Audio Excellence

The Congard Code
A new approach for Home Theater Sound Systems installation

The Congard code is a solution to provide the most realistic and powerful bass response in a multichannel sound system.
It comprises some dedicated components, some layout logic and a specific signal routing.
All the suggested installation assemblies in the Audio Excellence range are fully compatible with the Congard Code.

Overview

The routing

In the Congard Code, the low frequency content of the L,C,R channels is processed separately from the LFE. It is essential that these are separated as in a production studio during the downmixing, the LFE channel is mixed separately from the others. This means that it is not due to be phase coherent with the L,C,R channels. As a result, playing back the L,C,R low frequency content mixed with the LFE is not a good idea.

In the Congard Code, the LF content of the L,C,R channels are summed in one channel and low-passed crossover at 100 Hz. This allows the playback to be done by one single source, hence improving its coherence and impact.

This does not incur any drawback, as in reality there is definitely no localisation information below 100 Hz.

The hardware

Operating above 100 Hz allows the use of limited bandwidth loudspeakers for both the L,C,R channels and the surround channels. The same comment as above applies to the surround channels: As there is no localisation information below 100 Hz (the human ear could not detect it), there is no need for LF response in the surrounds.

Limited bandwidth speakers can be significantly louder than full band speakers of the same size, or can be a lot smaller for producing the same sound level.

There is a need for an active DSP crossover to separate the LF content below 100 Hz on the L,C,R channels and to sum these signals into a single output. Separate LFE outputs are also needed to adjust the delay times so that the whole setup is properly time-aligned. You cannot rely on the “distance” or time-delay adjustments in the AV processor, as many do not have the processing capability to properly adjust the extreme low frequencies delays involved in the LFE channels.

So, the required hardware is a 4 x 8 DSP crossover, limited bandwidth front, surround and ceiling speakers (in the case of 3D audio), at least one (2 preferred) LFE subwoofers and at least one bass extension subwoofer.

The positioning

The L,C,R speakers should be of the same type, located at the same height behind an A.T. screen.

The Bass extension subwoofer should be located on the floor, against the front wall, between either the L or the R channel and the C channel speakers.

The LFE subwoofer should be placed in the corner of the room nearest to the central channel speaker. If there are 2 LFE subwoofers (preferred solution), they should be in the 2 corners nearest to the screen.

Implementation of the Congard Code is the simplest and most efficient way to achieve the ultimate coherence and impact in the low-frequency response. However it can be done only in rooms of a roughly rectangular shape. L-shaped rooms, circular rooms or any fancy shaped rooms are not suitable. Neither are they suitable for an optimum installation of a Home Theater.

The measurement

It is essential that the initial response of the audio system (i.e. The combination of the loudspeakers, the amplifiers and the DSP controller) is even, as this generates the first wavefront.

This first wavefront is perceived by the brain as the most important one because it conveys all the information of the audio message. It is most sensitive to any alteration, that could be easily perceived as coloration.

To achieve this, the Congard Code includes an MLSSA (Maximum Length Sequence System Analysis) measurement to check the output of the sound system, and the possible need of DSP (Digital Signal Processor) correction.

The early reflections

Reflections from various acoustic objects in the room arriving at the listener with a delay comprised between 1ms and 20ms are called “early reflections”.
They can blur the perception of the audio message, and should be attenuated as much as possible by:

  • Absorption
  • Geometry

They do modify significantly the measured amplitude response if the measurement system is a traditional RTA (Real Time Analysis) one, but their effect on the perceived sound is not of the same importance: Due to the delay in arrival time, they are perceived as environmental only.

For this reason, it is very important not to modify the first wavefront by trying to equalize the amplitude response that includes these reflections

Control of LF modes

The control of LF (Low Frequency) modes is achieved by means of LF absorption below 120 Hz. This can be done either by placing bass traps in the 2 corners opposite to the screen (for very large rooms, this can be further improved by adding bass-traps in the ceiling corners above the 2 units placed on the floor).

Additional Low-Frequency absorption can also be achieved by the use of hollow cavities in the room, like floor-raisers for a second seats row, for instance.

Implementation of the Congard Code is the simplest and most efficient way to achieve the ultimate coherence and impact in the low-frequency response. However it can be done only in rooms of a roughly rectangular shape. L-shaped rooms, circular rooms or any fancy shaped rooms are not suitable. Neither are they suitable for an optimum installation of a Home Theater.

Powerful
Configurations

Please find here our favorite configurations. These are only examples of what is possible, but they provide an excellent base that will always provide the ultimate clarity and bass response.

Check this out
  • Loudspeakers

    Vertex and Raijuu are two complementary range of loudspeakers. The Vertex are small size, high efficiency loudspeakers of the limited range type: They operate only at frequencies higher than 100 Hz. Raijuu are subwoofers operating below 100 Hz to complement the Vertex.

    See all loudspeakers
  • Amplifiers

    In your “How-To” guide, you will read “an amplifier that does not clip always sounds better than an amplifier that is clipping”. Achieving this only means ample available power, headroom and high current capability.
 This is the core of the Audio Excellence amplifiers design.

    See all amplifiers
  • Configurations

    Please find here our favorite configurations. These are only examples of what is possible, but they provide an excellent base that will always provide the ultimate clarity and bass response.

    See configurations

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