Antdroid of Audio Discourse put on the Maestro SE, cued up Tinashe's "Talk to Me Nice," and felt as if he were sitting "in a car with massive subs in the back." Tinashe's vocals were, in his words, "still ever present and clear." That pairing is the FATfreq idea. Its Bass Cannon system gives the deepest bass, the kind you feel more than hear, a big lift while leaving the voices alone. Sajid Amit of Amplify Audio Reviews explains why that matters. Because the boost stays out of the upper bass, it doesn't cloud voices and guitars, and the Maestro Mini's midrange stays clean without sounding lean. The extra bass also appears only when a recording has real deep bass in it, and Vortex Reviews heard no big jump on acoustic jazz and a huge one on techno. FATfreq suits listeners who want the rumble of a live concert in an earphone and still want to hear the singer.

For listening, start with the Maestro Mini. It keeps voices forward, and Sajid found it small enough to wear while lying on his side. The Maestro SE is the step up, and Antdroid heard more bass texture and resolution from it. Plan your source around it. Guy Lerner of The Headphone List rates the SE among the hardest IEMs to drive he has used, so it needs a powerful player or amplifier. Try smaller tips too, since RNARexperience got a better balance on the SE with small SpinFit W1 tips. The Grand Maestro adds swappable vents in the shell, and with the vents and a vocal switch Amplify Audio Reviews counts four tunings, from analytical to bassy. The Deuce comes with an impedance adapter, and Matthew of Bloom Audio found its low end "monstrous" with the adapter or without it. Musicians have their own lines, with FATfreq recommending its Musician Series to drummers, keyboard players and guitarists and its Reference Series to engineers and vocalists.

FATfreq traces its start to a church band whose members found in-ear monitors too expensive. They made their own, and soon friends were asking for pairs, the team told STORM-ASIA Media in 2021. Engineers Aaron and Ben founded the company in 2016 as a repair and modification service, and FATfreq says that work covered more than 20 IEM brands. Its IEMs are still handcrafted in Singapore, with customs sculpted digitally from ear impressions and 3D printed. The Maestro Mini and Maestro SE, released together, carried the name abroad. Lerner calls the SE FATfreq's "big break," and RNARexperience said that if the Moondrop Variations is the sub-bass king, the SE is "the sub-bass overlord." Sajid met the team at CanJam Singapore and found crowds lined up at their booth. FATfreq has since built the Deuce with Bad Guy Good Audio Reviews, a reviewer with a big rap and hip hop library, and the single-planar Quantum with Effect Audio. Stephen Kostas of Bloom Audio called the 350-unit Grand Maestro Anniversary "one of the best flagship IEMs on the market right now."