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Wharfedale LoudPanel Speaker Systems

LoudPanel

The ideal of loudspeakers that blend perfectly into the surrounding environment has long been the ambition of all style conscious loudspeaker designers. With modern Home Cinema systems comprising anything between 5 and 8 speakers, this has never been more important.

The traditional solution has been to use moving- coil loudspeakers. These are the speakers most of us are familiar with. A cone is attached to a ‘voice coil’ which moves in and out of a magnetic field, depending on a music signal passed through the coil. It is the compression and rarefaction of the air due to this pistonic motion that produces the sound we hear. This ‘Driver’ as it is known needs to be enclosed in a box, so the air moved is projected forward rather than just around the edges of the cone.

Often several drivers (woofers and tweeters) need to be used as certain size and shape drivers produce certain ranges of frequencies and more than one is required to produce a full frequency response.

After nearly a century of engineering advances, even the most advanced box loudspeakers in the world follow these basic principles. It became clear that a different approach was needed.

NXT

Around 1995, Wharfedale became involved in a project with a UK government agency, researching an interesting effect that had become apparent during the testing of sound cancellation equipment in military helicopters. Sound was being produced from large, flat panels when they were ‘excited’ in a particular way. This was interesting because the soundboard, rather than moving in and out, in a piston motion, was amplifying sound from ‘bendy waves’ produced through the material. This is a similar principle to the way a piano soundboard works, amplifying the small strings to fill a concert hall with music.

A new company, NXT, was formed to research commercial applications for this exciting new technology, but it was immediately apparent that this was indeed the answer to the loudspeaker designers quest to make the most discreet and inoffensive loudspeakers ever produced.

Wharfedale were the first company in the world to develop a successful commercial product. and this is now the second generation of the resultant ‘LoudPanel’ range of products. They hang on the wall like pictures and weigh only a few hundred grammes. You can use any poster or print to disguise them completely, yet the sound they produce is gloriously rich and detailed.

The Nature Of NXT

LoudPanel offers a number of benefits to the listener beyond the absolute stealth of the design.

One of the key features is the ability to provide consistent sound pressure levels over a wide listening area. Conventional pistonic loudspeakers produce a very directional sound. Typically the dispersion varies greatly according to the frequency being produced, with big, low frequency waves dispersing well, but above around 5kHz, the sound becomes very beamy and directional, so you need to be sat with your ears directly in line with the drive units in order to be able to hear the full frequency spectrum. In systems with more then one speaker, these beamy mid-range and high frequencies react with each other to create interference patterns of sound pressure, so walking across a room, sounds get louder and quieter with very little consistency, even in the listening ‘sweet spot’.

With LoudPanel, these problems simply disappear. Because the sound is being produced by longitudinal waves across the entire surface of the panel and a maximum excursion of only a few microns, the resulting audio waves are entirely different in nature.

Rather than coherent waves produced (like throwing a pebble into an otherwise still pond) that you get from traditional drive units, the waves are much more complex, exciting the surface of the panel in numerous ways. This has the effect of virtually eliminating the interference patterns that are inevitable when coherent waves interact. The phase relationship between sound waves no longer has significance and, perhaps the most important consequence, the wave amplitude dos not decay logarithmically in relation to distance from the loudspeaker. Instead, a smooth linear decay occurs. The result is a large and consistent listening area, free of interference.

This has its own consequence. Gone are the days when you had to place the stereo speakers equidistant in a triangle from the listener. LoudPanel can be placed anywhere, even in Lshaped or irregular rooms, at different heights or orientations.

LoudPanel Technology

LoudPanel works in quite a different way from conventional loudspeakers. Instead of the pistonic motion that we have come to expect, exciters bonded to the surface of a specially designed laminate panel cause it to bend and flex. This board acts rather like a piano soundboard and amplifies the sound to normal listening levels.

Just like with a piano or such similar instrument, the shape and size of the soundboard is essential to tune the instrument, the positioning of these exciters on the surface of a LoudPanel dictates exactly how the board responds to particular frequencies. Unlike with a piano, where this knowledge has been accumulated over hundreds of years, passed down from expert to expert, the NXT system provides a computer model which can predict the ideal location of exciters on a panel surface to produce a flat and extended frequency response.

The way such panels work means the extent to LoudPanel technology which the panel can reproduce bass depends entirely on the size of the panel. The panel can only reproduce notes with a wavelength smaller than the panel.

Rather than trying to build panels which are several meters across (although entirely possible) the practical solution is to supply a system complete with a discrete powered subwoofer. Because bass frequencies are essentially directionless, this can be placed anywhere in a room, even behind a sofa.

The sound produced by LoudPanels comes from the entire surface of the board - not just a central impulse, like that produced from a pistonic loudspeaker. This causes the LoudPanels to behave in a different way from conventional loudspeakers. A much wider listening area and higher ambient level are just two of the advantages LoudPanels have over traditional loudspeakers.

The wave pattern produced by conventional drive units is coherent, directional and has a rapid decay in amplitude.

The wave pattern produced by an NXT driver is radically different, exhibiting a highly complex structure which eliminates interference, has a wide dispersion and shows linear amplitude decay.

Models and Specifications: