Sony is a Japanese company that specializes in various electronics products, including HiFi audio equipment.

Sony

The Sony APM-22 ES MK II is a vintage tower speaker system that was released in the 1980s. It features a 3-way design with wood cabinets and a large woofer for powerful bass response. The speakers are known for their clear and detailed sound quality.

APM-22 ES MK II


## Introduction to Acoustic Metrics

### Why Acoustic Metrics Matter

Sound is more than just what we hear; it's a wave that behaves in specific ways in different environments. To better understand and control how sound behaves in a space—be it a home theater, recording studio, or an open-office layout—we use acoustic metrics. These metrics provide us with a quantitative means of assessing and improving a room's acoustical properties.

### Brief Overview of NRC and STC

Noise Reduction Coefficient (NRC) and Sound Transmission Class (STC) are two of the most commonly used acoustic metrics. NRC tells us how well a material absorbs sound, thereby reducing echo and reverberation. STC, on the other hand, measures how effectively a material can block sound from traveling from one space to another. Both metrics are crucial for anyone interested in acoustics, from audiophiles to architects.

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## Exploring NRC (Noise Reduction Coefficient)

### What is NRC?

NRC, or Noise Reduction Coefficient, is a number between 0 and 1 that represents the fraction of sound energy absorbed by a material. A score close to 1 indicates that the material is very effective at absorbing sound, while a score near 0 means it reflects most of the sound hitting it.

### How to Interpret NRC Ratings

NRC ratings are often found on products like acoustic panels, carpets, and ceiling tiles. A material with an NRC rating of 0.75, for example, would absorb 75% of sound energy and reflect the remaining 25%. In spaces where clear, detailed sound is essential—such as recording studios or home theaters—an NRC rating closer to 1 is generally desired.

### Practical Applications of NRC

Understanding NRC is essential when you are looking to control sound within a space. In recording studios, materials with high NRC ratings are used to reduce ambient noise and improve recording quality. In home theaters, NRC-rated panels can significantly enhance the viewer's experience by cutting down on distracting echoes and reverberations. Even in noisy industrial settings, NRC can play a role in creating a more acoustically pleasant environment.

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## The Importance of STC (Sound Transmission Class)

### What is STC?

Sound Transmission Class (STC) is a metric that measures a material's ability to block sound from traveling through it. Unlike NRC, which focuses on absorption within a single space, STC helps us understand how soundproof a material is between two distinct spaces.

### Factors Affecting STC Ratings

Several factors can affect a material's STC rating, including its density, thickness, and how it's installed. Generally, materials like concrete and brick have high STC ratings, making them excellent for soundproofing. However, even a high-STC material can underperform if it's installed poorly, such as with gaps or cracks that allow sound to seep through.

### STC in Real-world Scenarios

In residential buildings, understanding STC can help you create a quieter and more private living environment by choosing walls, floors, and doors with higher STC ratings. In commercial settings, like offices or hospitals, STC-rated partitions can greatly enhance privacy and reduce noise pollution.

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## NRC vs STC - Knowing When to Use Which

### Different Goals, Different Metrics

While both NRC and STC are instrumental in shaping a room's acoustic properties, they serve different purposes. NRC is used for improving sound quality within a room by minimizing echo and reverberation. STC is used for isolating rooms from each other, ensuring that sound doesn't leak from one space to another. Knowing which metric to focus on is crucial for effective acoustic treatment.

### Complementary but Not Interchangeable

It's important to note that a material with a high NRC rating won't necessarily have a high STC rating, and vice versa. For example, foam panels may have excellent sound absorption properties but may not be effective in soundproofing between rooms.

### Case Examples

-   **Home Theater**: You'd likely be concerned with both NRC (to improve sound quality within the room) and STC (to prevent sound leakage into other parts of the home).
-   **Recording Studio**: NRC would be critical here to capture clean recordings, but STC would also be important to ensure external noises don't contaminate the recording.

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## Measuring and Evaluating Acoustic Metrics

### Tools of the Trade

Sound level meters, room analysis software, and specialized microphones can be used to measure and analyze acoustic metrics. These tools can provide a quantitative evaluation that can guide you in choosing the right materials.

### DIY vs Professional Analysis

Simple mobile apps can give you a basic understanding of a room's acoustics, but for critical applications like studios or professional theaters, you may need to consult with acoustics professionals for a more detailed evaluation.

### Understanding the Numbers

-   **NRC**: Generally, an NRC rating of 0.6 or higher is considered good for most indoor environments.
-   **STC**: An STC rating of 50 or higher is considered excellent for blocking out most everyday noises.

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## Practical Applications and Recommendations

### Tailoring to Your Needs

Your specific needs will dictate whether you should prioritize NRC, STC, or both. Are you trying to improve the acoustics of an open office, or are you more concerned with soundproofing an in-home cinema?

### Material Selection

-   For high NRC: Look for specialized acoustic panels, fabrics, and foams.
-   For high STC: Consider denser materials like mass-loaded vinyl, drywall, or even specialized acoustic doors.

### When to Consult an Expert

If you're dealing with complex acoustic challenges or need specialized solutions, it might be wise to consult an acoustics professional for a more in-depth analysis and tailored solutions.

simple sound insulating panel with a neutral-colored fabric finish.png

Introducing Acoustic Metrics: NRC , STC

Explore the essential acoustic metrics NRC and STC, learn their differences and applications, and discover how to measure and optimize them for better sound quality and isolation.


At this year's Munich Audio Show, Feliks Audio is captivating the audio community with its innovative tube amplification technology. Lukasz, a representative from Feliks Audio, shared insights into their latest offerings, which include the Envy 25th Anniversary headphone amplifier and a prototype of their first electrostatic amplifier.

**Envy 25th Anniversary Amplifier**

The Envy 25th Anniversary edition marks a significant milestone for Feliks Audio, celebrating 25 years of excellence in audio engineering. This limited-edition amplifier, with only 25 units available worldwide, has been designed to push the boundaries of what was previously thought possible in tube headphone amplifiers. Key upgrades include:

-   Custom-made amorphous core output transformers.
-   A specially designed power transformer.
-   Elrog 300B Feliks-branded power tubes.
-   Additional enhancements aimed at improving synergy and performance. The amplifier also features a stunning black piano finish, enhancing its visual appeal as much as its auditory prowess.

**Mystery Electrostatic Amplifier Prototype**

Feliks Audio also teased a "mystery" reveal—an advanced prototype of their first electrostatic amplifier, which has been in development for over three years. This new amplifier uses the 300B power tube, known for its exceptional quality, and is compatible with both old and new electrostatic headphones. Despite the prototype lacking a final chassis, Feliks Audio promises that the finished product will align with the high aesthetic standards of their current lineup.

**Sound Signature and Customer Feedback**

The new electrostatic amplifier aims to deliver robust bass reproduction—a notable challenge in electrostatic setups—while maintaining the high-resolution and detailed highs that Feliks Audio products are known for. The overall sound signature is described as neutral, consistent with the brand’s philosophy, providing an enveloping, light yet powerful audio experience. This setup is particularly optimized for headphones like the Stax SR-X9000, promising an immersive listening experience.

**Looking Ahead**

Feliks Audio is optimistic about making the electrostatic amplifier available by the end of the year, contingent on the progress of the final design stages. Additionally, the brand plans to focus on enhancing production schedules and reducing wait times for various models, particularly the Envy variants, which continue to be highly popular among audiophiles. Feliks Audio remains committed to innovation and eagerly anticipates community feedback to guide future developments.

Screenshot 2024-05-06 at 20.29.17.png

 Feliks Audio Showcases Groundbreaking Amplifiers at Munich Audio Show

Feliks Audio is a company that specializes in high-end audio equipment, particularly tube amplifiers and headphone amplifiers.

 Feliks Audio

Join Feliks Audio in celebrating 25 years of audio excellence with the launch of their Envy 25th Anniversary amplifier and a new electrostatic amplifier prototype

Tokyo, Japan - In a significant move blending traditional high-fidelity audio with modern streaming technology, Rotel has announced the launch of the RAS-5000 Stereo Integrated Amplifier. This latest offering from Rotel promises a seamless audio experience with robust Class AB power and extensive streaming capabilities.

The RAS-5000, designed to simplify the entertainment space, supports popular streaming services such as Spotify Connect, Tidal Connect, and Airplay 2, along with HDMI ARC for enhanced TV audio. The inclusion of a premium ESS 32-bit DAC ensures precision in rendering high-resolution audio.

Not just a powerhouse in performance, the RAS-5000 boasts a sleek design, available in black or silver, and is equipped with a user-friendly interface, making it a stylish addition to any décor.

Rotel's commitment to audio quality is evident in the RAS-5000's construction, featuring top-grade components and an oversized toroidal transformer. Delivering 220 Watts of power into 4 ohms, the amplifier is set to redefine home audio systems, offering both audiophiles and casual listeners an unparalleled sound experience.

Screenshot 2023-11-18 at 10.25.55.png

Rotel_RAS-5000_Internal.png

Rotel Unveils the RAS-5000: A Fusion of Tradition and Modern Streaming

Meet the Rotel RAS-5000, where high power meets high-tech streaming. Enjoy 220W Class AB power and exceptional audio clarity in a stylish package

APM-22 ES MK II

by Sony

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Interesting articles

Introducing Acoustic Metrics: NRC , STC

Feliks Audio Showcases Groundbreaking Amplifiers at Munich Audio Show

Rotel Unveils the RAS-5000: A Fusion of Tradition and Modern Streaming