With the SF Concerto, rolling the low end from the mains and adding a sub will increase the 'low end precision'. Ported speakers have poor bass transient response. Consequently avoid ported subs if you want good bass transient response. Hence, a crossover for the main amp is required. It can be a simple capacitor.
IMO, a sub must have a phase control, 0 to 180° and a phase inversion switch. Crossover contour with multiple filters is a plus.
With proper phase integration, the increase in realism is way beyond the extra octave.
See http://ielogical.com/Audio/#Basement and http://ielogical.com/Audio/SubTerrBlues.php for some sub integration experiences and tips.
IMO, a sub must have a phase control, 0 to 180° and a phase inversion switch. Crossover contour with multiple filters is a plus.
With proper phase integration, the increase in realism is way beyond the extra octave.
See http://ielogical.com/Audio/#Basement and http://ielogical.com/Audio/SubTerrBlues.php for some sub integration experiences and tips.