Hi mr. Cubo.
I'm doing a high efficiency portable "boombox" powered with a LiFePO4 battery, and I thought about getting the low end from a cubo12. My driver of choice is RCF MB12N251, which seems to be a good driver for the box.
Resonance frequency: 50 Hz
DC resistance: 5.1 Ohms
Mechanical factor: 5.4
Electrical factor: 0.36
Total factor: 0.34
BL Factor: 15 Tm
Effective Moving Mass: 49 g
Equivalent Cas air load: 83 litres
Effective piston area: 0.053 sq m
Max. linear excursion (mathematical): 4.8 mm
Voice - coil inductance @ 1kHz: 1.3 mH
Half-space efficiency: 2.70%
My question is, how low it would go. I think 40 Hz is the dream (with a little EQ maybe), given that I'm only gonna power it with a max of 50-70 watts.
Then I'm gonna cross over to the same driver but in either a sealed or ported box and lastly to a B&C DE250. I hope it's gonna work!
Although it's possible to EQ a Cubo 12 down to 40 Hz, you'll need a lot of EQ and thus a lot of power. I would consider building a Cubo 12 and using a 50 Hz high pass filter (going for maximum output) or building a Cubo 12 Mod (about 3 dB less output) but feasible down to 40 Hz, with a 40 Hz high pass filter. That way, going for 50 Hz strife's for the biggest impact and wow-factor from a small cabinet, while going for 40 Hz gives a warmer and more all round sound. Either way, I would also consider building the Cubo out of 9 - 12 mm Baltic birch, if it's ever only going to get 50 - 75 Watt.
The RCF MB12N251 is an excellent driver for boombox purposes. I would put it in a closed cabinet and cross it at 80 - 100 Hz for sound quality, or put it in a ported cabinet tuned to roughly 60 Hz and overlap it with the Cubo in the 60 - 100 Hz frequency range for maximum output.