64 Audio U4S VS ThieAudio Monarch MK4

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Priced between $1,150 and $1,300 depending on custom faceplate options like the butterfly design shown, the Thieaudio Monarch MK IV boasts exceptional build quality with a large but well-contoured titanium shell offering a secure and comfortable fit. Key features include the innovative rumble switch for adjustable bass levels on the fly, a durable two-pin connector, and a solid feel that inspires confidence in longevity. While the included accessories are considered fair but unexciting, the shell's customization potential and rugged construction are major highlights.

Sonically, the Monarch MK IV delivers a detailed, exciting, and clean sound signature that stands as the best in the Monarch lineage. The rumble switch provides two distinct profiles: the red switch (no rumble) offers a balanced, tactful bass presentation, while the gold switch (rumble) adds a satisfying sub-bass shelf ideal for genres like hip-hop. Treble performance is notably improved over the MK III, though a 10k peak requires careful ear tip selection for some listeners. It trades blows with flagships like the $3,000 Annihilator (better sub-bass focus) and the $1,800 Elysian Apostle (more vocal forward), often matching or exceeding their technicalities while offering its unique tuning flexibility.

Scoring a top-tier 9.8, the Monarch MK IV earns its place through a compelling combination of premium build, the highly functional rumble switch, and outstanding sound quality that feels both special and refined. While acknowledging the high price, it represents significant value against competitors like the $2,000 Thieaudio Valhalla or the fiddly Grand Maestro, offering a feature-rich, durable, and sonically excellent package that justifies its position as a current summit-fi favorite.