, it’s ALL resonance to the rescue……like more salt on French fries cooked in stale oil…..they taste good at first until.

Suitable 15” drivers for OB down to 40hz are best served with Pro drivers with high efficiency and xmax (read expensive) no free lunch here. You could build 3-4 small sealed subs with long excursion 10-12” woofer which would produce and even more effective, smooth and even in room response.
 
The Bianco driver is the new Eminence Alpha now that Alpha is much pricier…..same cheap stamped steel frame and weak motor.
You've obviously never compared them. The Bianco is in a completely different class, despite the initial superficial similarities. I have built a couple of systems with the Bianco and it works way better than expected in a simple H baffle and would likely work well in a minimal flat baffle too.
 
Your link describes a device that claims ‘over 100% ‘ efficiency…….i almost stopped at that half baked claim…..but went on to find that they’re less than 50% effective below 60hz…..as are most bass treatment solutions.

4 subs with DSP with one sub properly placed and out of phase is the most effective method for achieving a smooth, accurate in room response that IMO is much more practical and cost effective than half a dozen or more passive bass traps scattered around a domestic environment. Thankfully I don’t have to theorize, Harmon did the work. My own listening an almost purely subjective experience has been OB bass to 80hz or lower if you can spare the floor space supplemented by 4 small sealed subs. Two does an OK job but 4 along with EQ provides the sufficient amount of short period cancellations to make the system function as one. Those sealed units only need to provide a measured nearfield anechoic f3 of 35hz……combined output and room gain take care of another half octave. Barking fans of pipe organs need to review the spectral output of the recordings to see the 22hz claimed content is actually there…..or if the engineer smartly added a high pass filter or if the microphones used were even capable of picking that up with any integrity to the original signal.