Shaping the future?

Since its first appearance in the mid-late 90s the steerable loudspeaker array as made significant inroads into the installed sound market. It’s unique advantages over conventional loudspeaker systems have seen it applied in a range of hitherto troublesome applications. But things have moved on, new players have entered the market, and new technology has been developed, reports Chris Fitzsimmons.

Unless you’ve been living in a cave for the last decade or so (and I apologise here to any InAVate readers who are in fact troglodytes) you will have come across the phenomenon that has been the steerable loudspeaker array. You are probably also aware of the unique properties that their design imparts on them. But just in case you do enjoy a bit of spelunking from time to time, or don’t know how useful they are, here, first, is a quick steerable array FAQ.

What is a steerable loudspeaker array? Also known as steerable columns, digitally steerable arrays, beam-steering system a steerable loudspeaker array is just what it says it is. An array (usually, but not always vertically arranged) of drivers, controlled by a series of DSPs.

How does one work? When the centres of each driver are half a wavelength apart, lobe steering becomes possible. Basic steering of the lobe involves a progressive delay in each element of the array, with the topmost speaker transmitting first. This delay produces an effect, similar to that obtained by physically tilting the array. It becomes possible to steer the output away from troublesome areas such as highly reflective surfaces, reducing the effects of reverberation and thereby drastically increasing intelligibility. Each driver is treated individually via the dedicated DSP to ensure that all output arrives at the intended listening plane in phase, and on time.

What are they used for? One of the key benefits, apart from great intelligibility, is the ability of the array to produce remarkably consistent SPL all through the listening area, and over the same long throw lengths as a traditional line array. This means that spaces such as airport terminals and railway platforms, cathedrals and shopping centre galleries are great applications for steerable arrays. Couple that with the ability of the array to avoid reflections from the kinds of glass, and other shiny surfaces beloved of architects in such environments and you are on to a winner.

What are the required elements of a successful array? The steering effect is not new. It has been known about for a good half-century but until the 90s the DSP power didn’t exist to control the arrays. So processing power is one factor. A second factor is the drivers themselves. The steerability of sound a different ends of the frequency spectrum depends on different properties of the array. At the low end, the length of the array determines the lowest frequency that can be successfully steered. Longer array, lower frequency.

At the other end of the spectrum, in the high frequencies, the deciding factor is driver separation. The centre-to-centre distance of the individual speaker elements must be a maximum of double the shortest wavelength to be steered. Both of these requirements pose problems for full range audio (20-20kHz). For a 20kHz signal you would need driver centre separation to be 8,5mm and at the other end, you’re talking about half wavelengths around 8.5m for 20Hz. That’s a big array.

So the stage is set, but who is in the cast? Chronologically, Duran Audio is first on. As far back as 1995 the company introduced the Axys branded Octaray and Octavox products, which were followed in 1996 by the Intellivox 2c. Axys Intellivox was available in two main flavours for quite a while. First came DDC or digital directivity control (and then DDC2.0) followed by DDS (digital directivity synthesis). The DDC product is well suited to applications where the audience plane is flat – platforms, flat floors and so forth, in fact most applications. With the advent of DDC2.0, which offered improved functionality and audio quality thanks to more powerful DSP controllers, this control got even better.

DDS allows for the synthesis of a three-dimensional radiation pattern from the array. Meaning you can use it in much more geometrically complex spaces such as theatres or halls with raked seating. Starting with a desired SPL distribution in a hall or complicated room geometry, the optimum output filter for each channel of the array is calculated.

The DS and DC families, as Duran calls these two sets of products, come in a range of unit sizes from 1149mm in length for the smallest up to a 4930mm monster. These are monolithic arrays, which can make transport interesting for the bigger units. These offer throw distances of 2-70m.

The DDS and DDC products had HF pattern control up to around 2kHz, which limited them musically. The addition of the DSX range attempted to improve things with the addition of 1” horn loaded tweeters.

One of the other areas of significant development for Duran has been in the software to go with these products. DDA (digital directivity analysis) is a dedicated software tool allowing sound designers to simulate and optimise the performance of Axys based systems. You can import models from EASE or CATT Acoustic as well as tools such as Google SketchUp. Output designs can then be uploaded to DSP units via the WinControl software. DDA is constantly evolving, with the latest version focusing on assisting designers with complex system handling the interaction of many arrays in a single volume.

But as with any good idea, others are on the scene and doing just well. Renkus-Heinz’s Iconyx solution began with the fully DSP-enabled IC8 module, and was followed by a more cost effective, but mechanically steered IC7. With the addition of the company’s RHAON technology to the product things got interesting, the units can now communicate over a CobraNet network. The current Iconyx range contains four main units, all of which are assembled from multiples of the same IC8 module. This makes transporting them somewhat more convenient!

Each module contains eight independent, DSP-controlled, coaxial transducers, claiming effective beam control down to 200 Hz if you add an IC-R module.

Renkus took steerable arrays in a completely new direction in summer 2008, with the announcement at InfoComm of IC Live. Under the banner of Steerable, portable, powerful the company aimed to bring array concept to the rental market. It was designed for use at corporate events, political rallies and even in resorts and theme-parks.

IC Live has two different components – the HF element is simply called IC Live and is similar in structure and performance to the IC8 module. This can be paired with one or two ICL215S, which is a dual 15” sub unit, depending on the application. Both Iconyx and IC Live are controlled and programmed by Renkus’s BeamWare software.

The latest entrant to the digitally steerable market place, is Tannoy. Details of Qflex began to trickle out in the middle of 2008, with demos at InfoComm. As more information has emerged, it’s clear that it represents a significant challenge to the established players.

The company has paid close attention to what it sees as limitations in its competitors’ products. First comes the issue of pattern control. The current crop of products from Renkus-Heinz and Duran Audio claim effective pattern control of frequencies up to 3kHz.. Tannoy claims that Qflex offers good pattern control up to around the 12kHz range.

The second key differentiator is the angle of steering possible. Tannoy claims that it can delivery +/- 70 degrees as opposed to the +/- 30 of its nearest rival. The main advantage of this is that it allows the column to be placed higher off the ground and potentially further out of sight.

Tannoy also is currently using newer DSP chips than its competitors. By virtue of being a more recent product Qflex contains later and therefore probably cheaper DSP components. This clearly won’t last once the other players release newer versions of their products, but until that point the company is ahead of the curve.

All of the steering products on the market are highly complex beasts and whilst Tannoy claims to be significantly ahead in the frequency range for steering, one thing that all the players depend on is the tools that come with the products. The DSP algorithms that control the drivers are extremely complex and without a user friendly software interface installers and system designers would find it incredibly hard to specify, design and tune systems.

Duran Audio offers its constantly evolving DDA product, which whilst it looks intimidating is very powerful with the addition of the previously mentioned tools for analysing the interaction of multiple columns. Beam steering is relatively simple if your beams don’t cross, but if you have a large space with multiple beams, things can get a bit fraught. DDA also provides full 3D representation within the software package.

Tannoy has elected to emphasise the simplicity of its own control and design software, it is really designed for less complex installations with few columns, that interact in a limited fashion. If you want full 3D models you can export data from Qflex Beam Engine to EASE. Programmes generated in Beam Engine are exported to the column’s DSP chips via Tannoy’s VNet software.

Renkus-Heinz BeamWare works in a similar way to Beam Engine - define your audience area, adjust the beams for optimised coverage and then export the FIR (finite infinite response) filters that control the array. Again, you can export the software to EASE for full 3D simulation and analysis.

The arrival of new blood in the market is likely to shake things up over the next 12 months as the existing players wait to see how the product is received and then respond. Qflex is yet to establish an installed base, and whilst the response has been very positive to demonstrations and the specs, the proof of the pudding will be in the tasting.

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