NewsTech: Trucks & Audio Systems - TvTechnology

NewsTech: Trucks & Audio Systems

Uplink trucks and remote recording vans are a regular part of broadcast life in this new millennium. Invest in and upgrade them accordingly. Several studies
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Uplink trucks and remote recording vans are a regular part of broadcast life in this new millennium. Invest in and upgrade them accordingly. Several studies have demonstrated that if the picture goes fuzzy or even black, the average viewer will stay with the channel for at least one minute to see if corrections will be made if a broadcast's audio is maintained. If audio disappears, most viewers will abandon the defective channel after no more than 20 seconds. The particular mandate of remotely originated audio is to capture high-quality live sound from the location and deliver it intact onto a storage medium or to Master Control. As we'll discuss in this article, truck audio systems can be surprisingly complex.

Input sources remain much the same from situation to situation. A good selection of mics, cables, adapters, in-line attenuator pads, direct boxes, ground lifters and the like are the audio tech's stock in trade. Playback sources are similar too: audio from VTR, cassette deck, DAT deck, mini-disk, CD-ROM, discrete hard drive deck, and even open reel tape decks and the occasional cart machine can still be found in the audio gallery of a broadcast truck.

Consoles Consoles have developed significantly from their humble beginnings. For many years, TV audio was treated (incorrectly) as radio with pictures, and truck audio mix desks were nothing more than two or more radio boards ganged together. The early recording consoles were unreliable in a mobile environment because they did not tolerate the vibration and climatic changes inherent in remote broadcasting. Today's audio mixing systems, in addition to their more rugged construction, can be specifically selected from a menu of module types and configurations.

Of primary importance are sufficient input channels. It is rare to see a broadcast truck or van with less than a 16-channel mix board available. The potential on-air requirements of a live production - eight or 10 mics on set, an off-camera announcer mic, theme music playback, stinger effects, VTR insertion playback, etc. - quickly consume 16 channels. Provide for as many channels as you can possibly afford - it saves upgrading every two years. Don't forget to spec several stereo input channels, as many as you have playback sources. Your station may not stereocast its audio, but your private production clientele will almost certainly want their show in stereo.

A good EQ section is vital. The equalizers should have frequency shelving and roll-off for the very highest and lowest ranges, and preferably two parametric stages for the intermediate ranges. A vital factor is the judicious use of equalization. Too much push or pull in any frequency range on any given input is almost sure to create distortion, possible phase imbalance (among channels), and other audible artifacts. Good EQ gently enhances a signal and sets it in its own acoustic space. TV audio is far more critically sensitive to EQ overload than radio - a bit too much high-end boost make a videotape audio track impossible to play or duplicate. Excessive highs can cause severe aural transmitter clipping. Overboosting the bass to deliver that fat bottom end loved by some rock musicians will invariably result in massive distortion in the four- or five-inch loudspeaker still used in many home TV sets.

Checking your sound One of my personal pet peeves is the installation and dependence on a pair of beautiful wide-range speakers in the audio section, probably powered by 50 to 100 watts per channel. This is nice if you are performing multitrack audio recording and mixdown of music. However, for a broadcast truck, employ a set of small- to medium-sized computer loudspeakers. These are generally of reasonable quality, without being too good, and they more closely mimic the response of a consumer TV audio system. Several trucks have gone to the trouble of installing a consumer-type TV and feeding the input with audio modulated on a small Channel 3 sender. The engineer in charge of one so-equipped van stated that his audio monitor setup sounded more like the viewers' sets at home than the $2000 plus monitor system originally spec'ed for his truck. When listening to the result on air at home the following day, I had to agree.

Audio processing assumes an important role in truck-based production, especially because live, on-site audio is not usually studio quality. One of the niftiest devices in a sound tech's arsenal is a humbucking line-to-line transformer - even a couple of them - with I/O connectors and adapters. Hum and line garbage can often sneak along the interconnect cable fed from house audio. For the most part, hotel, convention and stadium audio staff are not disposed to consider live TV needs. Often, the truck audio tech is forced to accept a pre-mixed facility feed and bounce that along with a live announce mic or two.

When the truck tech has the option of placing mics and creating an original mix, some thought must be given to types and amounts of processing. Industry preferences drift toward a bit of limiting and often a gentle touch of reverb to enhance the live feel of the shoot. Too great a dependence on effects modules ends up creating a situation in which an inordinate amount of time is wasted in rehearsal, getting the mix right. After all, there is the video to deal with, and obtaining clean color imaging is more engineer-intensive than audio usually is. Extensive audio tricks are best left to a studio or to the post-production editor. If a broadcast vehicle sticks with a stereo limiter and maybe a few patchable individual limit modules, as well as simple digital reverb, great-sounding, workable audio can be delivered.

Mic-ing the truck Wireless microphone and interruptible fold-back (IFB) systems are almost essential in any remote truck. With today's crowded RF spectrum, careful engineering consultation is a must when choosing RF channels for wireless devices. Without restricting or over-specing, the usual complement on a remote TV production truck is two independent UHF wireless mic channels, with either lavalier or hand-held mics. As companions to these, two IFB packs, also UHF, should be available. The interrupt facility should be responsive to the truck producer/director's intercom mic, with straight-thru IFB listening originating from the station control room. In this fashion, talent can hear the cues to both studio and truck crew and be able to jump in and out on cue when multiple cut-ins are called for.

In considering the IFB question, further telemetry or local microwave interconnection is mandated to cleanly send IFB com audio to the remote truck. On occasion, this is also done via land line or POTS connection. The number and type of transmitters and receivers required for glitch-free communications during the production, as well as talent audio pickup, can be astounding. During a week-long production in a truck last year, six wireless lav mics, two announcer mics (headset type), and all manner of wired and wireless IFB were employed to get cues and talkback to all the talent. It was a hellish setup, but the trouble taken was worth it when several of the talent remarked that they enjoyed the challenge of that particular remote because they could effectively communicate with all the crew and each other.

AC power distribution is always a vital concern in remote trucks. Careful routing of AC feedlines is mandatory to avoid EMI with both audio and video circuitry. Careful grounding is also paramount when setting up a truck. It's all too easy to create ground loops between trucks that may pose a threat to human life. Ground lift connectors or adapters may prove invaluable in these situations, and well thought out cable runs can save time and avoid the nasty consequences of looped AC leaking back along improperly grounded audio lines. If you must set up portable equipment on site outside the physical truck itself, the safest move is to run heavy-duty extensions and draw all AC power from the truck. No ground loops can form if all devices derive their power from the same phase on board the vehicle and share the same ground source.

Smaller considerations Many of the newer trucks are boasting digital everything on board. The coming wave of EFP is indeed digital, but a word of caution here. Because many audio sources are still delivered in analog format - our voices into a mic being the prime example - it becomes vital to select a console that will permit both analog and digital inputs. Some manufacturers offer this as switched inputs into each module. By the way, widescreen HDTV audio is still audio. Unless we are specifically talking about 5.1 or a similar encoding scheme, stereo is still stereo. With the improved pictures available, we must produce cleaner, more pristine audio. Audio scopes and stereo waveform observation are critical to ensure that a mono-compatible audio track is being delivered. There are few things worse than a phase-imbalanced stereo track, causing mono phase-out and comb-filter effects. Instant viewer tune-out is almost guaranteed.

A word or two about operator comfort might be in order. In their zeal to maximize space usage, and offer good value to the purchaser, some remote truck designers shrink the human space to a minimum that is inoperable. Most techs need at least two feet of space around them in which to move. If too cramped, and hemmed into a tiny cubbyhole audio compartment, techs are unable to do their best work. Fatigue quickly sets in and show quality flies out the window. Watch out for too crowded overhead rack areas. Only non-essentials like power amps, DAs and such should be placed overhead. It's a very difficult area to work in, and ripe for bumped skulls and mistakenly turned knobs due to the inability to see clearly over one's head in dim light.

Although the remote truck is essentially a studio on wheels, there are some special considerations to ponder when purchasing or upgrading one of these rolling behemoths. Remember, high-quality audio output is the ultimate goal of this part of your truck. Attention to the details of the design of audio systems will help you and your staff achieve that goal.