Zaxcom has developed a new work flow for the production of audio in ENG/EFP applications. This system eliminates many individual devices currently used to meet the demand of today’s production environment. In doing so this system reduces the interference generated by multiple wireless transmitters and improves the quality of the delivered audio. Improvements in sound bag size, weight and elimination of interconnecting cables are also benefits.
The demands on the ENG/EFP sound mixer have evolved to the point where wireless audio transmission to the camera, confidence return from the camera, wireless time code distribution, and client monitoring with delay are now normal requirements.
Typical FM body pack transmitters used as a link to camera are, if you will excuse the pun, a weak link. These transmitters are designed to be used as body pack transmitters for talent. The issue with using these transmitters as camera links is that they use unbalanced audio inputs and will often share a common ground. So when powering the body pack transmitters from a common power source a ground loop can occur resulting in noise and distortion that can be transmitted to the camera.
Furthermore, modern analog FM transmitters utilize digital companders, noise reducers and up to four separate conversions between the analog and digital domain to get audio from the transmitters input to the receivers output. These wireless systems need to conserve battery power and as a result the analog to digital and digital to analog conversion are limited in dynamic range. Most audio today is received in the sound bag wirelessly. It is then transmitted to the camera wirelessly as well. The signal can go through as many as eight low quality analog to digital and digital to analog conversions before it is recorded on the camera.
Another issue in today’s sound bags is RF interference and intermodulation. Intermodulation occurs when the RF from multiple FM transmitters in close proximity to each other mix together and combine their outputs. Intermodulation can greatly interfere with the reception of talent audio in a sound bag.
The traditional RF transmitter system will use up to four separate transmitters to send two channels of audio to the camera, distribute wireless time code, and IFB audio. This can result in a lot of interference created by transmitter intermodulation. To solve these problems Zaxcom has come out with a new mixing, recording and RF transmission system to enhance the RF and audio capabilities of the typical sound bag used to gather sound for picture. The heart of the new system is the Zaxcom MAXX mixer / recorder with integrated stereo transmitter. MAXX coupled with a QRX100 ENG receiver with IFB transmitter option and one or more ERX2TCD IFB receivers, creates a full function audio bag that provides many new features and advantages over current methods.
The Zaxcom MAXX will mix and record up to six tracks of audio from up to eight isolated inputs. MAXX’s built in transmitter will send two mixed channels of audio with time code to the camera. The audio is received on a Zaxcom QRX100 camera mounted receiver. The QRX100 will provide two tracks of audio and time code to the camera. It will also transmit confidence return audio back to the sound bag so that the sound mixer can monitor it and know that audio was successfully recorded in camera. The IFB audio will also be transmitted to Zaxcom ERX2TCD IFB receivers so anyone on set can listen to the recorded audio and see the time code on the ERX’s LCD display. With the IFB transmitter now on the camera it will now have better range than a transmitter located in a sound bag because the camera is generally more centrally located and is physically higher as it is usually at shoulder height vs. waist height buried in a sound bag.
The QRX100 IFB transmitter option is also utilized to send a scratch track and time code to other cameras using the same ERX2TCD receivers.
Video and audio “lip sync” timing can often be a problem on location. Until now this problem could only be solved by utilizing separate audio delay devices that are not practical for use in sound bags. Using the ERX2TCD as an IFB receiver, a delay of up to 10 video frames can be set into each individual receiver. This will match the video delay commonly observed when video monitors are used on set. Master time code can either be the time code generated by MAXX or it can be time code generated by the camera. The Zaxcom system will wirelessly link and lock time code between the sound bag, camera and any number of slave cameras. Since the time code transmission is wireless, time code jamming is automatic and is sub frame accurate with no drift possible.
Some of the advantages of the Zaxcom system are:
100% digital transmission so there is no distortion added due to the compander, noise reduction and FM distortion that is common to most, if not all, commonly used analog wireless.With only one transmitter in the sound bag, the number of clear frequencies needed are reduced and intermodulation interference from the mixing of multiple transmitters in close proximity is totally eliminated.
The camera link transmitter that is integrated into the mixer eliminates interconnecting cables that normally provide input audio and power the transmitter. Since the audio is taken directly from MAXX the signal is kept in the digital domain so no additional analog to digital conversions are needed.
Maxx has an analog to digital conversion dynamic range of 137dB. All audio is kept in the digital domain and utilizes the Zaxcom patent pending NeverClip input structure. This eliminates the need for input limiters and compressors and provides the best audio fidelity possible.
IFB audio is noticeably better than traditional FM IFB monitoring systems due to digital transmission and a direct digital connection to MAXX through the stereo link.The system is very energy efficient, smaller, lighter, cost effective and provides a vast improvement in audio quality over existing wireless and bag style mixing solutions. Time code transmission, distribution and frame rate conversion are integrated into the IFB monitor transmission.With the IFB transmission at the camera position RF confidence monitoring is achieved without the need for a separate return link transmitter at the camera.
IFB monitor delay is integrated into the ERX2TCD IFB receiver to match the video delay common when video monitors are utilized for the production.
Please contact Zaxcom or your Zaxcom dealer if you have any questions on this new method of providing high quality ENG and EFP audio.
Scenario #1 – Small production with two talent, a boom and camera link with a confidence return.
In the bag
1 x Maxx, full loaded with a built in transmitter (Bk 21)
2 x QRX100Q receivers (Bk 25)
1 x ERX2TCD
On the camera
1 x QRX100Q w/QIFB option (Bk 21)
On the talent
up to 4 x transmitters – maybe 3 x TRX900LANC and 1 TRX742 or any other combo (Bk 25)
How they work…
Your talent wireless is received by QRX’s in the bag and go into the digital input of the Maxx. From there the audio is mixed down to two tracks and sent wireless via the built-in camera link to the QRX that’s on the camera. From there, you can have the QRX on the camera send the IFB audio / timcode signal back to the ERX2TCD in your bag for a confidence monitor.
Any blocks can be used, they just need to be spaced apart by two – the above was just an example.