Evolution of the Atrio:  
 
This IEM is the successor to the Future Sonics EM3, a rather ugly, but nice-sounding IEM that was used by a quite a number of on-stage performers as well as audio enthusiasts. Future Sonics is one of the pioneers in this particular audio niche. Their IEM devices are rather unique in that they use a diaphragm type transducer rather than the balanced armature that is typically used in hearing aids.  
 
According to Future Sonics, the diaphram type of transducer is capable of providing deeper bass and more lifelike vocals than is the balanced armature transducer. I own both the EM3 as well as the Atrios and can attest that they do, in fact, have a much deeper bottom-end range than most other IEMs that I have heard.
 
Description:
 
The Atrios at first glance are a rather unremarkable appearing set of phones. The exterior is a shiny black plastic, with a clear bendable tubing over about the first 2" of the cord as it leaves the phone. The headphone cord itself is a black Y lead with a sliding bead to adjust they depth of the "Y" and terminates in an L-shaped plug.  
 
Included in the packaging is a sturdy zipper case with a mesh enclosure that can hold an assortment of tips, etc. It is large enough to hold a couple of sets of IEMs, if so desired. Also included are 3 different sizes of silicone tips plus foam tips.  
 
One should be able to find a set that fits and seals well using the supplied assortment of tips, however I was not able to attain a really good seal using the supplied tips, but ended up using some of my Ety tri-flanges which work very well for me. 
While the EM3 used foam tips, they didn't actually go into the ear canal, whereas the Atrio is designed to insert further into the canal, so a good seal is necessary for optimum performance. The cord can either be directed downward or bent to contour over-the-ear, which is the configuration that I prefer.
 
Performance:
 
The Atrios are very easily driven, even without the use of an external amplifier. I could hear little, if any, difference between the sound of my iRiver H140 line out with no external amplification or with the same source fed through my Xin Reference. The soundstage is very expansive, much more so than is typically experienced with IEM type phones. Bass is deep and full, with natural sounding vocals and crisp highs.  Transient response is very good, with snares sounding like snares! External sound isolation with the Atrios is quite good, much better than the EM3 and on a par with that provided by custom IEMs.
 
The Atrios have the unique characteristic of sounding really good at very low volume settings unlike most balanced armature devices which need more volume for natural bass performance. Although the bass response is one of the more noteworthy characteristics of these phones, it is not boomy or thumping nor does it overpower the rest of the audio spectrum.
 
If I had to compare the Atrio sound signature to a circumaural phone, it would probably come closest to the Sennheiser HD6xx series. They really do sound more like a conventional headphone than an IEM.  
 
These phones have been widely discussed on the Head-Fi forum, accumulating a very long thread of glowing testimonials from very satisfied owners with a high percentage of the posts praising the excellent bass response.  
 
Considering the fact that nearly all custom-fitted IEMs cost in the $500-$1000 range, the street price of about $140 combined with their superb sound reproduction makes the Atrios a very good choice for a modestly priced IEM that can be used equally well with and without external amplification.
 
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