Product Review -
Mirage M 1090i Loudspeakers - October, 1995
By Daniel Long
Mirage M 1090i loudspeaker. Bipolar vented radiator, Two 1" vapor deposited titanium dome tweeters, two 6 1/2" polypropylene cone mid-range/low frequency drivers, max power handling 175 watts rms, frequency response 32 Hz - 20 kHz plus or minus 3 dB, sensitivity 85 dB/W/M, nominal impedance 6 Ohms, size 45 3/8"H x 11 1/2"H x 9 1/2"D, Black High Gloss, weight 71 pounds each. $1,200/pair. Mirage Loudspeakers, 3641 McNicoll Avenue, Scarborough, CANADA M1X 1G5, Phone (416) 321-1800, Fax (416) 321-1500.
Although speakers appear rather unassuming in their design (a box with one or more drivers attached), there is a great deal more to them than what most people realize. Granted, most speakers are the ubiquitous front-radiating dynamic transducer variety, but there are also many ribbon and electrostatic speakers, as well as what Mirage is best known for: the bipolar radiator.
What's the difference?
I'll start with a brief description on the various types of speakers. First, the dynamic front radiator. These are the most common type (should I use the term "garden variety"? OK, I'll use it, but the more scientific term is "MONOPOLAR"), completely surrounded with an enclosure usually made of MDF. The drivers are cones, attached to a metal frame, and which move piston-like when activated by the amplified electrical signal (the music). They actually radiate sound forward and backward (below certain frequencies, when the wavelength of the reproduced sound becomes larger than the diameter of the effective radiating cone, this becomes a 360-degree radiator). The back-wave is at least partially absorbed within the enclosure by damping material, such as wool or fiberglass, along with the material of the enclosure itself (usually MDF). Otherwise, the back-wave from some of the frequencies (particularly the low end) would cancel the front. Ports (vents) are found on many enclosures, and contrary to what some users think, the air coming out of a port does not interact with the air moved by the active driver to produce cancellation, but rather, enhances the total production of the sound wave (at least in a properly "tuned" port) of the loudspeaker's low frequencies.
The second type is what is known as a DIPOLE radiator. This can consist of two cone speakers, one mounted on the front of the enclosure, and the other on the back. The two speakers are wired so that when the front driver is moving out of the enclosure, the back driver is moving into the enclosure. Dipoles can also be made from long, thin pieces of metallic (coated) material that are suspended at both ends (or in the case of some, like the Quad's, many individually suspended pieces) and driven by the signal. [Click HERE here to go to description of speaker types in the primer] Sound radiates, again, both backwards and forwards. This time, though, the back-wave is allowed to travel back through a grill (cloth in the case of planar-magnetic speakers, metal in the case of electrostatic speakers) that is acoustically transparent, into the listening room, and this back-wave is 180-degrees out of phase with respect to the front-wave. As a result of this, placement of dipoles is critical if one is to avoid a loss (cancellation between the front and back-waves) of frequencies below 100Hz or so. In fact, if you stand at the side of these speakers, you will be in an area where the front and back-waves are canceling each other at low frequencies, and, thus, dipoles are also called figure 8 radiators.
Mirage first marketed the BIPOLAR design in loudspeakers, and their line includes the M-590i, M-890i, M-1090i, M7-si, M5-si, M3si, and M1-si. Bipolar subwoofers include the BPS-100, BPS-150, BPS-250, and BPSS-210. Mirage also makes other models that are not bipolar (they are of the forward radiating variety). The bipolar radiator has both front and rear waves fired in phase, that is, when the front radiator is moving away from the enclosure, the back radiator is also moving away. This means there is virtually no sound wave cancellation at the sides, compared with dipoles. In practice, the effect one gets (and borne out by listening) is a wider sound-stage with maybe a little less precise imaging than with the best monopolar mini-monitors (I am glad I only had to type this tongue twister instead of having to say it). Dipolar speakers, by the way, also have the less precise imaging, but expanded sound-stage, compared with monopolars. Some users feel that this phenomenon is actually more "natural" than the sound produced by front radiating designs. Was this what I got with the M1090i bipolar speakers? On with the review...
Physically, the 1090is are 45 3/8"(H) x 11 1/2"(W) x 9 1/2" D. This is pretty big, but the cabinet, which consists of a polished black top plate on top and an acoustically transparent sock all around (like all the other bipolar Mirages) make it look very elegant. Fiberglass damping is used to reduce standing waves and to help dissipate heat as well as to promote higher power handling with lower distortion. Another damping material, constructed from wool and man-made fibers, is used to reduce cabinet resonances that are not completely controlled by the MDF structure and internal bracing. The driver complement consists of two 6 1/2" injection molded polypropylene cone woofers and two 1" titanium vapor deposited on cloth dome tweeters (the ones used in the 1090i's larger siblings, the M-1si and M-3si, are solid titanium domes rather than cloth). The tweeters are mounted about 5 1/2" from the top plate, slightly off-center, and the woofers below. One set is on the front, and the second set is mounted behind. A 2 1/2" (diameter) port can be found at the rear, about 9" from the bottom plate. Electrical connection is made with two sets (for bi-wiring or bi-amping) of 5-way binding posts just below the port. These have a plastic nut, so hand-tighten you must!
I put the 1090is where my pair of Magnepan SMGcs normally sit, about 6' apart, and 33" from the back wall. The distances to the side walls are unequal, as to the right I have a wall about 24" from the right loudspeaker, but the left sees an open space which leads to the dining area. I listen about 8' away and to compensate for a slightly shifted center image, I sit on the right end of the sofa (which is the same distance from both speakers) and most of the other end lies on the left (i.e., the left speaker "sees" more sofa than the right).
The Mirages come with spikes that are not easy to screw in. I actually set them up and listened to Joe Beck ("The Journey", DMP CD481), moving them this way and that, getting the deeper bass stronger and trying to remove some of the emphasized mid-bass (about 100 - 200Hz, as measured with my trusty Radio Shack SPL Meter and Stereophile's Test CD 1) before I put in the spikes. Things got better though on certain CDs ("The Fairfield Fours' Standing in the Safety Zone", Warner Brothers 9 26945-2), male voices were rather chesty. As I listened, I decided it was something I could put up, and I wasn't entirely sure at this point that the Maggies were exactly the opposite in the 100 - 200Hz range. On them (the Maggies), male voices sounded, by comparison, a little light-weight, with some of the (musically pleasant) lower tones recessed in the SMGc's presentation. Of course, the chestiness could be a result of the room acoustics, and aberrant colorations can be a thorny issue with bipolar and dipolar designs, which are very sensitive to the room in which they are placed. Listening to the Test CD through the 1090is, I was able to hear an intense 30Hz, but almost nothing at 25Hz.
The upper octaves were terrific, extending (it seemed to me) even higher than the Magnepans go, and sounding sweet with "normal" playing volume, but with just a trace of hardness when I drove them loud. On Reference Recordings "From the Age of Swing" with Dick Hyman (RR-59CD), the sense of air around the musicians was immense. When I first played this CD, the front half of my room disappeared (I wonder if the 7.7 earthquake last night had something to do with that). I thought the Mirages might be exaggerating this effect until I put on Kenny Loggins' "Nightwatch" (Columbia CK 35387), when the sound stage closed in appropriately. Imaging did not suffer, however, as I though it might, due to the bipolar design. Images (the musicians) were easily located in space between and, depending on the recording, even beyond the 6' setting of the 1090is.
My last test was with laserdiscs, to see how the Mirages would perform in a home theater system. Playing "Jurassic Park", "The Abyss", and "True Lies", the 1090is proved they could reproduce intense sound tracks without any difficulties, driven by a 60W/ch integrated amplifier (Audiolab 8000A Mk II). I also listened to them at a showroom driven by a 100W/ch power amp, and I heard a difference in the region where the 1090is appear to have an emphasis: midbass. On "True Lies", when the helicopters arrive at and leave the island just before the nuclear bomb goes off (now where would anyone get the idea we live in a violent world?), the "WHUP! WHUP!" of the rotors was overly emphasized in my listening room. When I heard the exact same scene at the dealer's showroom, the emphasis was still there, but it was never intrusive. So, again, placement of the bipolar speakers is crucial.
I also tested the 1090is with a subwoofer (the HSU HRSW12V with the standard 91Hz HP/LP). In this setup, the 1090is were relieved of much of the 90Hz signal and below (the HSU employing a 24db/Octave high pass) information. Much better.
All in all, the Mirage 1090is are a very, very good value for the money. From the bottom up, the sound spectrum wasn't seamless, but there is an excellent bass extension, an emphasized (not unpleasant, on certain recordings) mid-bass, and nice, clean highs.
Verdict: (Five stars is highest rating):
Sound: Construction: Value:
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