In an ideal world I’d have a ninja-class boom operator with me on all of my documentary shoots, but short of that I usually place a wireless lavaliere on my subjects in order to capture the best dialogue possible while providing then with mobility along with the intimacy of a small crew. However, on some shoots, for a variety of logistical reasons, I can’t easily put a wireless lavaliere on a subject. In these circumstances I use the Audio-Technica BP4029 MS stereo microphone attached via a Rycote softie mount (no longer sold but replaced with their InVision Video Hot Shoe mount) as my on-camera microphone. The mount is part of the system, as it’s crucial to have a microphone mount that swivels for optimal placement, since often subjects are not directly in front of the camera.
The ability to swivel the on-camera short-shotgun is crucial for the best sound quality. The camera position is often too far from the subject to begin with when mounting the microphone on the camera, therefore proper on-axis placement is even more critical. If you look at the polar response diagram for any short-shotgun, you see that you get the highest signal to ambient noise ratio when the microphone is pointed right at the source, and you can hear the difference too (experimentation and listening is the best way to understand sound recording). Those silly camera mic-mounts that come with prosumer and professional camcorders are good for only one thing, a subject directly in front of the camera, which might be fine if you always place your subject in the middle of the frame, however, as a fan of the golden mean, I often place my subjects to the right or left of frame. This is where being able to swivel the microphone comes in. A good shock mount that can swivel will do more to improve the quality of your dialogue recording short of placing it on a boom and pointing the microphone in an optimal manner close to the subject.
But wait, there’s more. Since the Audio-Technica BP4029 is an MS stereo microphone, that means it has two capsules: a middle (M) capsule with a line-cardioid pick-up pattern and a second side (S) capsule with a figure-of-eight pick-up pattern. Normally the discrete M and S channels are decoded into stereo either by the microphone or later in post-production. But for cinéma-vérité shooting I’m not concerned about stereo, so I set the microphone to MS mode which provides the M and S as discrete independent channels recorded to channel 1 and 2 respectively. Thus channel 1 provides me with the dialogue in front of the camera and channel 2 provides me with whatever is happening to the right or left of the camera, sometimes it’s my dialogue and other times it might be someone talking to the subject in front of the camera. This second channel gives me a lot more flexibility in postproduction.
Thus the BP4029 provides a versatile microphone I can use in one of four ways, carrying one microphone that can play four roles saves weight and space in my kit:
- MS microphone. When the microphone is set to MS mode, it can be used for MS stereo recording with discrete middle and side signals in channels 1 and 2, respectively, in postproduction the independent M and S signals can be decoded to stereo using a plug-in like Voxengo MSED, or
- Two separate microphones, as I describe in the scenario above, or
- Short shotgun microphone. You can use the M channel and ignore the S channel and it functions as an ordinary short shotgun, I keep an XLR5-F to XLR3-M adapter cable in my kit since the microphone has a XLR5-M connector on the end in order to accommodate the additional channel, or
- Stereo microphone. The microphone has a built in MS stereo decoder which can be set to narrow or wide mode, giving you a choice of stereo fields. In this mode you end up recording a standard stereo signal that does not have to be decoded in post, I use this mode for recording stereo ambience tracks and sound effects.
Before purchasing the BP4029 I used to attach my TRAM-50 lavaliere to the back of my on-camera shotgun in order to capture myself or other people talking close to the camera, but I find the single microphone easier to deal with. In the end the proof is in the pudding, so take a listen to this collection of videos in which almost all of the audio was recorded with BP4029 on the camera. See my note at the end of this article for more details.
By the way, MS recording is a two way process, you can decode stereo from MS and encode stereo into MS. The stereo is derived algebraically from the M and S signals, where L = (M+S)/2 and R = (M-S)/2. When you adjust the levels on the MS signal you control the width of the stereo image. One useful trick in post is if you’ve got dialog that was recorded with a built-in stereo camcorder microphone, if you encode it to MS you can then pull out the middle for cleaner dialog, or simply boost the middle compared to the side signal to reduce unwanted side noises. The world of MS stereo is full of ancillary benefits.
The Audio-Technica BP4029 (which replaced the 835ST) stereo shotgun microphone produces a center-focused stereo image. The frequency response and overall sound quality is quite good. As with most professional condenser microphone without a built-in power module, phantom power is required. It contains two independent condenser elements: a “Mid” element with a line-cardioid pick-up pattern that primarily captures sounds in front of the microphone and a “Side” element with a figure-of-eight pick-up pattern that primarily captures sounds coming from the left and right of the microphone. One reason MS stereo was developed is because you can record a stereo sound field that doesn’t cause phase problems when played back in mono as you would when the two capsules are not coincident with each other.
The mic supports three modes: MS mode provides independent Mid and Side signals from the two independent microphone capsules. This allows the Mid-Side balance to be adjusted as desired with a mixer in the field or later in post-production. The microphone also has two internally-matrixed modes providing traditional “left-right” stereo: LR-W mode (wide) has a wider pick-up pattern with increased ambient pickup while LR-N mode (narrow) has a narrower pick-up pattern for less ambient pickup. The microphone has a switchable low-frequency roll-off filter (-12dB/octave @ 80Hz). On the back of the microphone you’ll find an XLR5M output connector. This is different from most microphones, which have a standard XLR3M connector. The extra pins are needed to carry the second audio signal. The microphone comes with a 24-in. adapter cable (XLR5F to two standard XLR3M connectors) that lets you connect it to separate XLR3F connectors on a camera, audio recorder, or mixer. I suggest purchasing an XLR5F extension cable so you don’t have to run two XLR cables when using the microphone for stereo recording at a distance from the camera or recorder. When using it as a standard mono short-shotgun, an XLR5F to one standard XLR3M adapter cable that ignores channel 2 is ahandy accessory to have.
Like any condenser microphone the BP4029 is very sensitive to handling noise and should be mounted on a pistol grip, a boom with a shock mount, or camera mount with a shock mount. Using on a standard camera microphone mount is not recommended. Proper placement is critical in most situations, since the microphone is quite directional and off-axis sounds exhibit distinctive coloration. For the best results it is critical that the microphone be precisely aimed at the source, regardless of whether you’re in the narrow or wide matrixed modes. Short shotguns are a good choice for recording when it is desirable to focus on a specific sound source and where isolation from unwanted sounds or noise is needed. Another reason for using a short shotgun is when a greater working distance is required than could be achieved with a cardioid microphone. Of course, in an ideal world we would rarely have need for short-shotguns (and long shotguns for that matter), since ideally dialog would be recorded with a hyercardioid close to the source. So when ideal microphone placement is possible, yes, go for the hyercardioid close to source, they offer a lot less off-axis coloration, but for most everything else, the BP4029 is a handy one-size-fits-almost-all solution for the documentary maker who wants maximum versatility form the least amount of gear. I’ve been recording sound effects, ambient tracks and dialogue with this microphone for about five years now, and I’ve been very happy with the results.
Note on the Documenting Bumpkin audio recording
I wrote above that “almost all” of the sound in these videos was recorded with the BP4029 because sometimes I mixed in some stereo ambient sound recorded with the built-in camera microphone. This is one of many reasons I like shooting with the Panasonic HPX170 (and its fine successor, the HPX250), the external microphones are recorded on channels 1 and 2 while the built-in stereo microphone is recorded on channels 3 and 4, so you always have some ambient sound from the camera’s perspective you can mix in with your primary audio tracks. In addition, there are a small number of dialogue segments that were recorded several months after the event for which I used a Roland R-09 (the R-05 is their current model which I highly recommend if you need a small and robust sound recorder) and a pair of Giant Squid Audio Lab omnidirectional condenser microphones (which provide a nice balance between price and performance for consumer plug-in power condenser microphones).
BP4029 polar pattern diagram from Audio-Technica, who retains their copyright.