Leading the Engineering team at Meridian and working with the JLR Audio and Infotainment teams, three Meridian Sound Systems were designed and developed for the Land Rover SUV range of vehicles.
The cross-functional teams collaborated on the design of loudspeaker drive units and their location within the cabin, the equalisation of the sound balance, HMI design/functionality and developing communication assests for promotional activities.
In addition to Dolby PLIIx and DTS Neo:6, Meridian’s proprietary Trifield processing was configured to provide the optimum performance for automotive applications and is featured on the optional Meridian Surround Sound System to provide authentic rendering of a musical performance for all occupants in the vehicle.
The Meridian Sound System is a multi-speaker stereo system, while the Meridian Surround Sound System additionally offers surround sound decoding. In addition to the Dolby PLIIx and DTS Neo:6 systems, the Meridian Surround Sound System incorporates Trifield technology, a system unique to Meridian in the consumer electronics field. Trifield takes a stereo signal and “decodes” it for multiple speakers. In particular, it uses the centre front loudspeaker of a surround array and the surround speakers to create a stereo image that is not only much more stable than one created simply by left and right: it is also remarkably stable in all locations in the vehicle.
Trifield is based on a unique British surround-sound invention, Ambisonics – and both have been included in Meridian home entertainment systems for many years: Meridian was a prime mover in implementing the system in the home environment. Unlike conventional surround systems, Ambisonic technology doesn’t simply feed one channel to one loudspeaker. Instead it decodes the entire sound field and generates a specific loudspeaker feed for each loudspeaker in the array, so that they all work together to create a coherent surround image. Trifield does exactly the same, but derives its source from a stereo signal, giving it new life.
Because the stereo signal is decoded to multiple loudspeakers around the vehicle, the image that listeners experience is not only more stable, it is essentially similar wherever you are seated in the vehicle. In the case of a normal stereo system with only left and right loudspeakers, the stereo image you experience tends to be pulled into the nearest loudspeaker. If you sit on the left, it’s pulled to the left, and if you compensate by adjusting the balance, listeners on the right, for example, will hear the image pulled even further to the right.
Some systems attempt to deal with this simply by placing a speaker in the dashboard and feeding it with a left/right mix. This, however, is not a very convincing solution and tends to narrow the stereo image.
Meridian’s Trifield system, however, uses all the loudspeakers in the vehicle, working in concert to deliver a superb stereo image, spread naturally across in front of the listener instead of being drawn into the doors. This applies to listeners in the rear of the vehicle as well. The surround speakers are used to derive a stereo image too, so the experience is very similar to that in the front of the vehicle, with stable imaging that is much less listener-position-dependant than in a conventional stereo or surround system.
The loudspeaker drivers used in Land Rover vehicles have been specifically designed and developed by Meridian engineers, in collaboration with Jaguar Land Rover’s drive unit suppliers. Bass and midrange drivers feature mica-filled polyproplylene cones. The mica filling adds both stiffness and damping, which helps to ensure a smooth frequency response throughout the operating bandwidth. To minimise total weight while delivering the highest possible performance, low-mass materials have been specifically-selected for the drivers.
Low moving mass drive units store less energy and provide better transient performance as the voice coil and cone can respond rapidly to input signals. The materials selected are also very stable and thus ideal for use in an automotive environment where extreme conditions are commonly encountered.
The tweeter features an ultra-light aluminium alloy dome to maximise efficiency and provide extended high frequency performance. Again, a low moving mass design provides superb transient handling and negligible distortion across the operating bandwidth of the driver.
All the drivers used in Meridian sound systems feature powerful neodymium magnet assemblies. These combine high, uniform magentic field densities with low mass, improving efficiency while once again keeping weight at a minimum.
The materials selection process has resulted in a series of drive units that, taken together, deliver tight bass, coupled with a very natural mid-range and high frequency performance. As a result, less filtering and compensation is required in the electronics, resulting in superior sound quality throughout the system.
Meridian Audio Cabin Correction
Derived from the Meridian Room Correction system used in Meridian’s home entertainment surround controllers, Cabin Correction tunes the audio system precisely to the acoustics of the vehicle cabin.
The interior of any vehicle has various resonances and problem areas. However, it is a known, fixed environment and can be compensated for. A series of sophisticated digital filters tunes out resonances and standing waves in the vehicle cabin and these are an integral part of the DSP driving the system.
Dynamic Volume Control
The Dynamic Volume Control feature of the system constantly monitors ambient noise levels in the cabin. As a result, when that level changes – for example as a result of a change of road surface, or a window being opened – the system can automatically compensate by varying the system volume, and provide the occupants with a consistent listening experience in which the ratio between audio system volume and ambient background is always balanced as desired.