Introducing reSpeaker Flex: The Smart Ear for Robotics and Embedded AI

Voice is becoming a core interface for the next generation of physical AI systems, from robots and smart terminals to interactive devices embedded in everyday environments. To enable reliable, far-field, and noise-robust voice interaction in these scenarios, the underlying voice interface hardware needs to be both powerful and flexible.

reSpeaker Flex is designed exactly for that.

It is a versatile 4-microphone array voice solution, with seperated mic array board and main board, built for robotics and embedded applications such as smart digital signage, kiosks, and smart toys. Powered by the XMOS XVF3800, it combines advanced on-board audio processing with a modular hardware design, making it easier than ever to build scalable, high-performance voice-enabled systems.

Powerful Voice pickup and Audio Processing for Real-World Voice Interaction

At its core, reSpeaker Flex integrates AI acoustic algorithms directly on the device. This includes:

• Acoustic Echo Cancellation (AEC): removes speaker playback echo from the microphone input for clearer two-way communication(full-duplex communication).

• Multi-beamforming: focuses on voices from specific directions while reducing surrounding noise for better voice interaction in multi-speaker environments.

• Noise suppression (NS): reduces background and device inner noise(e.g., motor noise) to deliver higher-quality voice pickup in noisy environments.

• De-reverberation: minimizes room echo and reflections for cleaner voice capture in reverberant spaces.

• Direction of Arrival (DoA): detects where sound is coming from, enabling robots to locate, face, or track speakers for more natural interaction.

• Automatic Gain Control (AGC): automatically adjusts volume levels to keep speech clear and consistent, providing better audio input for downstream STT and voice AI tasks.

For example, in a robot project, reSpeaker Flex 4-Mic Array first uses Multi-beamforming to focus on the speaker’s voice while reducing surrounding noise. Noise Suppression and De-reverberation then further clean the audio by removing background noise, motor noise inside the robot and room reflections. At the same time, AEC eliminates playback echo from the robot’s own speaker to ensure clear full-duplex communication. AGC automatically balances voice levels for stable and consistent audio input, improving downstream STT for the robots’s brain to better process with. Meanwhile, DoA detects where the voice is coming from, allowing the robot to turn toward or track the speaker for more natural voice interaction.

These algorithms work together to ensure that voice input remains clear, stable, and accurate, even in noisy, dynamic environments like public spaces or robotic systems with moving parts.

Innovative Modular Split Design Microphone Array

One of the defining features of reSpeaker Flex is its split architecture.

The system separates:

• The core processing board
• The microphone array board

These are connected via a flexible FPC cable.

This design enables much greater flexibility in product integration:

• The mic array can be placed closer to the sound source
• The core board can remain inside the device enclosure

In robotics or smart digital signage, this is a game changer. For example:

• Mount the circular mic array on a robot’s head, forehead, or chest for 360° voice pickup.
• Embed the linear mic array into the top or side bezel of smart digital signage for directional 180° voice capture in front of the display.
• Keep the processing board away from motors and servos

Flexible Microphone Array Configurations

reSpeaker Flex supports two standard array designs:

1. Circular 4-Mic Array (360° Pickup)

• Omnidirectional voice capture
• Supports 360° DoA detection
• Ideal for robots and open interaction scenarios

2. Linear 4-Mic Array (180° Pickup)

• Directional voice capture
• Optimized for front-facing interactions
• Ideal for smart signage and kiosks

This flexibility is designed for space-constrained projects, allowing developers to choose the right configuration based on how users interact with the device.

reSpeaker Flex’s Powerful Far-Field Voice Capture

Voice interaction shouldn’t require users to stand right next to a device.

Far-field voice capture up to 5 meters:

Powered by advanced on-board AI acoustic algorithms, reSpeaker Flex delivers reliable wake word detection at distances of up to 5 meters, as shown in the demo below. In real deployment scenarios, its performance can extend even further depending on the environment. With beamforming, reSpeaker Flex significantly enhances voice pickup from target directions, with recorded capture distances reaching 7–8 meters in some cases. This greatly improves the responsiveness and natural feel of voice interaction.

Accurate sound source localization (DoA-Direction of Arrival):

reSpeaker Flex Circular can accurately detect the direction of incoming sound in real time, enabling robots and smart devices to locate, face, or follow speakers more naturally. This creates more responsive and intuitive voice interactions, especially in dynamic environments.

This enables:

• Natural interaction in larger spaces
• Better user experience for public-facing systems
• Reliable performance in multi-user environments

The circular mic array further enhances this by enabling full spatial awareness, allowing systems to detect where a voice is coming from and respond accordingly.

Compact Yet High-Performance Hardware Design of reSpeaker Flex

Despite its capabilities, reSpeaker Flex is built for space-constrained embedded systems.

Key design details:

• Circular array: 73 mm diameter, 44 mm mic spacing
• Linear array: 110 mm length, 33 mm spacing
• Bottom-firing microphones to reduce interference

This allows seamless integration into:

• Robot heads and bodies
• Display bezels
• Compact enclosures

Smaller size, but no compromise on performance.

reSpeaker’s Developer-Friendly Integration

reSpeaker Flex is designed to reduce friction for developers.

Dual Interface Support

• USB (Plug-and-Play)
  • Works with Raspberry Pi, NVIDIA Jetson, PCs
  • No drivers required
• I2S (MCU Integration)
  • Compatible with microcontroller platforms like Arduino and XIAO

Preconfigured Variants

• No XIAO versions (100005504, 100099135)
  • Pre-installed USB audio firmware
• XIAO ESP32S3 versions (100070894, 100026178)
  • Pre-installed I2S firmware
  • Ready for embedded and IoT scenarios

All versions support DFU mode, allowing developers to switch firmware as needed.

Ecosystem Compatibility

• Native support for ESPHome and Home Assistant (XIAO versions)
• Easy integration into smart home and IoT systems

Scalable and Customizable for Production

Beyond prototyping, reSpeaker Flex is built with production in mind.

Customization options include:

• Microphone array size and shape adjustments
• Hardware modifications for specific form factors
• Acoustic and algorithm tuning

This makes it suitable for companies looking to deploy voice-enabled products at scale, not just experiment.

reSpeaker Flex’s Application Scenarios

Robotics and Embodied AI

reSpeaker Flex enables robots to:

• Detect wake words
• Perform speech-to-text (STT)
• Understand intent
• Execute voice commands

With support for ROS2, it integrates smoothly into robotic systems.

Its flexible placement allows microphone arrays to be mounted on:

• Head
• Ears
• Chest
• External structures (e.g., robotic arms)

An upgraded design also supports a 10W amplifier, enabling strong text-to-speech (TTS) output for more natural interactions.

Smart Toys and Companion Devices

For interactive toys and educational devices, reSpeaker Flex offers:

• Accurate voice capture in noisy environments
• On-device processing for privacy protection
• Support for conversational AI experiences

This makes it ideal for:

• Voice storytelling
• Learning assistants
• AI companions

Smart Voice Terminals

In kiosks, vending machines, and digital signage:

• Linear arrays fit seamlessly into narrow bezels
• Far-field + noise suppression ensures accuracy in public spaces

This enables:

• Touch-free interaction
• Faster user experiences
• Improved accessibility

Voice Assistants and Smart Home

reSpeaker Flex integrates with:

• Amazon Alexa
• Google Assistant
• Home Assistant

It enables reliable far-field voice control for smart home automation and connected devices.

Conference and Communication Systems

With USB connectivity, it works directly with:

• Microsoft Teams
• Zoom

The 4-mic array supports:

• Multi-person voice pickup
• Beamforming for clarity
• Real-time interaction feedback

Industrial Voice Control

In industrial environments, reSpeaker Flex provides:

• High recognition accuracy under heavy noise
• Hands-free control for machinery and systems

This improves both efficiency and safety in:

• Factories
• Retail operations
• Commercial environments

Designed for the Next Generation of Interactive Voice AI

reSpeaker Flex is more than just a microphone array. It is a complete voice interface solution designed for real-world voice interaction deployment.

With:

• Advanced on-device audio processing
• Flexible hardware architecture
• Developer-friendly integration
• Scalable customization

It provides a solid foundation for building embodied AI systems that can hear, understand, and respond reliably.

reSpeaker Flex is the smart ear for embodied AI.

Get one here and start building now!

Check the Getting Started Tutorial: Getting Started with reSpeaker Flex | Seeed Studio Wiki

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