My love affair with ribbon drivers dates back to the Kelly tweeters in a speaker system that I had as a student, back in the 1960s. Even now, I suspect the Kellys would provide some of the cleanest treble around, though only within their narrow frequency range and their limited dynamic range. But today's ribbons, reflecting 30 years of evolution, offer smoother frequency response (including full midrange coverage), excellent dynamic range, much better dispersion, and reason able efficiency; they also present relatively normal loads to an amplifier. Ribbons have unique sound qualities and provide a great deal of information and detail in an exceptionally musical, natural form. I am not sure that current ribbons are measurably or audibly "faster" or "cleaner" than the best current dome tweeters. Yet they are certainly competitive with the best domes, and some ribbon drivers have better upper-octave performance than any electrostatic I've heard.
above: Slant 6 is the smaller of the two; the larger is Slant 8.
These qualities are a key reason I use the Apogee Acoustics Studio Grand as one of my reference speakers, and the ribbon in the Slant 6 has many of the same advantages. (Apogee is phasing out the "Centaurus" designation that appears on the Slant 6 I reviewed.) However, the Slant 6's ribbon is not a full-range exotic driver but a 26-inch dipole, crossing over at 1.2 kHz to a 6½-inch cone woofer. This hybrid design offers many of the benefits of a full- range ribbon in a less expensive ($2,500/pair) and much smaller package.
The Slant 6 looks surprisingly small, considering its size (14½ inches wide x 14¼ inches deep x 52½ inches high), because its rounded and slanted shape makes it seem less obtrusive. Further, it weighs only 80 pounds, enough to be solidly built without presenting the weight-lifting challenges posed by full-range rib bon loudspeakers.
The 26-inch ribbon in the Slant 6 may be too small to cover the entire midrange or create the broad, spatially fixed image of a full line source, but it sounds exceptionally clean and coherent. It is smooth and sweet but doesn't sacrifice life or dynamic excitement. As a result, this is a highly competitive speaker in one of the most demanding price ranges in the high end.
The Slant 6 demonstrates that hybrid speakers can deliver a remark ably smooth transition between their cone woofers and their ribbon or electrostatic top-end drivers, which was not the case a mere half decade ago. Today's best hybrids minimize the differences in driver directivity, efficiency, and apparent speed that once made such speakers' crossover points all too audible, and they no longer pose dauntingly complex loads to amplifiers.
The Slant 6's woofer has a large voice coil and heavy magnet, placed in a well-designed, solidly built reflex enclosure that produces no audible port noise. The speaker is easy to bi wire, uses very high-quality speaker connectors, and comes with spikes. A three-position switch enables you to adjust the relative level of the woofer and ribbon, helping to compensate for inevitable interactions between the room and the speaker.
The Slant 6 needs extensive breaking in (I put some 50 hours of music into the speaker before I felt it sounded its best), but this is becoming common and is scarcely a big deal. In spite of rubbish you may hear, breaking-in does not require special CDs or tone generators. Just use FM interstation hiss, or set your CD player to repeat a disc indefinitely while you're at work or out of the room. Moderate volume seems to work fine; there's no reason to annoy yourself or your neighbors.
Do pay close attention to the Slant 6's setup instructions. To get the best imaging and highs, it's critical to adjust the speaker's tilt to optimize its sound at your listening position. (A small mirror is provided to help you get this right.) And pay equal attention to the manual's instructions about placement, spacing, and toe-in-at least as a starting point. The Slant 6 is sensitive to all these factors, perhaps because it is a di pole and has a large radiating area to the rear. I've read ads, articles, and engineering tracts that say dipoles are less sensitive to room effects than other speakers are; all of my practical experience tells me that's not the case.
Speaker placement and room characteristics always have a major impact on a speaker's sound character, and this seems to be especially true of dipoles. Relatively minor changes in the distance between the speaker and the wall behind it often affect the apparent energy and focus of the upper octaves, softening them or making them seem slightly bright; placing a dipole too close to a side wall or piece of furniture can smear or confuse the soundstage. The absorption or reflectivity of the wall behind the speaker can also affect upper-octave energy and the sound stage, as can placing ribbon drivers too close to furniture or a shelf.
To get the very best out of the Slant 6, you have to go beyond the manual and find how far apart the speakers must be to yield the widest soundstage without loss of center fill, imaging quality, and depth. Tweaking the toe-in may not be vital, but the soundstage is so well focused that you'll miss a lot of sonic nuance if you don't take the time to experiment.
It also takes experimentation to find the room placement that simultaneously gives you the best sound from both the Slant 6's ribbon tweeter and its cone woofer. Fortunately, this was significantly easier than with many hybrid speakers I've tried. To some extent, I credit this to the Slant 6's woofer, which appeared to emphasize speed and dynamics over deep bass power. (Its bass rolloff tapered smoothly below 35 or 40 Hz, without rising to an audible peak.) These woofer characteristics not only improved the sonic match between the ribbon and the cone but also made the Slant 6's bass less sensitive to room placement. In three different rooms, I could position the speaker for optimum midrange and treble performance without making major sacrifices in bass.
Even after I played around with room placement, I found the Slant 6's woofer just a bit warm in the mid-bass, upper bass, and lower midrange. Fortunately, this warmth sounded pleasant with many close-miked recordings and was not accompanied by the bass overhang that blurs detail and corn- presses musical pas sages that have lots of deep bass energy. The bass was good, not great. There was a surprising amount of bass energy and de tail, and the low bass was audibly present when required. However, as is common with speakers in this price range, real bass power kicks in only above 45Hz.
The Slant 6 handled percussion transients and dynamics more naturally than most of its competitors and did an equally good job of reproducing bass guitar, synthesizer, piano, and bass viol. Organ notes were well defined, with minimal blurring and little tendency to compress the organ's dynamic range.
I could hear some transition problems in the lower midrange that went beyond a touch of warmth. Although the woofer's sound blended well with the ribbon's, the blend was not as seamless as in some far more expensive hybrids. Because those speakers have larger ribbons or electrostatic panels, their crossover frequencies can be low enough to be nearly unnoticeable. (To make the crossover truly inaudible, it would have to be at 90 Hz or lower.) A lot of the coloration could be minimized by slightly altering toe-in, slightly adjusting the speaker's distance from the wall behind it, and changing the setting of the switch on the speaker's rear.
The Slant 6's ribbon does not cover the entire midrange, as the ribbon of Apogee's Studio Grand ($13,000/pair) does. I found the Slant 6 had a bit too much upper-mid range energy and life above 1 kHz, which sometimes gave it a slightly forward sound stage perspective. To compensate, this speaker offered the exceptional midrange transparency, detail, and speed above 1 kHz of the best ribbons and electrostatics. It had a great deal of upper-octave life and energy, without hardness. There were no significant rough spots. When I moved my head a bit, I heard no sudden shifts in imaging or treble energy. The treble and soundstaging were surprisingly stable over a relatively wide horizontal listening area. You could probably fit two or three listeners into the listening area at reasonable distances.
The Slant 6 had a slight rolloff in the top octave, but this complements most recordings, especially digital recordings. I doubt that even those audiophiles who are used to far more expensive speakers will miss much when listening to the Slant 6, provided their ears are below the top of its ribbon driver. (The Slant 6's upper-octave energy seemed to fall off sharply if I was standing or sitting too high.) The soundstage produced by the Slant 6 was large and open and had lots of depth. At the same time, the image was of natural size and had excellent stability and focus. This speaker was about as good as Apogee's Mini Grand in its ability to reproduce soundstage depth, soundstage width, and ambience. And it did so even with complex classical music recordings, such as the LP of the Drottningholms Barokensemble's Barock (Proprius 7761), which has a very complex mix of tenor voice and strings and a lot of depth and space. One CD passage was especially revealing of the Slant 6's strengths, the seventh and eighth minutes of the Dallas Symphony Orchestra on Shostakovich's Symphony No. 7 (Dorian DOR 90161).
The Slant 6 combined particularly good depth reproduction with good back-to- front imaging. Some speakers tend to do better at left-to-right than front-to-back imaging; others tend to shift instruments away from the center and cluster them near the left and right speakers. The Slant 6 was scarcely perfect in these respects, but its performance was competitive with any thing I have heard in its price range.
The Slant 6 needs an amplifier that produces far more than 50 watts per channel and one that is load-tolerant. I would not recommend using a solid-state amp that doesn't have considerable current as well as voltage capability or a tube amp that has trouble delivering deep-bass power or con trolling woofers.
This speaker is not particularly cable sensitive. Symo cable seemed to work best with the Slant 6, but a variety of Audio- Quest, Discovery, and Wireworld cables performed very well. Goertz cable did less well, and I'd be particularly careful of speaker cables that have trick terminators.
Auditioning the Apogee Acoustics Slant 6 reminded me that very good ribbon drivers are available in very affordable hybrid pack ages. This speaker brought musical pleasure and life to a wide range of recordings, and its trade-offs were always musically natural, regardless of the instruments or voices being reproduced. Its sound was outstanding, in one of the most competitive price ranges in high-end audio.
[by ANTHONY H. CORDESMAN. Orig. publ. in Audio magazine/APRIL 1997 ]
Also see:
Apogee Acoustics Scintilla Loudspeaker (Dec. 1985)
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