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Innovations: Lectrosonics D Squared Digital Wireless Microphone System

By Karl Winkler. Digital microphone systems are expected to meet three performance criteria—high channel counts, decent battery life and long range—but achieving any two of those goals generally comes at the expense of the third. Lectrosonics aims to change that expectation.

This article originally appeared in the July 2019 issue of Pro Sound News. Innovations is a monthly column in which different pro audio manufacturers are invited to discuss the thought process behind creating their products of note.

As wireless mic users, we face tremendous challenges today due to the ever-shrinking spectrum and the increasing RF noise floor. Between 1998 and 2018, we’ve lost more than half of the UHF frequencies we once had, and the spectrum that’s left is quite crowded. Having more wireless technology in general has raised the noise floor and put additional demands on us as operators. In our business, the demand for “all things wireless” never slows, as stage and production design continues to evolve. Though in recent years, the move to digital wireless microphones has brought us some amazing technical advancements.

The Engineering Triangle

Amid this technological transformation, we manufacturers have focused to a large degree on different performance criteria for our system designs, depending on what our core customers expect based on intended applications. Digital technology gives us new options and new tradeoffs that we didn’t have when these systems were analog. Battery life has become more of an issue, as D/A converters, digital signal processors (DSPs) and field-programmable gate arrays (FPGAs) consume more power than the old, pure analog circuits. Digital transmitters are more immune to intermodulation issues, giving us the potential for increased channel counts—important with the shrinking spectrum. Audio quality can be enhanced as well, since we no longer must rely on analog companders to yield decent signal-to-noise performance.

As any good engineer will tell you, it is usually possible to meet any two of these performance criteria but not all three. For digital wireless systems, we can have high channel counts and decent battery life, but range and audio quality might suffer. Or we can have long range with high error correction, but the bit rate is reduced and latency is increased. “No compression” audio encoding might yield pristine audio, but channel counts and battery life become real challenges.

Related: Lectrosonics Unveils D Squared Digital Wireless Mic System, June 4, 2019

4th Generation Digital

Lectrosonics introduced its first digital wireless microphone platform in 2002 with the 700 Series, a system featuring a 44.1 kHz sampling rate and 24-bit depth, and offering 128-bit encryption. The company has introduced two additional generations of digital products since then: the D4/Quadra series in 2008-2011, and the Digital Secure Wireless 24-bit/48 kHz encrypted system in 2014. As an inkling of what was to come, the Duet digital IEM system debuted in 2017.

The new D Squared system capitalizes on everything Lectrosonics has learned about digital wireless during the past 17 years. The system comprises the DSQD receiver, DBu beltpack transmitter and DHu handheld transmitter. The 4th generation digital architecture allows for excellent flexibility, ultra-fast setup, studio-quality audio and ultra-low latency. System features include 24-bit/48 kHz digital audio, analog and Dante outputs, 2-way IR sync, three encryption key policy choices and a tuning range from 470–608 MHz (470–614 MHz for export versions) in a single range.

The main goal of the D Squared system is to provide top-level performance in both the RF and audio side, with extremely low latency, then finely balance the other parameters. Lectrosonics has long been known for performance in these two areas—long range with impeccable audio—and the D Squared is designed to raise this bar even further.

Legacy Systems Not Abandoned

One of the main problems with system innovation is the obsolescence of perfectly serviceable older equipment. Starting with the Digital Hybrid Wireless platform in 2003, Lectrosonics has kept the installed base of users in mind. With this award-winning technology, those with older 100 and 200 Series systems, analog IFB systems, and even those with other brands of equipment could continue to use their gear. Such interoperability was unheard of at the time.

The new DSQD digital receiver breaks even another barrier: it is backward-compatible with Lectrosonics Digital Hybrid transmitters such as the tiny SSM, the SM Series, LT, HM Series, HH Series, older UM400 and UM400a, LM Series and the watertight WM.

Diversity of Diversity

Three different receiver diversity schemes can be employed in the DSQD depending on the needs of the application: antenna switching, accomplished during packet headers for seamless audio; Digital Ratio Diversity, using two channels simultaneously with continuous blending; or Digital Frequency Diversity for the ultimate in reliability of complete transmitter-side redundancy. Continuously tunable tracking filters ensure excellent RF performance even in difficult environments. The DSQD includes digital talkback capability when used with any talkback-enabled transmitter, including the new DBu and DHu digital transmitters, and the previous-generation LMb, LT and HHa Digital Hybrid Wireless transmitters.

New Components

The new DBu beltpack and DHu handheld digital transmitters include specially developed high-efficiency digital circuitry for extended operating time on two AA batteries and offer RF power selections at 25 and 50 mW, using the robust 8PSK modulation scheme and proprietary audio encoding. The pure digital architecture enables AES 256-CTR encryption for high-level security applications. Studio-quality audio performance is assured by high-quality components in the preamp, wide-range input gain adjustment and DSP-controlled analog limiting. Input gain is adjustable over a 44 dB range in 1 dB steps to allow an exact match to the input signal level, maximizing the dynamic range and signal-to-noise ratio. USB ports on the transmitters allow for firmware updates in the field as features are added in the future. Two-way IR ports ensure quick setup and allow for encryption key transfer and other data sharing between units.

The DBu beltpack unit features a removable antenna with SMA connector and incorporates the standard Lectrosonics TA5 connector with servo-bias input for compatibility with a wide range of lavalier mics, dynamic mics and line level sources. The unit ships with a tough wire belt clip but is also compatible with an accessory clamp-style belt clip. A multifunction switch on top of the transmitter can be configured as power on/off, mute, talkback, or bypassed altogether. The DBu’s housing is constructed of solid machined aluminum, finished with an ultra-hard electroless nickel plating for lasting ruggedness.

The DHu handheld transmitter is compatible with the Lectrosonics HHC cardioid condenser capsule and can also be used with a wide range of microphone capsule heads incorporating the standard 1.25 inch opening and 28 thread pitch. A programmable button on the outside of the housing can be configured as a cough or mute switch, a power switch, or be bypassed altogether. The DHu housing is milled out of aluminum alloy and powder coated for lasting ruggedness.

The half-rack DSQD receiver includes a headphone jack for audio monitoring per channel. Ethernet and USB ports allow the receiver to connect to Wireless Designer software for programming and monitoring, and a serial port enables connection between receivers for data sharing and frequency coordination. Antenna bias power can be engaged in the menu, and front panel LEDs show the status. Each DSQD ships with half the rack hardware needed to mount two units together, yielding eight channels in 1RU.

Related: For Pink Bassist Eva Gardner, Lectrosonics Wireless Is All Beautiful, No Trauma, June 25, 2019

As for D Squared system performance, audio frequency response is 20 Hz – 20 kHz +/-1 dB, with dynamic range of 108 dB and THD+N of 0.05 percent at 1 kHz, -10 dBFS. Latency is 1.4 ms, transmitter input to analog output, using a digital transmitter, and <2.9 ms with any Digital Hybrid Wireless transmitter.

The company is extremely excited about the release of this new platform, as it represents a new era for Lectrosonics and our customers, with many new possibilities for wireless microphone performance when applied to broadcast, theater, touring, house of worship and TV/film production.

Karl Winkler is vice president of sales at Lectrosonics.

Lectrosonics •

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