Pros - Affordable, Decent Value, Relatively Accurate Frequency Response, Proprietary Driver Technology
Cons - Subjectively Prone to Midrange Distortion, Needs Better Interchannel Matching and Overall Quality Control, Pink Cables Not For Everyone
This is a short review intended for concise information presentation.
The data presented in this review was provided by a good friend and a disinterested third party to whom I owe many thanks!
All data is uncompensated (except for 1/12th octave smoothing), and measured with a fully IEC-60711 (IEC60318-4) compliant ear simulator.
Why Review the AM70?
Over the past few years, audio companies in China have gotten very serious about raising the overall competency of their products. Astrotec is one of the companies leading the charge. In the past, Astrotec has released a number of budget-oriented products: the well-received AM90, the AM800, AX7, etc. They're now embarking on the higher end, with the AX60, a dual BA, single dynamic driver hybrid IEM.
However, for IEMs, Astrotec has long used balanced armature drivers sourced from the venerable Knowles Electronics (and been at the mercy of Knowles' pricing). Determined to integrate vertically, a number of Chinese companies, like Japanese electronics giant Sony, have begun extensive research into creating their own balanced armature drivers (with the help of support from the Chinese government). We are now seeing the results of this development, first with the Hisound BA100, and now with the Astrotec AM70. There are a number of Chinese companies that make balanced armature drivers, such as Hearonic and DTS, but only Astrotec and Hisound actually make earphones as well.
I was curious to see how a Chinese-developed balanced armature driver performs.
Ergonomics, Build Quality, Aesthetics, and Accessories
Included with the AM70 are what you'd expect for a ~$35 IEM: a few pairs of ear tips (three pairs of S/M/L silicone and one pair of foam) and a soft carry pouch. Nothing fancy.
The design of the AM70 is that of a traditional ear bud, but with a fully metal (aluminum?) body, nozzle, and screen. Insertion depth is, as expected, shallow.
Nozzle diameter is somewhat wide (~5mm), but that means that most dynamic driver ear tips are applicable.
Y-split and 3.5mm plug are plastic, but build quality is acceptable. Colors are black, however, and contrast oddly with the pink cables and brushed metal bodies.
The metal body construction is lightweight and does not feel hefty on the ears, but may perhaps lead to a false perception of flimsy build quality.
As per usual from Astrotec, cables are made from thermoplastic polyurethane (TPU), and are study/flexible, but have a tendency to unravel when curled up.
Also, the cable color is reddish-pink. I'm unaware of other color options at the time of writing.
Frequency Response & Other Electroacoustic Properties
Red and blue traces denote right and left, respectively.
Green trace shows the left side earpiece measured from an output amplifier with an output impedance of ~0.7 ohms.
Gold vertical line denotes high frequency bandwidth limit.
One side is wired to normal polarity, the other is wired to reverse polarity. This is perhaps a QC issue, and has been seen before in other products.
Overall: Neutral, with warmish midrange cast
Clarity: Decent, especially for the price, but midrange can at times sound slightly distorted, leading to a slight haze-like presentation.
Soundstage: Neither small nor large, feels slightly constrained (perhaps due to limited high frequency bandwidth)
Sounds Most Like: Sony XBA-1
For 248 RMB (~$35 USD), the Astrotec AM70 is not a poor performer at all. It offers a relatively neutral presentation, and while it can display some midrange distortion, the overall sound signature is pleasant and offers a good degree of clarity. Bandwidth, however, is slightly lacking (forgivable for its price range) and interchannel balance, as well as overall quality control should be better.
I would harbor to say that the Sony XBA-1, now discounted to about $30, is a slightly better overall earphone. In a few areas, the AM70 is better: it offers better clarity and a metal body. However, the execution of that metal body is somewhat rough, compared to the level of practiced polish that you expect from a company like Sony. The comparison is a little unfair --- the XBA-1 began life as a higher-priced item (~$80, IIRC), while MSRP for the AM70 begins at ~$35. After all, even though Sony has fallen off significantly over the last few years, it is still the most recognizable consumer electronics company in the world, and Astrotec is not quite Sony (understatement).
Also, the merits of using a balanced armature driver for an IEM in the $30-40 price range are arguable. However, I take this more as a preview of things to come. I trust that Astrotec, as well as other Chinese companies developing their own, proprietary BA drivers (such as Hisound), will improve over time to become more competitive with their western counterparts in Knowles and Sonion. Manufacturers in the western world and in Japan should be worried about the prospect of these companies becoming so vertically-integrated into the audio market. They will be able to manage costs like few companies can. Already, we're seeing hints of this development. The yet-to-be-released (as of November 2013) AX30/35 hybrid IEMs from Astrotec are to be priced at around $70, yet offers a degree of fit and finish closer to the level of their flagship AX60.
Would I recommend it? It's difficult to say. My experience in sub-$40 IEMs is limited, but my inclination would be, "Why not?" At worst, I take the AM70 as more of an encouragement --- change is coming to this market.