There are still only two proper ways for a transducer to propagate sound in a room: a point source, and a line source. Anything else, or everything in between, is a compromise.
Nothing has changed in theoretical acoustics since John William Strutt (Lord Raleigh) published The Theory of Sound in 1877.
In order for all frequencies of sound from the loudspeaker to reach the listener at exactly the same time, a coherent wave front is important – not just “time-alignment” of drivers. The ideal is either an infinitely small pulsating point, or a pulsating line with a size on the order of the room dimension.
Obviously, a long line-source is much easier to mechanize than a tiny point source.
The line-source (if long enough), can approximate the ideal, and in doing so, provide sufficient radiating area for dynamically and spatially realistic sound reproduction.
A line source has no vertical dispersion at any frequency. Hence, there is no sound bouncing from either the floor or the ceiling. No deleterious interference from these surfaces is created (as in virtually all other kinds of speakers).
Another advantage of the line source is that the vertical spectral content of music is virtually the same throughout the length of the line source.
Hence, the seating height does not matter with this speaker; unlike point source speakers where it is important for the ears to be aligned in relationship with the tweeter.
A third important advantage of a line source is that it attenuates at -3dB with a doubling of distance whereas a point source attenuates at -6dB with a doubling of distance.
John William Strutt (Lord Raleigh)
For example, for a loudspeaker of average efficiency, say 90dB/watt at 1m, the efficiency of the speaker will be 84dB/watt at 2m for the point source, and 87dB/watt at 2m for the line source (twice as efficient). At 4m, the corresponding efficiencies are 78dB/watt and 84dB/watt, or 4 times more efficient. At 8m, the point source will be 72dB/watt and 81dB/watt. The line source advantage grows logarithmically with larger distances.
For large loudspeakers, since we generally have a seating position between 4m to 6m away, the line source will be 4 times to 6 times more efficient. In real world terms, this translates into:
The line source loudspeaker sounds more at ease, more relaxed and effortless using the same amplifier power.Since amplifier efficiency is the square of the power, a point source will need an amplifier 16 times more powerful to achieve the same result. Because less power is needed at any listening level, the line source is more dynamic and rock music has more energy and vibrance.
At normal listening distance and sound level, there is much greater detail and transparency due to the much greater efficiency of the line source. Since small changes in distance result in much smaller changes in perceived loudness, the sweet spot is much larger, accommodating a whole family on a couch instead of a solo listener. At normal listening distance, the line source system will play much louder without distortion (from either the amplifier or the drivers).