Thanks guys for joining in, and that this driver proves to be a good one in your memories of previous designs is interesting and intruiging. I can wait to see some previous DIY work with those.
I have no concerns about the crossover, i can calullate it or even better use one of the famous automatic X-Over calculators. Why i am not that worried about it, it is because every single driver of the system will work in a frequency range that is very forgiving. For example the midrange driver is flat from around 500Hz but there will be some distortion below 600Hz. The producer recommends 700Hz for a safe point, I am gonna cross it at around 800Hz. The mids are linear practicly up to 5kHz and even above. Here comes the HiVi ribbon tweeter which can be crossed according the manufacturer from 1.7kHz and above but i am going to cross it at 2.5kHz so it's going to be easy and very forgiving on the mid and on the tweeter as well wenn distortions are concerned. The woofer will be also a high quality one and there will be no exception here about making it easy for it as well. As mentioned lower X-over frequency for the mid will be 800Hz, in this way for a quality driver such as Seas Prestige oder Peerless Gold this is not of a concern. I intend to use a high pass filter for the woofer tuned at around 50Hz so the driver will operate again a bit higher than designed thus minimizing the distortion for frequencies around Fs and below. Once again X-Over Points: High Pass at 50Hz, X-Over points 800Hz and 2.5kHz. I am going to trust the drivers as they are and not worrying about possible FR nonlinearities like + or - 1 to 2 dB across the entire frequency range. That could be the case in reality but in general those are tricky to compensate with passive X-Over. But taken into consideration the very forgiving frequency range for all 3 drivers are going to work with i am kind of confident that such phenomena won't occur at all.
About crossing low i agree its not that capable like a cone driver, but i also think that crossing below 700Hz won't be necessary as the 6.5inch woofer Seas Prestige oder Peerless HDS will handle frequencies up to 800Hz with ease.
I am hearing what you say about previous designs, can you please tell me approximately where did you see those?
What do you mean with that the center to center space will suffer because the mid is huge? Yeah it will take more space but do you think i need a lot of extra empty unused space in between the mid and the tweeter? Or you mean kind of unsymetrical alignment to save space in therms of the height of the speaker?
I have found here a speaker that uses 2 ribbon midrange drivers along with one tweeter, two 9 inch wofers and two 15 inch subs to handle the frequencies down to 20Hz. It's the Adam high end of the line main monitor S7A MKII.
It costs 15 999 EUR though. Solution design a speaker yourself.