Exploring Purifi Woofer Speaker Builds

Driver like PTT6.5X that goes deep in a small box needs to have high Mms as dictated by laws of physics. The causes more reaction force at a given SPL. the metric Mms/Sd is relevant here (essentially the SPL to force ratio). This ratio also determines the relative length of the port since a similar mass to area ratio is need for the port (mass is the air mass in the port). Ultimately why passive radiators are more fun in very small boxes since mass can just be added
 
Sorry for the beginners questions here but I was looking to build a purifi-speaker with 6,5x rear but only below 100 hz because I thought that’s where sound gets omnidirectional.

Won’t the rear wall diffuse the sound coming from rear driver compared to what’s coming from the front?

By now you wil know I’m a complete noob so I’ll take any search words you can throw at me and I’ll educate myself 🤓
 
This is why I suggested that the dual opposed approach is not necessary nor advantageous at this stage of your learning to design... follow the KISS principle because there are lots of other larger (more important) knots to untangle first.
I’m not the one building the dual force cancellation speaker but got curious. A driver for sub 100 hz in rear can’t be too hard to untangle.
 
Hi guys, just wanted to add my grain of salt to the discussion about Purifi midwoofer in closed enclosure and show you my prototype in progress.
Actually the PTT6.5X04-NAA-08 is working flawlessly in sealed enclosure of 7 liters, and its frequency response and sound are top notch. Hi to @lrisbo and Purifi! <3
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How do you compare Aluminium and composite woofers from Purifi ?
 
That sounds like an amazing system! What do you plan to use for the T25B waveguide? Also, it would seem to me that even a small waveguide would not be needed when matching the T25B to the M74. What are your thoughts there?
Well, I have used waveguides on the last 2 loudspeakers I've built and beside the gain in the low range, I like the power response and DI ithey gave.

For information I did preliminary tests on a "quick and dirty" 30 cm by 50 cm baffle of the M74B and T25B in 5.75 " Augerpro waveguide.

I found that DI of both drivers will let you choose easily a crossover from 3 to 5 kHz. Overall Flat DI around 5 from 500 Hz to 3 kHz rising to 8 at about 5 kHz,, flat up to 15 kHz rising to 10 at 20 kHz.