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Audio-Technica BP4029 MS Stereo Condenser Microphone

Thrown together by David Tamés on August 24, 2013, Revised February 10, 2026

Overview

The BP4029 is a versatile stereo shotgun microphone containing two independent electret condenser capsules: a narrow cardioid (Mid element) and the other is a figure-of-eight (Side element), arranged in an MS (Mid-Side) configuration. The microphone provides switch-selectable internal stereo matrixing, which provides the choice of selecting left-right stereo output (wide or narrow) via the internal matrixing system, or choosing discrete Mid-Side signals for later processing during postproduction. The microphone also provides a switch-selectable low cut filter. The microphone operates with phantom power and sports an XLR-5M connector. Accessories include a microphone holder (for use on a microphone stand), a foam windscreen, and an XLR-5F to dual XLR-3M adapter cable for splitting the stereo output to 1/Left and 2/Right mono connectors. Among all the microphones in my sound kit, this is my favorite.

Configuration

MS mode switch configures how the microphone capsules are routed/matrixed to the output and has three positions:

  • MS mode provides independent Mid and Side signals (1/L, 2/R) for maximum flexibility during postproduction.
  • LR-W (wide) provides a matrixed stereo output with increased ambient pickup (approximately 80° angle of acceptance).
  • LR-N (narrow) provides a tighter matrixed stereo output with more off-axis rejection (approximately 20° angle of acceptance).

Low-cut filter switch can be sent on or off:

  • Disabled: Flat response, or
  • Enabled: 80 Hz low-frequency roll-off at 12 dB/octave, as sound designer Ty Ford as pointed out, the roll-off filter on this mic has an unusual characteristic where it actually increases mid-bass response between 100–500 Hz while cutting more steeply below 100 Hz, so it’s not a straightforward high-pass filter.

The advantages of MS stereo recording

Stereo MS recordings have several advantages:

  1. The conversion between MS and Left-Right stereo is reversible and lossless;
  2. MS is the only stereo system where the width can be adjusted from hard mono to extreme diffuse out-of-phase sound after recording;
  3. MS is coincident and mono compatible (the S-signal cancels out when summed to mono so there are no phase issues); and
  4. With MS, one microphone points directly in the main direction, unlike other systems in which the main direction is covered by the microphones off-axis. 

The MS to LR conversion process: 

  • L = M + S
  • R = M - S 

The LR to MS conversion process:

  • M = (L + R) / 2
  • S = (L - R) / 2

For more technical details, refer to the references below.

Use scenarios

This microphone is idea for a variety of contexts:

1. Camera-mounted stereo and mono capture: The BP4029 is compact and light enough for on-camera use. For run-and-gun documentary or micro-budget narrative work, mounting it on a camera with a shoe-mount adapter gives you stereo ambience capture without a separate rig. The LR-W mode is suggested as the best “set it and forget it” option. In postproduction you can then extract the middle channel for mono dialogue, the side channels to capture a speaker to the left or right of the camera if needed, and stereo at various widths for stereo ambience and sound effects. MS can do it all in one stereo recording with many possible derivatives.

If you plan to record dialog with subjects speaking close to the camera, use a microphone mount that swivels so you can point the microphone directly at the speaker when using off-center compositions, this will make a big difference in the quality of your dialogue recording. For examples of documentary footage with dialogue recorded in this manner (using the Mid channel only for mono dialogue, and MS stereo recordings for ambience and sound effects), watch—preferably with headphones—the following videos:

Sharon Dunn: 4-D Map: Portraits of Stones & Plants Found Along the Water’s Edge (David Tamés, 2011, 2:21), documentation of the 2010 Bumpkin Island Art Encampment, excerpt from a video loop originally exhibited at the Bumpkin Forward exhibition, Mobius Gallery, Boston, April 1-10, 2011, mono dialogue and stereo ambience recorded using the Audio-Technica BP4029 microphone.

Mark Davis: Bumpkin Sky-Land (David Tamés, 2011, 2:15), documentation of the 2010 Bumpkin Island Art Encampment, excerpt from a video loop originally exhibited at the Bumpkin Forward exhibition, Mobius Gallery, Boston, April 1-10, 2011, Music: Overlands by moby, licensed from mobygratis, mono dialogue and stereo ambience recorded using the Audio-Technica BP4029 microphone.

2. Boom operation as a mono dialogue microphone: The BP4029 can be used as a mono dialogue mic on a boom by setting it to MS mode and using only the Mid capsule (channel 1), which requires an XLR-5F to XLR-3M adapter cable passing pins 1, 2, and 3 while ignoring pins 4 and 5. The BP4029 is my favorite microphone in my kit because this microphone can serve double duty: mono dialogue on the boom, and a stereo microphone for recording sound effects or ambience in stereo.

3. Stereo field recording and sound effects: An MS microphone is the ideal tool for recording stereo amnbience and sound effects that may need to be able to collapse to mono. Unlike X-Y and ORTF stereo recordings, MS recordings can be mixed to mono without phase shift artifacts because the microphone capsules are coincident.

Important caveats

The BP4029 requires phantom power on both XLR connectors, so you’ll need to use it with a sound recorder or camera that provides +48V phantom power on the XLR microphone inputs.

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.

For correct left-right stereo with the BP4029, position the microphone with the word “UP” on top.

Shotgun microphones are not ideal for small, reverberant spaces since off-axis sounds exhibit significant coloration. In those situations a cardioid or hypercardioid would perform better.

Placing the microphone closer to the sound source enhances the apparent stereo image width while decreasing room ambience.

When recording outdoors, always use a windjammer, blimp, or in heavy winds, a blimp with an add-on windjammer. Microphone wind protection comes in three variations:

  1. foam windscreens (basic, only good enough to reduce the wind noise of moving the microphone indoors);
  2. windshields (a.k.a. “dead cat” or ”furry”) made with synthetic fur providing good wind diffusion for outdoor conditions; and
  3. blimps (a.k.a. zeppelin) consisting of a rigid cage and mesh that surrounds the microphone, often paired with a fuzzy cover for maximum wind protection.

Listen to this video—preferably with headphones—to hear the difference between using the windshield and a foam windscreen while recording stereo dialogue on a windy day with the BP4029:

Rycote Softie Windshield vs Foam Windscreen Comparison

For more on sound recording, visit the following pages on this site:

References

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