1. A passive loudspeaker system that is favorably applicable for use with a current-output amplifier, said system incorporating a driver unit that has a first voice coil and a second voice coil, said system also incorporating a circuitry to divide the signal current for said voice coils and fulfilling all the following criteria:
− said first and second voice coils operate in a series fashion so that at least part of the signal current that flows through the first voice coil flows also through the second voice coil
− at 2 kHz frequency the ratio of current through said first voice coil to current through said second voice coil is substantially less than at 200 Hz frequency
− at some frequencies between 1 kHz and 10 kHz, current through said first voice coil is less than 1/3 of current through said second voice coil
− the impedance seen by each of said voice coils in said system, without external connection, is greater than 1.5 times the DC-resistance of the voice coil itself at all frequencies that exceed 150 Hz and that are reproduced mainly by said driver unit in said system and which frequencies said driver unit is substantially able to reproduce.
2. A loudspeaker system as in claim 1, in which the force factors of said first and second voice coils are unequal.
3. A loudspeaker system as in claims 1 or 2, in which said first and second voice coils are connected in series in the inner structure of said driver unit, so that only three connection terminals are needed in said driver unit.
4. A loudspeaker system as in any of the preceeding claims, wherein said first voice coil is a series or parallel combination of first voice coils from several dual coil driver units, and said second voice coil is a series or parallel combination of second voice coils from the same dual coil driver units.
5. A loudspeaker system substantially as herein described with reference to figures 3 to 5, 7 and 8.