The Caliper, which inspired a brand of alcohol free lager, is the baby Apogee, the smallest model from the only known manufacturer of full range ribbon loudspeakers. Small, of course, is a relative term. The Calipers stand over 1.2 metres high and about 70cm wide - and weigh 35kg each. My arms and back can testify to the practical difficulties of schlepping them into and out of my listening room.
The Caliper has two planar drivers; a large trapezoidal bass ribbon and a thin suspended treble ribbon which are the full length strips positioned on the inside edge of the speakers. The speaker is fronted only by a thin, stocking-like netting, and is therefore extremely fragile, which the author has had cause to discover the hard way.
The frame to which everything is mounted clearly plays an important role in panel speakers. The Caliper has a complex and heavy wood and steel frame, and whilst there's some flexibility in the structure, it's significantly less than with any of the other planar speaker known to the author.
The Caliper is propped in a near upright position (a plumb line is provided to get the lean angle right) by an adjustable foot attached to an outrigger at the rear. As with many US loudspeaker designs, there's no provision for spiking and, from what I can tell, not much thought has been given to the question of physical support. The Caliper sounds considerably better completely upright, and better still a few inches above ground level.
Lab Report
Though not fully tested anechoically, evidence indicates that the Caliper has a deep, extended bass (there's useful output well below 50Hz) and that the response shape is surprisingly smooth (when set up properly see later) throughout, albeit with a mild tendency to favour the bass.
Treble output is a little down on the most favourable axis. The other relevant factor is that the Caliper is not easy to drive. Impedance is very low and sensitivity even lower, though the figure-of-eight radiation pattern gives the speaker a good 'throw' in large rooms. The Caliper is a nominal 3ohm load, and reactive too, which combined with ultralow sensitivity makes it something of a graveyard for amplifiers lacking very healthy current as well as voltage delivery.
Sound Quality
The Caliper ain't your normal bag of potatoes. It requires care, attention, has very expensive tastes in amplifiers - and when that's all taken care of, it needs even more care and attention. Altogether you could call this a prima donna among loudspeakers, but we'd be forgetting the bigger and even fussier (by virtues of their extra bass extension) models in the range.
The load sensitivity is beyond dispute. I have used an old series Krell KSA-50 power amp with the Caliper for some time and, although it works, the combination is almost subliminally uncomfortable, The idea that this is an Apogee suitable for use with receivers, which was an idea prevalent at the launch, begs the question, 'What kind of receivers are we talking about and which planet are they made on?' The Caliper really is both inefficient and hard to drive, The Musical Fidelity A370, on the other hand, turned out to be ideal.
Positioning must be approached in a thorough and painstaking way. Simply by varying the distance from the speaker to the wall behind in steps of, say, 10cm or so, the bass can be made to sound bloated and uneven, or correctly focused and integrated. As already said, the Caliper does tend to sound a little obvious in the bass, however, the real surprise is how deep and potent the bass is, and the level that can be sustained before the excursion limited diaphragms run out of room. (No harm appears to be sustained as a result of occasional overload.) Some surprisingly deep organ pedal stops can be reproduced without obvious doubling, and the Caliper's ability to move air barely stops short of producing an output that can be felt as well as heard.
But we need to look further to find tire real reason for shelling out £2.5K for a pair of Calipers. On audition, bass quality was remarkable for a panel loudspeaker, but less so for a box speaker except in one detail - the free-breathing, open way bass was delivered.
No, it is the sheer musical competence of the mid and top that really marks the Caliper out. and than cannot be readily duplicated by conventional box speakers. The Caliper is totally seamless through this region, and capable of a rare combination of fluidity, resolution and - positiveness. The freedom from the usual box-type 'cuppy' mid-band colorations, hardness and/or hollowness was expected, the natural, subtle ease of the sound wasn't, or at least not altogether. The most likeable quality perhaps is the individuality and presence of individual instruments which in the Caliper is combined with an otherwise unobtrusive quality bordering on gentleness when confronted by tape hiss or record surface noise.
One problem with Calipers is that they're a bit like enormous headphones. They're definitely 'hot seat' designs. Imaging is best for one or, at most, two people, and those listening well off-axis hear a rather syrupy and distant sounding mix. Like other panel designs, image scale can be disconcertingly large and forward, but with good recordings individual instruments are well separated and have very specific, localised imagery.
Those used to normal box speakers, which most of us are, may find the soundstage disconcertingly big at first, but it's also very outgoing, inviting, and is easy to adapt to. The baby Apogee has a marvelously natural sense of dynamics. Resolution is also of a high order, but there is a slight veiling which is partly associated with a reticence bordering on slowness' at the high frequency extreme. A little rejigging here wouldn't hurt, but this isn't a make or break matter.
Conclusions
Antisocial yes, expensive certainly, but the Apogee Caliper offers a touch of real magic, allied to a sometimes excessive bass and a slightly dull treble, Probably the equal of the bigger Apogees in most respects apart from the reduced bass extension and maximum output level, the Caliper is recommended subject to the various caveats discussed in the review.
Reviewed by Alvin Gold
Rating Recommended
Hi-Fi
CHOICE JULY 1988