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APOGEE

STAGE STARS

'Oh tie a silver ribbon around the old oak tree.' Well, mahogany frame really, in the case of the latest ribbon speakers from Apogee, the £2350 Stages. Alvin Gold, proud owner of the earlier Apogee Calipers finds that these smaller versions sound even sweeter

Apogee loudspeakers have always turned heads. Their bluff appearance - rather like squashed, upended coffins (some have even assumed they are room dividers) - is guaranteed to get some reaction.

Apogees are all baffle, all face, and their almost art deco appearance means that they are not of the shy, retiring school of hi-fi that many prefer. Apogees generally need a lot of explaining to visitors. However, puzzlement quickly turns to astonishment followed by delight as the speakers are fired up and music issues forth, for all the world as though the players were sitting in the same room. Apogee's ribbon speakers have this uncannily lifelike quality.

That at least has been my experience. I have been happy to sacrifice my view of the street through the listening room window for the sake of, well, art I suppose, but it remains a sacrifice, as is the high capital cost of buying a pair and feeding them in the style to which they aspire. The Stage requires fewer sacrifices than previous Apogees. For a start, it's shorter than the other models in the range, so my view of the outside world is restored. And at £2,350 it's also less of a burden on the pocket.

In case you don't know, Apogee is one of the comparatively few extant makers of ribbon loudspeakers. In a typical ribbon drive unit, the ribbon actually a strip of aluminum foil - is suspended between the poles of a magnet, bathed in its magnetic field. The audio signal is applied along the length of the ribbon, the current flow producing a magnetic field of its own, modulated by the changing music signal. It is the interaction of the two magnetic fields that causes the ribbon to vibrate in response to the signal.

It is the lightness of the ribbon that has given this sort of speaker its credibility. Transient and frequency response tends to be up in the gods (who or whatever they are), and this, as much as any other factor, gives ribbons their very special speed and transparency. But ribbons are not without their fair share of problems. For instance, their very low impedance means that impedance matching transformers are required. And since practical ribbons are fragile, output level is restricted, necessitating horn loading to improve sensitivity. In short they're a real pain to drive to high listening levels.

The Apogee full range ribbon is a very different kind of animal, one that shares only its basic modus operandi with the foregoing - not its geometry or materials. At first sight, the bass driver appears to consist of a large sheet of aluminium, stretched side to side across a trapezoidal frame. But the aluminium isn't just a foil section. If it were, the structure would collapse or tear itself to shreds the first time it was played.

In previous Apogee designs, the foil was bonded to one surface of a plastic sheet to provide the necessary dimensional stability. For the Stage, however, Apogee his gone a stage further (sorry) by using two layers of aluminium film sandwiching the plastic sheet diaphragm. This improves sensitivity, which should enable a smaller amplifier to cope. This was a primary design goal.

Closer examination shows that the diaphragm isn't a single continuous sheet. It is cut into zigzags, forcing the current to weave its way from side to side as it traverses the ribbon. A matrix of ceramic bar magnets is fastened to a metal backplate, the perforations allowing sound radiation from the back of the diaphragm to spill through.

Again, however, there's a difference to Apogee previous practice. Other Apogees use straight cuts in the diaphragm, but the Stage uses a sine pattern cut, which according to Apogee, turns out to be an effective means of reducing distortion. The shape breaks up the regularity of the ribbon strips, and this must help by inhibiting standing waveforms on the diaphragm.

The tweeter is made in much the same way, except that it is a single, thin strip, once again consisting of a double layer of foil with a plastic substrate to add mechanical strength and stability. The tweeter is oriented vertically along the inner edge of the speakers (the Apogees are supplied in mirror image pairs) which means that lateral dispersion is good. The spread of sound means, in theory, that the speaker should provide good stereo over a broad area.

Ribbons have other distinctive properties too. A ribbon can be regarded as a traditional moving coil loudspeaker laid flat. All the working bits are exposed directly to the air, and the whole diaphragm is in good thermal equilibrium because aluminium is an excellent conductor. Heat build-up in the voice coil is a prime (though poorly recognised) cause of compression in traditional drive units. Ribbons are largely free of compression from this mechanism. Next, as the drive unit area is large, diaphragm excursion is very low, and this reduces harmonic distortion products, primarily second and third order. Finally, ribbons like electrostatic diaphragms are 'direct coupled' units; the driven part being responsible for energising the air. In a moving coil unit, the motor is quite separate from the diaphragm, which is why different drive units sound so distinctive. Their inherent resonance is more difficult to control.

The Stage, Apogee's best speaker to date, is a full range transducer. It routinely produces bass output that can be felt as well as heard. It is a remarkable performer, going like a train and stopping on a penny when necessary

The transparency of large area ribbons makes them unsuitable for mounting in an enclosed box - you'd hear the internal colorations - and an open baffle is therefore de rigueur. Like almost all flat panels except Quad Electrostatics (which use electrical delay lines to modify their behaviour), the Stage has a classic figure-of-eight radiation pattern. The high level of back radiation must be dispersed into free air, which demands a meter or more for free air behind the system. The benefit is that interaction with side walls is very low, and the unit 'throws' sound well. At short listening ranges - a couple of meters or less sensitivity is subjectively below average, but it appears higher at greater ranges.

The crossover plays a part in all this too. The bass driver rolls out of the picture from about 600Hz, with a slow first order (6dB/octave) slope at first, increasing to a higher order later. The tweeter leg of the crossover is handled in the same way. Thus much of the midrange as well as the treble is handled by the much lighter treble ribbon. The gentle nature of the electrical network near the crossover point reflects in a gentle phase response too, so that listening to one side of the stereo hot seat is not rewarded by the phasiness that afflicts most speakers with high order slopes. The crossover is also so designed that the speakers snap into focus at normal listening distances with no (or negligible) angling of the speaker towards the listener. The relatively compact size of the driver panels also helps to improve dispersion and uniformity in the lower midband, but I have to say that I found the Stage to be, like its predecessors, to some extent a 'sweet spot' design. The soundstage does drift out of focus, and coloration levels do increase away from the centre line between the speakers, and if you don't 'toe-in' the left and right speakers, the image centre drifts quickly across to the side where you're sitting. Vertical dispersion is almost nonexistent. Stand up while you're listening and the sound recedes a thousand miles. But tilting the panels back can control this.

The physical build and aesthetics of the Stage follow established practice. The panel itself is a complex, composite construction consisting of frameworks for the drivers with facings applied to each side (mahogany or silver) for aesthetics and protection.

The drive units are protected by a layer of material with a very open weave which is held under considerable tension to help prevent impact damage to the drive unit, which would mean sudden (and expensive) death. The rear of the bass panel is protected by the perforated metal frame, which supports the magnet array.

There are no sharp edges on the front of the Stage, a move that restricts unwanted refraction, and finish is to a high standard being based on textured anthracite or taupe major panels with wood side cheeks. White piano lacquer is available for an extra £400. The feet take the form of ingeniously designed spiked aluminium frames. They lift the speakers a few centimetres clear of the floor and have a built-in adjustment for lean angle. They don't provide ideal support but they're better than past Apogee designs.

System impedance is three ohms, so it's important to choose an amplifier, which can cope with this type of load. At least the speaker's reactance is said to be very low. Even so, the Stage turned out to be too much for one amplifier on test. But most of the amps I tried did work well. A Threshold SA/4 Class A power amp did the honours for much of the critical listening.

Setting up is simply a matter of positioning and plugging in - I used bi-wired DNM and Mission solid core cables. A switch on the crossover cover can be used to increase or reduce tweeter level. The switch simply controls a 1.5ohm resistor, and in practice it's best to leave this set to 'high' (i.e. with the resistor out of circuit) unless the room is very bright.

As well as being unique in its advocacy of ribbons, Apogee is among the select handful of producers of full range panel loudspeakers, their most prominent competitors being Quad, Magneplanar and Martin Logan. I note from my records that when the next model up the Apogee range - the Caliper - was released in 1987, it cost just £2,500. The ravages of inflation (and other ravages too, I should think) have now taken the Caliper to £3,150 in its improved Signature form. The Stage knocks about 25 per cent off that figure to arrive at the new selling price of £2,350. To give some sense of perspective to this figure, which I confess must remain pie in the sky to most mere mortals with Poll Tax to pay, the Quad ESL-63, a speaker with much lower ambitions, costs £1,690, the grossly inferior Magneplanar MG2.5 costs £2,000 and the brilliant but sometimes edgy and fat sounding Martin Logan CLS II costs a staggering £4,000. The Martin Logan Sequel II is a closer price match to the Apogee at £2,650, but this hybrid dynamic electrostatic has one significant flaw. I've never been able to get it to work. The Stage does work, and how! I wouldn't like it thought that I've come to snap judgments about this speaker. I had the Stage for about three weeks, and have spent a good deal of that time putting them to good use. But I knew the very instant I put them on that I was in love. It has always been that way with Apogees in the past too, but I confess to a mildly unexpected shock followed instantaneously by a thrill of pleasure as I realised before the first note had faded that the Stage was more than just another routinely good speaker.

Apogee have largely resisted the temptation to boost the bass where it begins to fall off naturally as a result of waveform cancellation as sound spills around the baffle. As a result, the bass isn't as deep as some.

The Stage also proved adept at reproducing the subtle LF information on purist recordings like the Cowboy junkies Trinity Sessions, rendering the soundstage solid and the sense of physical presence all but corporeal. Time after time, the Stage repeated this trick, only being caught out by the odd near-DC pulse when something like a kettle drum for example, is hit hard, sucking in the area for yards around. Bottoming the speaker isn't recommended, though no damage appears to result.

The real joy of the Stage, however, isn't the bass, but its supremely clear, uncluttered and uncoloured midband and treble. There is no hint of any discontinuity indicating a crossover point. And like all Apogees, the Stage is utterly seamless and completely without spite or edge. String tone is as good as the recording will allow; the speaker itself responds faithfully to the smallest nuance, but has little character of its own.

Compared with other Apogees, the stereo soundstage is more naturally distanced when the speaker is optimally positioned (which can take a great deal of experiment to achieve), but it Is as beautifully layered as always, and lateral positioning is specific and stable. In addition, however, the Stage is a remarkably lively performer.

The Stage is, in a word, gorgeous. In almost every respect I can name, it is the best Apogee yet. I'd go so far as to say that if you happen to have a spare £2,350 knocking about in your pocket, you owe it to yourself to buy a pair.

Reviewed by Alvin Gold, reprinted from Audiophile July 1990

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