The Green Mountain Rio loudspeaker combines time coherent technology and a proprietary 'Balanced-Phase' crossover circuit to bring an impeccable musicality to medium size and small rooms.
So much so, that this discreet little standmount turned out to be one of the most exciting speakers to come my way in years.
It might look small and unassuming, but clever design gives it a marvellous freedom from time-smear, which makes it musically very communicative with vivid dynamic expression. Indeed, the only regret is that the Rio, being GMA's smallest loudspeaker, did have some inevitable limitations in terms of bottom end weight, scale and sheer welly.
Massive marble
A closer inspection reveals numerous examples of the considerable and painstaking care that has gone into selecting every one of its ingredients.
Take its weight, for example. Most standmounts of this size weigh around five to eight kilograms, so it's simple enough to pick one up and pop it onto a stand. The Rio tops the scales at 19 kilograms, more like that of a typical floorstander and that's because the cunningly shaped enclosure has been moulded from Q-stone – a marble/ polyester resin mix.
A lot of mathematical calculation went into designing the dimensions of this very complex multi-faceted enclosure – essentially eight faces, as it's larger in the middle than the top or base. This is partly in order to minimise the focusing of internal reflections and standing waves, assisted by 15 carefully positioned layers of low-density, fibreglass wadding.
Small-to-medium
Because the Rio is primarily expected to be used in small-to-medium size rooms (between 100 and 600 square feet), the designer has tried to limit the dispersion from the two drivers. This is achieved by the shape of the enclosure and, in particular, the way the baffle is inset behind a proud edge, while the tweeter is surrounded by absorbers. All this is meant to to minimise reflections from nearby walls.
Another feature of the enclosure is a 'tilted back' front panel, one crucial reason being that this helps ensure that the listener-to-voice-coil distance is the same for both drive units, in order to maintain accurate phase coherence across the band, especially through the crossover region.
To this end, Green Mountain Audio provides recommendations for the optimum stand height for any given seated ear-height and listening distance. Relatively low (e.g 500-millimetre) stands are suggested.
Similar care has clearly gone into selecting the other ingredients. The bass/mid driver has an 'under-hung' voice-coil, operating in a large field generated by neodymium magnets. The lightweight (damped, pressed steel) 153-millimetre frame accommodates a 115-millimetre diameter cone made from a mix of paper and carbon fibre. The tweeter has a 25-millimetre doped fabric dome diaphragm with a relatively wide (twomillimetre) surround.
Internal wiring consists of Audio Magic Teflon-insulated 14 gauge (1.6-millimetre) silver-plated OFC feeding the bass/mid driver and Jena Labs polyethylene insulated, cryogenically treated 22 gauge (0.64-millimetre) OFC.
The crossover also uses high-quality components and is essentially a simple first order (six-decibel/octave) affair, albeit modified by a Zobel network. The objective is to minimise phase shift right across the band, and a very impressive +/-2 degrees, 200hz- 8.5khz is claimed.
Texture-Koting
The cast Q-stone marble composite enclosure gives massive weight and rigidity, as well as an interesting and clearly effective shape. It can be difficult to achieve an acceptable surface finish with such material, but the black Texture-Kote preparation used here gives a sort of suede look and feel that is very acceptable.
Enclosure detailing also looks very good, above and below the thin acoustic foam grille, which may be left in place without influencing the sound in any way.
Your comments (2) Click to add a new comment
audioabc
April 1st
2. The Rio is a really impressive speaker. I found the tonal balance to be quite neutral compared to other monitors of this size. Moreover, the imaging was fantastic. The ability to pinpoint the location of musicians on stage was effortless.
Rio presented the musical information with great detail. I found myself hearing things that I didn’t hear on my HD-600 headphones.
I believe that the heavy stone cabinets contribute to the neutral sound. You can walk up to the speaker while it is playing music and truly recognize the care that has been taken in dampening the cabinet. Put your hand on the cabinet and you notice that vibration/sound is nearly all gone. The cabinets do not produce a sound of their own.
The time coherent design provides immediacy to the music which really involves the listener. Listening to a digital to analog converter without jitter is the best example I can give. The time domain distortions were not there – which I now can easily recognize in other speakers.
-Owner/Audio Engineer/Music Lover
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royj
March 29th
1. Thank you for the thorough review of our Rio loudspeaker, Paul. I'm glad you found your time with them rewarding!
The tight time-focus of Rio is responsible for much of what you heard, including the slight upper-mid forwardness you reported, as did Keith Howard of HiFi News in his new review of our Eos model.
As time goes by, one finds this to not be a tone-balance irregularity, but rather what time-coherent clarity does to the sound of music.
An indication of this, in my experience, is that you and Keith both remarked this slight forwardness was not of particular bother, nor even noticed on some music.
Most speakers are not time-coherent between their woofers and tweeters, so that's what we hear every day. One audible effect of time-smear is to 'distance' a listener from the music.
With sounds between woofer and tweeter arriving out of sequence, such speakers remove much of the 'directness' and immediacy of the performance.
We do re-adapt to hearing time-coherent sound, which is why our long-term owners' comments have always been about hearing far more of the 'real' sound.
Of course, 'real' sound is whatever the microphones picked up and the engineers modified. Therefore, we never get to hear 'reality', but at best only a pleasing semblance!
Much recorded sound is very direct and forward-- just think about how close microphones must often placed! When one does hear a speaker that allows any directness to emerge unscathed, many familiar recordings change. But the improvement to the musicality is clearly audible and quite enjoyable, as you so graciously point out.
Thank you again for the lovely review, Paul, and your hard work!
Best regards,
Roy Johnson
Designer
Green Mountain Audio
Colorado, USA
PS: This is the first we've heard about some unevenness to Rio's bass response, but I would not disagree.
Rio is often used in smaller rooms, less than 4.5m wide. Therefore, its LF-response was tailored for smaller rooms.
In any speaker, the enclosure's shape and size support the loudness of high-bass notes by being quite literally 'in their way'. Also, any enclosure always 'gets out of the way' of low-bass notes. In between is where the room's surfaces come into play.
The nearby surfaces of smaller rooms boost the bass beginning much higher up the scale than do the more-distant surfaces of a large room. Therefore, Rio's enclosure was shaped and sized to 'get out of the way' higher up the bass scale than other speakers. The resulting bass response is then as smooth as possible in smaller rooms. The details behind the design of Rio's enclosure are on our website.
Therefore, when Rio is placed in a larger room, this could lead to a slightly uneven bass response, depending on placement. I'm glad you noted that, Paul!
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