Mirage M-1090i Floor standing speakers
Mirage is the company that first popularized the concept of "bipolar" loudspeakers, which use identical sets of drivers, driven in phase with each other, on the front and rear of the cabinet. The Canadian manufacturer has recently enlarged its family of bipolar speakers with the introduction of three handsomely styled, moderately priced systems.
Heading the group is the M-1090i, a columnar speaker covered on all four sides by a black elastic cloth "sock" grille. The top and bottom surfaces are wood, finished in glossy piano-black lacquer. The "footprint" of each speaker is remarkably small - less than a square foot. The basic driver configuration consists of a 6.5-inch molded polypropylene cone with a butyl-rub-ber surround and a 1-inch vapor-deposited titanium dome tweeter, both located at the top of the speaker, one set on the front panel, another on the back. A bass vent is near the bottom of the rear panel. The speaker's recessed input connectors, just below the vent, are two pairs of gold-plated binding posts joined by jumper strips. They are compatible with bare wires, lugs, or banana plugs (single or dual). With the jumpers removed, the system can be bi-wired or bi-amplified.
Like other bipolar speakers, the M-1090i is designed to produce a nearly omnidirectional pattern of coverage in the horizontal plane, with slightly reduced output to the sides (but much more than one would get from a dipole speaker, such as a panel model, whose front and back outputs are out of phase with each other). For best performance, a bipolar speaker should be freestanding, placed at least 18 inches in front of a wall and well away from the side walls (Mirage also recommends using spiked feet if the speakers are to be installed on a carpeted floor). A properly designed and installed bipolar loudspeaker system can create a distinctive sense of space that is a hallmark of the genre, resulting from the slightly delayed reflections from the wall behind it.
Mirage's specifications for the M-1090i include a frequency response of 32 Hz to 22 kHz +/-3 dB, both on-axis and 30 degrees off-axis, with "usable bass response" (-10 dB) down to 28 Hz. The system's sensitivity is given as 85 dB sound-pressure level at 1 meter (anechoic) or 89 dB in a normal room. (Since the anechoic measurement effectively applies to the output from only one set of drivers, it would be expected to be about 3 dB lower than a room measurement, which would include the outputs of both sets.) The rated nominal system impedance is 6 ohms, with a minimum of 4 ohms. Recommended amplifier power is from 50 to 175 watts per channel.
We installed the Mirage M-1090i speakers roughly as recommended, although circumstances required them to be several feet in front of the wall behind them (which did not degrade their performance in any way we could detect). The averaged room response of the two speakers indicated exceptionally good bass extension, with the normal response irregularities of a room environment. From about 300 Hz on up, the output was very smooth, sloping gently downward with increasing frequency. The overall change in response from 300 Hz to 20 kHz was about 6 dB.
We measured the front woofer response with close microphone spacing. It was flat within +/-3 dB from 20 Hz to 1 kHz, sloping downward above 2 kHz. The woofer and room-response curves overlapped over a range of almost three octaves, from below 300 Hz to just over 2 kHz (apparently the crossover frequency to the tweeter). Combining the two responses yielded a composite curve that was flat within +/-3 dB from 20 to 800 Hz, sloping down smoothly by about 5 dB from there to 12 kHz and rising again by about 6 dB at what appeared to be the tweeter resonance in the vicinity of 15 kHz.
Since these measurements, though consistent with each other and with what we heard, were inevitably influenced by the room environment (as they would be, though perhaps differently, in your listening room), we were interested to see the results of quasi-anechoic measurements using the MLS capability of our Audio Precision System One test system. At 1 meter, on the front tweeter axis, the MLS response decreased above 2 kHz to about -5 dB at 6 to 7 kHz, rising to its original reading at the tweeter resonance peak (13.7 kHz). We measured virtually identical response at 2 meters as well.
The tweeter's horizontal dispersion was typical of 1-inch metal domes, with little change in output, relative to the axial response, below 10 kHz and about a 14-dB drop at 20 kHz at 45 degrees off-axis. Group delay, which is a function of phase linearity, was very uniform from 2 to 20 kHz (less than 150 microseconds variation overall) and clearly showed that the transition from woofer to tweeter was at 2 kHz.
System impedance was essentially as rated, with a minimum of 4.3 ohms at 180 Hz, a bass rise to 13.5 ohms at 63 Hz, and readings in the 6- to 10-ohm range at most frequencies above 500 Hz. Sensitivity measured 86 dB sound-pressure level (SPL) at 1 meter with a 2.83-volt input of random noise.
We measured the woofer distortion as a function of frequency, with an input of 4.3 volts (corresponding to a 90-dB SPL output). It ranged from 0.3 to 0.6 percent between 100 Hz and 2 kHz, rising to 2 percent at 70 Hz and 7 percent at 30 Hz. In single-cycle pulse power-handling tests, the woofers bottomed at 600 watts input to the speaker's 6-ohm impedance at 100 Hz. At higher frequencies our power amplifier clipped before there was any significant audible sign of distress from the drivers.
Our listening experience with the M-1090i was totally positive and consistent with the test data. It had the believable imaging and airy quality characteristic of good bipolar reproducers, plus a sweet, musical quality that audibly confirmed the smoothness of our measurements. It came as a pleasant surprise to find that the low bass was as audible as it was measurable. Playing test CD's, we established that while 17 Hz and 20 Hz sounded pretty much alike (obviously low in frequency but with enough harmonic content to dilute the effect considerably), 31.5 Hz filled the room with clean, ear-pop-ping bass - a surprising achievement for the modest driver complement (and size) of the pair of M-1090i speakers.
Our final assessment of these speakers was completely favorable. If we had not already been convinced of the advantages of bipolar speakers, this experience would have converted us. At any rate, if you are in the market for new speakers (and are not committed to placing them close to the wall), listen to these, or others of similar design, before making a final choice. You won't regret it.
