June 13, 2007
Some notes on the Zaxcom stereo camera hop
by Nick Masiuk

Hey there. I work deep in the bowels of Gotham Sound’s rental department. From time to time I mix freelance on the weekend, usually for folks on a low budget, and usually into a video camera. I had a job like this over this last weekend. Just for kicks, I brought the Zaxcom stereo wireless with me. People rarely seem to rent the thing, so it is usually available – and I’d been curious. This article is about my experience using it as a wireless hop to camera. I didn’t use the recording feature at all, and cannot comment about it whatsoever.

My setup was: A MixPre, a channel of Lectrosonics Block 22, a 416 and the Block 28 Zaxcom TRX900 Wireless Transmitter. I brought along a straddle bag to mount the receiver to the camera, but the camera (a JVC something) ended up being too small to accommodate it. The cameraman ended up tying the bag to his belt – which seemed to work out fine for him. He also agreed to put a pair of headphones on – a lucky break for me.

Setting my gain structure with this setup was easy due to the transmitter’s comparatively articulate metering. Getting identical levels for both channels was a cinch. Structuring the gain of two channels of Lectrosonics is a kind of voodoo: you’ve only got two LED’s that can show two different colors each – meaning that the meter has five bits of resolution with which to describe your audio’s dynamic range. You’ve also got some metering on the receiver, too – but frankly I trust that as much as I trust its “scan” function. Most of the folks I talk to get the tone from their mixer metering at 0dBu, and tweak the gain rotary knob on the TX until one or both LED’s shines green. Nobody I talk to says: “I tweak the knob until the first LED is solid and the other is faintly flickering.”

By comparison, levels on the TRX 900 are described by two vertical lines that move across the length of its LCD screen, and gain is set via two inset screwdriver pots on the stereo adapter. The meter proved extremely sensitive to even slight tweakage. I found this metering to be way more descriptive and therefore useful. That said, it was still far from empirical metering: I still don’t know for sure what information that meter was giving me. There is some metering on the receiver, but unfortunately it seemed Lectro-inspired – even more disappointingly it appeared to contradict what I was reading on the transmitter, in that the receiver indicated clipping before the transmitter did. On this and other subjects the TRX manual is ambiguous. I proceeded with the assumption that I was metering dBFS.

What assisted me further was the fact that you can sort of monitor the transmitter itself in a perfunctory kind of way using the 1/8” Audio/TC output on the stereo adapter. I found that when I connected this to my mixer’s return, I heard whatever I was sending to the TX’s right channel in both headphones, after the TX’s input stage. This didn’t and still doesn’t make sense to me (why right only?) and referencing the manual explained next to nothing. “The audio output connection is used to monitor the audio functions of its host unit or to allow time code to pass through the STA100. The mode on the host unit determines if audio or time code is sent through output.” Gently put, this statement is misleading. I could find no such mode.

In any event, it was easy to hear when I was clipping the transmitter. I set the MixPre’s “0dBu” to roughly 1/3 of the TRX’s dynamic range, and then I adjusted the video camera’s gain until I metered there at –20dBFS. My intent was to create a situation in which I would clip the mixer’s output before I clipped the transmitter’s input, and to ensure that the transmitter’s clipping point measured slightly less that 0dBFS at the camera. The TRX900’s stereo adapter has no input limiter, and when it clips it does so in a fatal, intolerable way. Because of this it would be smart to use a mixer featuring an output limiter like the Sound Devices 302 or 442.

So I set up what I felt to be a pretty foolproof gain structure, the cameraman has his headphones on, and we began to shoot. After the first interview, I walk over to camera and ask if I can hear some playback. Simply put, it didn’t sound wireless. It definitely wasn’t exactly what I’d heard at the MixPre’s headphone amp during the shot, but it didn’t sound like wireless. I’m willing to imagine that a wired connection would have sounded better – but the point seems academic to me, as I am sure that this is as much fidelity as I will ever need on a video camera.

It must be said that my conditions were extremely favorable: I was never further than 15’ away from the camera, and we were in a park in southern New Jersey, far from any serious urban area.

I’ve set up dozens of reality TV packages for Gotham’s customers. I’ve become very familiar with the sound of a TR-50 being stepped on by two gain stages of Lectrosonics wireless. The audible result at the last stage is acceptable because it is a compromise on behalf of necessity, not because it sounds any good. The Zaxcom hop represents an incredible step forward in convenience without perceptible loss in quality.

The shoot went flawlessly. Early on, the producer would ask for playback during every break in shooting. She’d never heard of “Zaxcom”, and I think that the setup made her nervous. After the third time, the cameraman promised her that it was unnecessary. He was deeply impressed with the sound quality. Finally, there is at least one videographer out there that thinks I’m awesome. It occurred to me that the people who are going to love this product the most are the camera operators, who will be free now to indulge in their weirdest, most unpredictable physical impulses without worrying about the audio tether.

Range was never an issue for me, nor did the Zaxcom transmitter’s proximity to my Lectro receiver appreciably affect the Lectro’s performance. The only time I was able to create an interaction between the two was under the following conditions: Lectro channel powered ON with the lav unplugged and the TRX’s antenna physically meeting with the UCR411’s, with the MixPre’s gain potted all the way up as well as the headphones’. At the shop at Gotham, I left the TRX plugged into my iPod way in the rear of our office and walked out of the building carrying the receiver and a small mixer from which to monitor. I got halfway to 9th Ave (more than 500 feet, and through an exterior wall) before I exceeded the range.

As perverse as it sounds, I even like the way in which the Zaxcom wireless fails. The performance of a channel of Lectrosonics seems to be infinitely varied. The same units will literally sound very different in different places due to the local RF environment. In my experience the Zaxcom either sounds perfect or it doesn’t sound at all. There is seemingly no middle ground between total fidelity and silence – fatal-error dropouts begin to occur resulting in a completely useless recording. Leaving aside the on-board recording option, as we are, one is left with no option other than to break the camera snake out of its Pelican. This is appealing to me, but I can see why folks would prefer a gentler failure curve.

People will say that the TRX’s interface is too obtuse to understand. I agree with them completely. All the same, I’m putting the public on notice: if you’re unable to operate the TRX’s basic function of accomplishing a stereo link between mixer and camera, chances are you can’t use a computer, either. If you’re reading this, you are perfectly capable of using a TRX.

Why aren’t more people using these things? When you consider that a channel of Zaxcom stereo costs less than two channels of Lectro 411, you’d think that these things would have long since taken over the industry if only as a convenient but expensive replacement for the breakaway cable. It has been available now for a whole year. Nevertheless, at least in New York, the reality industry and ENG crews have continued to neglect it. Here is a product that outperforms its competitors not only in performance but also in price. From my perspective as a lower-level monkey at a sound rental house, I have to wonder why. This all seems terribly tragic to me, because I think that this camera hop is the most important innovation since the boom pole. But folks, don’t take my word for it –what you people should do is come on in and listen to the dang thing.

Editor’s note: In that spirit, Gotham is offering a special deal for the rest of the summer. Rent a Zaxcom TRX900 Wireless Transmitter for 50% off our usual rate. If you like it enough to buy one, make your purchase within 24 hours of returning it and we’ll credit the cost of the first day’s rental towards your purchase.


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