Mirage M-1 Floor standing speakers
Although it bears a striking resemblance to the extraterrestrial monoliths in Stanley Kubrick's film 2001: A Space Odyssey, the Mirage M-1 loudspeaker has arrived from a bit closer to home: Ontario, Canada. Despite its unusual appearance-and sound quality - the M-1 is a rather conventional vented system using dynamic drivers.
The system's uniqueness originates from the two complete sets of drivers contained in each enclosure, one set of three (woofer, midrange, and tweeter) on the front and an identical set on the back. All the drivers, which are designed and manufactured by Mirage, are aligned vertically and are slightly offset from the center of their baffles. The speakers are therefore sold in mirror-image pairs; Kubrick's monoliths came one at a time.
The M-1 tweeters are magnetic-fluid-cooled 3/4-inch hyperbolic dome units with diaphragms made of pressure-treated cotton that is, as a preliminary product brochure says in a phrase reminiscent of the famous Monty Python crunchy-frog skit, "handcoated several times with a damping compound to bring it to the ideal mass and density." Seriously, this treatment is meant "to eliminate resonant peaks and breakup problems that would otherwise translate into distortion."
A mineral-filled polypropylene material is used in the 4-1/2-inch midrange drivers. These are located in a sealed enclosure within the larger cabinet to isolate them from the woofers. The midrange subenclosure is shaped to reduce possible colorations caused by internal cabinet resonances. The woofers are 8-inch mineral-filled polypropylene cone units with 1-1/2-inch dual-layer voice coils. Each woofer in an M-1 cabinet is housed in its own subenclosure, but both are served by a single port (located near the bottom of the back panel).
The M-1 crossover is said to be a 19-element unit employing high-quality components and 12-gauge oxygen-free copper wire. Crossover points are 300 Hz and 2.3 kHz. However, the front and rear woofers have been given slightly different rolloff points to avoid any mutual-interference effects. Crossover slopes are first order for the rear woofer, second order for the front woofer (which also has the higher rolloff point), second order for the midrange drivers, and fourth order between the midrange and tweeter units. Mirage says the crossover design produces time alignment of the drivers.
To reduce unwanted cabinet vibration, the high-gloss, black-finished speaker has very thick (1-1/4-inch) wooden front and rear panels. Extensive bracing is used throughout the cabinet interior: Each woofer assembly is braced to the panel opposite the one it is mounted in; the subenclosure for the midrange (which itself braces the front and rear panels) has an internal brace; while a final support divides the woofer compartment so as to eliminate all parallel surfaces. Although I think that the M-1's extraordinarily unboxy sound quality stems from other sources, the heavy construction and all the internal buttressing cannot hurt-unless, of course, one of the 185-pound cabinets happens to tip over on you.
The stretch grille cloth is not removable, so I was not able to verify that the bass-driver and port recesses have rounded edges to reduce diffraction, as the company says. All the cabinet edges, however, are definitely rounded. Connections are made to a set of multiway binding posts located on the rear side of the small base on which the enclosure stands.
The double-driver complement and the shape of the M-1's enclosure are intended to give much of the sound quality of a flat-panel speaker, without the problems common to such devices. Accordingly, Mirage calls the M-1 a bipolar speaker, meaning that it radiates sound equally from front and back and that the rear-directed radiation is in phase with that from the front. In contrast, a dipole loudspeaker-such as an electrostatic or other flat-panel design-also radiates equally in two directions, but has a "back wave" that is out of phase with the front-panel radiation.
Dipole operation has two distinctive characteristics, both resulting from the partial or complete cancellation of the front wave by the back wave. First, throughout much of the audio range, the speaker's overall radiation pattern has a figure-8 shape, with comparatively little sound radiated at 90 degrees off-axis (theoretically, there should be no side radiation at all). Second, at low frequencies, the front and back waves tend to cancel each other completely, so that the low-frequency response is attenuated, sometimes to the point where a dipole requires a supplementary bass driver of conventional design. Neither of these characteristics applies to the M-1. Because the front and back radiation are in phase, the radiation pattern of the Mirage is approximately omnidirectional. Furthermore, the M-1's low-frequency output doesn't cancel itself.
Diversified Science Laboratories found the speaker's on-axis frequency response to be unusually extended. Ignoring the floor-reflection dip at 300 Hz (which is common to nearly all our speaker tests), the on-axis response shown can be described as extending from a very deep 32 Hz up to about 18 kHz, ±2-1/2 dB. Between 20 and 25 Hz, response is only about 10 dB down from the average upper-midrange level, and this was measured with the speaker 38 inches from the wall behind it-a location that would produce a very rolled-off bass response with most speakers. Also notable is the lack of a hump or rise in the response at midbass frequencies (between, say, 50 and 200 Hz), which makes many other speakers sound muddy or bass heavy. Off-axis, the response is about equally flat, with no discernible treble rolloff caused by "beaming" and with a curve that follows the smoothness of the on-axis response quite closely from about 1 kHz on up, even to the depth and location of the slight dip at around 3 kHz.
Distortion for the M-1 was consistently on the low side, remaining below 1 percent throughout the audio band at the 85-dB sound-pressure level (SPL). At 90 dB SPL, distortion was less than 1-3/4 percent below 160 Hz and less than 1 percent above that frequency. Even up through the 100-dB-SPL test, distortion was only 3 percent at 31 Hz and usually less than 1 percent above 250 Hz. At that high level, however, midbass distortion was up at around 7-1/2 percent at 63 Hz and averaged around 3 percent between 80 and 160 Hz. This is still very good performance, considering the ability of the speaker to reach lower frequencies very cleanly.
Much of this low-frequency ability results from a direct tradeoff with speaker efficiency: At 85 dB SPL for a 1-watt input, the M-1's sensitivity is rather low compared to that of typical front-radiating vented systems. It can, on the other hand, withstand quite a bit of amplifier power, and accepted the full 27.9-dBW (613-watt) peak output of the test amplifier in DSL's 300-Hz pulse test, thereby producing a calculated 113-dB sound level at 1 meter. Mirage recommends the use of amplifiers rated from 200 to 400 watts (23 to 26 dBW) per channel, but I was able to cleanly drive the M-1s as loud as I wanted with a 50-watt (17-dBW) amplifier, albeit one with 7.5 dB of dynamic headroom, which enabled it to put out a hefty 280 watts (24.5 dBW) on peaks. The M-1 should be an easy load for any competent amplifier to drive, with a minimum impedance of 5.2 ohms reached at 20 kHz and a maximum figure of 15.8 ohms at 40 Hz. DSL arrived at an average impedance for the M-1 of a little more than 8 ohms. Mirage's ratings are 6 ohms nominal, 4 ohms minimum- which strikes me as a little conservative.
DSL's lab results show a speaker of unusually good performance. However, since I had conducted my listening before I saw the test data, the measurements merely confirmed what I already knew. From listening to a very wide variety of vocal and instrumental selections, I found the M-1's overall sound quality extremely well balanced, quite neutral, and very extended at the bottom end. Pipe-organ pedal notes in the 20-Hz region that I had observed on 1/3-octave spectrum-analyzer displays, but had despaired of ever hearing, came through clearly. Pitches this low are more felt than heard, arid the M-1s provided that sensation. One might think that a speaker capable of reproducing such low notes would have an overly prominent bass in more conventional program material, but such was not the case with the M-1. The relative flatness of the response throughout the bass merely reinforced the impression of sonic neutrality produced by the flatness of the rest of the frequency range.
At higher frequencies that impression remained, orchestral strings sounding especially realistic. In certain brass-instrument passages and in a few recordings of female vocalists I detected a slight coloration, possibly due to the dip in response at 3 kHz. But at the same time the rest of the frequency range was being reproduced so well that whatever that slight effect was from, it was easily ignored in favor of the excellent overall sound quality, abetted by the speakers' most easily heard trait: their imaging.
What DSL's test results do not indicate-and, indeed, what no lab measurements presently made anywhere can show directly-is the sonic image conveyed by the M-1s. And that can be described in a word that comes right out of Kubrick's movie title: space. As the product brochure puts it, "… the speakers just seem to disappear." With some classical program material, a sonic stage of such convincing and realistic depth is produced that you might think an ambience-recovery/generation system were operating. Large orchestras sounded especially good. An outstanding, close-miked classical piano recording (Beethoven sonatas on Denon CO-2203) almost had me believing that the instrument was in the room. The sonic stages for various types of pop music also floated free of the speakers to produce some interesting and very pleasant effects.
Much of this "disembodied" sound quality is common to speakers that project much of their sound away from the listener. But rarely are those types that I have heard so uncolored in their perceived frequency balance, as adept at playing loudly without a sense of strain, and as capable of reproducing low bass information so cleanly as the M-1.
As far as I can hear, the M-1 has only three sonic drawbacks, none of them very serious. First, the tweeter, being about 4-1/2 feet above the floor, is above the ear level of a seated listener; even the front-panel woofer is 2-3/4 feet off the ground. The basic stereo image, therefore, is elevated, and for some types of music and recordings this is simply unrealistic, as is the slight change in image elevation as some instruments change musical registers. Second, the stereo image itself is not as razor-sharp as I have lately been hearing from some conventional front-radiating speakers. Then again, this slight image fuzziness is also typical of omnidirectional and quasi-omnidirec-tional loudspeakers. The M-1 compensates for image imprecision with image solidity and maintains a properly distributed sonic stage even as you move around the room. Besides, I find the present-day mania over pinpoint imaging itself a bit unrealistic: Most live music doesn't present nearly so precise a soundstage.
The third and last sonic drawback to the M-1 is its sensitivity to room placement. I have been lucky to audition the M-1 in two rather different sonic environments, and both times the sound has struck me as I describe it above. But a proper frequency balance in your listening room may take a little experimentation (which the M-1 manual encourages). In the listening room I found that the speakers really should be at least 3 feet from the wall behind them to prevent undue bass emphasis by the room and to achieve a pleasant sense of spaciousness in the sound. Mirage suggests placing the speakers 3 feet from the back and side walls, 6 to 8 feet apart, and possibly angling the speakers inward to tighten the central image. With these kinds of recommendations, and from the sheer size of the speakers, you can see that the M-1s are not ideal, say, for a college-dorm-size room. At this price level, you are fully justified in asking your dealer for permission to try out a pair of M-1s in your listening room.
Well placed, and in a large enough room, the Mirage M-1 will provide a spacious yet well-defined sound reminiscent of dipole speakers at their best. Yet, unlike many dipole models, the M-1 will generate large amounts of sound, will reproduce very low frequency material without added subwoofers, and will reproduce a very wide range of musical material cleanly and with very little coloration. What more can one ask of a speaker?
