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Event Opal

Studio Monitors
Published August 2009
By Paul White

Event's new owners make some extravagant claims for these new high‑end monitors, whose design is said to put quality first. Do they live up to the hype?

Event Opal

Event have been building studio monitors for 15 years, but since they were acquired by the owner of Australian mic manufacturers Rode, there have been big changes, and the new, high‑end Opal monitor signals a completely new direction. It comes from a new design team, is manufactured in Australia rather than the Far East, and is aimed squarely at the audio professional and the top end of the project studio market.

Overview

On paper, the Opal follows the familiar active, two‑way, ported box format, with an eight‑inch woofer and a one‑inch tweeter, but there's a lot going on in there that isn't obvious at first glance. It has been in development for several years, and It seems that the designers were instructed to aim for the best possible performance and worry about the price later. The design brief was to achieve the performance of a three‑way system using only two drivers, with the aim of delivering an extended bass and accurate mid‑range with the lowest possible distortion. The laws of physics impose certain boundaries, but this design pushes them back by using novel technology in both the driver design and the cast-metal enclosure. For example, the bass ports are shaped to present a 'Variable Impedance', to minimise port noise, while the aluminium cabinet's shape is based on gentle curves, to avoid cabinet-edge diffraction and to keep box resonances to an absolute minimum. In fact, the very heavy cast casework is reminiscent of that used in the ATC SCM20A and some of the modern Genelec designs — although the details of the cabinet design obviously differ. Each speaker weighs 21.2kg, with overall measurements of 295 x 450 x 273mm, so they're very substantial. Whereas tapping a conventional speaker cabinet often produces a noticeable 'thunk', tapping these has about the same sonic result as tapping a car cylinder head!

The ULD beryllium‑copper dome tweeter has a one‑inch voice coil, driven by a neodymium magnetic assembly, and sits inside an elliptical waveguide that is itself a removable plate, so that it can be rotated through 90 degrees when side mounting is necessary. It is also possible to rotate the illuminated Event badge, and an Allen key is included for removing and refitting the four bolts holding the waveguide plate in place. Waveguides place additional air loading on the tweeter diaphragm, so a metal dome was chosen to provide correct pistonic action over its working frequency range; softer dome material can deform under load and introduce distortions. We're told that the performance of this tweeter in terms of distortion is significantly better than existing high‑end hi‑fi designs, and while some metal tweeters, particularly undamped titanium, can sound harsh and splashy, this one seems very well behaved. A fine‑mesh grille protects the front of the tweeter, and behind this is a phase plug.

Underpinning the sound is the eight‑inch EX8 driver, which it is claimed has a 30Hz to 10kHz raw response (measured without the filtering effects of the crossover or the ported cabinet). This uses a carbon-fibre‑reinforced, paper‑pulp cone, driven by a 66mm copper‑clad aluminium voice‑coil, wound onto a robust polyamide/glass‑fibre former and powered by a neodymium magnetic assembly. The roll surround is S-shaped for mechanical symmetry, but what really sets the EX8 apart from the vast majority of other drivers is the use of a second, series‑connected, static voice‑coil, which is effectively part of the magnetic motor and is wired out of phase, so that it pushes against the voice coil on the cone. Event call this technology X‑Coil, and they claim that it provides greater control over the cone, resulting in better transient handling and lower distortion. Similar dual‑coil systems have been tried in the past, with varying degrees of success, so the general idea isn't new, but the driver needs to have a large physical excursion range to make this work correctly. Event also employ their XBL split‑gap geometry for the magnetic gap surrounding the voice coil, although there's no real technical explanation of the benefits of this. The EX8 is built with a cone‑travel capability of a huge 36mm within its linear range, and has an impressive power-handling capability of 240W pink noise and 720W peak.

The Cabinet

The rear of the Opal, dominated by the heat sink, includes sockets for wall‑mounting.The rear of the Opal, dominated by the heat sink, includes sockets for wall‑mounting.

The Opal's 28‑litre cabinet is pressure cast from aluminium, finished in a black powder coating, and the inherently rigid shape is curved in two dimensions to discourage resonances, as well as internal reflections that might cause standing waves. Twin bass‑reflex ports are built into the front sides of the baffle to avoid unfavourable interaction between rear ports and nearby walls — which is a potential problem with rear ports. The transition between the woofer and the baffle is also smooth. Asymmetrical port geometry with an internal 180‑degree bend is used to reduce port noise (sometimes known as 'chuffing'), and the variable impedance that comes about as a function of the port shape results in a lower air velocity at the port's outlet. Not only does this reduce noise, it also helps to further cut down distortion. The 180‑degree bend at the end of the port also works as a mechanical low‑pass filter, to reduce the amount of mid‑range sound leaking out of the port.

The Electronics

Having established the credentials of the drivers and the cabinet, what about the amplifiers driving them? As you'd expect, the designers looked at various options, but decided on a traditional 'Class AB' circuit, with no DSP in sight. This circuit is built onto a four‑layer circuit board and specified to have less than 0.005 percent total harmonic distortion (THD). A soft‑clipping circuit is used to maintain a better wave shape, should the generously rated amplifiers ever be driven into clipping, and has the effect of reducing the perceived level of distortion when the monitors are used at very high levels — but with up to 1kW peak capability you'd have to be running pretty hot to induce clipping! The woofer amplifier is continuously rated at 387W into 5Ω (270W long term), while the HF amp is rated at 112W continuous or 50W long term, again into a 5Ω load. All the cooling is done by convection, so there are no noisy fans. When no audio is being fed to the speakers, the resting power consumption is around 20W.

Opal's 1.6kHz crossover is a very steep, eighth-order (48dB/octave) type and, along with the user adjustable filters, is based on phase-coherent filter circuitry that maintains a flat phase response over the crossover region. The controls for the user-adjustable filters used to match performance to room position are on the front panel, where they can be seen and adjusted with minimum effort, but they're covered by a rubber panel when not in use. Rubber base pads are included for use between the speaker base and the stand. The cabinet base is slightly curved so that the position of the speaker on the pad can be used to adjust the vertical angle.

The Controls

The controls go a little further than those on the majority of active monitors, as there's a variable-Q filter, with a frequency range of 40‑280Hz, which can be set to cut by up to 6dB in 1dB steps. This is the region where reflections from a large desk or mixing console can cause problems, so it's a useful addition. The Level control has a ‑6 to +6dB gain range in 3dB steps, and Space offers bass tailoring for full-, half- or quarter-space positioning. There are also LF and HF shelf controls, each with a ±1.5dB range in 0.75dB steps. These operate at 200Hz and 5kHz, and can be adjusted to suit taste or the room characteristics. Finally, Dim sets the brightness of the Event illuminated logo!

At the opposite side of the front panel from the logo are four status LEDs, a secondary function of which is to monitor the power‑on sequence, which includes some self diagnostics that last around 10 seconds. Under normal operating conditions, the top LED shows green for signal present and yellow when you're cooking things a bit too hard, although this is said to be an advisory warning, rather than the usual hard clip indicator, so I assume that it comes on when the soft clipper starts to operate. The middle LED is used in the startup sequence, but after that will only come on (white) if an excessive input level is detected, or (orange) if the amplifiers overheat. If the third red LED lights, there's a fault requiring service. There's also a blue LED designed to be used in conjunction with an external expander module, its meaning dependent on the module in use.

The rear panel is dominated by a large, finned heat-sink, and there's a lifting handle built into the rear top edge of the cabinet, making it easier to position these heavy speakers. There are also four M4 mounting points, should you want to wall-mount the Opals, and all the electrical connections are at the bottom of the back panel. Mains comes in on a two‑pin IEC connector (there's no ground, presumably to avoid ground loops), and there's also a power switch and mains voltage switch alongside. A Combi socket allows balanced jack or XLR inputs to be used, and there's a small D-connector, labelled Module Dock, that provides access to the signal path for planned additional expansion modules, one of which is likely to be a digital interface. Event also offer an optional calibration microphone and computer software package to aid speaker setup in the control room, but this wasn't supplied for review.

In short, what we have is a monitor that's capable of levels of up to 111dB at 1m (long term 80Hz‑20kHz) or 114dB peak, and a frequency response, between ‑3dB points, of 35Hz to 22kHz. Third-harmonic distortion is quoted (measured at 90dB SPL, 1m) as: 500‑7kHz, 0.08 percent; 200‑20kHz, 0.2 percent; and <200Hz, 1.5 percent. This wouldn't look that special on a power amp, but for speakers, where distortion figures of 10 percent are not uncommon, it's very impressive. Paper specifications, though, don't tell the full story: the only valid test is to see how well it does the job in a typical control room, and how well mixes made on this speaker 'travel'.

Opal Fruits

Like the best hi‑fi speakers, the Opals deliver their best when they've been allowed to warm up for half an hour or more, after which time the sound takes on a slightly smoother and better integrated character — although that's not to say that they sound in any way bad when first switched on. When fed with high‑quality material from a known audio CD, the first thing you notice is the lack of upper‑mid coloration that can make a monitor sound squawky or over‑presumptuous. Instead, the mid‑range is laid out clearly, revealing things that other speakers might miss, so when you feed in a mix that has problems, they show up very obviously. The low end is deep and powerful, but at the same time very tightly controlled: when playing a damped kick drum, you don't get that resonant overhang that afflicts many more budget speakers, where the port is tuned to a relatively high Q to hype up kick drum and bass sounds. In this respect, there are parallels with high‑end speakers from the likes of ATC and PMC.

The stereo imaging is exceptionally clear and wide, with a solid sense of centre‑panned sounds as well as those things off to the side, and transient detail is rendered very precisely and smoothly. Some 'ultra accurate' speakers attract criticism for sounding a little uninteresting, but that's not the case with the Opals: they just act as a clean window into the mix, so if you have a lively‑sounding mix, it will still sound lively played over the Opals. Indeed, I'd love to have a pair of these in the lounge for serious music listening.

I'm impressed: I can't remember when I last enjoyed working with new monitors as much as I did with these, and there was nothing about the sound that felt wrong or out of place. Inevitably, a high‑end speaker costs high‑end money, but even so, the Opals cost less than the monitors with which they stand comparison, and they should appeal to the more serious private studio owner as well as to professional studios — and possibly even to mastering engineers.

An Event To Remember

Reinventing the Event brand in this way is a brave move, as the accepted marketing wisdom is to come out with a high‑end product first and establish a reputation, before building more affordable spin‑offs to cash‑in on the accumulated kudos. On the face of it, Event might seem to be doing exactly the reverse, but by making their first new model since the company's change of ownership a very high‑end speaker that can live up to its not inconsiderable marketing claims, they seem to be on the right path to establish a provenance that will see the brand viewed in an entirely different light in future years.  

Alternatives

If you have this much to spend on two‑way monitors, you have a huge choice, with many models costing rather less than the Opal. However, the build quality and 'designed for accuracy' performance of the Opal puts it up there with the PMCs and ATCs of this world, and the original metal-case ATC SCM20A probably comes closest in both concept and price.

Published August 2009

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