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Product Review - Monitor Audio GR10 Bookshelf Speakers - Part 2 - February, 2002


Arvind Kohli


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The Design

All Monitor Audio drivers are built in-house of a material developed by Monitor Audio called C-CAM.  C-CAM stands for Ceramic coated Aluminum Magnesium and is said to have a very high stiffness-to-mass ratio. All GR series drivers are built to a 1 dB tolerance. C-CAM has also gained popularity as a driver material outside of Monitor Audio, as it is featured in other high-end brands like the B&W Nautilus and some products from Theil.

The GR line is outfitted with a 1” gold-colored C-CAM tweeter that has become the calling card for Monitor Audio. This is practically the same tweeter as in the Studio Series with a few improvements.

The rear of the tweeter now has three chambers of absorption. It is common for the better speakers with soft dome tweeters to dampen the rear chamber of the tweeter, since the reflected backwaves can pass through the driver fabric and reach the listener’s ear out of phase with the original signal. I had never heard of speakers with solid domes that find this necessary to do. David Solomon of Monitor Audio USA explained that the unabsorbed backwaves would hit the rear of the tweeter and potentially induce spurious sounds. This perhaps could also be some of the cause of the ringing or harsh sound often associated with hard dome tweeters. In my experience, it is only such pursuit of perfection and painstaking attention to detail that yields quality products like the GR10.

The mid-bass driver is a 6.5” C-CAM unit. This is the same material that has been used in the past on the Studio Line, but the GR Line has a lot of changes made since. Theoretically, you want the driver to weigh as little as possible so it can move easily and fast. You also want it to be stiff so it does not bend or break up while trying to create a sound. To this end, the thickness of the C-CAM material is a whopping 25% thinner than in the Studio Line, down to 0.03mm. The dimpled surface (given the proprietary name Rigid Surface Technology) makes it stiffer. I never realized how light and stiff this stuff is till David told me that the breakup point of these drivers is nearly 8,000 Hz. By contrast, the treated-paper woofer in the Triangle Titus XS slopes off at about 6,200 Hz, and I thought it was incredibly light. The dimples on the surface are also said to displace standing waves across the surface of the driver.

The mid-bass driver also sports a machined aluminum phase plug. This plug is an extension of the voice coil and eliminates the dust-cap to modify the dispersion, frequency response, and standing wave behavior
of the cone for higher frequency reproduction.

[ Notes by Colin Miller: While entirely pistonic motion is a theoretical ideal for some, diaphragm flexure is not necessarily a bad thing. Electrostatic panels can only operate because of flexure, as is the case with ribbons. Many conventional cone drivers are designed to flex in a controlled fashion, so that the flexure is damped, so not to exhibit break up or standing waves on the cone. One could make the argument that it would be better not to flex at all, rather than to do it gracefully; however, there are benefits to flexing. Aside from the tendency for stiffer drivers, particularly those made of metal, to have much nastier break up tendencies (which to be fair can be avoided to a great degree with a crossover), consider that a 6" mid-bass that radiates evenly throughout the surface of the driver, due to extremely high stiffness, will beam like mad at 2 kHz. If the designer places importance in both on-axis frequency response, as well as off-axis response, then the usable bandwidth of the driver has been severely limited, regardless of break up frequency, and the designer can either turn the project into a much more expensive and complicated three-way design, or make the tweeter go down to 1 kHz or possibly lower, which would severely stress that driver, assuming that it could handle that range anyway. In this specific case, perhaps the main purpose of the phase plug is to some way alleviate that. Diaphragms that flex, on the other hand, if properly damped, radiate higher frequencies primarily from the center of the cone, perhaps mostly from the dust cap itself, or not, and will have a wider, more even high frequency dispersion pattern.  I am not saying that one is necessarily better than another, only that when it comes to skinning cats, there are a whole mess of knives to choose from, let alone techniques, that work very well.

While having a light weight cone is a theoretical ideal for some, it is only for the theorist when it comes to any real driver. A lighter cone means a higher suspension resonant frequency, so that lightening the cone reduces bass extension, or in the case of a tweeter, midrange extension. While you do want a cone no heavier than required for the necessary low end bandwidth in order to maximize efficiency, it should be noted that a light cone does not necessarily start and stop any faster, in terms of transient response or bandwidth, but simply moves more under any given force applied, hence the greater efficiency.

Stiffness itself will drive the resonant frequency of the diaphragm up, but mass itself has little to do with it in itself, except if you consider that adding mass may make the cone stiffer, thereby achieving one
by the other, though the correlation can be misleading.

See also my review of the M&K Xenon Speakers for a discussion on dynamic range of speakers.]

Cabinets are hand built in-house from 22mm (0.87 inches) MDF, and are internally braced at critical points. They pass the knuckle rap test quite well considering their size. The top and bottom are extremely inert, and the sides are relatively less so, as would be expected with a larger surface.

Other changes made to the GR series include use of polypropylene capacitors in the crossover, thicker binding posts, and pure silver wiring for internal hookup. The crossover is a second order design at about the 3 kHz mark.

With a claimed sensitivity of 88dB/W/M and peak power handling of 300 watts, the GR10 can theoretically deliver up to 102 dB at a realistic distance of 4 meters (~13 feet). This is exceptional for a stand-mounted speaker, and invalidates the main argument against that speaker profile. I really don’t understand the fuss about power handling and peak SPL,  I have never had a reason to complain about the output of speakers with much lesser ratings. Remember, permanent hearing loss occurs at repeated exposure over 90 dB (about 21 watts with the GR10) and that is why OSHA requires workplace monitoring and hearing protection above those levels. Nonetheless, if sound level is a concern, you need not worry with these puppies. If you need more, you better get your ears checked, at a minimum. 

The Sound

This is the fifth and final mini-monitor that I used in my direct comparison listening sessions a while ago. The other speakers were the previously reviewed; Totem Model 1 ($1995), Dynaudio Contour 1.1 ($1695), Triangle Titus XS ($495), and Silverline SR15 ($1799). I tested each with a ‘pink noise’ reference track and marked the point on my volume dial where each registered at 70 dB ± 1 dB. I then repeatedly listened to a single track on each speaker and noted the differences. Before I get into the details, let me say they all sounded closer to each other than not. The differences I note below are apparent in a critical listening setup, i.e., I heard the difference only because I was specifically listening for any. In a casual listening session, most of these differences would have been unnoticed. Here is what I heard on some select tracks.

"Come on in this house" (Junior Wells, Come on in this house, Telarc, CD83395) is a fairly complex track with a lot going on. All five speakers did very well with rendering detail and separation of instruments. On this track I also used the kick-drum to evaluate bass response. The GR10 fell in the middle of the pack in terms of weight and extension. It was deeper and louder than the Totem or Dynaudio, but just as tight. It was not as deep or loud as the Silverline or Triangle, but definitely tighter. I would say that the GR10 is in the league of speakers that do not compromise bass quality for quantity, and yet deliver extension not expected of stand-mounted speakers.

"Acoustic drum solo" (Russ Henry, Stereophile test CD 2, Stereophile, STPH 004-2) is an excellent minimalist recording done at the former Manley Labs with their reference microphone. With proper placement and toe-in, I could experience a holographic image of a life-sized drum kit about 6 to 8 feet in front of me. With the GR10s firing straight ahead, I recreated such an image that was a little laid back, placing itself just behind the speaker plane. The tonality of each drum in the kit was superior to all but the Dynaudio Contour 1.1, and this is a very telling recording for judging this aspect. The depth of image was also extremely precise, allowing me to picture which drums were placed towards the rear of the kit and which ones in front. 

"Yesterdays" (Dave Brubeck, Nightshift, Telarc, CD-83351), is perhaps the best recording I have ever heard of a live performance, complete with ambient sounds from the audience. The GR10 fell just behind the Totem and Dynaudio, which were tied at first place for their amazing ability to render detail. Admittedly, this level of difference is only found in the most focused and nitpicky listening sessions.

"All or nothing at all" (Diana Krall, Love Scenes, Impulse, IMPD233) is my favorite test for a Double Bass, and the dynamic range in Diana’s voice is also a test I often use. The GR10 did full justice to the double bass, with its excellent balance of bass extension and tightness, subjectively sounding the best of the lot. The GR10 surprised me with its ability to be nimble enough to keep up with changes in the loudness of her voice. Subjectively, it tied with the exceptionally fast Triangle Titus and Totem.

"Girl From Ipanema" and "Para Machuchar Meu Coracao" (Stan Getz and Joao Gilberto, Getz/Gilberto, Verve 314521414-2) is a well recorded classic, except for the slight chestiness in the male vocals. Speakers weak in this area tend to magnify the problem with these tracks, and thus has become a standard test in my reviews. The GR10 performed as well as the Totem and Dynaudio or a shade behind them, depending on which day of the week you asked the question. My point is that, in subjective listening tests when the results are this close, I would take the resulting verdict with a grain of salt since there are so many variables that could throw the results the other way.

"O Grande Amor" (Stan Getz and Joao Gilberto, Getz/Gilberto, Verve 314521414-2) is one of the few older pieces I can think of that makes me appreciate an analog master tape, from which this album was re-mastered. The microphone puts you right in the mouth of the Tenor Sax to the point you can hear the horn chuffing. All five speakers did an excellent job of revealing all that delicious detail. Only the Silverline SR15 sounded different from the others, with a little more depth, yielding a very pleasant albeit unnatural sound.

"Pawn Shop" (Sublime, Sublime, Gasoline Alley, GASD-11413) is a surefire test for testing dynamics and power handling. The GR10 again equaled the Totem and Triangle for speed and dynamics. Electric bass was tight and deep like the Totem and Dynaudio. The tonality of the tight snare seemed very lifelike on the Monitor Audio, Totem, and Dynaudio. The Silverline was distinctly poor in this aspect, the snare sounded like a much larger drum, one with a deeper and slower sound.

Finally, "Mar Azul" (Cesaria Evora, Mar Azul, Nonesuch, 79533-2) is a must for female vocals. The hands-down winner was the Dynaudio with a very natural sound and rendering the dynamic range, especially the small changes in loudness. The GR10 sounded very natural but a little shy on the full dynamic range only when compared to the Dynaudio.

Overall, the GR10 delivered on my expectations and more. It definitely excelled in imaging, naturalness, bass depth and control, detail, and a smooth midrange. On parameters of speed and dynamic range, my listening notes were not consistent, sometimes placing it ahead of the pack and sometimes in the middle. My general impression left nothing to be desired. There were no weaknesses that I could complain about. 

Conclusion

I am thrifty with praise, as my wife often says. When I say there were no weakness to complain about, I mean exactly that. I could live with this speaker happily ever after, and heartily recommend it to you for audition. Unfortunately, I was not able to compare them with their predecessors and cannot comment on the relative improvements. However, compared to their current competition they deliver everything I would expect from them.

Associated Equipment:
 

Speakers: Dynaudio Contour 1.1; Triangle Titus XS; Totem Model 1 Signature, Silverline SR15

Amplifiers: Bryston 4B Pro; Krell KAV 250a; NAD 317 (Integrated)

Preamplifiers: PS Audio IV

Digital Source: Panasonic A320; Pioneer D414

Outboard DAC: MSB Gold Link III with P1000 Powerbase

Power Conditioner: PS Audio P300

Connectors: Self designed.

 

- Arvind Kohli -

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© Copyright 2002 Secrets of Home Theater & High Fidelity
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