You may recognize the Oskar name, since this Swiss company's other model was featured on the cover of UHF No. 57. That speaker was small but well-balanced, and astonishing less for what it has, than for what it doesn't have: a big peak in the upper midrange.
     Most speakers do in fact have one. This isn't because the designers don't know what they're doing, but because the peak is inherent in the usual kind of tweeter. Good designers know how to minimize it, of course.
     And the resonance, bad as it sounds, hides an even worse problem inherent in most tweeters. The voice coil in a typical tweeter is large enough to act as a low-pass filter...it actually blocks the very frequencies it is supposed to reproduce. The resonance appears to "bring up" what would otherwise be a drooping top end by storing high-frequency energy and then re-releasing it (slightly later, of course) to augment what is there. Not good!
     The Heil tweeter used on this speaker, designed many years ago by Dr. Oskar Heil, gets around this problem by using a totally different method of reproducing the highs. We described it in our review of the Oskar Aulos (UHF No. 57). The usual dome or cone is replaced by a large corrugated membrane, driven from its edge, so that its folds move the air. It doesn't require a huge coil, and it can be built so that its resonant frequency is outside the frequency band it needs to reproduce.
     This tweeter shown in the print edition) is much larger than the one on the Aulos, and it can handle an extra octave, operating down to an astonishing 700 Hz! It is inherently bidirectional, and so it sits atop the enclosure rather than in it. It is complemented by a 25 cm woofer which points straight up. The reflex port is on the bottom, and so the wooden feet supplied are not an option. We wish the Kithara came with spikes, as most high end speakers do, but we should add that the woofer, because of its vertical position, will tend to move the speaker up and down rather than forward and back.
     The tweeter itself looks hand-made, and in fact it is. The Kithara looks much better with its two cloth grilles on, and the woodwork is strikingly handsome. We didn't much like the binding posts, which are of so-so quality, and are too close together to be convenient.
     These speakers are both too large and too heavy to go into the superb but small room where our Alpha system is located, and so we did the review in the Omega system, where we had plenty of room to play with. We also have plenty of amplifier power in that room, but the Kitharas, with their 94 dB rating, needed only a fraction of it. Sensitivity figures are notoriously optimistic, but comparisons to speakers of known efficiency seemed to bear this one out.
     We did most of the listening with vinyl, starting with the opening cut from the Opus 3 Test Record 4 (9200), which is different from the selections on the CD version. It's a jazz number called Nobody's Blues But Mine, with a mixture of trumpet, sax, piano, percussion and even a sousaphone. Keeping the timbres of those instruments straight is a task and a half...

Model: Oskar Kithara
Price: C$5500 (equivalent to US$3740)
Dimensions: 40 x 40 x 110 cm
Warranty: 3 years, transferable