The efficiency and impedance of the most popular dynamic speakers solely depend on Faraday's Law i.e. on the driver itself.
The impedance of the coil rises with the freequency growth
Z=wL
For DC current the coil impedance is zero(w=0)or same may apply for freequencies close to zero.
In order to reproduce lower freequencies the coil should be quite massive to hold a large current hence the impedance of such will drop. Hence the full range speakers require powerfull amplification with good current drive.
Larger drivers can reach higher SPL with smaller current and smaller amplification hence more efficient.
Small drivers need larger amplification power to move the air hence less efficient. The advantage of the small driver full range speakers (Dynaudio,Totem) is WAF, compact soundstage and imaging.
The impedance of the coil rises with the freequency growth
Z=wL
For DC current the coil impedance is zero(w=0)or same may apply for freequencies close to zero.
In order to reproduce lower freequencies the coil should be quite massive to hold a large current hence the impedance of such will drop. Hence the full range speakers require powerfull amplification with good current drive.
Larger drivers can reach higher SPL with smaller current and smaller amplification hence more efficient.
Small drivers need larger amplification power to move the air hence less efficient. The advantage of the small driver full range speakers (Dynaudio,Totem) is WAF, compact soundstage and imaging.