Hi
@Trdat Yes, the JBL cinema speakers can be ordered with or without a passive XO. The specs specify what XO frequency to cross at and sometimes gives the slope as well. Previously I had a 3 way that came with passive XO and I bypassed it and used a 3 way digital XO in it's place. I used the same XO points as the passive, but under further investigation, changed the midrange to woofer XO point to a bit higher based on examining the drivers raw response. When I sold the speakers, I wired back up the passive XO.
Speaker design/building is big on sites like
diyAudio,
AVSforum,
Parts Express and
Troels Gravesen among many others, including kit sites like
DIY Sound Group. The digital XO part is fairly easy as most speaker specs will indicate range of operation and recommended XO frequency. With a measurement mic and software like REW, one can sweep each speaker in it's intended range and verify the XO point. Usually the digital XO's are linear phase so that they sum perfectly in the frequency and time domain. See
http://www.acourate.com/XOWhitePaper.pdf Also, the slopes are steep enough that the driver's response beyond the passband is convolved with the slope of the digital XO, retaining the perfect summing. It also gives you an opportunity to time align the drivers and choose amps you want to drive the individual speakers with. e.g. woofers lots of watts and damping factor, tweeters maybe a low watt tube or single ended Class A design. Just opens the door wide open for any possibilities.
Personally, I am a fan of ridiculously huge, high efficiency speakers. If you get into speaker building the sites listed above will assist as you will need to model box sizes with Thiel & Small parameters if the manufacture does not have a recommended cab size, but most do. Then you will need to familiarise yourself with various speaker parameters that provide that kick and punch. Usually a combo of subs and a large 15" PA type woofer(s). Lots of good recommendations on the sites listed above. It's a lot of work, but also a lot of fun. Good luck!