Any 20-something system tech caught bemoaning his duties might well be reprimanded by more senior professionals with the classic “you don’t know you’re born”. And not without justification, or so it would appear after an investigation of today’s Swiss-army-knife-esque (thanks to VMB for the analogy) DSP device and the history of its cornerstone, the crossover.

Based on the work of Bell Telephone engineers Campbell and Zobel, the earliest loudspeaker crossovers were crude, to put it mildly. This was because little attention was paid to the design of them – a puzzling fact, but one that a bold statement from John Lenard Burnett on his website lenardaudio.com, might go someway to explain: “People who make speaker systems rarely have electronic knowledge.” Controversial, but nevertheless, the limits of these circuits offset the multi-way loudspeaker’s potential advantages of increased frequency response and sound pressure levels.

The familiar and more elegant Butterworth filters of the 1950s were a major progression, but it wasn’t until the mid 70s that understanding and technology finally permitted the advancement of these filters to the point where they could accurately and adequately attenuate frequencies outside a driver’s operational bandwidth.

Even so, these were rudimentary passive crossovers, which were bulky, caused power loss and often sounded a lot like a passing Golf GTI occupied by local rudeboys. As a less inflammatory Burnett points out: “The auditory difference between an active and passive speaker system is noticed by everyone. A correctly set up active sound system has greater clarity and realism and is free from inter-modulation distortion.”

Many would say therefore that the most significant development in the field, at least as far as the pro industry is concerned, was the onset of digital audio, which ultimately made it possible to cram not only an active crossover (one with gain in its filters), but eqs, limiters, delays and all manner of other sharp audio tools into a single rack unit. Being comprised of firmware – and therefore almost virtual – this can even be squeezed into a touring amplifier without making it any bigger, which is precisely why many manufacturers have recently done just that.

Those involved with the development of these devices truly have excelled themselves, but whether you opt for the amplified controller or the standalone DSP, it is without contention that any of the following units will make your system tech’s life infinitely easier than it once was…

Lab.gruppen
Following Lab.gruppen’s acquisition of Dolby’s Lake technology, it has now introduced its own standalone processor to replace the discontinued Dolby Lake Processor. A prototype of the new device, named LM 26, was recently showcased at the Prolight+Sound show in Frankfurt.

The LM 26 is a full-featured two-in/six-out Lake processor in a 1U frame. It will accept audio signals as analog, AES digital or via Audinate’s Dante digital audio network at 48 and 96kHz sampling rates. Lake processing features include raised cosine equalisation, linear phase and classical crossovers, LimiterMax peak and RMS limiters. A Super Module capability allows flexible grouping of processor channels across separate hardware frames, including prior Lake products and PLM Series units.

The new processor is scheduled for launch later in 2009, but Lake fans can still access the technology through LG’s PLM (powered loudspeaker management) amplifiers, in which it is built in. These units are now a mainstay of Live Sound Agency’s L’Acoustics V-Dosc PA system, which has provided sound reinforcement for Slipknot, Iron Maiden and Santana.
www.labgruppen.com

BSS/Crown
BSS’ Omnidrive series of live loudspeaker management processors marked the first pro audio application of Precision Audio’s Whiseworks NTM crossover filters. Developed by Neville Thiele, the crossover uses a notched response to achieve a very steep roll-off outside the pass band, which allows operators to push loudspeakers extremely close to their operating bandwidths without risk of over-excursion.

The Omnidrive devices have been deployed on numerous high-profile tours by firms such as Adlib Audio, Britannia Row and Audio Analysts, but many users are now turning to Crown’s I-Tech HD amplifiers, which incorporate a version of the technology co-developed by BSS and Crown, Omnidrive HD. With 24-bit, 192 kHz converters Omnidrive HD’s features include linear phase FIR filters and the LevelMax limiter, which links peak, thermal and RMS limiters for more effective protection and maximum SPLs.

For the installation market, BSS also manufactures the Soundweb London devices, which provide a distributed, programmable DSP system on a single Cat 5 cable, with network audio via CobraNet. The latest high-profile installation of Soundweb London devices was undertaken by sound integration firm Acme Professional at Verizon Hall in Philadelphia, a 2,800-seat grand performance hall.
www.bss.co.uk
www.crownaudio.com

Alcons
Alcons’ ALC 4 and 6 units combine speaker controllers and power amplifiers, tuned to work as the ‘engines’ of its ribbon line array system. They can be loaded either with analog SDP modules or DDP digital drive processors.

The SDP circuit affords multiple processing functions that operate at the same time, including protection from over-excursion and power overload, dedicated filtering with fixed cross-over settings cater for the best system performance, optimised power response and system equalisation. The DDP also offers level control, mute, a user-controllable, four-band parametric equaliser and up to 340ms delay.

At the output stage the ALC units feature Alcons’ proprietary Signal Integrity Sensing (SIS) circuit. This extends the control-loop of the amp to the input terminals of the speaker, by means of two additional sense wires, compensating for the influence of speaker cables, which offers cable-length dependent damping, which is virtually infinite.

SIS also maintains signal level by detecting the amount of signal loss at the end of the cable. As a result of pre-compensation of the self-induction of the cable, non-linear harmonic and intermodulation distortion are reduced, while offering a more linear frequency response. The result is tighter and more accurate low and mid response.
www.alconsaudio.com

dbx
Spring 2009 will see the arrival of the new Driverack PA+, the successor to the popular Driverack PA.

New features of the processor include an updated library of stored speaker and amplifier presets, USB connection, front panel mute buttons, an improved auto eq wizard and an enhanced set up wizard process, which now includes an industry first auto-level wizard function. These functions should allow speaker systems to be configured and ready for performance within minutes.

The new Driverack PA+ also includes all the features of the original Driverack, including an industry-standard dbx stereo compressor module, the dbx 120A subharmonic synthesizer function on the input and a high quality six-channel output system that includes parametric eqs, Peak Plus limiters and the Advanced Feedback Suppression system.
www.dbxpro.com

XTA
British DSP manufacturer XTA Electronics has just announced the latest addition to its 4 series – the DP426, a two-in, six-out audio management tool that has been introduced in direct response to demand from customers following the discontinuation of the popular DP226. It is ideally suited to stereo three-way applications.

The DP426 shares exactly the same features as all the other models in the 4 series, including the flagship DP448, such as 28 band graphic eq and eight bands of fully parametric eq on the inputs, nine bands on the outputs, crossover filters with various slopes from 6dB/octave to 48dB/octave, delay, limiting and Audiocore remote control.

Prominent audio companies Audile and SSE are likely to use XTA 4 series devices across a number of the biggest festivals in the UK this summer. Between them, they handle stages at Reading and Leeds, V2008, Glastonbury, Bestival and many others.
www.xta.co.uk

dB Technologies
Featuring two inputs and four outputs, dB Technologies’ DSX 2040 boasts 96kHz, 40-bit floating point signal processing with 115dB dynamic range and is ideally suited to widely used two-way active stereo systems comprising subwoofers and mid/high units. Two separate crossover filters per input/output include Butterworth, Linkwitz Riley and Bessel types, with slopes from six to 48dB/octave.

An extensive set of signal processing tools such as input compressors, delays, 31-band graphic input eq and six parametric eqs for each output let users tune speaker systems with precision to suit the given venue and operating conditions. Each output also features a tunable digital limiter to protect speaker components.

With the controller software, users can create presets for dB Technologies speakers as well as custom configurations and load them on to the DSX2040. The integrated RS232 and USB interfaces allow remote management and control via a PC, but for those who prefer the handling convenience of analog features, front panel hands-on controls afford direct access to key parameters.
www.dbtechnologies.com

LD Systems
To complement its first range of speakers aimed at the pro market, LD Premium, LD Systems launched its very first DSP controller at Prolight+Sound last month.
The DPA-260 is a six-channel 19-inch speaker processor with 32-bit DSP and 24-bit DA converters. Five bands of parametric eq are provided, with low shelving or high shelving also available. Crossover range is 20Hz to 20kHz with slope, types and bandwidth selectable. Maximum delay time is 10ms and the device also features a limiter with threshold, attack, release and hold parameters.

With phase invert function, the unit is also equipped with a USB port and fully programmable software, which offers 40 presets for those flying in the dark. While the DPA-260 is primarily designed for use with the LD Premium VA-4 and VA-8 line array systems, there is no reason why it shouldn’t be considered a ‘more bang for buck’ controller for other systems.
www.ldpremium.com

Electro-Voice
EV's flagship digital sound system processor is the two-in, four-out Dx38, which provides 48-bit filter algorithms, 24-bit conversion and a dynamic range of 115dB. The Dx38 can be used in networks of up to 31 controllers with a maximum networking distance of 1,000 metres.

The Dx38 was put to use earlier this year alongside indie band, The Notwist, who gave three concerts with the Andromega Mega Express Orchestra at the Volkstheater in Munich. No less than five of the controllers were used in conjunction with 18 EV XLD enclosures, ten Dynacord V17s and a 20-strong combination of Dynacord LX3000 and H5000 power amps.

For users of small to medium sized sound systems, EV also manufacturers the DC-One, based on a two-in, six-out topology. Built on the same DSP heritage as its Dx38, the DC-One uses powerful Sharc processing, something normally associated with units in higher price ranges.
www.electro-voice.com

Ohm
Ohm’s flagship Cred Mk2 is a two input, four or six output, PC controllable speaker management unit with a 96kHz sampling rate, employing powerful third generation Sharc processors, a Burr-Brown AD converter and Wolfson multi-bit DA converter. 

45 complete sets of parameters can be stored giving pre-set input and output gains, delays, limiting and eight parametric eqs per channel. In addition to the Bessel, Butterworth and Linkwitz-Riley filter shapes there is a fourth and eighth order Hardman crossover filter, which produces much steeper cut-off slopes for a given order than conventional crossover alignments. This allows a lower order filter to be used without sacrificing cut-off characteristics, but with smoother group delay and less severe phase penalties, giving a more natural sound.

For installations and small to medium touring systems, the company also offers the Cleo Mk2, which is a fully featured controller at a more affordable price. Up to 60 user programmes can be stored in the unit and saved and transferred between units via the MIDI facility. All controllers are pre-loaded with the recommended settings for Ohm loudspeakers. The Cleo Mk2 was recently used in an installation of Ohm speaker products at Manchester’s Walrus Bar.

Alternatively, Ohm’s DSP-A3 switchmode amplifier combines Class H output with a fully featured DSP, including filtering, delay, eq and limiting. Setup, monitoring and controlling can be done locally or by use of the in-built Ethernet communication system.
www.ohm.co.uk

VMB
Arkeops is the latest generation of VMB’s processors, which have been continually developed for the last ten years. VMB assures that the device uses absolutely the best converters available, ensuring very low distortion and a 120 dB dynamic range. Earlier this year, the firm released Version 3 of the Arkeops, which now boasts air absorption compensation.

The Akeops allows the user to apply a filter to compensate for absortion losses caused by distance, relative humidity and temperature. Calculations and compensations of different distances can be made at the outputs, each of which offers both an RMS compressor/limiter and a peak limiter. The first stage uses a RMS detector algorithm to obtain high quality compression. The sound system can then gradually reach maximum power while maintaining clear sound, before the second stage is activated for a mechanical control and maximum speaker excursion.

“There is an impressive improvement in sound quality for common distances such as 20 or 30 metres,” notes Javier Matali, VMB’s director of marketing. “With a weather station on top of the mixer, users from the desert in Las Vegas to humid Singapore will wonder how they could have managed without air absorption compensation for so long.”
www.vmb.es