BoB- So "co-located" means stacked?

And, if you extrapolate the "1/12th octave 'notes'. The western musical scale, from A (27.5 Hz) to Middle C (261.63)" slightly below 20 Hz, what would the freqs be? (I'm still trying to figure out if ETF will allow me to define the freqs the test uses.)

I did try L & sub, and R & sub separately and there were some differences, but still the nulls were there. One thing I need to look at further, is increasing the 60 Hz crossover to 80 Hz. For the few tests I did last night, it *might* have looked better.