OT12 2nd order vs 3rd order crossover question

[dlv]

I'm at the stage of my OT12 build that I'm about to start putting some crossovers together.

I'm going with a 1.2 KHz crossover with a CD horn. In looking at the design I noticed that the high pass is a 3rd order while the low pass (if I'm not mistaken) is a 2nd order filter. Now I have zero experience with designing crossovers but the engineer in me got very curious about this. Wondering what the advantage/reasoning for this is?

I'm not looking to change the design and I've bought components exactly to Bill's specs and will follow the plans but I just wondered about this and thought I might learn something.

Thanks for sharing any thoughts!

-Dave

[Bill Fitzmaurice]

3rd order is used with the HF for better protection. There's no need for protecting the LF. Also when you use 2nd/2nd there's a total of 180 degrees of phase shift, which will cause polarity problems. With the 270 degrees of phase shift ond 2nd/3rd there is no polarity problem.

[dlv]

Thanks Bill!