Just build a TM centre speaker using the Soprano design which is available. If you really want an MTM, it wouldn't be too hard to adapt the Soprano TM crossover.
I can understand the Meniscus situation as around 2005 I ran an online speaker driver business for a couple of years as a hobby and was not worth the effort as margins were small with shipping and supply hassles.
I can understand the Meniscus situation as around 2005 I ran an online speaker driver business for a couple of years as a hobby and was not worth the effort as margins were small with shipping and supply hassles.
If you really want an MTM with those drivers use the Soprano TM crossover and change the woofer filter but leave the tweeter as is.
For the woofer filter change the values for using 2 series SB12NRX25-4 to Lx2 // C/2 + Rx2 which gives 2.4mH // 7.5uF + 4R. I ran it through PCD and the FR and filter transfer function remain the same but of course the impedance changes due to the series woofers. You may have to change the tweeter padding to suit your taste as even though the woofer SPL remains the same theoretically there can be variations in the real world.
I'm experienced with those drivers as I have built the Soprano and also did a SB12NRX MTM design and build but with a Scan Speak 970000 tweeter and a AR Series xo.
It always has been this way, at least since the eighties, dealers on a shoestring struggling with supply challenges. Distributors make their money in the big numbers, not in the DIY business. If you’re lucky, a distributor has some passion for it and takes the hassle to cooperate with a few DIY dealers. And since distributors are always under pressure of being cut out of the supply chain, it takes a big DIY heart for one to do so.