Designer Notebook: A Convergence Of Technologies
The back-story on AKG wired/wireless mics

By Walter Rührig and Tom Stofler

This Designer Notebook was submitted by AKG. Live Sound makes every effort to eliminate any use of marketing inspired hyperbole.

Wired that can be converted to wireless.

The vision for what has become the new AKG Emotion/ TriPower started with a pretty basic circumstance: the current TriPower microphone range had become aged and it was time to replace the series with new models that had better performance, a new structural design and improved cosmetics. However, this rather humble impetus took on a larger life rather early in the process as we surveyed the state of the professional stage microphone market. Let’s face it - many companies produce high quality products, and as far as technological advantages are concerned, we’re all faced with a situation of coming close to reaching the limit of technical possibilities. With this firmly in focus, our thinking evolved. We didn’t want to “just” do another new microphone range.

INCREASING AND DIVERSE

However, something else has evolved over the past few years: wireless technology has become more affordable. And since using a wireless microphone is so comfortable and convenient, why would anyone still use a cabled microphone when a wireless microphone is available at near or the same cost level?

Of course, this isn’t quite yet true for higher end wireless, but the pricing structure of wireless microphones compared to an expensive cabled microphone in some cases is already comparable. Thus increasing and diverse potential user groups can more easily afford professional wireless microphones.

For example, the AKG WMS 40 series has reduced cost because it’s normally used in small areas and isn’t designed to fit into complex multi-channel use with added-cost features like multi-couplers and active antenna distribution. The reality is that there are also many users who don’t really need a wireless microphone, but because of the “cool” factor still enjoy working with one.

The D 3700M with the TM 40 wireless module.

Because all wireless products at any price level have risks involved in their use such as drop outs, RF interference etc. it makes perfect sense to have a cabled microphone on standby, or in some instances, a back-up wireless system. So our big question revolved around the possibility of combining two technologies. Cabled and wireless into one? Another factor in play before we started our basic market research was whether there were technical possibilities already on hand which would allow us to produce handheld wireless microphones in much smaller housings than conventional handheld transmitters.

Based on the fact that conventional handheld microphones are (except for the transducer) empty inside, we tried to find a solution to make use of the empty space inside the mic handle.

With the idea in mind to combine wireless and hardwired mic technology, and with the desire to design these new mics to be as small as possible, including a wireless transmitter, we wanted to create a solution which made the choice of a wireless transmitter or of an XLR module a possibility.

TECHNICAL NECESSITIES

From the user’s point of view, a handheld transmitter shouldn’t be as big as most transmitters are currently today. Users prefer the microphone’s handle to be the same size as a cabled microphone. Yet there are technical necessities that define the size of a handheld transmitter, such as the size of the battery, the circuitry and the antenna.

With the help of borrowing technology from the WMS 40 microtools, a series of UHF wireless with miniaturized transmitter elements, the goal of a smaller handle seemed achievable. But to make this concept work, we had to create a miniature sub-PCB board, which is mounted directly behind the microphone capsules in the Emotion/TriPower range. The transmitter and the XLR modules both mate with this sub-PCB board inside the mic handle.

A cross-section of the D 3700M handle showing the hole for the mounting screw of the XLR modules and the snap-in that holds the wireless module.

Fortunately, the transmitter module of the WMS 40 microtools range already had basic dimensions that could fit easily into a microphone handle. So all we had to do was to design two modules: one with housing around the transmitter PCB, and another one which basically just holds the XLR connector as well as the preamp circuitry for the condenser mic models. Both of these modules slide easily into the mic housing. The XLR module is held in place with a screw, which is important because as soon as a cable is connected, the XLR module needs to be held securely inside the housing in order to prevent disconnecting the whole module if somebody pulls on the cable.

The TM 40 transmitter module snaps securely into the housing and doesn’t need a screw to hold it in place. It only takes a few seconds and is relatively easy to insert or pull out the TM 40 module for replacement with another module or switch to an XLR output module.

The module with battery compartment that holds a single AAA battery and the off/mute/on switch above it.

The Emotion/TriPower Series is made up of both entry-level high-end professional touring microphones. Considering the entry-level user group, who doesn’t need extensive multi-channel capability, our thinking was that maybe it would be possible to lower the number of technical parts inside a handheld transmitter to a minimum, in order to make the operation of a wireless mic more comfortable for the user. The microtools technology presented the possibility of doing this because we had already developed one of the industry’s smallest snap-on transmitters, the SO40.

And from there we started to envision the full concept - a combination of a cabled and wireless microphone into one single housing that was the size of a standard cabled mic-rophone using all the modern technologies we had on hand in order to produce a microphone range which represented the very top-level of performance for both types.

Later, market research afterwards confirmed that our initial thinking held promise in the view of the potential customer base.

Contact points on the TM 40.

MODULAR OPTIONS The Emotion/TriPower line consists of two sets of models. Emotion models D 880M dynamic and the C 900M condenser are acoustically identical to their predecessors with the modular wired plus wireless capability added. TriPower models D 3700M and D 3800M are dynamic mics, joined by the C 5900M condenser. These TriPower models are completely new mics with upgraded performance, more rugged mechanical structures and stylish cosmetics.

Since the WMS 40 technology we used meets mainly the needs of the entry-level customers, we offer the D 880M, C 900M and D 3700M of the new Emotion/TriPower range with this new modular design. A customer who wants a premium high-end microphone like the D 3800M and C 5900M are not the typical customers for a WMS 40 system.

However, we decided to make the modular option available for these top-quality products for customers who want a higher-end microphone combined with a very affordable wireless. By having the D 3800M and the C 5900M with the modular option, we are also preparing the product line for the next generation of design when it might be possible to have a pro tour level TM transmitter module.

Another cross-section of the D 3700M with the TM 40 installed.

The acoustic concept intention for the two top-of-the-line models ­ the D 3800M and C 5900M ­ was to create sound tools that meet high-end demands but still meet a reasonable price point. For the dynamic D 3800M microphone, we worked with our Varimotion capsule design, while the C 5900M uses a similar capsule design from several AKG studio microphones, with the acoustic parameters adjusted to meet the needs of live stage use. The TM 40 plug-in transmitter module is compatible with our SR40, SR40DIV and PR40 UHF receivers and is offered in four different UHF compatible frequencies.

The transmitter is designed with a silent on/mute/off switch, 10 hours of battery life (using a quality AAA alkaline battery) and offers integrated charging contacts used with the CU40 charging station and rechargeable batteries.

Alpha- and beta-testing of the D 3800M and the C 5900M with numerous tour sound companies and on national TV and radio were enlightening and we got a chance to learn about the capabilities of the mics in “real world” situations.

Some of our other goals for the new models were to come up with shock mounting systems that were both effective and rugged enough to handle the rigors of being dropped, baked, frozen and mistreated. Our tests showed us that we accomplished these goals.

Walter Rührig is product marketing manager for AKG Acoustics, Vienna, while Tom Stofler is market development manager, pro music and tour sound, for AKG’s U.S. operations.

December 2003 Live Sound International