4 Driver 15" Woofer kit

Pbn audio have some diy plans for multiways with large woofers (? 12"). Haven't heard them myself. Troels gravesen has a few - TLS and faital 3 ways among them. Can't think of any others that spring to mind. I'm sure other will chime in with option i'm not aware of.

Will depend on size and budget constraints.

Of course u could make any 3 way and seperate massive sub(s).
 
Pbn audio have some diy plans for multiways with large woofers (? 12"). Haven't heard them myself. Troels gravesen has a few - TLS and faital 3 ways among them. Can't think of any others that spring to mind. I'm sure other will chime in with option i'm not aware of.

Will depend on size and budget constraints.

Of course u could make any 3 way and seperate massive sub(s).
TY. Yeah, Pbn is one of the sites I visited that came closest. Thanks for the comments.
 
TY, will look into it.
If the woofer is suited to open baffle or basically all other designs too (sealed, ported..) will depend on the actual woofers that you have
or better, depend on the Thiele&Small-parameter and especially so the Q-values and fres.
If you want to get better suggestions, I´d recommend posting the values here or the model of your woofer.