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Review: Ultimate Ears Sound Guard IEM Processor/Limiter

Russ Long. UE radically improves IEM performance via limiting circuit and more.

Since developing in-ear monitory (IEM) technology for the recording and live sound industries in 1995, Ultimate Ears (UE) has been at the forefront of personal monitoring products. Its innovation shows no signs of slowing, either; this past January, I had the opportunity to take a peek into the future of IEM technology with UE at Winter NAMM 2015. Gone are the days of an audiologist taking a mold of your ear cavity to assure the IEMs provide proper fit; UE now incorporates a digital scanner to capture digital ear impressions of the ear canal, then utilizes a 3D printer to build the earphone shell. This results in IEMs that fit perfectly and can be manufactured in a shorter period of time. This is a notable innovation when, for example, touring artists misplace their IEMs and need an immediate replacement or a new musician is hired who doesn’t have a set of IEMs but need a pair immediately. Check out coverage of the process through the links at

Ultimate Ears’ Sound Guard Along with UE’s manufacturing process update, the company introduced a unique new product earlier this year, called Sound Guard. This small (2- x 2- x 0.5-inches), battery-powered $199 box has the ability to radically improve IEM performance while providing a protective limiting circuit. Intended for UE Pro IEMs, it offers the same sonic improvement and protection for balanced armature design IEMs by other manufacturers. Sound Guard I/O works via a pair of eighth-inch stereo TRS jacks, and the unit includes a removable belt clip, 6-inch patch cable and a pair of 3 VDC CR2450 lithium batteries. Power is activated via a recessed on/off switch. LEDs illuminate to indicate power status and battery condition, respectively.

Connecting in-line between the headphone output of a sound source and a pair of balanced armature IEMs, Sound Guard is a fantastic device. I’ve spent hours listening through it with both my UE Reference Monitor and UE 900S IEMs; in both instances, I found that its impedance matching circuitry significantly improved the performance of the monitors, resulting in a smoother top end with improved clarity and rich low frequencies with improved definition.

The limiter works well, too. It activates when a signal reaches approximately 107 dBA; once it kicks in, it becomes somewhat audible but not until then. The limiter instantly suppresses audio spikes and surges caused by feedback, wireless interference, microphone drops, etc., making it a wonderful asset for performers. While the plug-and-play approach makes for simple operation, users who like to monitor extremely loud may wish it kicked in at slightly louder volumes. Perhaps a three-position sensitivity switch would make it a bit more versatile. That said, I like my music to rock and I was always able to monitor without the limiter kicking in.

The batteries provide around 20 hours of use. That’s great, but stock up, since the CR2450 isn’t always the easiest battery to find; the unit ships with an extra pair of batteries. The back of the Sound Guard has a removable battery compartment cover and a pair of threaded holes located to accommodate the belt clip.

Russ Long lives and works in Nashville, engineering and producing a wide variety of music and film projects.