I'm still not totally committed to the tuning point of these towers, as I'm still debating if the drop in headroom (albeit slight) in the 20-30hz region is worth the gain between 8-12hz. Given my listening habits, and the fact that I will have two of them, i'm leaning towards a 11.4hz tune, although 12.4 is also in the running.
here are the theoretical numbers, with the 800W/ch of the Crown K2:
13.4--- 107.3 ----- 117.1 ------ 118.0 dB
12.4--- 108.9 ----- 116.4 ------ 117.7 dB
11.4--- 110.0 ----- 115.8 ------ 117.4 dB
the cross over point is around 12.3 hz, which comes in at around 113.2 dB. ABove 30hz, they are pretty much a wash.
another point of consideration is that the lower tune pushes the cone Displacement further down as it approaches Xmax. The only real negative I see with going lower and lower, is that I will be closer to Xmax before tuning freq. Example, with an 11.4hz tuning point, we will approach 24.2mm at 16.6hz, whereas with a 12.4hz we will approach 23.2mm at 18.5hz.
thus, safety first tells me to lean towards 12.4 to get some of the headroom back (compared to 13.4) for the 20-30hz region, but there are a lot of pros in going lower to 11.4hz, specially with 2 of them! I mean, we are talking 116.4 dB at 20hz for one, so a nice +6dB on the second one, and this aint too shabby!