Shotgun (Mic) Wedding: Interference Tubes and Digital Technology

The mono shotgun microphone has been the workhorse for long-distance pickup in sports broadcasting for decades. The interference tube — a ported tube with a mic capsule at the bottom in which sound entering the tube from on-axis interferes with and partially cancels sounds coming from off-axis and thus reinforces sound arriving on-axis — is the microphone’s fundamental underlying technology concept and remains the basis for their use. However, new wrinkles in the concept are emerging: more stereo versions , multichannel iterations, digital adaptations.

“Digital microphones offer more clarity and depth while reducing self-noise generated from preamps and copper,” says Robb Blumenreder, channel manager for pro systems at Sennheiser-owned Neumann. “This allows the audio mixer to catch up to the effects that we’ve been seeing with progressively better HD video over the past three to five years.”

Chad Wiggins, category director for wired microphones at Shure, agrees in principle, despite the fact that Shure makes neither a digital nor a stereo shotgun at the moment. He sees digital shotguns as inevitable but expects their uptake to be slow, given their current price levels and the fact that they need conversion from the AES42 input format. But he certainly concurs that shotgun use has increased and, in the process, has added substantially to the effects palette available to sports-audio mixers.

“What we’re really seeing is so many more camera and point-of-view angles being introduced into sports, and you want an audio experience to go with them,” he says, referring to the increase in camera-mounted short shotgun microphones. He adds, however, that, with more microphones being put into harsher environments by the pursuit of new angles, shotgun construction and durability are getting new emphasis, as is the need for consistent performance across multiple microphones on the same shoot: “You want characteristics like rejection consistent across the entire bandwidth so that the [A1], who now has so many more inputs to mix, can have a more effortless mix because the microphone performance is going to be more predictable.”

At Audio-Technica, David Marsh, director of sales and marketing for installed sound and broadcast, says the company’s two stereo shotgun mics are doing well, adding that they are picking up additional traction as more cameras that have integrated 48-volt phantom power become available. He notes that smaller DSLR cameras are penetrating the secondary and academic sports-broadcast markets more deeply now and that is creating more demand for short shotgun mics. The issues, he says, will be increasing sensitivity and directionality at the ever lower price points demanded by these markets.

Marsh says that A-T is looking into digital-shotgun designs but has not announced plans for any new products along those lines. That’s true also for application of one of A-T’s strong points, large-diaphragm–condenser technology, to shotgun products. But he points out that such technological synergy would help overcome the loss of the umpire ambient-microphone position for NFL games: “A solution that could get that level of intimacy back into the sound without subjecting it to the hits on the field, to be able to capture that sound from a distance, would be a useful thing.”