Originally Posted by
RMC
Hi Louis,
Maybe the easiest way for you, instead of trying to "duplicate" the 12" 121a driver for which you know very little, would be to approach the problem from the other end (i.e. from the box end instead of the driver end).
Take the box as a given, measure precisely its internal dimensions re net volume and port dimensions, to figure out Vb and Fb (If need be, I may be able to help you on this in spare time).
Then, among the brands mentioned or others, based on driver size and budget, look for a new driver that would be a technically appropriate companion for this box. In your shoes, if the box is good, this is what I would do, saving the work of making a new box.
Naturally, this implies you know driver/box dimensions, box Vb, Fb and have access to driver/box software modeling with new woofer T/S parameters in order to run some scenarios involving the most interesting candidates.
It's possible that you may not be faced with a large selection of 12" woofers, after important dimensions (e.g. baffle hole cutout, driver depth, etc.) and buget are considered, leaving you with less software work and easier choice!
If the K-120 dimensions fit the box well it should be a good guide to start with. Maybe the box permits a little "cheating" on driver dimensions or on box volume (Bullock temporarily used some books in the box when Vb was a little too high for a driver. I'd rather use some wood blocks for permanent fill in such case). There are many ways to save a good box, if need be, even when driver hole cutout is a little to large. Regards,
Richard