Review: EAW NT Series
Portable PAs were once the preserve of a select group of companies. These days they’re a dime a dozen and the list of contenders is growing. EAW’s new offering, however, sets itself apart with some real design advancements.
8 September 2006
Review: Glenn Helmot
The no-holds-barred, enormo line arrays that go touring with the likes of U2 and Metallica grab most of the headlines, but manufacturers know that they ignore the two-way portable PA market at their peril. The market for these loudspeakers is enormous when you consider the requirements of small audiences all over the planet, and the frequency and variety of applications where a compact loudspeaker can and is used. Almost a sales no-brainer, the proliferation and popularity of ‘plastic’ two-way boxes bears testimony to the importance of this sector.
There is, however, another end of the compact, self-powered, two-way spectrum where the loudspeaker enclosures are constructed of wood. Here the buyers and users are looking for something more sophisticated and powerful; sonically superior… maybe more ‘pro’.
WOOD ON THE OPPOSITION
I think it would be fair to say, particularly in Australia, that at the ‘wooden end’ of the buying market one manufacturer has dominated. Meyer Sound, with its UPA, has been the long-standing champ and something of a de facto benchmark. The UPA is frequently used by other manufacturers as the loudspeaker against which they compare their latest offerings. As with any apparent hierarchy, a would-be contender will periodically take a tilt at the title and recently we have seen two of the loudspeaker industry heavyweights, EAW and JBL, both releasing new product ranges with an eye firmly fixed on Meyer’s championship belt. From the EAW camp comes the NT series. This review won’t go down the direct comparison path but the EAW NT Series does feature some innovative developments worthy of discussion that, without question, put these loudspeakers in serious contention for the top spot.
Reportedly three years in development, the NT series comprises five loudspeaker models, all featuring the first implementation of EAW’s Gunness Focussing – more on that a little later. After quick inspection it’s easy to see that the NT is not simply a rehash of a predecessor. These loudspeakers comprise a very practical-looking package with a rugged feel. They look purpose-built – made for loading in, putting up and tearing down, loading out again, day in and day out. While the NTs could be equally at home in a permanent installation, I personally find the look a bit chunky, preferring a sleeker permanent ‘install-only’ enclosure.
The NT Series comprises four two-way, bi-amplified, full-range loudspeakers and a matching dual-driver subwoofer. Of the full-range loudspeakers, the NT26 and NT29 each have direct radiating 12-inch diameter, three-inch coil, low frequency cone drivers in sealed enclosures, with three-inch coil on 1.4-inch exit compression drivers for the high frequencies. The difference between the NT26 and NT29 lies in the dispersion of the HF horn – 60° (H) x 45° (V) and 90° (H) x 45° (V) dispersion patterns respectively. The NT56 and NT59 have the same HF horn and driver combinations, sharing space with a direct-radiating 15-inch unit with four-inch coil in a sealed enclosure. The HF horns in all the full-range loudspeakers is in a fixed position and therefore not rotatable if the loudspeaker was to be installed in a horizontal orientation. To round out the NT series, the NTS22 subwoofer utilises two high-powered 12-inch devices with a four-inch coil loaded into a vented enclosure, utilising EAW’s well-regarded push-pull driver configuration.
WATTS GOING ON
Constructed from ever-faithful Baltic Birch plywood, the NT cabinets feature protective bumpers across the corners, composed of a nylon-type polymer EAW calls Santoprene. There are integral alloy fly tracks that run the full length of both sides and rear of the full-range boxes, while the sub sports two tracks on either side. The fly tracks are a structural element of the box construction and transfer any stresses from weight loading into the fly track itself and not the wooden cabinet. Cleverly, the fly tracks have also been utilised as the ‘grip’ component in the handle cutouts on the sides of the cabinetry. As you’d expect, built-in pole cups allow the full-range speakers to be neatly mounted with an NT sub as the base.
The power behind the drivers is provided by a modified Class D amplifier delivering 1000W to the LF and 500W to the HF (in the full-range boxes) and, in the case of the subwoofer, 1000W to each driver. The amplifier has all the protection circuitry expected of modern amplifiers along with integral 24-bit/48k DSP managing the speaker processing side and the Gunness Focussing algorithms – as I say, more on that later. A rear panel houses the analogue signal input and loop thru on XLR connectors, LED status indicators and Neutrik PowerCon for the AC mains. A loop thru Neutrik AC mains connector would have been a handy addition given the current draw of these amplifiers is a modest 1 Amp at full power – it’s possibly a regulatory consideration, but would be neat for multiple loudspeaker setups. Another notable omission from the back panel is a connector to provide a means of networking or remote control of the loudspeakers. With the onboard DSP one can only assume that EAW would be intending to add this feature in the future.
The amp modules are ‘field replaceable’ and identical for all the full-range NT models (with another amplifier for the sub). There are 12 screws to remove the entire amp module from the loudspeaker enclosure, while a dip switch changes the pre-programmed onboard DSP settings to suit the specific NT model it’s slotting into. Incidentally, the 55Hz/110Hz high-pass filters, EQ contour and (on the sub) gain and polarity switches represent the only user-configurable settings. While limited, there’s enough control to configure the correct sub/full-range crossover point or to decrease mid-range coupling when multiple speakers are used in an array.
NEED TO KNOW
NT packs a variety of weight-saving measures to offer what must be the best power/weight ratio in its class.
BRACE YOURSELF
It’s worth noting that the amplifier modules only add 4.1kg to the total weight of the loudspeaker. Clearly, EAW has gone all out to produce the highest power-to-weight ratio in its class. One thing’s certain, the NT’s robust exterior belies the sophisticated weight reduction measures evident on the inside of the enclosure.
It’s not unusual to find neodymium (or another low-weight, space-age alloy) magnet structures on loudspeaker drivers these days. The advantages of neodymium are well documented: apart from its low mass, it exhibits reduced flux modulation and higher energy density compared to traditional ferrite magnets. The cone drivers on the NT Series also use neodymium and have taken the weight reduction a step further with an ‘orbital’ magnet array structure. Instead of using a large single magnet that surrounds the voice coil gap, the ‘orbital array’ uses a number of distributed smaller magnets. Other than the weight saving, EAW claims this technique improves air circulation to increase cooling around the voice coil, which therefore increases the continuous power handling and reliability of the driver.
EAW’s quest to trim the fat has turned to the construction of the loudspeaker cabinetry itself. EAW has experimented with construction and joinery techniques, coming up with a cabinet that eliminates traditional internal support cleats and heavy bracing, as well as shaving excess wall thicknesses in areas that don’t require it. Admittedly it’s a case of ‘a little here, a little there’ but cumulatively the results speak for themselves: the NT26 and 29 loudspeakers tip the scales at a waif-like 24kg. That’s around 11kg lighter than those rival loudspeakers I mentioned earlier. Doubtlessly, EAW has given these new cabs a kicking to ensure they hold up to the rigours of daily work but, like all new innovations, only time will tell.
COPS A HIDING
I checked out the new system when an NT demo rig was used by the Victorian Police Showband for one of its concerts at the outdoor stage in Federation Square, Melbourne. Fed Square is a large, concreted open space surrounded by office buildings and cafés, and the opportunity for sound checking is extremely limited. The band normally uses all its own production equipment but on this occasion the NT system was set up next to the crew’s PA rig. The idea was to do a bit of an A/B comparison by switching across from one system to the other during one of the breaks between the bands set. The NT system comprised two NT26s pole-mounted above two NTS22s per side in a standard stereo setup. The system was pretty much the equivalent, box for box, with the system owned by the Police Showband.
As I observed long-time sound engineer Michael Parker at work, a few things became obvious. I’m sure every sound engineer has had to mix on systems where, from the onset, you feel like you’re in a battle you’re never quite going to win. It’s just a struggle to pull a good mix and you can’t really put your finger on what the problem is. Not with these NT26s – they’re smooth, detailed and provide great imaging. During the band’s set I walked the audience area, listening. Most apparent was that the imaging held up over a very wide area. The articulate instrument and vocal detail was obvious and the throw was quite impressive. My thoughts on the system were mirrored by Michael’s aftershow comments: “With the EAWs I can hear all the instruments. Our players are very good and use high quality instruments. They play with detail, which you want to be able to reproduce. This system is doing that. It has no honks and whistles. It is truly reinforcing the acoustic sound and not adding or colouring it in any way. For the Police Showband it is not about volume. For us it’s about an even spread and detail. We usually play to audiences who don’t want it loud, or we play in venues with sound level limits. I did notice I had to run the masters on the desk harder with the EAW system – my system has more grunt – but you can probably get away with a bit more volume with the NT system without it becoming offensive”.
Back in the warehouse I took some Smaart measurements of a pair of NT26s and NTS22s. The characteristics I heard in Fed Square were immediately apparent in those measurements. The NTs displayed a balanced frequency response and a very linear, full-bandwidth phase response. This would account for the clarity and definition of the NTs, with stereo imaging more akin to a direct radiating nearfield studio monitor than high-powered horn-loaded loudspeakers. More importantly, the phase response remained linear when measured off-axis and at distance. This phenomenon goes to the heart of Gunness Focussing – named after EAW long-time Director of R&D, David Gunness.
STAYING FOCUSSING
Before we consider the results of what Dave Gunness and his team have achieved, it would be worthwhile briefly discussing the general engineering principles behind the development of Gunness Focussing and the NT loudspeaker range.
The attributes a high-powered loudspeaker should possess (other than good sound reproduction) are projection, pattern control and efficiency. To achieve this, most loudspeaker designers turn to horn-loading. Horns make it easier to achieve the stated aims but often at the price of degrading the loudspeaker’s sonic qualities with the introduction of certain sonic anomalies (see ‘Horn Compromises’).
EAW argues that these sonic anomalies fall into two categories: those that do not vary with the loudspeaker’s operating conditions or environment (linear, time invariant, and spatially consistent anomalies; eg. the design of the phase plug exits in a HF compression driver); and those that do change with the loudspeaker’s operating conditions and environment (non-linear and time variant; eg. changes to the rigidity of a compression driver diaphragm as a result of drive power applied). To compensate, manufacturers often use DSP-based smarts to correct both types of anomalies. It is acknowledged that the currently available DSP, of itself, cannot correct some loudspeaker problems. However, using DSP, pre-conditioning corrections are often made using measurements that lump together both types of anomalous behaviour. When non-linear, time variant, and spatially variant behaviours change, the corrections used are no longer relevant and in some cases are detrimental to the loudspeaker’s performance. So, EAW reckon this ‘one size fits all’ approach to DSP-based correction is a big ‘no no’ and contend that it should only be applied to those anomalies that are linear and non time variant.
Using this rationale, EAW set about isolating those anomalies that are linear, time invariant and spatially consistent. With the help of partner company, Acuma Labs, the R&D team developed high-resolution spectrographic software to painstakingly measure and analyse their loudspeakers’ behaviour. The team was able to accurately map the loudspeaker’s transient response and, as a result, build up data on what anomalies were stable and correctable and what were not. Importantly, they now had a tool which could be used to objectively and accurately test and develop the R&D team’s theories and prototypes, in their quest to only isolate and correct linear loudspeaker anomalies. For the NT Series, EAW then set about re-engineering components such as compression driver phase plugs, horn throat exits and cone drivers. Finally, proprietary ‘Z transform’ algorithms were designed, along with a custom hardware platform to apply the DSP. Leaving aside what the hell a ‘Z transform’ is for a moment… you might ask ‘why?’. Answer: because the NT design team found the standard filters in currently available digital devices could not provide the correct response shapes or accuracy. The filters had to be precise in both the frequency and time domain, with an ability to ignore those anomalies that are considered to be un-correctable. Clearly the design of the algorithms (and the application of the filters) EAW has used in its DSP goes beyond the commonly used EQ and time alignment preconditioning filters of the past.
I think it’s reasonable to say that the last 10 years have seen the dominance of the ‘smaller, lighter’ principle in loudspeaker design and pro audio in general. People have been hell-bent on making things more portable and more powerful, all the while using advances in DSP processing as a safety net – the push for miniaturisation may not make things sound better, but a few SHARC chips will compensate for that, is the implication. But the fact of the matter is, adopting DSP in this way has many trade-offs and, arguably, is responsible for as many loudspeaker problems as it has solved.
GUNNESS – PURE GENIUS?
And so we come back to the Gunness approach – that of applying precise DSP filters only to the ‘correctable’ anomalies – and whether that approach has been vindicated in practise. I’d suggest it has, both in the subjective appreciation of the NT’s performance (superior detail and imaging) and the objective test measurement I undertook (excellent off-axis linear phase response). The bad news is that while it is theoretically possible to apply Gunness Focussing to any loudspeaker, it’s highly unlikely that EAW will be broadcasting that detail on the bush telegraph. It will now be interesting to hear Gunness Focussing adapted and applied to other loudspeaker designs in the EAW line up.
Despite the spin marketing departments put on loudspeaker technology, DSP alone does not and will not change the laws of physics… it might massage the laws, or distort them a little… but never change them. In the end, a loudspeaker that adheres to correct engineering principles is always going to be a better product. And with the judicious use of up-to-the-minute DSP algorithms, a high quality loudspeaker will then be free to yield exceptional results. The EAW NT series is the product of such an approach.
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