Articles and whitepapers

Ceiling Speakers Using NXT Technology (1/12/2006)

By Morgan Sousa, Armstrong World Industries, and

Kevin Sherwood, CIE

The demand for professional quality sound reproduction in the home, combined with a modern, pared-down design aesthetic has acted as an impetus for ever-more innovative approaches to speaker design. In particular the top end of the market has seen a move away from traditional stand-mounted speakers and an increased adoption of in-wall or in-ceiling speakers.

Traditional 'cone' speakers have been adapted to this new mood in both aesthetic and acoustic design. Thinner and more discreet, there are several models that can be incorporated into a ceiling, with their wires completely hidden in the ceiling cavity, without compromising the level of sound quality that they offer.

However, installation of these traditional speakers still involves alteration to the fundamental fabric of the building, and breaking the integrity of the ceiling. Holes need to be cut through to the cavity, and additional support is therefore required. Furthermore, health and safety regulations demand that a smoke hood be fitted behind the speaker in the ceiling cavity, adding extra weight to the structure.

Consequently, there are a number of circumstances in which even the thinnest of these speakers cannot be used: in concrete structures, in buildings with a narrow ceiling cavity - or even those where the existing ceiling is particularly low. Furthermore, any attempt to fit such speakers during the refurbishment of a listed building is likely to fall foul of planning regulations.

There are, of course, flat electro-static panels available. But these tend not to be suitable for domestic use, and are designed to be floor mounted, or hang on the wall. They cannot be embedded into the structure of the building itself.

Specifiers faced with this dilemma - the desire for in-ceiling speakers in a building whose structure cannot be compromised for whatever reason - are turning to the non-domestic environment for the solution. Flat panel speakers that have both the necessary design and acoustic credentials have been deployed in schools, conference halls, hospitals and hotels for some time, and are usually incorporated into a suspended ceiling alongside standard ceiling tiles. However, in the domestic setting these panels can be plastered directly into the ceiling so that they lie flush with the final structure.

A new breed of flat panel speakers

These speaker panels have a maximum depth of 44mm and therefore fit well within the 400mm between centre spacing commonly used in wood or metal stud-work construction methods. They can even be used even where the ceiling cavity is only 70mm. Their size also means that the fabric of the walls or ceiling need not be compromised when they are installed, and there is no wire mesh or grid to interrupt the integrity of the ceiling plane.

The Armstrong CS-1000 sound panel

Instead, an aperture is cut into the plasterboard, the speaker panel inserted and screwed in. It is then surrounded by plaster tape and skimmed. Conventional cables that run from the back of the panel to a standard termination block can be hidden in the ceiling cavity, or roof, or embedded in the wall's plaster if they are running to a termination block at the skirting board. Alternatively, copper tape can be inserted into the plaster and, again, skimmed over. When a panel is placed in the ceiling, some form of wadding is required as backing to prevent sound leaking through to the floor above, but a smoke hood is not necessary. Installation time is therefore approximately 75 per cent less than with traditional speakers.

NXT versus cone technology

Behind these flat panels lies a radical rethink in the way speakers work: NXT technology. Instead of the 'piston' action of a standard cone speaker, these panels use an electronic transducer system to transform the sound input into mechanical vibrations that use the gain ratio of the panel's material to create resonant vibrations to the entire surface of the panel. In effect it is the panel itself that creates the sound that we hear.

Unlike conventional cone speakers which operate with a piston-like action, NXT technology introduces resonant vibrations to the entire surface of a lightweight flat panel via an electronic transducer system

In this sense, NXT panels work rather like the vibrating string on a violin or piano. This also leads to certain acoustic advantages over traditional cone speakers.

With cone speakers, the sound quality and volume lessens the further it is from the source. If the sound quality they produce can be described as hot at the centre and cold at the edges, then NXT produces an evenly dispersed, highly diffused 'warm' acoustic - similar in nature to the light produced by a fluorescent lamp.

Cones also create a compromised acoustic quality due to the immediate reflection of sound energy from side walls, or other objects in the room. Such reflected energy combines and interferes with the direct energy from the loudspeaker, resulting in some strange acoustic effects.

In contrast, the NXT panel produces a multi-layered sound wave that works with the environment rather than against it. The diffuse source creates a high-definition sound field over a very wide area, ensuring that surround sound or a stereo sound field is heard whatever the room and wherever the listening position.

It also means that only one NXT ceiling panel is needed for every three traditional cone speakers. The result is that this kind of ceiling speaker can produce a near-enough replication of 5:1 surround sound, approved by Dolby Labs, even in the most awkward-shaped rooms.

NXT speakers can work with any amp system, including LINN, Bose and Bang & Olufson, that uses local amplification in multi-room environments. And their design means they can be used in any room in the house, including those such as the bathroom or kitchen, that have traditionally been no-go areas for A/V systems.

Of course, NXT panels are not without their downsides. They cannot create the masses of bass level and sound pressure produced by a standard woofer or sub-woofer, so are unlikely to be used in live music or club environments. Nonetheless, even small NXT panels can achieve a far greater frequency range than a standard cone speaker, and one panel can do the combined job of a woofer, tweeter and a mid-range cone speaker.

Since there is less directional sound compared to traditional speakers; NXT ceiling panels have an acoustic dispersion between 160 and 180 degrees. This means that certain cinema effects, such as sound moving from left to right as a car crosses the screen, are reduced - although this can be countered to an extent by careful placement.

The future

Ceiling panels are just one example of the 'speaker that isn't a speaker.' Because of its unique principles of operation, NXT panels can be made of many different materials. So the glass of a TV screen or computer monitor could become a 'speaker'. Eventually, rather than having a panel embedded in the walls, the plaster itself can become a 'speaker' with specific flat panel driver technology to excite it.

NXT ceiling panels are changing the way that architects and designers approach acoustics in the home. They are making cinema-quality sound more widely available, and lowering the costs of top-quality sound reproduction in every room in the house, countering the problems created by uneven, asymmetrical spaces. They are easy and quick to install, and fit with modern interior design. And because they do not have hot spots or dead zones of sound, they create a more comfortable acoustic environment.

Ceiling panels are unlikely to replace traditional speakers in specialist and controlled environments: the local multiplex is unlikely to abandon its cones any time soon. But as our demands for the highest quality goods and services for our homes increases, ceiling panel speakers can only become more and more popular.

Morgan Sousa is the i-ceiling product manager for Armstrong World Industries, and Kevin Sherwood is the i-ceilings product manager for CIE Ltd. Armstrong Holdings, Inc. is the parent company of Armstrong World Industries, Inc., a global leader in the design and manufacture of floors, ceilings and cabinets.

www.armstrong-ceilings.co.uk