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Tannoy Ellipse

Active Nearfield Monitor
By Hugh Robjohns

A striking monitor from Tannoy couples a revitalised dual-concentric driver design with a new Supertweeter, providing increased resolution for 24-bit/96kHz playback.

Tannoy has had a long association with dual-concentric loudspeakers, with patents dating back to 1947. The argument supporting the design cites the single-point sound source for all frequencies, with claimed benefits for more accurate stereo imaging. Needless to say, the arguments are rather more complex than this simplistic description, and the concept has a few inherent foibles, but the arrangement certainly has its devotees.

Tannoy Ellipse near field monitors.Photo: Mike CameronThe company's new Ellipse monitors build upon the dual-concentric tradition, but have been designed to complement the current fashion for wide-bandwidth recording by combining a dual-concentric bass/treble driver with a Supertweeter providing the vital top octave. The Ellipse is so named because of its rather unusual elliptical, ported cabinet design, which carries the Supertweeter in a separate pod fixed to the top of the main cabinet.

Driver Technology

The dual-concentric driver will look familiar to fans of the marque and appears very similar to that employed in Tannoy's 600-series monitors. The outer 165mm polypropylene bass/mid-range driver is used to span the lower six octaves of the audio bandwidth, while a physically independent treble driver, with its own motor and magnet assembly mounted concentrically with that of the bass/mid-range driver, covers the next 3.5 octaves up to 14kHz.

Tannoy Ellipse £1800
pros
  • Very accurate, stable stereo imaging.
  • Fast, precise transient response.
  • Flexible response tuning and level matching.
  • Optional port plugs to change the system character at low frequencies.
  • Styling.
  • Can replay recordings of 'silent' dog whistles!
cons
  • Can tend towards sounding hard.
  • Some mid-range confusion can occur in busy mixes.
summary
An attractive and substantial active nearfield monitor employing Tannoy's unique dual-concentric driver technology with a separate Supertweeter to extend the response to 50kHz. Generous amplifier power ensures natural dynamics, and sophisticated analogue signal processing guarantees accurate time alignment and a linear response.

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As with other dual-concentric designs, the central treble driver interfaces to the outside world through a hyperbolic short horn, referred to as a Tulip Waveguide. The proximity of the bass/mid-range cone to the treble driver acts to extend the effective length and flaring of the horn, which improves upon the efficiency of the design and helps to provide greater headroom at high frequencies.

So much for the traditional Tannoy dual-concentric drivers — what of the Supertweeter? The concept is not a new one; other manufacturers have adopted similar approaches in the past, although not always achieving such an extreme bandwidth. In this case, though, the tweeter was specifically developed for the purpose, and uses a metal dome fabricated from aluminium alloy and carbon fibre, driven by a coil within a rare-earth magnet assembly. The unit takes over from around 14kHz via a fourth-order Gaussian high-pass filter, and is claimed to provide a useful output to 50kHz. The Supertweeter is mounted in such a position relative to the dual-concentric driver that time-alignment is maintained in the horizontal plane.

All of the drivers are magnetically compensated, so these Ellipse speakers can be placed close to VDU monitors or moving coil meters without too much concern — although the handbook warns of some stray magnetic field escaping from the front of the drivers. This won't be a problem in regard to VDU monitors, since it is highly unlikely anyone would be daft enough to put such a thing in front of the loudspeaker! However, if the speakers are mounted on stands close behind a sound desk, it is just possible that there may be some magnetic influence over moving-coil meters.

Cutting Corners?

The 12-litre cabinet design is certainly a rather unusual shape, but is all the more attractive for it and is finished in a grey 'suede' paint. It is also rather large and bulky, measuring 210 x 340 x 260mm (hwd) and weighing 15kg. Not too dissimilar from the more traditional 600-series cabinet dimensions, in fact. A further unusual design element is the rear-panel heat sink, which looks more like a hairbrush!

The elliptical cabinet shape brings several practical advantages — the most obvious being the removal of flat side panels, which tend to resonate and vibrate in simple rectangular designs, as well as helping to create internal standing waves. The curvaceous shape of the Ellipse also reduces significantly the problem of high-frequency diffraction. The corners of conventional rectangular cabinets can act as secondary sound sources by serving as a diffraction point for high frequencies, unless they are carefully rounded. The net result can be a confused stereo image, so the elliptical design used here not only has a rounded baffle edge to minimise diffraction, but also provides a constantly changing distance between the driver and cabinet edges — distributing any diffraction effects across both time and position.

Rear panel.Rear panel.Although the front and rear panels are constructed from substantial panels of MDF — chosen for its suitability for machining — the main cabinet shell is built from laminated birch wood, which is easier to bend into the required shape. The front panel is finished with a brushed aluminium face plate and not only supports the dual-concentric driver, but also a pair of front-facing ports. Much of the rear panel is taken up with the amplifier chassis and its novel heat sink. The electronics are relatively sophisticated, with Tannoy referring to the use of 'analogue signal processing' to optimise the crossover level and phase alignments. The user is also provided with a handy selection of tweaks on the rear panel to help fine-tune the response of the speaker in situ. Apparently, the amplifier module contains no less than 350 discrete surfacemount components and 28 integrated circuits, with each of the three amplifiers carefully tailored to its respective driver to ensure the best dynamic damping.

The base of the Ellipse's cabinet is as unusual as the rest of the design. Clearly, a loudspeaker with an elliptical cabinet would not be stable on a flat surface — the curved underside allows it to rock from side to side! Tannoy have overcome this inherent problem by fitting a circular rubber base which is both a non-slip surface and vibration resistant. This rubber base can also be removed, if required, after which the mounting holes can be conveniently used to fix the speaker to a suitable heavy-duty Omnimount wall bracket.

The single XLR input on the rear panel is balanced, but will accept unbalanced signals if pins one and three are connected together. The rear panel sensitivity control allows a wide range of both professional (+4dBu) and semi-pro (-10dBV) levels to be accommodated, and I had no problems aligning the speaker sensitivity with my own equipment. The input circuitry is also apparently fitted with two-stage RF filtering, so should reject electromagnetic interference, and it seemed to reject the advances of my mobile phone very well.

Following the balanced input section the signal passes through a muting circuit on its way to the crossover. This prevents the thumps when you switch on or off, and also provides protection against certain faults. A simple manual equaliser stage comes next, allowing gentle room tuning with high, mid-range and low frequency trim controls. The high and low controls each span ±3dB, while the mid-range control extends to ±2dB, centred on 1.4kHz. This is more than sufficient to serve the purpose, but there are also more complex, fixed narrow-band EQ circuits which have been designed to correct any response variations of the drivers.

A further degree of 'tweakery' is available for the low-end response — and a physical element rather than an electronic one, too. The two bass reflex ports mounted either side of the dual-concentric driver can be 'bunged' with a pair of supplied soft foam plugs. This has the audible effect of reducing both the amount and the apparent extension of the bass output, but blocking the ports also shifts the cabinet's operating characteristic towards an infinite baffle design, which sharpens the transient response as well.

Foam plugs are provided to alter the bass response by partially blocking the ports.Foam plugs are provided to alter the bass response by partially blocking the ports.The crossovers are based on Rauch filters with additional all-pass sections designed to correct the relative time alignment between drivers. The crossover frequencies are set at 1.7kHz and 14kHz, the former for the dual-concentric treble horn driver, and the latter for the separate Supertweeter.

A front-panel tricolour LED provides information about the status of the system, illuminating red for fault conditions and during the initial power-up phase, green for normal conditions, and yellow when excessive subsonic information is present at the input. Low-frequency information below 20Hz is removed by a sixth-order high-pass filter to protect the LF amplifier and driver unit, but the LED at least warns of potentially problematic mix signals.

A pair of 150W power amps drive the bass/mid-range and treble dual-concentric drivers, with a separate monolithic wide-band 30W module powering the Supertweeter. The difference in power rating is entirely appropriate given the tiny amount of signal energy carried in the top octave to 40kHz. Overall, the amplifier complement is capable of producing peaks of 118dBSPL at one meter from a pair of Ellipse speakers, with less than 0.8 percent distortion. This is more than enough for any nearfield situation, and allows natural source dynamics to be replayed with considerable fidelity.

In Use

The owner's manual for the Ellipse speakers contains some useful information about setting the speakers up, suggesting they are spaced around four feet apart, with the waveguide at the centre of the dual-concentric driver positioned at ear height and angled such that the listener can see the golden diaphragm at its centre. Oddly, there were no diagrams in the manual, despite references to them, so I presume that pre-production manuals were dispatched with the review speakers.

The speakers were easy enough to hook up, needing only an IEC mains power lead and an XLR line-level audio input each. Matching signal levels to either the monitor output of my mixer or the preamp output from my hi-fi was simple enough, although I found the self noise of the onboard amplifiers to be higher than I was expecting. In comparison with my reference system (a Bryston 4B feeding a pair of PMC IB1 three-way monitors) the Ellipse speakers were much noisier when at rest than the quiescent output from my own system.

I started my auditioning with the bungs removed and the controls all set flat, but I soon found myself turning down the HF and mid-range controls just slightly, to tame what initially appeared to be a slight tendency towards brightness (compared to my reference system). Looking through the Owner's Manual, the performance plots included at the back appear to confirm the mild lift towards the high end that I had perceived. The specs quote a 40Hz-50kHz response within ±3dB, which seems realistic — at least for the bottom end. My ears could neither confirm nor deny the presence of ultra high-frequency signals, and the dog was more interested in dreaming of chasing cats than helping me review another pair of speakers! I can say, though, that I could not detect the crossover between the dual-concentric horn and the Supertweeter.

The response plot in the handbook suggested a pronounced dip below 100Hz, followed by a lower-level resonant peak around 50Hz, but I have to say that, when auditioned within my listening room, the overall bass response sounded a lot smoother than the plot would suggest. Experimentation with the foam bungs in and out of the ports soon left me preferring the sound (but not the looks, sadly) with the bungs in place. With the bungs inserted, the LF response needed to be increased slightly with the appropriate rear-panel control, but the Ellipse speakers seemed faster and more detailed this way and with less of the typical reflex-port character — the slightly reduced LF extension seemed a small price to pay. There is an impulse response plot included at the end of the manual, which shows a good initial reaction, followed by a single half-cycle of a low-frequency ring, and a well damped response thereafter. But whether this plot was obtained with or without the bungs is not clear — it would be interesting and informative if Tannoy were prepared to publish both plots.

Stereo imaging was found to be very precise and stable, as might be expected from the dual-concentric design, particularly on simple coincident-pair recordings. The speakers were very 'fast' in their transient response and although the treble range seemed a tad hard to my ears, it was well detailed and natural. The mid-range is well balanced — much like the 600A monitors in character, and certainly far better than some of the old Tannoy dual-concentric designs. However, when the going gets busy, the mid-range can start to sound a little confused and muddled, slightly lacking in definition — but no more than most other speakers at this price.

Obviously, playing normal CDs wouldn't have provided much of a challenge to the Supertweeter. However, I recently upgraded my hi-fi to incorporate a Meridian DVD-A player and I have been building a library of high-resolution discs over recent months. So it was with great enthusiasm that I sat down to audition my small, but perfectly formed, collection of discs, switching the replay mode to access the 24/96 stereo tracks. I certainly enjoyed listening, but, to be perfectly honest, I'm not really convinced there is a significant sonic benefit to having the extra top octave, although I think maybe the stereo imaging seemed a little crisper and deeper on occasions.

It makes sense to use speakers explicitly designed to reproduce super-high frequencies if you are bothering to record them. Most conventional speakers will tend to tail off beyond 25 or 30kHz, whereas the Ellipse is still going strong above 40kHz. Is this a material advantage? I doubt it, but some reading this may have better (certainly younger) ears than I have and be able to perceive more of a benefit. Nevertheless, the Ellipse is well built, elegant, and provides accurate, detailed monitoring regardless of the source material. On those grounds alone it is certainly worth adding to your short list when auditioning new active monitors.

information
infop.gif £1800 per pair including VAT.
infow.gif www.tannoy.com
Published March 2003