Performance

The Ultimate Ears Personal Reference Monitors where pitted against the usual suspects in terms of high performance in-ears—namely, the Westone ES5 (ES5), Westone 4R (4R), Jerry Harvey Audio JH16|Pro (JH16), and Ultimate Ears In-ear Reference Monitors (IERM). All of these in-ears sound ridiculously good right out of almost any type of device. Our tests use a Samsung Galaxy S3 with the Boeffla kernel (all sound tweaks applied) installed and our JDSLabs O2+ODAC modded to unity gain. The source material obviously has to be of a very high quality in order for these to make any sense so we used FLAC files and predominantly good masterings.

Based on memory, the custom version of the PRMs turned out sounding slightly darker than what I heard at the audiologist's office. It is only off by a very small amount, which might be due to the change in enclosure and the better fit of these. This is something to bear in mind when tuning your PRMs at the office. This facet is probably very hard to eliminate completely as every ear is different and the fit of the silicone tips differs greatly from one person to another.

First of all, the PRMs we got were tuned for extra bass with the bass dial at 35, midrange at 45, and treble at 55. Changes during the tuning of the earphones are audible if you turn the dial up or down by around five points. Plus 10-15 in the bass departments changes them from being bass neutral to slightly bassy. The treble was, compared to the midrange, quite dominant with the 50 setting, so a little more attenuation brought the midrange a bit more forward and took away a chunk of sibilance, which made them very entertaining to listen to. The PRMs bear some resemblance to the IERMs in that they both sound very open per default. The midrange is slightly warm, although a bit more neutral than the ES5s, which is not a bad thing. The JH16s are right in the middle here. Overall, the PRMs tuned to our liking were very close to slotting in just between the JH16s and ES5s, but with a detail-level closer to that of the IERMs, which is the most resolving in-ear solution I have ever come across.

The IERMs are way more analytical and have more treble intensity as well. The bass is not quite as powerful as it does not extend as low, but it is snappier. For analytical listening, the IERMs are still the king of the hill, but the bass seems underrepresented. For longer listening session, the PRMs are more comfortable to listen to since the IERMs are just a little too bright. This can of course be tweaked on the PRMs, and we did. Soundstage-wise, the PRMs are even better than the IERMs.

The PRMs definitely represent the next level in both customization and general sound qualities. They do come at an insane price, which is a bummer; the only pair that is comparable is the JH Audio JH-3A system, but it is a lot bulkier as it uses a dedicated DSP and active crossover box. These two solutions are currently the only custom in-ears with user-customizable sound signatures, and they both cost close to $2000.

Compared to the JH16s, the midrange is more detailed. Crunch guitar sound is so much more alive on the PRMs, which is really nice. The soundstage is also slightly deeper on the PRMs, and both are equally coherent, as you would expect from a set of high-quality custom in-ears. The midrange and treble performance of the PRMs matches and exceeds that of the ES5s in that you get the same spacious sound with even more details in the lower midrange, which is just crazy.

The PRMs will sound brilliant out of just a decent PMP, but going up a notch on the source yields a decent performance gain. Our jump from the Samsung Galaxy S3 to the O2+ODAC brought the listening experience closer to perfection than I had ever dreamed off. The bass is taught and extends really low; in fact, lower than any of the other custom in-ears we have available as a comparison. The amount of bass while playing back a neutral source with a preset of 35 is around what you get with a set of HiFiMAN HE-500s with velour pads, which is perfect for most types of music. There is just zero coloration of the midrange even after cranking the bass up, and the transition from bass to midrange is flawless and smooth.