By Kevin Hilton in Technology January 28, 2022 0

The basic principles of the loudspeaker have remained constant for decades. New takes on the technology, notably the line array, have appeared over the years but the fundamentals of what should be considered when selecting loudspeakers remain the same. Kevin Hilton looks at the technologies and system types available for different applications.

Selecting the right loudspeaker for the job can be challenging in any audio sector, but AV is multi-faceted and has several areas under that umbrella term which broadens the choice of loudspeaker. In some cases there are crossovers with live sound, corporate presentations being the obvious example, but for other commercial applications, including meeting rooms and public address/voice alarm (PA/VA) situations, there are more specialised technologies to consider.

Loudspeakers have always played a part in meeting rooms, particularly if video playback was involved. That role has increased in recent years, initially driven by the desire for better quality audio – often due to business people having good sounding TV and music systems at home – but now further accelerated by the Covid pandemic. This trend is also seen in lecture theatres and classrooms, with a move away from playing the sound from speakers integrated in the screen to either column or ceiling loudspeakers.

Column – or line source – loudspeakers are well-established but, in some ways, an often overlooked form of audio reproduction technology.

As the name suggests, these have a long, narrow design that lends itself to installations where the equipment needs to be inconspicuous. Columns offer broad coverage in the horizontal plane with negligible vertical coverage at the top and bottom of the cabinet. They are also known for good speech intelligibility, which is why they have been used widely in PA installations for public areas, such as railway stations. A variation of the column loudspeaker features ‘digitally steerable’ capability. In this, each driver unit features its own amplifier, delay and equaliser, which enables the vertical coverage of the column to be angled up or down, as well as directed for long or short throws.

In small to medium-sized meeting rooms and classrooms, columns would be the most popular and practical choice of loudspeaker. The alternative to such a ‘single source’ set-up would be a distributed audio system. This can be used for similarly sized spaces where column loudspeakers would otherwise be utilised and is based on a series of ceiling speakers running on a 70 volt infrastructure. Commonly found in offices, gyms, supermarkets and restaurants, these are also known as constant power systems because the sound is distributed uniformly via the transformers and dedicated ampilifers built into the speakers.

Ceiling speaker technology continues to evolve through companies, such as Bose. Its EdgeMax EM180 in-ceiling loudspeaker has been combined with Sennheiser’s TeamConnect Ceiling 2 beamforming microphone to create the ES1 Ceiling Audio Solution. Certified for Microsoft Teams in addition to also working with Zoom, this operates with one EM180 at the front of a room. It uses Bose’s proprietary PhaseGuide technology in conjunction with high frequency compression drivers to cover an entire room from a single point.

For other AV applications, the traditional loudspeaker cabinet – which can be mounted on a stand, floor stacked or ‘flown’ from a specially constructed rig – is still a reliable and popular option. It can be used for small presentations featuring one or two people speaking, plus some play-in and play-out music. Larger models built up into big systems feature in more lavish corporate launch productions, as well as on major concert tours and performances.

Presentation theatre featuring Active Audio Step Array column loudspeakers.

Mathieu Pobeda, technical director of the Arbane Group, which includes loudspeaker brands APG and Active Audio, observes that other than intelligibility, the main features systems integrators are looking for right now are thinner main speakers for easy and discreet installation into an existing environment, plus sub-bass units that can be hidden away, plus options for custom painting and compatibility with standard AV rigging.

Cabinet loudspeakers can be categorised in several different ways, one of them being whether they are active or passive. Active speakers have built in amplifiers, which means they have their own power source (hence the alternative name ‘powered speakers’). Passive speakers do not have integral amplification and need to be powered by external, standalone ampflifiers. Pobeda comments that active speakers have the advantage of offering the ‘right’ amount of power per channel.

There is also the ability to control the signal for each individual speaker, meaning it is easier to steer and has active driver control. On the downside, Pobeda adds, active speakers are less versatile and more expensive than their passive counterparts, with one or two power supplies per box instead of one power supply for several cabinets in passive set-ups. The major advantage of passive cabinets is seen as not having to run power cables to the speakers, which saves time and effort.

Line array versus point source In recent years, the big debate in loudspeakers has been line arrays versus point source. Over the last 30 years the line array has become the preferred technology for the majority of touring and large-scale outdoor events or installations.

It comprises a series of typically identical loudspeaker components arranged in a line, receiving sound signals in phase. This produces a near-line source of audio, which is claimed to project the sound further and more consistently than previous horn-loaded cabinets. Although the concept dates back to the 1980s, it was not until the mid 90s that the line array started to make a mark on live sound. French developer and manufacturer L-Acoustics led the way with its V-DOSC system; other companies later picked up the trend with their own takes on the technology.

Even though line arrays can be seen as the dominant loudspeaker configuration for large-scale applications and L-Acoustics as still the leading exponent, the company’s view is that the choice of system should be down to what suits the production best. Cédric Montrezor, L-Acoustics’ executive director of application projects, comments that a festival with an audience of tens of thousands demands an extremely long throw, such as that offered by the K Series line source array. But for more intimate performances or smaller venues, he says point source or constant curvature type loudspeaker systems would be the right choice.

KV2 VHD5 system at West Lake Music Festival in China 2021.

In a constant curvature array, such as JBL Pro’s VRX Series, three compression drivers are mounted on a continuous arc and work together effectively as a single driver. This type of system is regarded as filling the gap between line arrays for large events and point source for smaller productions. Point source, by contrast, is a single loudspeaker or arrangement of multiple loudspeakers placed some distance apart. From this single source a full range sound can be produced, radiating in a spherical pattern. While this generates a smaller range than a line array, point source is still a viable loudspeaker configuration for night club installations and theatre productions.

These markets have been targeted by KV2 Audio, an enthusiastic proponent of point source as an alternative to line arrays. Angus Davidson, KV2’s technical support director for North America and Asia Pacific, says the company is also looking to break into touring and big events, while acknowledging that it is slightly at odds with the rest of the market. A major reason for this is that the majority of the signal flow in the KV2 VHD large format system is analogue. The only digital used is 20MHz (1-bit) PDM, which is a very different technology to the PCM DSP favoured for other systems.

While the merits of line arrays and point source systems will continue to be debated, there is no doubt that there is now a wide variety of loudspeaker types available to suit the needs of AV.

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