The Linux Foundation Adopts Sound Open Firmware Project Enabling Developers to Adapt Operating Systems for Audio Devices
During the Embedded Linux Conference in Portland, OR, The Linux Foundation announced that Sound Open Firmware (SOF) has become a Linux Foundation project. With significant engineering and code contributions from Intel Corp., SOF includes digital signal processing (DSP) firmware and an SDK that together provide infrastructure and development tools for developers working on audio or signal processing. Intel and Google support SOF and invite others to join them in advancing the projectRead More

Arturia Releases New Software Packages Recreating Famous Vintage Studio Preamps and Synth Filters
Arturia launched an exciting new range of software plug-ins leveraging the company's expertise in analog circuit emulation. The first of two new packages includes recreations of Rupert Neve's classic solid-state 1973 Preamp, Trident Studio's A Range console preamps, and a classic Telefunken V76. The filters package includes modeled circuits from Bob Moog, Tom Oberheim's Matrix-12, and the famous SEM-filter. All software recreations include valuable tools and add-ons.   Read More

A New Turntable from McIntosh and It's Not That Expensive
McIntosh has unveiled a new turntable that brings its famous McIntosh sound and build quality to a new "low price" point. The new MT2 was announced with a suggested retail price of $4,000, which is significantly less than the brand's flagship MT5 ($8,000) and MT10 ($6,000). Of course, you don't get the glowing green plate, but according to the company, you get the latest turntable technology with the New York giant's legendary aesthetic, design, and build quality.    Read More

Jabra Elite Third-Generation True Wireless Earbuds Establish the Benchmark
Among the many new true wireless earbuds unveiled at CES 2018, Jabra was a clear stand-out with its new Elite 65t and Elite Active 65t models. Benefiting from extensive experience in wireless audio and hearing aids, Jabra engineered the new Elite 65t earbuds for the best on-the-go true wireless calls and music experience - including an "Active" version for those doing sports. Among the new features is also the integration for Amazon Alexa on-the-go and integrated one-touch access to Siri and Google Now.   Read More

Audio Precision Expands Microphone Product Family 
Audio Precision announced the expansion of its line of measurement microphones with the introduction of the 376M03, a calibrated microphone system combining a 1/2" microphone cartridge with a phantom-powered preamplifier - the 426M16 - in its 1/2" configuration. The new preamplifier combines the precision of calibrated, standardized measurement microphones with the convenience of ubiquitous mic accessories offering phantom power, balanced connections for improved immunity to induced noise, and easy connectivity via common XLR cables.   Read More

Celestion New Ferrite Magnet AF Line Array Driver Series
First unveiled at the 2018 Winter NAMM Show, Celestion will be highlighting its new value-priced range of weather-resistant, compact, low-profile drivers, the AF range, at the upcoming Prolight+Sound 2018 show in Frankfurt. The new range was designed for use in compact line arrays, column speakers, and compact single-speaker applications. It also complements the existing AN Line Array Driver range, which has proven extremely popular with pro audio manufacturers.   Read More

Astro Spatial Audio to Demonstrate Object-Based 3D Sound with Third-Party Integration at Prolight+Sound 2018
Astro Spatial Audio (ASA) will highlight its brand's agnostic approach to true object-based immersive audio when it returns to Prolight+Sound at the Frankfurt Messe, from April 10-13. The company will offer special presentations throughout the show, highlighting the deep integration between ASA's SARA II Premium Rendering Engine and third-party systems including TTA's Stagetracker II next-generation performer tracking, Alcons Audio loudspeakers, and QLab playback automation software.   Read More

Bose Introduces Audio Augmented Reality Platform at SXSW 2018
At SXSW 2018 (, Bose has introduced Bose AR, the company's concept for an audio augmented reality platform, in the shape of glasses to hear. According to Bose, the prototype "launches the future of mobile sound," and Bose also announced an SDK schedule date for developers, manufacturers, and research institutions, along with collaborations currently under way, and venture funding for related start-ups.   Read More

Mike Klasco

Guest Editorial

Near-Field Magnetic Induction (NFMI) Technology for Hearables and More

Previously in The Audio Voice we explored the development and ongoing capabilities of Hearables in the form of True Wireless Stereo (TWS) earphones. The appeal of TWS is undeniable - surely Hearables in the form of smart earphones will become as ubiquitous as smartphones. Sooner or later we won't even have to take our smartphones out of our pockets anymore, just listen to the voice in our ears and respond with a quiet utterance. On-board music libraries, continuous access to the Internet, total hands-free control by voice command, and a health tracking functionality will infuse TWS earphones into our lives more intimately than even the smartphone.

True Wireless Stereo (TWS) Earbuds are a fast-expanding application area for NFMI technology.
Hurdles to overcome include very dense mechanical packaging and battery size constraints, making it hard to include additional features while chasing the long battery operation that users crave. Some of the most intriguing use cases are literally all day long and well beyond the battery charge duration of Hearables today. Imagine your Hearable working hands-free while keeping your smartphone pocketed, filtering outside sounds to what you would like to hear, or even acting as hearing sound enhancement and hearing protection at concerts.
Game-changing technology that would move Hearables' performance closer to consumers' expectations such as much higher density batteries and next-generation Bluetooth antenna technology are not low-hanging fruit. But more positive news is the gains made with the integration of Near-Field Magnetic Induction (NFMI) into TWS earphones. NFMI has proven pivotal for TWS Hearables, enabling longer battery life, stable performance, reduced signal latency, and increased security over existing Bluetooth designs.
Today, the dominant technology implementing the connection with the smartphone is Bluetooth, but this approach alone is not a fit for TWS earphones. Sending a stereo audio stream to two distinct earbuds is not possible using standard Bluetooth A2DP profile: it is a point-to-point solution. As current Bluetooth profiles do not allow for sending stereo audio from a smartphone to two wireless earbuds at the same time, the solution attempted by first generation TWS was to send a stereo stream to one earbud and next forward one of the audio streams to the other earbud reusing the same Bluetooth device. This does not work reliably with head movement, a hand touching or passing your ear, etc. would lead to dropouts, constant re-pairing, along with increased power consumption and in the end too many product returns.
Bluetooth is simply not the right choice for communication between earphones as these microwaves are mostly soaked up by the brain between the earphones. Aside from performance, there is the open question of long-term health impact implications of Bluetooth cross-body and especially ear-to-ear communications for users. NFMI topology uses Bluetooth from the smartphone as the server to one earpiece, which then passes the alternative audio channel to the second earpiece using NFMI rather than RF Bluetooth.
When we think of electromagnetic waves, we're typically thinking of radio frequency (RF), and in the case of wireless Personal Area Networks (PAN), that has been Bluetooth. RF signals are all essentially the same. The signal is loaded with energy and sent out of the antenna to travel until the signal runs out of energy; that's why RF is called a far-field transmission. Far-field transmission is appropriate over long distances, but there are real problems when lots of devices use RF or Bluetooth simultaneously. When too many devices use the same radio frequency too close to each other, they interfere with each other. When you pack a signal with enough energy to travel way past the device with which you need to speak, you're wasting power. We can't stop RF signals from propagating into space, and out there with it goes the handshake and encryption protocols... that's why Bluetooth devices have been hacked over a mile away.
Bluetooth has its appealing attributes including a large established user base, relatively low power consumption, and mature support. Many designers and product managers have come to accept Bluetooth's vulnerabilities but there is significant room for a better user experience. At trade shows, we all have seen too many wireless products (Bluetooth, Wi-Fi, ZigBee, cordless phones, baby monitors, and even microwave ovens) all using the same frequency bands shut each other down. The commercial success of RF wireless products and the resultant crowding of the bands is now the cause of their shortcomings. Then, we also have Bluetooth's lack of security and excessive latency vs. quality trade-offs.
Bluetooth True Wireless Stereo enhanced with Cross-Body NFMI Streaming.
Our focus here is Near-Field Magnetic Induction (NFMI), which offers characteristics appropriate for use with short-range wireless audio and data connection between earbuds. NFMI works at a very low frequency (typically 10.6 MHz), resulting in a radio that is ultra-low power. In the January 2017 edition of audioXpress you can find a Near-Field Magnetic Induction overview by Dr. Michael Abrams of FreeLinc, debating those benefits and applications.
FreeLinc began by manufacturing and distributing NFMI-enabled radio accessories to law enforcement and public safety officers, where the need for secure and reliable short-range wireless connectivity was the most immediate. There are now more than 2,500 US Public Safety agencies using FreeLinc products, including the FBI and the Secret Service. NFMI has evolved through multiple product cycles in the highly demanding law enforcement market.
The first practical NFMI integrated chip solution for TWS applications was introduced by NXP with the NxH2280 in 2016. The NxH2281 introduced further improved audio performance at the start of 2017. Future NxH series enhancements will maintain performance and low power while shrinking both cost and package size.
NFMI uses a tightly coupled, low power, non-propagating field between devices - sort of a lossy transformer.

What Is Near-Field Magnetic Induction?
NFMI is a modulated low-frequency magnetic field - not RF but a loose coupling of low power, non-propagating magnetic field between devices for near-field communication. Essentially, the operation can be modeled as a weakly coupled transformer - AC current in primary induces AC voltage in secondary winding. The antenna design rules are basic and range can be accurately defined by the size and positioning of the antenna(s) up to a distance of 1 meter. NFMI is human body friendly - the magnetic field goes through (body) tissue with negligible absorption so there is no degradation of signal strength, and the specific absorption rate is 10,000 times less than for Bluetooth. For these reasons, NFMI has been used for more than a decade in medical devices such as hearing aids.
Most of the second wave of hearable TWS earphones have evolved to NFMI designs such as: The Headphone and The Dash by Bragi, Yevo1 from Yevo Labs, Alpha Skybuds, Earin M2, Click Mymanu, Jabra Sport Elite, andIQ Buds Nuheara. Apple's AirPods use their own proprietary solution and there are viable Bluetooth TWS examples that have implemented sophisticated directional and diversity antenna schemes.

NXP Semiconductors introduced the second-generation fully integrated NxH2280 NFMI single-chip radio transceiver in 2016. In 2017, the NxH2281 introduced further improved audio performance.

RF and NFMI and How They Differ
Near-field communication as a modulated AC current (such as an audio signal) in the primary induces AC voltage in secondary winding (antenna). For TWS, NFMI earphone applications, typically a 2 mm x 6 mm antenna coil is used in each earpiece. Longer distances up to a meter can be achieved but with a larger antenna and optimum orientation. Multiple antennas can be used as well for stable low power over highly defined range - like your inflight entertainment business class seat area. A flight with a few hundred Bluetooth systems in use would never work, while NFMI could be interference free.
Magnetic fields decay much faster than Bluetooth so NFMI actually creates a very tight coverage area around you. Steep degradation of magnetic induction signal strength as function of distance reduces interference level, therefore, it increases robustness and privacy, enabling separate use of the same carrier frequency for multiple headsets in a shared area.
Within this area multiple devices reliably connect, and outside they simply cannot be seen. Invisible to Bluetooth and Wi-Fi, NFMI does not cause interference in other devices or wireless networks. Once you've moved a distance away from the coverage area, the same frequency can be used to create another distinct coverage area. It's not physically possible to overcrowd the airwaves with NFMI like RF. And NFMI uses a fraction of the power used by Bluetooth to move the same amount of information. The power level is so low that NFMI communications are below the EMC background thresholds set by the Federal Communications Commission.
Aside from TWS earphones, NFMI has been successfully applied in hearing aids, pacemakers, and other applications where the robustness and integrity of the wireless link must be trusted. Future near-field applications range from super low latency bi-directional streaming for gamers, in-ear monitoring (IEM) for musicians, and interference-free inflight entertainment headphones without the mess of cables.
A future issue of audioXpress magazine will feature in-depth and exclusive coverage of NFMI.


From The Vault
A Hybrid Tube/MOSFET Headphone Amplifier
By Erno Borbely
A popular hybrid amp design available for headphone use, this single-ended (SE) pure Class-A amplifier is capable of driving headphones between 32 Ω and 600 Ω and was derived from an original tube/MOSFET line amplifier project, published by Erno Borbely in Glass Audio (1/98). Originally published in audioXpress in April 2005, this project was also extensively discussed in multiple DIY audio forums all over the world and is probably one of the most tested of Erno Borbely's designs, with multiple iterations frequently published on blogs and other publications. We thought it was time to make it openly available directly in audioXpress (no more need to search for shady PDFs on the Internet...). To illustrate this post we even selected a build effort from Denmark (theslowdiyer), which includes some nice tips and alternative component choices, complete with additional useful project files. The link is included in the article. If anyone else has alternative builds, please let us know. We are also interested to know of any companies making the original EB-804/421 kit available today, since Erno's original website and web shop is no longer available.  This article was originally published in audioXpress, April 2005.   Read the Full Article Now Available Here

Voice  Coil Test Bench
The 745NEOBe Compression Driver from Radian Audio 
By Vance Dickason
For this Test Bench article, I examined the 745NEOBe, a pro sound 1.4" beryllium compression driver from Radian Audio Engineering. Radian Audio was founded in 1988 by its president, Dr. Richard Kontrimas, however, Kontrimas has since retired and the company is under new ownership. Radian Audio's initial offerings were replacement compression driver diaphragms. The diaphragms did so well that it wasn't long before the company started making compression drivers. Several major loudspeaker manufacturers quickly identified Radian Audio as an important source for their compression driver needs and became OEM customers. Coaxial loudspeakers were introduced shortly thereafter, followed by woofers and finally, complete loudspeaker systems. Today, Radian Audio, based in Orange, CA, is a major player in the OEM loudspeaker component business, the sound contractor/fixed installation market and the portable/tour sound industry. With more than two decades of success under its belt, Radian Audio is now entering its third decade as a pro sound manufacturer. In terms of features, the 745NEOBe has a 5-to-20-Hz frequency range, a 76.3 mm (3") voice coil diameter wound with edge-wound copper clad aluminum wire on a high temperature polymer former, available with both structural aluminum or beryllium diaphragms, a neodymium ring magnet motor structure, a heat stabilized polymer suspension that greatly reduces second- and third -order harmonic distortion, a self-aligning diaphragm assembly, 220 W continuous program power handing, 111 dB sensitivity, and gold-plated color-coded push terminals. This article was originally published in Voice Coil, October 2017.   Read the Full Article Online

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