My first experience with a 64 Audio product was with the $3000 U18t which, while impressive for a lot of things including meeting its goals as a set of professional in-ear monitors, was a lot of money to justify. I then tested the $1200 Duo which was, at the time of its launch, the least expensive UIEMs from the brand and did something different to interest a few folks no doubt. However, it was not until CanJam London 2022 that I had some time with a few more of the 64 Audio products, including the famous U12t that remains a recommendation for audiophiles and prosumers alike at the $2000 mark. When 64 Audio reached out to me about doing a review of its newest, and now its least expensive UIEMs, I said yes but also asked about getting my hands on the U12t at the same time. I am still going to do a review of the more expensive set—especially now that we also have new m12 Apex modules that I suspect I might like with the U12t too—but I was not expecting to see the new U4s come in at $1100 and make it hard to justify purchasing the U12t in the first place!

Yes, $1100 is also a lot of money and well beyond the reach of most people reading this review. You don't need to have something this expensive of course, but I do think there has never been a more compelling argument from 64 Audio to get people to open their wallets. I will go further and say the U4s is my favorite 64 Audio set I've listened to, and this includes items that cost less and significantly more too. The addition of the m12 Apex modules, which are currently exclusively available with the U4s, also help sweeten this deal given how well this combination works out to produce a balanced sound that comes off more pleasing with a variety of music genres. You can then customize the bass response with the other three Apex modules too, and common to them all is the added comfort that comes with the controlled release of any built-up pressure in your ears. I've taken the U4s for week-long work trips with me now and have left my CIEMs behind—quite a big compliment if I say so myself.

Do not think the U4s is a neutral set of IEMs, it's deliberately colored to be engaging in a few places and non-fatiguing or harsh throughout. This does result in a set that can come off slightly boring at times, especially if you are looking for a warmer sound or want a more sub-bass focused tuning. The different Apex modules do help here, but overall I can't say the U4s is the most technically competent set at the asking price. There are a few options from others which cost the same—or less—which can be more resolving and dynamic. I instead see the U4s, as with the U12t before, as an excellent all-rounder that you can purchase now and not worry about outgrowing with time. The added comfort, customization, and build quality plus points swayed me further to award it with a strong recommendation given I truly think the U4s is a new benchmark at the $1000 price range and possibly higher too.