A significant part of the decision to abandon ship on the driver modifications (despite being successful in other ways) was the lack of linear excursion. This would have compromised the build too much and not given me the low end dynamics I was after.
Here's a quick explanation regarding where I'm going with all this -
Its quite hard to find a high output 12" LF driver that goes down to 40 hz in a reasonably sized box and has the efficiency to keep up with a 95 dB/W coax. On its own, the coax would have to deal with all the LF and while it's capable of going quite low, it would limit low end output due to IM distortion from the coax cone being part of the HF WG. Hence the addition of a suitable LF driver. Under normal circumstances I would have gone active xover considering the low turnover frequency, but I wanted to keep the design simple so my son doesn't have to mess with multiple amps and outboard xover when he inherits them. Yes, the xover won't be cheap on parts with this low xover point, but its worth trying to do passively for the sake of a complete ready to go package. The key thing here is hoping to minimize BSC on the coax with the LF driver assisting to retain mid band efficiency. May be a bigger challenge than i initially realize, but thats at least the thought behind it.
IMO, the KL3012LF drivers are the best compromise for this design. This will be a 2 - 2.5 way with KL3012CX coax drivers in a 30 ltr sealed partition and LF drivers in a 90 ltr vented section, crossed around 150 hz 1st order (give or take) in efforts to keep IM distortion down on the coax and extend dynamic range. This HP will allow for good coax power handling with low distortion and a sealed box will keep phase response smooth. The final xover will depend on measurements. Despite the setback with the first drivers, I still feel it will turn out great based on the coax performance. I'll be starting a new thread when I measure the coax with various other CDs in a baffle to pick the most suitable combination.
Here's a quick explanation regarding where I'm going with all this -
Its quite hard to find a high output 12" LF driver that goes down to 40 hz in a reasonably sized box and has the efficiency to keep up with a 95 dB/W coax. On its own, the coax would have to deal with all the LF and while it's capable of going quite low, it would limit low end output due to IM distortion from the coax cone being part of the HF WG. Hence the addition of a suitable LF driver. Under normal circumstances I would have gone active xover considering the low turnover frequency, but I wanted to keep the design simple so my son doesn't have to mess with multiple amps and outboard xover when he inherits them. Yes, the xover won't be cheap on parts with this low xover point, but its worth trying to do passively for the sake of a complete ready to go package. The key thing here is hoping to minimize BSC on the coax with the LF driver assisting to retain mid band efficiency. May be a bigger challenge than i initially realize, but thats at least the thought behind it.
IMO, the KL3012LF drivers are the best compromise for this design. This will be a 2 - 2.5 way with KL3012CX coax drivers in a 30 ltr sealed partition and LF drivers in a 90 ltr vented section, crossed around 150 hz 1st order (give or take) in efforts to keep IM distortion down on the coax and extend dynamic range. This HP will allow for good coax power handling with low distortion and a sealed box will keep phase response smooth. The final xover will depend on measurements. Despite the setback with the first drivers, I still feel it will turn out great based on the coax performance. I'll be starting a new thread when I measure the coax with various other CDs in a baffle to pick the most suitable combination.
