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Figure 1 shows the mechanical structure of balance armature driver techology. Photo courtesy of JA Davidson at English Wikpedia
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The Shure SE846 quad-driver SE846 earphones carry a list price of $999.
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Figure 2 illustrates how multiple drivers are assembled into tiny ear buds. Photo courtesy of Ultimate Ears
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Audio-Technica's new E-Series includes three models priced from $99 to $399
In-ear monitors (IEMs) have played a major role in a “quiet stage” revolution that has transformed worship in many churches. Instead of escalating “dB wars” – with vocals and instruments fighting for dominance on stage – we can create a controlled environment. Everybody on the worship team can hear themselves and each other, while the FOH engineer can create the optimum mix for the congregation.
Despite the importance of these innovative devices, many worship musicians don't really understand how they work – and why they can cost so much. That's understandable, because most IEMs are based on a quirky audio technology not used elsewhere in pro audio. In fact, it was largely refined in pursuit of a better hearing aid for grandma.
A question of balanced
The vast majority of loudspeakers and headphones use dynamic driver technology to create sound from an electrical signal. A dynamic driver suspends a circular voice coil in a magnetic field and attaches it on one side to a cone or diaphragm of some type, whether metal, fabric, plastic or combinations thereof. When an electrical signal passes through the voice coil, it moves in the magnetic field, vibrating the attached cone or diaphragm, thus creating sound.
Most IEMs use a different driver technology, called balanced armature. It leverages the same principles as the dynamic driver, but with a completely reworked mechanical structure. Most importantly, balanced armature devices can be made much, much smaller. See Figure 2.
As shown in the diagram, a balanced armature driver has an arm suspended midway on a pivot point wrapped with a wire coil, and surrounded by a magnetic field. When the electrical signal activates the coil, the armature goes up and down, and the energy is transmitted via a connecting rod to an external diaphragm (usually metal foil) in an adjacent sealed chamber. The entire mechanism is squeezed in a tiny rectangular box, with a port at one end for the sound to exit.
The balanced armature driver is not new technology. In fact, it's been around for almost a century. What's new is the ability to make these transducers extremely small, to the point where you now can fit up to a dozen of them inside your ear!
Why more is better
All dynamic over-the-ear headphones, at least that I know of, are single-driver devices. Some expensive ones have multi-layered driver diaphragms, but all are attached to a single voice coil. It might be possible to make multi-driver dynamic headphones, but the benefits likely would be minimal.
It's a different case with the balanced armature driver. Here, there are significant – and clearly audible – benefits to splitting up the frequency spectrum and reproducing different bands by using anywhere from two to twelve drivers. (It should be noted that no IEMs I know of are more than three-way: if more drivers than that, dual or quad drivers are used in one or more frequency bands.) See Figure 3
Curiously, in this respect the tiny IEM has more in common with the big line array loudspeakers over stage than it does with conventional headphones. By spreading the audio spectrum over multiple drivers, a premium IEM can deliver extended bandwidth (deeper bass and more transparent highs) with a flatter response and lower distortion. But remember, a two-way design also requires a crossover network (signal splitting circuit), and a three-way requires two of them, all shrunk to fit inside your ear. And that also adds to the cost.
Seal the deal
Dynamic headphone drivers are vented devices: they won't function properly if the back is completely sealed off from the outside air. Balanced armature drivers, in contrast, are occluded devices that function best when the ear canal is sealed from outside air. This is why they are also known as “noise isolating” earphones, as most will cut outside sounds by at least 20 dB when used properly.
There are two approaches for creating the seal: universal fit and custom fit. Universal fit models use soft silicone or memory foam earpieces that allow you to press the output port snugly into the opening of the ear canal. More expensive universal fit models will include three or four different sizes of both earpiece types, allowing you mount the one on the IEM body that gives the best fit.
But even the best universal fit models can come loose with enough jiggling, bouncing and tugging. For critical use, you will want to invest in a custom fit model where each earpiece is individually created from a plastic mold or laser scan of your ears. This does cost a few hundred dollars more in most cases, particularly after you factor in the cost of a visit to your local audiologist. In most cases will have to wait a couple weeks for delivery, although one maker – Ultimate Ears – is launching a pilot program using laser ear scanners operated by trained technicians located at key dealers.
What works for you?
This is the hard part, because regarding the sonic characteristics – as with the earpieces – one size does not fit all. What works for a vocalist or keyboard player may not be best for a drummer or bass player.
Here's a personal example. When I auditioned my first triple-driver IEMs I was quickly captured by the high-end clarity, vocal presence, and fullness of the bass. And, when I put my electronic drum kit into the mix, I was taken aback by the clarity of the cymbals. For the first time, they sounded like the real thing!
But then, for comparison, I put on my usual drumming headphones – from drum accessory maker Vic Firth. Alas, the luscious bass and shimmering cymbals receded. But the kick drum attack, upper bass punch and rhythm guitar all moved forward. Since that's what I focus on when drumming, I'd go shopping for a different IEM pair – if I were our church's main drummer. But since I'm the FOH guy, I'll keep enjoying this pair with recorded music.
So before you buy, audition as many models as you can. Check reviews and manufacturer web sites, as several makers listed below will specify which models work best for which applications. (Not surprisingly, my pair was not shown as preferred by drummers.) If you're looking at custom fit, check to see if the model is also available as universal fit, and try it that way before making the extra investment.
New and Noteworthy
Here's a quick cross-section of what's available, leading off with some new entries that debuted at the NAMM Show last January.
Audio-Technica bowed its new E-Series, with three models priced from $99 to $399. The top of the line ATH-E70 packs in three balanced armature drivers and also features a flexible memory cable with a new type of detachable connector, dubbed A2DC.
New from Westone, and slated to ship in the spring of '16, is the Ambient Pro Series, also with three models. As the name implies, these IEMs use a proprietary design to admit more ambient stage sound into the ear without affecting bass performance. This allows more connection with the audience and bandmates without the hassles of mixing in ambient mics.
Jerry Harvey Audio, a pioneer in the technology a major player on the high end, has debuted the V2 version of the JH13, which boasts six balanced armature drivers, 10 dB of adjustable bass per ear, and Moon Audio 4-pin connectors. Pricing hits above four digits, but this is about as good as it gets.
Speaking of premium IEMs, 64 Audio is the choice of many notables, including Kirk Franklin and the Newsboys. The flagship A12 is a 3-way system with a mind-boggling 12 drivers plus the company's proprietary ADEL technology, which incorporates a “secondary eardrum” to mitigate long-term fatigue. Pricing for this one (as custom fit) hits close to double kilobucks, but the company's universal fit models start around $400.
Sennheiser pushes the limits of dynamic technology with the IE80 (about $450), which employs neodymium magnets to extend bass response down below audible limits. A continuously variable control adjusts the bass response to your tastes.
Shure's IEM line also includes two dynamic models, but the upper end is balanced armature (“High Definition MicroDriver”) territory. Shure stakes out the high end with the quad-driver SE846, but a popular midline option is the triple-driver SE535 ($499) which reproduces a flat 18 Hz to 29 kHz. These are universal fit, but custom fit is available through a partnership with Sensaphonics.
Ultimate Ears has captured a large segment of the market by offering a full line of options and fast turnaround on custom fitting. A model preferred by many drummers (and thus on my wish list) is the UE11 Pro, a four-driver, three-way model with dual drivers for more power and definition in the bass frequencies.
That's a quick survey of the landscape, focused on companies attuned to the pro market. But other more consumer-oriented companies also have models well worth an audition, particularly if on a tight budget, including Bose, Etymotic Research and Aurisonics.
Bruce Borgerson is head of audio at the First United Methodist Church of Ashland, Ore. He fills in on drums only in cases of extreme desperation.
