Audio-Technica BP4029 Stereo Shotgun Microphone

The Audio-Technica BP4029 is a stereo shotgun microphone that produces a center-focused stereo image. It contains two independent condenser elements: a “Mid” element with a line-cardioid pick-up pattern and a “Side” element with a figure-eight pick-up pattern. The frequency response and overall sound quality is quite good. As with many professional condenser microphones, phantom power is required.

Stereo modes

The microphone can be used in one of three modes. M-S 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. Choose M-S when you want to use the middle capsule for mono recording or if you prefer to record discrete middle and side channels and encode as stereo 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.

Configurations

The microphone has two configuration switches: a low-frequency roll-off filter switch (-12dB/ octave @ 80Hz) and a stereo mode switch for selecting M-S, LR-W, or LR-N.  Ty Ford writes, “One very noticeable difference between these AT mics and others I have used is in the design of the LF rolloff filters. […] Engaging the LF rolloff switch actually increases the LF response between 100Hz and 500Hz. Below 100Hz it then drops off more steeply at 12dB/octave. is means you get more mid bass and less low bass with the LF filter engaged.” In my experience this provides slightly richer dialogue when recording people who have a deep voice compared to other microphones in the same price range.

Connector and adapter cables

On the back of the microphone you’ll find an XLR5-M output connector. This is different from most microphones, which have a standard XLR3-M connector. The extra pins are needed to carry the second audio signal. When referring to professional audio connectors, XLR designates the type of connector, the number following XLR designates the number of conductors, and the F and M designate whether the connector has sockets or pins, respectively.

The microphone kit includes a 24″ adapter cable (XLR5-F to two standard XLR3-M connectors) that lets you connect it to separate XLR3-F connectors on a camera, audio recorder, or mixer.

XLR5-F to XLR5-M extension cable are available if you want to use the microphone on a boom or with a pistol grip away from the camera, mixer, or reorder. In addition, a short XLR5-F to XLR3-M cable is available to adapt the microphone for use as a standard, mono short-shotgun microphone.

Mounting options

The microphone is very sensitive to handling noise and should be mounted on a pistol grip with a good shock mount, a boom pole with a shock mount attached, or a camera mount with a shock mount. Using this microphone on a stock camera microphone mount or a microphone mount without a shock mount is strongly discouraged.

A windjammer or zeppelin should be used when it’s windy outdoors, the foam windscreen that comes with the microphone only protects you from wind noise caused by microphone movement or very light wind.

Placement considerations

Proper placement is critical in most situations, since the microphone is quite directional and off- axis sounds exhibit distinctive coloration. For the best results the microphone should be precisely aimed at the source, regardless of whether you’re in the narrow or wide matrixed modes.

Usage recommendations

Short shotgun microphones are very versatile in that they are easily used as either an on-camera microphone or a boom mounted microphone, or mounted on a pistol grip. This microphone works well for both dialogue recording (using the M channel as a mono short- shotgun) as well as stereo sound effects and ambient sound recording.

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 and you can’t get as close as you’d like with a cardioid or hypercardioid.

Shotguns are not so great for recording in small reverberant spaces since as off-axis sounds exhibit quite a bit of coloration, in these situations a cardioid or hypercardioid is a better choice.

Frequency response

Polar patterns

 

 

Diagrams courtesy of Audio-Technica

Using the mic on a camera

In an ideal world you’d have a ninja-class boom operator with you on every shoot, however, if you’re working solo lobo there are times when a wireless lavaliere on your subjects is not practical, or you don’t have one, and then the only option becomes  mounting the BP4029 on your camera. I suggest avoiding built-in microphone mounts or rigid microphone mount because they transmit too much handling noise to the microphone. A Rycote Lyre or InVision Hot Shoe mount are good options. Whatever you get, make sure you can swivel the mount, so in situations where you are framing a subject to the right or left of frame, you can offset the microphone so it’s pointing directly at the sound source for the best sound quality.

Mono dialogue recording on a boom

If you are using the microphone on a boom, especially a boom with a mono cable running inside the boom, the use of an XLR5-F (stere0)  to XLR3-M  (mono) adapter cable comes in handy for connecting the microphone.

Cinéma-vérité style shooting

Since the BP4029 is an MS stereo microphone,  it has two discrete microphone 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. However, for cinéma-vérité shooting, when you are primarily concerned about the dialogue of your subjects, you can  use the microphone in MS mode which provides the M and S as discrete ;independent channels recorded to channel 1 and 2 respectively. In thus case channel 1 provides you with the dialogue of subjects in front of the camera and channel 2 provides you with the dialogue of subjects to the right or left of the camera. This second channel gives you a lot more flexibility in postproduction when shooting cinéma-vérité style.

Recording discrete M and S and decoding in post

The discrete M and S signals recorded to channels 1 and 2 of the camera or sound recorder can be decoded to stereo in Adobe Premiere Pro using a plug-in like Voxengo MSED.  You can use the M channel and ignore the S channel and it functions as an ordinary short shotgun or you can covert the M and S channels to stereo using the plug-in during post. The plug-in allows you to vary the width of the stereo field.

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
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.

Parting thoughts

The BP4029 is a handy one-size-almost-fits-all solution for media makers who want maximum versatility form the least amount of gear. I use mine for recording dialogue in mono, as well as sound effects and ambience in stereo, and I’ve been very happy with the results.

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