Editor’s Note: iFi Audio provided the iEMatch free of charge for the review
What is the iEMatch and why would you need one?
iFi Audio markets the iEMatch as a tool to eliminate hiss, restore dynamic range and give you more volume headroom — sounds pretty simple but in the world of in-ear monitors, and in particular balanced armature based in-ears, it’s pretty important to understand how this type of product affects your in-ears’ performance and your perception of sound, so let’s first take a deeper dive into some of the common issues in-ear users face.
Specifications
Ultra (-24dB)& High-Gain(-12dB) sensitivity adjustment
TRRS-Balanced® for Single-Ended and Balanced operation
6N silver/copper matrix wiring with FINAL 6063-T5 aluminium-magnesium alloy shell
Gold-plated printed circuit board with audiophile components (eg MELF resistors)
Gold-plated 3.5mm male/female connectors
Input Impedance: > 16 Ohm
Output Impedance: < 2.5 Ohms (High-Sensitivity) < 1 Ohms (Ultra-Sensitivity)
Weight: 12.2g
Total Length : 116mm
Sensitivity
Many, or more accurately, most of the current crop of in-ears are extremely sensitive. They are sensitive in that they require very little power to generate ear-splitting levels of volume. Many can hit 115+ dB’s at 1mW of power. This sensitivity manifests itself in an overall monitor design with very low impedances. However manufacturer specs really don’t tell you the entire picture, as their impedance specs only show a snapshot at 1,000 kHz; perhaps something like 21 ohms at 1 kHz. While single dynamic driver based in-ears will have a (mostly) flat impedance response over the full spectrum of 20 Hz to 20 kHz, single and multiple armature designs can and will have wildly fluctuating impedances, sometimes ranging from 4 or 5 ohms at some frequencies to maybe 20, or 30 or 40 and more ohms at other frequencies, so that 1 kHz specification really doesn’t tell you much.
Hiss and Noise
This ultra sensitivity, high SPL with little power at low impedance, means many in-ears are going to be microscopes to the noise floor of you audio chain. The more sensitive a monitor, the more revealing of hiss and noise one can pick up, especially when music isn’t playing. A user’s sensitivity to hiss can vary widely between users, so while one may not notice or become distracted by varying levels of hiss between certain in-ears, another user may be much more distracted. The iEMatch helps to eliminate these issues with -12 dB and -24 dB settings of gain reduction. The end result is a blacker, quieter background, while requiring increasingly more volume adjustment from your source. The iEMatch is very successful in this regard, which makes it a useful accessory for airline travel, as well as taming hiss and noise in your home or portable chain.
Dynamic Range
iFi claims that the reduction of volume and gain required with many set-ups, to bring these ultra sensitive in-ears to tolerable levels, is actually reducing available dynamic range of the system. Reducing the volume levels by -12 dB and -24 dB may allow usage of a higher gain setting on the amplification stage, which might bring perceived improvements in sound quality based in amplifier topology employed for gain control. Or it may simply allow greater volume usage in a set up that is using digital volume control from the DAC, which will certainly improve dynamic range. This concept was a design intention, as discussed and confirmed in my conversations with iFi.
Listening Dynamics
In my usage with Campfire Andromeda and the Questyle QP1R, I felt the iEMatch softened listening dynamics if I remained in low gain, but I did hear improvements as I moved up to high gain, so sound will be a mixed bag and very dependent on your specific audio chain set up.
Output Impedance
Output Impedance is probably one of the more important factors of an audio chain when discussing balanced armature based in-ears. As mentioned earlier, impedance graphs of balanced armature in-ears can vary wildly at different frequencies. In general you would want 8 times less output impedance (impedance value at amp output plus cable to in-ear) than the in-ear’s lowest impedance measurement across frequency response. This is to ensure you are not altering the frequency response of the monitor’s design. It should be noted that altering the frequency response with added impedance can be desirable but more often than not can be very detrimental to sound quality and overall enjoyment. Some designs will lose or boost presence and quantity of a frequency with increased impedance. Depending on the monitor design, this may take many ohms of impedance to affect (30, 50 or 100) or could take very few ohms (2, 3 or 5). The iEMatch has output impedance settings of 1 ohm in Ultra setting and 2.5 ohms in High setting, assuming your source feeding the iEMatch is under 16 ohms output impedance itself.
Examples:
- The discontinued EarWerkz Legend-R will lose treble presence and quantity with just 2 or more ohms. Since the treble was already laid back, losing more is not desirable.
- The Shure SE846 bass will get wooly and boomy by just adding 3 or more ohms.
- The newly revised Jays Q-Jays will start to sound similar in frequency response to the Jerry Harvey Audio Angie with an added 90 ohms of impedance.
Take for instance the Campfire Audio Andromeda, it has an impedance of approximately 4 ohms from 200 Hz on down through sub bass. Even minimal addition of output impedance to 2 or 3 ohms starts to reduce overall bass levels, in even amounts of quantity, without impacting extension. Andromeda’s impedance rises to 24 ohms between 7 kHz and 10 kHz, so the overall effect will be a more neutral frequency response with a just a couple of ohms added but will become pretty lean and bright as the value increases to about 4 ohms and more. In this use case, many consider this a feature, as it allows them to gradually tailor the sound to their preferences. The problem then becomes in finding a source that has just 2 or 3 ohms output impedance, if that gives you your desired frequency response, as source ‘rolling’ is not a cheap endeavor. This is were the iEMatch excels. If gives you the ability to either lower your source impedance, if it is less 16 ohms to begin with, and it gives you the ability to slightly raise your already under 1 ohm source.
Detailed listening notes of Campfire Audio Andromeda changes with Questyle QP1R as source (0.15 ohms output impedance)
Straight from the QP1R, Andromeda bass is at its fullest and richest, and treble is at its most relaxed (which is still pretty sparkly) due to the very low, near zero, output impedance of the QP1R (0.15 ohms).
iEMatch in Ultra setting has slightly less bess presence overall, while retaining the same depth of extension. Due to the reduction of bass levels, the Andromeda treble feels a little more present and clear. While still maintaining a very low output impedance, the Andromeda sounds slightly more neutral than straight from the QP1R.
iEMatch in High setting reduces bass another notch or two, while elevating treble quantity perception a noticeable amount in the Andromeda. While overall sounding more neutral in bass through the midrange, the treble peaks of the Andromeda become more prevalent, lending itself to a much brighter presentation that isn’t quite as smooth as it is with lower amounts of output impedance.
Design
What is the iEMatch? iFi remains vague and secretive, unwilling to disclose to potential competitors their secret sauce. One thing it is not is a simple in-line resistor (this much iFi has made clear to me), and is referred to as a gain setting without amplification. A simple in-line resistor would just add more impedance to the chain. For instance, a 10 ohm impedance adapter, added to a 3 ohm output impedance amplifier will have the in-ear monitor seeing a total of 13 ohms output impedance in your chain (please note that this is an approximation based around the principle that impedance approximately equals resistance in the absence of reactance, which is determined by capacitance and inductance in an alternating current circuit such as audio). If you are trying to lower frequency response impacting impedance, an in-line resistor will not help.
This leaves two possibilities that I’m aware of: a buffer or a voltage splitter. A buffer, usually implemented as a unity gain buffer, can be thought of as an amplifier with no gain. The idea here is to raise input impedance, amplify the signal without gain, and release the signal with a much lower impedance, usually around 1 ohm or less. This design is somewhat more complicated and can color the sound quality, besides the obvious output impedance values, depending on topology and design employed (think transparency, clarity and warmth). An example of this kind of product is the Ultimate Ears Line Drive at approximately $150. Can iFi fit such a device into the size of the iEMatch and run it passively? It’s certainly possible. Apple has proved as much in their ability to fit a DAC/AMP/ADC into the new, diminutive iPhone 7 dongle, which they sell for a mind boggling $9. However, the iEMatch is lowering gain by two different values, and it just seems very unlikely they’ve gone with this more complex design.
The second possibility is a voltage splitter/divider (link to Wikipedia). The iEMatch seems to act as a passive gain attenuator based on a voltage divider circuit. According to my googling abilities, a passive gain attenuator is simply a passive (no supply) resistive network that can extend dynamic range by adjusting signal levels, provide impedance matching of oscillators or amplifiers, or to provide isolation between different circuit stages. It seems this type of circuit, that attenuates gain, improves dynamic range and lowers output impedance can be accomplished with four resistors, or perhaps 8, since the iEMatch does balanced connections as well. Although other, more elegant modalities are very possible, such as capacitive and inductive voltage dividers (such as the one employed by the now-discontinued TDK BA200 [review here]), they usually need to be designed specifically to match the output circuit, i.e. the impedance profile of the IEM itself. Considering the size, simplicity of design, and diverse overall effectiveness, I’m heavily leaning towards a resistive type of voltage divider device.
Additional design and functionality include the ability to use with TRS single-ended and balanced TRRS gear with the flip of a switch on plug side of the iEMatch. Left and right pin-out can be found on iFi’s product page to determine balanced configuration compatibility, which appears to be the same as HiFiMAN, Cowon and LH Labs’ implementations. The iEMatch uses 6063-TS aluminium-magnesium alloy for the plug and receptacle bodies and 6N silver and copper wiring for a high-end, audiophile look and feel. The iEMatch also comes with an old style, two-prong airline adapter (are there still airplanes in use with this?), memory foam earplugs and a velvet draw-string carrying pouch.
At a retail price of $49, the iFi iEMatch makes for an intriguing accessory to help tailor and perhaps improve the sound quality and listening experience of many balanced armature in-ears in a variety of set-ups.
CYMBACAVUM 