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Product Description

Line Circle
The 64 Audio U4s is a quad-driver hybrid IEM featuring flagship technologies like tia™, apex™, and LID™ at an accessible price point. It delivers deep sub-bass, balanced mids, and airy highs in a lightweight, beautifully designed shell. With customizable isolation and reference-level performance, it’s built for audiophiles who want premium sound without the premium price.
Get the Details

Features & Specs Line Circle

Quad-Driver Hybrid Setup
Combines dynamic and BA drivers for rich, controlled sound
tia™ High Driver & Single-Bore
Open treble response with minimized distortion
apex™ Module System
Includes mX, m15, and m20 for pressure relief and tuning options
LID™ Circuit
Ensures consistent sound across any audio source
Electrical Low-Pass Filter
Reduces low-frequency distortion before driver output
Full Accessory Kit
Includes case, ear tips, cleaning tool, modules, and more
Quad-Driver Hybrid Setup
Combines dynamic and BA drivers for rich, controlled sound
tia™ High Driver & Single-Bore
Open treble response with minimized distortion
apex™ Module System
Includes mX, m15, and m20 for pressure relief and tuning options
LID™ Circuit
Ensures consistent sound across any audio source
Electrical Low-Pass Filter
Reduces low-frequency distortion before driver output
Full Accessory Kit
Includes case, ear tips, cleaning tool, modules, and more

Expert Insight

Line Circle

U4s completely exceeded my expectations—the sub-bass is punchy, mids are smooth, and the treble is beautifully airy without being harsh. It’s the perfect mix of musical and analytical with long-wear comfort. Easily my favorite in this price range.

Expert Img
Dylan Crane
Brand Manager

Details

Line Circle

64 Audio U4s Universal Hybrid In-Ear Monitors

The 64 Audio U4s is a breakthrough 4-driver hybrid UIEM that brings flagship technology to a more accessible price point without sacrificing sonic performance. Combining one dynamic driver with three balanced armatures—including a patented tia™ high driver—the U4s delivers impactful sub-bass, neutral mids, and an open, airy treble for an immersive, fatigue-free listening experience. Enhanced by LID™ for consistent sound across devices and apex™ venting modules for pressure relief and expanded soundstage, U4s offers both comfort and tuning flexibility. Housed in an anodized Slate Blue aluminum shell with a meteorite-inspired faceplate, U4s is as stunning as it is sonically refined.

Specifications

  • Driver Configuration: 1 tia High Driver, 1 High-Mid Driver, 1 Mid Driver, 1 Dynamic Low Driver
  • Frequency Response: 10 Hz – 20 kHz
  • Sensitivity: 107 dB/mW @ 1 kHz
  • Impedance: 11 Ω @ 1 kHz
  • Crossover: Integrated 4-Way Passive Crossover with Electrical Low-Pass Filter
  • Apex Isolation: -10 dB (mX), -15 dB (m15), -20 dB (m20)
  • Shell Material: Anodized Aluminum with Meteorite-Inspired Faceplate
  • Color: Slate Blue
  • Cable: Black Premium Cable – Silver-Plated OCC Copper (7x7x4 Multi-Twist, 26 AWG, 0.23Ω), 3.5mm Termination
  • Included Accessories: Premium Leather Case, TrueFidelity Foam Tips (S/M/L), SpinFit Silicone Tips (S/M/L), Standard Silicone Tips (S/M/L), Apex Modules (m20, m15, mX), Cable Clip, Cleaning Tool, Round Sticker
  • Technology: tia™ Driver & Single-Bore, apex™ Venting System, LID™, Electrical Low-Pass Filter
  • Fit: Universal
  • Designed & Assembled: In the USA with globally sourced components

Expanded Key Features List

  • Hybrid Quad-Driver Design: Combines dynamic and balanced armature drivers for full-spectrum performance and low distortion.
  • tia™ High Driver with Single-Bore: Delivers open, extended treble with reduced resonance and enhanced detail.
  • apex™ Venting System: Includes three swappable modules (m20, m15, mX) for pressure relief and customizable isolation.
  • LID™ Circuitry: Ensures tuning consistency across various devices regardless of output impedance.
  • Electrical Low-Pass Filter: Reduces low-frequency distortion by filtering unwanted signals before reaching the driver.
  • Balanced, Engaging Sound: Deep sub-bass, clear mids, and smooth highs ideal for all genres at any volume.
  • Premium Slate Blue Shell: Anodized aluminum housing with a unique meteorite-inspired faceplate design.
  • Black Premium Cable: Durable silver-plated copper cable with low resistance for optimal signal transmission.

Q&A Section

Q: What type of sound can I expect from the U4s?
A: U4s offers rich sub-bass, smooth mids, and airy treble with a spacious soundstage—perfectly suited for both casual listening and critical enjoyment.

Q: How many drivers are in the U4s?
A: U4s features four drivers: one dynamic low, one mid, one high-mid, and one tia™ high driver for a full, coherent sound.

Q: What is the benefit of the tia™ technology in the U4s?
A: The tia™ high driver and single-bore design eliminate traditional tubing to reduce resonance and distortion, improving treble clarity and realism.

Q: Can I customize the sound of the U4s?
A: Yes, it comes with three apex™ modules (mX, m15, m20) that alter isolation and subtly shift the tuning to match your preferences.

Q: What makes the faceplate design unique?
A: The faceplate is inspired by Muonionalusta meteorite fragments and features a reflective finish that changes with light, making each unit visually distinctive.

Q: Does the U4s sound the same with different devices?
A: Thanks to LID™ technology, U4s maintains its intended sound signature across a wide range of sources, including DACs, amps, and smartphones.

Q: Is the cable included and upgradeable?
A: Yes, U4s includes a 3.5mm black premium cable and uses a standard 0.78mm 2-pin connection for easy upgrades.

Q: What accessories are provided with the U4s?
A: You receive a premium leather case, full tip kit (foam, silicone, SpinFit), apex modules, cable clip, cleaning tool, and sticker.

Reviews

Line Circle
Product Descriptiondown arrow

Product Description

Line Circle
The 64 Audio U4s is a quad-driver hybrid IEM featuring flagship technologies like tia™, apex™, and LID™ at an accessible price point. It delivers deep sub-bass, balanced mids, and airy highs in a lightweight, beautifully designed shell. With customizable isolation and reference-level performance, it’s built for audiophiles who want premium sound without the premium price.
Get the Details
Features & Specsdown arrow

Features & Specs Line Circle

Quad-Driver Hybrid Setup
Combines dynamic and BA drivers for rich, controlled sound
tia™ High Driver & Single-Bore
Open treble response with minimized distortion
apex™ Module System
Includes mX, m15, and m20 for pressure relief and tuning options
LID™ Circuit
Ensures consistent sound across any audio source
Electrical Low-Pass Filter
Reduces low-frequency distortion before driver output
Full Accessory Kit
Includes case, ear tips, cleaning tool, modules, and more
Quad-Driver Hybrid Setup
Combines dynamic and BA drivers for rich, controlled sound
tia™ High Driver & Single-Bore
Open treble response with minimized distortion
apex™ Module System
Includes mX, m15, and m20 for pressure relief and tuning options
LID™ Circuit
Ensures consistent sound across any audio source
Electrical Low-Pass Filter
Reduces low-frequency distortion before driver output
Full Accessory Kit
Includes case, ear tips, cleaning tool, modules, and more
Expert Insightdown arrow

Expert Insight

Line Circle

U4s completely exceeded my expectations—the sub-bass is punchy, mids are smooth, and the treble is beautifully airy without being harsh. It’s the perfect mix of musical and analytical with long-wear comfort. Easily my favorite in this price range.

Expert Img
Dylan Crane
Brand Manager
Detailsdown arrow

Details

Line Circle

64 Audio U4s Universal Hybrid In-Ear Monitors

The 64 Audio U4s is a breakthrough 4-driver hybrid UIEM that brings flagship technology to a more accessible price point without sacrificing sonic performance. Combining one dynamic driver with three balanced armatures—including a patented tia™ high driver—the U4s delivers impactful sub-bass, neutral mids, and an open, airy treble for an immersive, fatigue-free listening experience. Enhanced by LID™ for consistent sound across devices and apex™ venting modules for pressure relief and expanded soundstage, U4s offers both comfort and tuning flexibility. Housed in an anodized Slate Blue aluminum shell with a meteorite-inspired faceplate, U4s is as stunning as it is sonically refined.

Specifications

  • Driver Configuration: 1 tia High Driver, 1 High-Mid Driver, 1 Mid Driver, 1 Dynamic Low Driver
  • Frequency Response: 10 Hz – 20 kHz
  • Sensitivity: 107 dB/mW @ 1 kHz
  • Impedance: 11 Ω @ 1 kHz
  • Crossover: Integrated 4-Way Passive Crossover with Electrical Low-Pass Filter
  • Apex Isolation: -10 dB (mX), -15 dB (m15), -20 dB (m20)
  • Shell Material: Anodized Aluminum with Meteorite-Inspired Faceplate
  • Color: Slate Blue
  • Cable: Black Premium Cable – Silver-Plated OCC Copper (7x7x4 Multi-Twist, 26 AWG, 0.23Ω), 3.5mm Termination
  • Included Accessories: Premium Leather Case, TrueFidelity Foam Tips (S/M/L), SpinFit Silicone Tips (S/M/L), Standard Silicone Tips (S/M/L), Apex Modules (m20, m15, mX), Cable Clip, Cleaning Tool, Round Sticker
  • Technology: tia™ Driver & Single-Bore, apex™ Venting System, LID™, Electrical Low-Pass Filter
  • Fit: Universal
  • Designed & Assembled: In the USA with globally sourced components

Expanded Key Features List

  • Hybrid Quad-Driver Design: Combines dynamic and balanced armature drivers for full-spectrum performance and low distortion.
  • tia™ High Driver with Single-Bore: Delivers open, extended treble with reduced resonance and enhanced detail.
  • apex™ Venting System: Includes three swappable modules (m20, m15, mX) for pressure relief and customizable isolation.
  • LID™ Circuitry: Ensures tuning consistency across various devices regardless of output impedance.
  • Electrical Low-Pass Filter: Reduces low-frequency distortion by filtering unwanted signals before reaching the driver.
  • Balanced, Engaging Sound: Deep sub-bass, clear mids, and smooth highs ideal for all genres at any volume.
  • Premium Slate Blue Shell: Anodized aluminum housing with a unique meteorite-inspired faceplate design.
  • Black Premium Cable: Durable silver-plated copper cable with low resistance for optimal signal transmission.

Q&A Section

Q: What type of sound can I expect from the U4s?
A: U4s offers rich sub-bass, smooth mids, and airy treble with a spacious soundstage—perfectly suited for both casual listening and critical enjoyment.

Q: How many drivers are in the U4s?
A: U4s features four drivers: one dynamic low, one mid, one high-mid, and one tia™ high driver for a full, coherent sound.

Q: What is the benefit of the tia™ technology in the U4s?
A: The tia™ high driver and single-bore design eliminate traditional tubing to reduce resonance and distortion, improving treble clarity and realism.

Q: Can I customize the sound of the U4s?
A: Yes, it comes with three apex™ modules (mX, m15, m20) that alter isolation and subtly shift the tuning to match your preferences.

Q: What makes the faceplate design unique?
A: The faceplate is inspired by Muonionalusta meteorite fragments and features a reflective finish that changes with light, making each unit visually distinctive.

Q: Does the U4s sound the same with different devices?
A: Thanks to LID™ technology, U4s maintains its intended sound signature across a wide range of sources, including DACs, amps, and smartphones.

Q: Is the cable included and upgradeable?
A: Yes, U4s includes a 3.5mm black premium cable and uses a standard 0.78mm 2-pin connection for easy upgrades.

Q: What accessories are provided with the U4s?
A: You receive a premium leather case, full tip kit (foam, silicone, SpinFit), apex modules, cable clip, cleaning tool, and sticker.

Reviewsdown arrow

Reviews

Line Circle
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