Press event with multiple microphones

The President with two mics connected
to a press box.

Press box in a suitcase

Press box in a rack

mPress™ Development

If you look at the images on the left, you can quickly deduce the problem: Each reporter placing a microphone in front of the podium makes for an awful mess. The first press boxes provided a ready solution. With a press box, instead of placing dozens of microphones in front of the talent, a single mic is used to feed a press box and then the signal is evenly distributed to the press gallery.

Establishing the architecture

Many of the first press boxes were built into a suitcase with a mic input and a host of mic outputs. Early press boxes were passive designs that employed transformers to split the signal to feed the recorders in the press gallery. Transformers are magical devices that provide isolation against hum and buzz caused by ground loops and stray DC currents. Later on, active buffers (ICs or integrated circuits) replaced the 'transformer-based' system as a means to boost the mic signal and improve the audio quality. Although this works in principle, there is a dark side: Removing the isolation transformers results in noise creeping back into the audio system. Anyone familiar with ground loops knows all too well that hum and buzz has a nasty habit of getting into the audio system at the most inopportune times.

When Radial decided to build a press box, we wanted to fix the problems with both the earlier designs and some of the more modern alternatives. First challenge: We wanted to eliminate the spaghetti of cables running to a single box. Just imagine the mess of cables you get when you have 50 mic cables all connected to a single location. Second challenge: Think about all of these cables feeding 50 reporters… where do they go? How do you keep everyone from tripping over the cables, accidentally disconnecting microphones or today’s army of mini-recorders?

So, we erased the black board, started over and came up with a modular concept that would allow external modules called ‘Exo-Pods’ to be strategically positioned in the venue using a single mic cable. Each Exo-Pod™ could now serve a smaller number of reporters, cleaning up the spaghetti.

Click images to enlarge

We then pushed the envelope by adding a ‘thru’ connector on each pod to enable the audio system technician to create a ‘network’ whereby one Exo-Pod could feed another and so on. In fact, by the time we got the electronics figured out, the mPress was able to supply as many as 480 outputs! This is done by combining a ‘high octane’ active drive circuit with a series of isolation transformers at every stage. In other words, the mPress is the best of both worlds in an innovative modular system.

Establishing the feature set

The mPress is made up of two parts with a master ‘host’ (the mPress) and a series of external slaves called Exo-Pods. The mPress is housed in a standard 1RU 19" rack enclosure. This makes it easy to integrate it into an existing 19" system rack for a permanent installation or inside an off-the-shelf suitcase for field work. In order to avoid any perceived ‘digital trickery’ the system is 100% analog.

The design begins with two mic inputs, both equipped with separate on-off switches and 48V phantom power for condensers. Either one or both may be turned on at the same time. This allows a quick changeover should a microphone stop working during an event (see the image of President Obama with 2 mics above). It also enables the mPress to be used in a town-hall meeting where one mic may be at the podium and the other in the audience. With front and rear mounted XLR inputs, the mPress can be connected in whatever manner is most convenient. We then thought about how rock stars tend to overload podium mics at award ceremonies&helip; and how a disgruntled person may scream into a mic, overloading the system and causing distortion. To solve this problem we added both a high-pass filter to reduce proximity build-up and an easy to use limiter.

Making it easy to set up

As evident by now, the mPress is not a simple passive box. It is an active device with low-noise preamps, phantom power and driver amps that enable it to feed a multitude of Exo-Pods. For powering, it employs an external power switching supply that can accept any voltage from 100V to 240V. All one needs to do is replace the power cable to adapt to local powering systems and you are set to go. This approach also benefits when using a power generator or a DC to AC inverter as these can often fluctuate which, if left unchecked, can degrade performance.

No one likes to wait so we thought that it would be a great idea to allow the system operator to play background music while the press gallery gathers and systems are being put together. To accommodate ‘walk-in’ music, we equipped the mPress with ¼", RCA and 3.5mm stereo inputs along with a separate level control. This enables the system tech to connect an iPhone®, laptop or CD player with any host of cables. The mPress can then be connected to a couple of powered speakers via the main stereo outputs to provide background entertainment while the gallery waits for the ‘talent’ to arrive. The main microphone outputs also feed the PA to enable the audience to hear what is being said without requiring an additional audio mixer. A headphone output on the front panel is available for local monitoring and trouble shooting.

Going as big as you need

Next question: How many outputs do you need? After redesigning the mPress master section several times, we finally settled on eight dual-level outputs. Set to mic level, these could easily do the job in a municipal government office or for interviews at a sports field or arena. To this end, we placed eight specially designed balanced outputs on the mPress with two on the front panel and six more on the rear. Each of these may be configured using the standard mic level (out position) or set to a high output level to drive the Exo-Pods. This allows the mPress to be used as a compact eight-channel ‘distro’ for smaller events or expanded as needed by adding Exo-Pods on the outputs.

The Exo-Pod is a passive floor box that does not require local power to work. Made ‘Radial tough’ to handle the abusive nature of our business, it features an XLR input, a thru-put to feed additional Exo-Pods, a volume control plus ten XLR microphone level outputs and four 3.5mm mini TRS outs to interface with those that are equipped with a mini recorder or need this type of connection to feed their camera. All of the Exo-Pod outputs are further isolated to eliminate hum and buzz caused by ground loops. During setup, a 1kHz test tone may be activated to allow the reporters to test for signal and check their levels. Because of the mPress’s modular nature, you can feed up to eight Exo-Pods directly from the mPress by simply setting the outputs to high. From each of the Exo-pods, you can use the thru connector to feed as many as five more Exo-Pods in series and theoretically feed 480 microphones and 144 recorders at the same time. Since the Exo-Pods are completely passive, power is only needed at the mPress master box making it extremely easy to deploy using standard XLR mic cables.

The Radial mPress represents a major advancement in press box technology by delivering a totally analog solution that is both modular and expandable.