Who doesn't like EQing a room? I mean, you have all the power in your hands. You choose the music. You choose the pink noise level. You get to say, “I will now listen to Steely Dan.” And then you get to twist all of those knobs. The lights bounce, and the LEDs pulsate. It is dizzying, exhilarating. It's boring. Let's get real. Does anyone really enjoy listening to pink noise for an hour? Or the same three minute song over and over again? When it is my choice, I don't listen to Steely Dan — no offense. I usually choose the Asylum Street Spankers or some other mildly offensive but amusing music, or maybe a David Sedaris story. And then there is all the work you have to do to prepare for an EQing session. You have to set up the rig, whether it is SIM®, SIA SMAART Live®, TEF®, or whatever. You also have to set up the microphone, and that can be quite a task. It means running 100' or more of cable through, around, and over seats. And if you are planning ahead, then you have someone running cable into the balcony while you work on the stalls. By the end of the session, there is a spider web of cable all over the venue, which has to be coiled and put away. I am exhausted just thinking about it. I am constantly trying to simplify my EQing process, and at AES in October, when I came across Lectrosonics TM400 — a wireless system designed specifically for testing and measuring — I was instantly drawn in by how much it could help the process.

What It Does

The TM400 replaces long cables between a calibrated microphone and test equipment. It uses 24-bit, 88.2kHz digital signal handling for compandor-free audio and has 256 synthesized UHF frequencies from which to choose. The receiver has a feature called SmartTuning that uses a graphic display for easy selection of clear RF frequencies. The transmitter has selectable 5V, 15V, 48V powering and a 100mW RF output power for long range. The system was designed for use with measurement equipment such as SIM®, SIA SMAART Live®, TEF®, or other systems. Without the cable restrictions, the microphone can even be moved around the venue while the audience is watching the show.

Lectrosonics Digital Hybrid Wireless encodes the digital audio information into an analog format using a proprietary algorithm. Once encoded, the signal can be transmitted over an analog FM wireless link. This digital/analog hybrid technique digitally encodes the signal before transmitting it, which means the usable dynamic range is much higher than when a compandor is used. The TM400 has no compandor in the audio signal to interfere with the measurements. This offers the audio quality of a pure digital system and the operating range of an FM wireless system. The digital audio chain eliminates compandor artifacts and provides audio frequency response flat to 20kHz.

The standard system consists of a UH400TM transmitter, R400A receiver, and CCTM400 water-resistant case. The components can be ordered separately, and the R400A receiver can be ordered with a rack-mount front panel.

How It Came To Be

Karl Winkler, director of business development for Lectrosonics, Inc., explains, “For many years, audio techs have wanted a wireless system for system tuning and have cobbled together systems which included a belt pack and an adaptor to externally supply phantom power to the calibrated microphone. In 2004, we realized we had a plug-on transmitter used extensively for voice, such as for interviews and boom mics for film production, that could be used for the purpose of sound system tuning. It provided phantom power for condenser mics, but the only problem was it had a cut-off around 90Hz where a lower response would be needed for proper SPL and response measurements. We changed three components in the transmitter on the front end, and now it is flat from 40Hz to 20kHz to create the TM400 system.”

Lectrosonics has a unique approach to wireless systems. “One of our engineers came up with an idea in 2000 to use a predictive algorithm and DSP to transmit the audio stream digitally over an analog RF link, thus doing away with the audio compandor,” explains Winkler. “The resulting digital/analog hybrid system provides a wide frequency response, low distortion, and excellent dynamic range.”

Among wireless companies during the past couple of decades there has been sort of an “arms race with compandor technology, because for the most part, compandors are a necessary evil,” he continues. “With analog wireless, the issue is channel noise. Similar to the method used for noise reduction with analog tape, the audio signal is compressed on the front end and then expanded at the receive side. By doing so, reasonable signal-to-noise performance is achieved. However, companding the audio signal has certain drawbacks, including distorting the dynamic envelope and mis-tracking high-frequency transients. Each manufacturer has its own scheme for delivering the maximum performance from its own wireless, but the drawbacks remain to one degree or another.”

What's Next?

After using the TM400, there is little improvement I can see for it, but Winkler still sees room to grow. “We see the product evolving in the user interface, including an LCD and membrane switches like with our SM Series transmitters,” he says. “It might also go to our completely digital platform as well, but other than that, it is a working system, and there is nothing else out there like it.”

The TM400 also has expansion capabilities. “The usual system includes the UH400TM transmitter with R400A single-channel receiver,” adds Winkler. “There is another receiver, called the Venue, which can house up to six channels in one rack space. At AES, such a system loaded with three channels was being used to show the new SysTune software. I could see the multi-channel version becoming more and more involved with system tuning as programs use more inputs.”

What End Users Have To Say

When asked about using the TM400, Paul Bauman, director of Tour Sound Product & Application Engineering for JBL Professional, says, “The first time I used the TM400 was to align a large format sound reinforcement system at the Stade de France in Paris for Turandot in 2005. The TM400 performed flawlessly, and, given the sheer size of the stadium system to be aligned, it was very convenient and a huge timesaver to be able to go wireless. The second time I used the TM400 was on tour with Bob Dylan throughout Europe in Fall 2005. Again, the system performed very well and proved to be an extremely useful tool in a daily touring situation.”

Bauman goes on to explain, “I like to base system EQ on the spatial average of a number of measurement locations throughout the coverage pattern of a given part of the sound reinforcement system. For example, once the initial system check is completed, and it has been verified that FOH left and right are matched, I'll take a series of measurements, 10 to 12 locations throughout the coverage pattern of FOH left or right. When you have a limited amount of time for system tuning, as is the case in a touring situation, the faster I can take these measurements, the better. Once the raw data has been collected, I do a weighted spatial average, electrically sweep the system EQ unit while it's flat, and then divide by the inverse of the spatial average in order to monitor the effect of system EQ on the system's spatial average. This allows you to EQ the system offline and is a very efficient way to work. Apart from speed, another benefit is that it is quiet, and you don't have to make a lot of disruptive noise in a working environment. The TM400 has definitely been a big timesaver and has become an important part of my measurement tool kit. I use it every time I tune a sound reinforcement system. Recently, I've used it to tune the JBL VerTec systems installed at Gibson Amphitheatre at Universal Citywalk, Walt Disney Concert Hall, and the installation at the recently-opened Nokia Theatre LA Live.”

It didn't take much to get Blair McNair, an independent systems consultant, to talk about how much he likes the TM400. “I'm just giddy about my TM400,” he says. “I use it all the time with my TEF rig. I was one of the early adopters. One of the interesting benefits is that the weight of the TM400 set is less than the weight of a 100' microphone cable and more compact. In these ever-tightening weight restrictions with the airlines, that is important. I now can get considerably further away than 100' and without the added weight.”

McNair continues, “Another less obvious benefit is the safety for my rather expensive P48V powered measurement microphone. With a cable trailing about, it presents a tripping hazard and the possibility that someone will get snagged on the cable and pull my microphone out of the stand or topple it along with the stand; last time, the repair alone on my microphone was $995 — not an issue with the TM400.”

McNair explains the benefits of using the TM400. “The obvious benefit is the freedom to move around without having to wrangle a microphone cable to do so,” he says. “The time savings with that alone is significant. I use the TM400 almost any time I use my acoustic analyzer equipment, for all the reasons previously mentioned. Just a couple of weeks ago, I was working in the 1,600-seat Midland Evangelical Free Church facility in Midland, MI on a recalibration of the sound system and had to make measurements in around 25 to 30 locations. If I had to tote a microphone cable behind me for each of these locations, it would have easily taken around 30% longer to accomplish the task. How much is 20% to 30% if my time worth? A bunch more than the cost of a TM400. I use it because it works and saves me time.”

For further information about the TM400, visit the Lectrosonics website at www.lectrosonics.com.

Shannon Slaton is a sound designer and engineer living in New York and is currently mixing Legally Blonde and Spring Awakening on Broadway. Other Broadway mixes include Jersey Boy, Man of La Mancha, Sweet Charity, Dirty Rotten Scoundrels, and Bombay Dreams. He designed the current national tours of Hairspray, The Producers, The Full Monty, Contact, The Wedding Singer, and Kiss Me Kate.