Ultimate Ears is breaking new grounds with the level of customization for their already custom-shaped in-ears. The process of getting the PRMs is a bit tedious since you have to visit a UE audiologist, but once that is out of the way, you get the thrill of having a set of in-ears that sound just the way you like them.

The finished product has roughly the same tonal characteristics as the universal model you sample, but it is even better when it comes to detailing and fit. Ours turned out sounding a bit darker than the generic fit model at the audiologist’s office. It was a very minor shift, but that is, nonetheless, something to be wary of.

The PRMs are straight up the best set of custom in-ears we have tried and not just because the sound signature has been customized. All of the small details, such as sound stage, layering, and micro-detailing, are very good and definitely ahead of the other "fun-sounding" in-ears we have. The PRMs are truly one step above what you can get from a set of Westone ES5s or regular JH16|Pros. All the fancy technology and manual labor that goes into the PRMs does come at a cost, and at $1999, a pair is still roughly twice as expensive as any other set of high-end custom in-ears on the market. The IERMs are still the king of neutral.

The cost of perfection can be very high, but the PRMs are not horribly priced at all because they deliver the right sound for you straight out of the box. Sound enthusiasts are willing to add a lot of fancy devices after their source in order to tweak the sound to their liking, easily spending upwards of a $1000. Here, it is all in the earphones, which is quite handy since doing so reduces the bulk of your on-the-go system considerably. The PRMs do of course sound better with a brilliant amplifier but pair well with anything neutral-sounding, so there is literally no need for a fancy amplifier. A modded Samsung Galaxy S3 or other good portable source will do them justice. Powering them with an O2+ODAC, like the one from JDSLabs, does increase the sound quality, but it is just so far past the point of diminishing returns that it is definitely not worth the bulk when you are on the move.

The Ultimate Ears Personal Reference Monitors are for the audiophile who wants the perfect frequency response straight out of the box without the hassle of having to carry around a dedicated DSP.