Line source and history



In 1940, in his book called “Elements of acoustical engineering”, Harry Ferdinand Olson already talk about the theoretical concept of an acoustic line source.



Starting in the 50s, column speakers were used as public address systems because they could direct the sound over a wide horizontal angle and a very narrow vertical angle instead of dispersing it where sound was not wanted or needed. This reduced the amount of reverberant sound and increased intelligibility in large rooms and auditoriums. It also reduced the possibility of acoustic feedback to the microphone. The response did not cover the entire frequency range but was adequate for voice range.



Harold Beveridge was probably the first to create a line source system to cover most of the frequency range in 1965.
It was also the only one before RUEL to create a wide dispersion, one-way, line source system!
It was using an electrostatic driver, a lens and an Helmoltz resonator (bass reflex).
The system was complicated to build, expensive and cumbersome but the Beveridge Cylindrical Sound System (BCSS) was universally acclaimed as the Rolls Royce of loudspeaker systems.
It was commercialized in 1973.

Harold Beveridge criteria for his speakers:

  • It was a full range electrostatic system: no crossovers.

  • It was full height: at least 3/4 of the distance from floor to ceiling.

  • It was full Width: 180 degree dispersion, starting essentially at the wall.

50 years later, and without knowing the Beveridge system in the first place, RUEL criteria:

  • full range dynamic drivers with no crossovers.

  • more than 80% of the floor to ceiling distance

  • wide 180 degree dispersion for all frequencies



In the 70s, Roger Russell, who was working at McIntosh, designed the XTR20, a 3-way system, which was a line source for the high-frequency drivers only.

Several designed followed, the XTR22, XTR18, then full 3-way line source, the XR290.

The XRT2 is the current 3-way line source system from McIntosh.



In the early 90s, researches of the French Dr. Christian Heil, better defined the requirement to create a true line source with several dynamic drivers.

His researches were applied to large PA system with his brand L-Acoustics.



Roger Russell leaves McIntosh in 1992, but never created the system that he really wanted.
In 2005, he continues his researches and creates a crossover-free line source system using dynamic drivers, the IDS-25.

However, the IDS-25 has 3 problems:

• it is not a line source for the high frequencies and creates comb-filtering
• the directivity index grow rapidly in the high frequencies, the directivity is not linear
• it is still cumbersome



50 years after the first Beveridge system, RUEL creates the R+.

We believe that the Harold Beveridge criteria are right.
We believe that a crossover free, wide dispersion line source system is what is needed to create an accurate sound reproduction in a room.

We also believe that the RUEL R+ comes even closer to perfection.
RUEL meets the criteria completely differently, with the last technology, in a more controlled and compact way.

It uses full-range dynamic drivers, a diffraction slot for a wide dispersion, passive radiators, a DSP optimized frequency response, and a state of the art amplification system.

The R+ is also modular, can be adjusted to the ceiling height, is easy to ship, and is beautiful.

Our system was first shown in 2017 and the R+ is commercialized since 2018.

It is a new beginning in sound reproduction.