The UE 18 Pro delivers voicing characteristics that are undeniably different from those offered by the IERM, whose tonal balance—as I noted in my earlier review—“comes very, very close to the ideal of sonic neutrality.” You might infer from this statement that the UE 18 Pro is more tonally colored than the IERM and therefore less desirable for purposes of listening to recorded music, but in practice this isn’t the case at all. Here’s why.
The IERM is geared for recording studio monitoring applications, and for this reason it that takes a pretty rigorous “what-you-hear-is-what-you-get” approach to music reproduction. If records are beautifully and vibrantly mastered then that’s how the IERM will sound, but if recordings are mastered so that they are a bit flat, lifeless and dull, then that, too, will be how the IERM will sound. In short, the IERM gives you exactly what’s on the record, whether for better or worse. The UE 18 Pro, however, takes a somewhat different tack.
Those of you old enough to remember what color photography was like back before the advent of digital cameras may recall that certain film stocks were known for their incredibly accurate colors while others deliberately delivered colors that were ever so slightly oversaturated and thus a touch more vivid and intense than those found in real life. I would liken the UE 18 Pro to those latter types of color films in that it provides, by design, tonal colors that are just slightly more vividly and intensely painted than the real thing. The key, here, is that the UE 18 Pro’s deviations from neutrality are quite subtle—never garish—so that when you hear music through it you tend to think, “Wow, these babies sound really vibrant and engaging” (as opposed to thinking, “Blecch, these things are hopeless colored and inaccurate.”). It’s as if UE has gently turned up an imaginary “intensity control” on your listening experience, yet without making instruments or voices sound unnatural.
Exactly how does UE pull this off? I would say the sonic recipe calls for two ingredients, both of which are applied with a light hand. The first is an added touch of mid-bass warmth or emphasis, which tends to give many kinds of music a more solid mid-bass foundation and a slightly warmer cast than they might normally have, yet without making naturally bass-heavy types of music sound insanely overdone. The second ingredient is an also delicate touch of upper midrange/lower treble emphasis, which tends to make many types of music sound more expressive and bit more detailed, yet without becoming overly bright or aggressive. Indeed, the upper treble response of the UE 18 Pro, if anything, a tiny bit recessed (more so than the IERM, at any rate), which keeps the top end of the music from ever sound unduly “glassy” or “hot.”
In direct comparison to the delightfully neutral IERM, you can easily identify the characteristics I’ve mentioned above, but you’ll also notice how subtly and deftly they’ve been dialed-in. Heard side-by-side, the UE 18 Pro tends to sound at once a bit darker and warmer in the bottom end, with upper mids and lower treble that is a bit—but only a bit—more forward in the mix. Another way of phrasing this is that the UE 18 Pro offers a very subtle variant on the theme of what some of my musician buddies call a “smiley face” EQ curve—meaning that if you looked at a graph of the UE 18 Pro’s frequency response it would probably look a bit like a gentle smile, with slightly prominent mid-bass at one end of the graph and gently upturned upper mids and lower highs at the other.
Interestingly, this means the middle of the midrange on the UE 18 Pro can, on some records, sound just slightly withdrawn. This is actually an illusion, though, caused by the touches of response lift found immediately above and below the center point of the midrange. In contrast, the IERM sounds smoother and more neutrally balanced across the audio spectrum, with subtly more extended and silvery highs. At the end of the day, this means that accuracy mavens will, I think, instinctively lean toward the IERM (which is also a bit less expensive than the UE 18 Pro), while those who seek a “total immersion” listening experience (even at the expense of some degree of accuracy) might gravitate toward the UE 18 Pro. To each his or her own.
Interestingly, the added points of frequency emphasis in the UE 18 Pro can, in moderately noisy environments, help the UE 18 Pros sound more accurate, because their output rises above the noise floor in a very convincing way. This characteristic, I suspect, is exactly what Ultimate Ears had in mind for its premier stage monitor.