Temperature, barometric (atmospheric) pressure and input power have a great effect on loudspeaker response. The magnitude and phase response of passive filters in traditional loudspeakers change with temperature and input power and also time (component values drift). The driver characteristics change as well.

Digital filters don't suffer from these problems. Phase response is linear and pass-band ripple is pretty much nil under all conditions. Amplitude and frequency dynamic range are an issue though and have to be carefully designed for in a digital filter. Couple a digital filter with feedback incorporating each driver's condition and you'd have a very expensive but maybe better sounding speaker.

Maybe though a better use of time and money is to use digital filters to compensate for deviations in the family of curves. That's what Axiom is doing for Bryston and will soon do for the LFR1100s as a purchasable option.

Having said all that, I don't know why I am hearing poorer sound in my environment as the temperature climbs. There may be effects I am not aware of like eddy currents and the like in my room.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated