Stereo shotgun ? at DVinfo.net

Gints Klimanis · October 23rd, 2006, 02:40 PM

Are any of you using stereo shotgun microphones, especially for action footage ? I've been using a wide pattern stereo X-Y (AT822 or AT825) , but want to move to a stereo microphone that won't pickup everything in back of me. Will this microphone sound make the audience noise from the side weird?

Bill Southworth · October 28th, 2006, 07:30 AM

I use a booomed Sanken CMS-10 M-S microphone and sometimes a Sennheiser 418. I prefer the Sanken. A bit warmer sound. I put these either into a Sound Devices 744T recorder or 422 mixer, both of which have M-S decoding. I monitor as de-muxed stereo so I can narrow or widen the stereo imaging to get more or less shotgun.

Ty Ford · October 28th, 2006, 07:52 AM

Quote:

Originally Posted by Gints Klimanis

Are any of you using stereo shotgun microphones, especially for action footage ? I've been using a wide pattern stereo X-Y (AT822 or AT825) , but want to move to a stereo microphone that won't pickup everything in back of me. Will this microphone sound make the audience noise from the side weird?

There is no such thing as a stereo shotgun mic. There are several stereo/shotgun mics. The point being, a stereo/shotgun mic can be either but not both at the same time.

Most stereo mics do have reduced pickup off the rear, but I don't know any that won't pick up anything. Your best solution at this moment is to create a rig of two super cardioid mics like two Schoeps cmc641 in a bracket.

Regards,

Ty Ford

Seun Osewa · November 8th, 2006, 02:31 AM

Shouldn't the dialogue go into a central sound channel?

Ty Ford · November 8th, 2006, 06:59 AM

Usually. Then it's panned as needed. I wrote an article about the LaFont preamp; a french design. They said foley is frequently recorded in M/S in France.

I have more reviews on my web site. Here's the LaFont.

Regards,

Ty Ford

The LaFont LP-21 Dual Microphone amplifier

Ty Ford

The LaFont Dual Microphone amplifier ($1,495) is an AC-powered, transformerless, two-channel, solid state mic preamp with a discrete front end. Before you dismiss it as another in the cavalcade of solid state preamps, I should mention that it comes rigged for M/S (mid/side) recording. You can use either or both channels independently, or together with a cardioid and figure of eight mic for M/S. (Some have experimented with omni and hypercardioid patterns instead of the cardioid. The results vary by mic, source and acoustical environment.)

In the US, M/S is routinely used in the recording of film sound ambience, not dialog. Briefly, M/S recording involves recording a cardioid mic aimed at the sound source to one channel and a figure of eight mic aimed sideways (null to the source) to another channel. The mics are placed with capsules, one on top of the other, to minimize phase differences. Back at the studio, an M/S matrix box makes three channels out of the two. The cardioid is the mid or mono channel. The figure of eight signal is sent to the left channel and a reversed-polarity figure of eight signal is sent to the right channel. On the console, the left and right channels are each panned to their respective extremes. Listening in stereo, the cardioid mic provides the mid channel (mono) signal. As the two side channels are brought up, the stereo spreads out increasingly. Because the mics are placed as coincidently as possible, a stereo recording will survive being reduced to mono, showing only minimal, if any, phase cancellation.

After the director has decided whether the shot will be a closeup, medium or wide shot, the mixer adjusts the degree of stereo width of the shot to complete the aural vision of the director. Extreme closeups with really wide stereo can be disconcerting. Panavistic wide shots demand more than a narrow slice of audio. However, all of this is done in post production at line level.

In a trans-atlantic chat I had with Jean-Pierre LaFont, he explained that, in France, Foley effects are frequently recorded in stereo. In many cases, by the time the production is ready for Foley effects, the shots have been determined. The Foley artist is looking at a rough cut of the footage while he or she creates the sounds that accompany the scene. The LP-21 is used to record in stereo on the Foley stage. That stereo could be a sound centered in a stereo ambience, to one side, or moving through the stereo field to match the motion on the screen. Being able to quickly change widths and the balance between stereo field and center channel allows the work to get done more quickly.

Both preamps of the LP-21 are identical, with both fine and coarse continuously variable gain knobs, a polarity reversal switch, 20dB pad, 48V phantom switch, a switchable filter section with both 12dB/octave high pass and low pass filters, a channel on (or mute) button and an eleven LED output display with a 13th clip LED. There is no input clip light, but you'll probably have problems downstream of the output before the input clips. To the right of these two sections; the Midside Stereophony controls include a M/S mode switch, width control and center gain control.

Standard gain settings range from 20dB to 65dB. The circuit is designed for 23dB to 25dB above 0dB before clipping the output. There's also a high-gain button on each preamp that adds another 10dB, making the range 20dB to 75dB. The 20dB pad before the preamp is designed not to changed the 1.2k Ohm input impedance of the preamps. Impedance-altering pads usually change the sound of the mic because they alter the impedance relationship of the mic and preamp input.

The channel I/O button operates silently, muting each channel. As long as the filter section buttons are engaged or disengaged quickly, they are also silent. The high-pass filter is adjustable from 35Hz to 65Hz. The low-pass filter goes from 1kHz to 20kHz. Maximum output is +27.5dB. Frequency response is listed at 10Hz to 25.3 kHz (-1dB) and 7Hz to 50kHz (-3dB). Mic amp noise is listed as -52.2dB @200 Ohms (22Hz-22kHz) at 75.5dB gain. EIN is -127.8dB, 131 dB shorted.

The back panel features two XLR mic inputs, three line level outputs (M-S, M+S, Mono), a TRS jack for an external mute switch for the two channels and a jack for a 10-pin HE10 cable for consoles with logic circuits for operating the channel mutes. This simple but useful feature can be used to mute the monitors in studios with mics and monitors in the same room. There's also a standard IEC power jack on the back.

HOW DOES IT SOUND
In the noise test with the RCA 77DX, the LP-21 did as well as most good preamps with transformerless inputs. For quiet sources, especially with low level ribbon mics, you will hear preamp noise. The low-pass and high-pass filters did come in handy for taming unwanted frequencies without noticeable phase smearing.

I compared for sound, the LP-21 preamps with my GML preamps and those in the new Mackie VLZ/XDR, through a 1604 VLZ/XDR mixer. The XDR preamps sound darker and smoother than all previous Mackie preamps I've heard. The GML was the most natural sounding, the LP-21 a bit more bright, and the XDR brighter still.

In the quiet of the studio I plugged in a set of Sony 7506 phones and cranked up a new pair of Neumann TLM 103s with Gotham GAC-3 mic cable in search of preamp noise. In order to hear the noise, the gain was loud for the Neumann's to plainly pick up the sound of my lunch of leftover Indian food making its way through my upper intestines from a distance of about two feet. At that level, both the GML and XDR preamps appeared to have similar amounts of noise, which was slightly less than that of the LP-21. I switched mics, re-balanced gains and tried different inputs, but the noise differences remained the same on both channels of the LP-21.

I set up for M/S using a Neumann U 89 and a TLM 103 and connected the three outputs of the LP-21 to the VLZ/XDR, panning both side channels to their extremes, and bringing all faders up to unity gain. Because the side mic is 90 degrees off axis from the sound, thereby only getting sound as it skips across the diaphragm, you'll want to use the quietest and best figure of eight you can get. Otherwise, as you increase the stereo spread, you'll begin to hear the self noise of the mic. I positioned the mics to keep the figure of eight from nearby reflective surfaces to keep it from hearing bounced sound that would mess with the stereo spectrum.

I recorded acoustic guitar at different distances; three feet , two feet and a foot or less. As I got closer I realized that I could "center" the guitar so that it nulled out much of the proximity effect caused by having a guitar sound hole within a foot of the mid TLM 103. When I moved the guitar slightly to the left or right, the proximity effect started to emerge on the respective side. Using the width control on the LP-21, I was able to go from mono to a very wide guitar, filling both speakers. When I pushed the width control to extremes, I got V e r y W i d e S o u n d and, finally, an increase in noise.

The next application was to try to record a guitar duo. The thought being, making a simple stereo recording of two acoustic guitars sometimes gets really complicated and "phasey" when multiple mics are used on each guitar. Guitarist Bob Showacre and I formed a more or less equilateral triangle with the M/S mic array, each of us from about 18 inches to over several feet from the mics. Placement and movement have a major bearing on where the sound ends up on the stereo spectrum. At one point, the midrange tones of my D28S Martin came from more or less the center of the stereo spectrum, while the higher notes came more from the right side. And that was without moving the body. I was very pleased with how quiet the recordings were and how natural they sounded; just a couple of guitars in a nice space. Summing the channels to mono revealed that the phase anomalies were not great enough to compromise the high-frequency response. Summing did seem to cause a very slight increase in upper bass or lower midrange.

I decided to push the envelope a bit by adding a third guitar; a Telecaster played by my wife Bette. It was plugged into a Fender Super Reverb a good seven or eight feet to one side of the M/S array. Bob moved slightly more on-center to allow the Telecaster to fill up the right side. The Tele sounded "in the room and over to the side somewhere". The hazard of this approach is that you do lock yourself into the placement on the stereo spectrum and that everyone playing must be very conscious of the dynamics and levels of everyone else. If you get it right, it sounds pretty sweet.

IN CONCLUSION
Although the LP-21 was not designed for the music studio, it performed rather well. If stereo Foley is your bag, the LP-21 is a natural; that's what it was designed for. Regardless of its minor noise, which I had to dig deeply to find, it offers two nice sounding preamps, filters, and the all important M/S matrix controls. It'd be nice to have a line level input to matrix M/S recordings, but you can do that with three inputs and one polarity-reverse switch or cord. I wanted to record a drum kit, thinking M/S would sound great on the right drums with the right player in the right room, but I ran out time and words. Hey, make that your next project.

Technique, Inc. (C) Copyright 1999. Ty Ford may be reached at http://www.tyford.com

PRO: M/S matrix and filters are a plus.
CON: Slightly more expensive due to added features.
APP: Foley and other stereo or two channel recording.

George Ellis · November 10th, 2006, 06:51 AM

Ty hates the term stereo shotgun if you have not figured it out :P

I have an A-T 835ST. I find it very versatile and easy to use. On narrow, rear and side rejection are good (I had a band director drop the F bomb standing next to me during a performance and it was not in the audio.) While never as good as a set of crossed over and split pairs, it does give me enough seperation to hear the left and right side of the fields. It is portable and does give the audio some depth. BUT, it can at times seem to cross the audio over (left is right, but when I have heard that, it could be echo delay - I am in a football stadium with a set of reflectors, err opposing team stands, on the other side.)

Footnote that has nothing to do with this - I just finished a 17 band video. While working through it, I realized I had this slight hmm which sounded like 60 cycle humm. What the!!!... I am DC. Where is this coming from? I had my wife listen to it. She said, "Oh, it was nothing you did. It was the stadium." All of the empty aluminium seats in the stadium would resonate when the bands were playing. The louder they were, the louder it got. It got better as the day went on because more people were sitting on the seats.

It explains something I always heard and never processed. When a band marches on or off, somethings a snare will beat a single hit cadence. The echo has a buzz to it. All those empty seats singing along.

Ty Ford · November 10th, 2006, 08:56 AM

Hey George,

That would be stereo/shotgun, not stereo shotgun. ;)

The weird sound you're hearing in the 835ST is what happens when sound gets around the rear of the mic on either side. I talk about it in my review of the mic which is in my online archive. It's what happens when you have an M/S array with the mic elements not in the same vertical space.

I can't remember whether the figure of eight capsule is in front of or behind the cardioid in the 835ST, but as the sound source swings around the side, at some point the arrival of sound doesn't get to the front capsule first. At that point, there's a little flip flop in the stereo image.You get the same thing as the sound source continues around back and comes back around front on the other side.

If you don't have a lot of sound coming in behind the mic, you'll never hear this.

Regards,

Ty Ford

George Ellis · November 10th, 2006, 10:41 AM

That explains it. I suspect it happens when the crowd cheers which seems to make sense.

October 23rd, 2006, 02:40 PM	#1
Gints Klimanis Inner Circle Join Date: Jun 2003 Location: San Jose, CA Posts: 2,222	Stereo shotgun ? Are any of you using stereo shotgun microphones, especially for action footage ? I've been using a wide pattern stereo X-Y (AT822 or AT825) , but want to move to a stereo microphone that won't pickup everything in back of me. Will this microphone sound make the audience noise from the side weird?

November 8th, 2006, 06:59 AM	#5
Ty Ford Inner Circle Join Date: Nov 2004 Location: Baltimore, MD USA Posts: 2,337	Usually. Then it's panned as needed. I wrote an article about the LaFont preamp; a french design. They said foley is frequently recorded in M/S in France. I have more reviews on my web site. Here's the LaFont. Regards, Ty Ford The LaFont LP-21 Dual Microphone amplifier Ty Ford The LaFont Dual Microphone amplifier ($1,495) is an AC-powered, transformerless, two-channel, solid state mic preamp with a discrete front end. Before you dismiss it as another in the cavalcade of solid state preamps, I should mention that it comes rigged for M/S (mid/side) recording. You can use either or both channels independently, or together with a cardioid and figure of eight mic for M/S. (Some have experimented with omni and hypercardioid patterns instead of the cardioid. The results vary by mic, source and acoustical environment.) In the US, M/S is routinely used in the recording of film sound ambience, not dialog. Briefly, M/S recording involves recording a cardioid mic aimed at the sound source to one channel and a figure of eight mic aimed sideways (null to the source) to another channel. The mics are placed with capsules, one on top of the other, to minimize phase differences. Back at the studio, an M/S matrix box makes three channels out of the two. The cardioid is the mid or mono channel. The figure of eight signal is sent to the left channel and a reversed-polarity figure of eight signal is sent to the right channel. On the console, the left and right channels are each panned to their respective extremes. Listening in stereo, the cardioid mic provides the mid channel (mono) signal. As the two side channels are brought up, the stereo spreads out increasingly. Because the mics are placed as coincidently as possible, a stereo recording will survive being reduced to mono, showing only minimal, if any, phase cancellation. After the director has decided whether the shot will be a closeup, medium or wide shot, the mixer adjusts the degree of stereo width of the shot to complete the aural vision of the director. Extreme closeups with really wide stereo can be disconcerting. Panavistic wide shots demand more than a narrow slice of audio. However, all of this is done in post production at line level. In a trans-atlantic chat I had with Jean-Pierre LaFont, he explained that, in France, Foley effects are frequently recorded in stereo. In many cases, by the time the production is ready for Foley effects, the shots have been determined. The Foley artist is looking at a rough cut of the footage while he or she creates the sounds that accompany the scene. The LP-21 is used to record in stereo on the Foley stage. That stereo could be a sound centered in a stereo ambience, to one side, or moving through the stereo field to match the motion on the screen. Being able to quickly change widths and the balance between stereo field and center channel allows the work to get done more quickly. Both preamps of the LP-21 are identical, with both fine and coarse continuously variable gain knobs, a polarity reversal switch, 20dB pad, 48V phantom switch, a switchable filter section with both 12dB/octave high pass and low pass filters, a channel on (or mute) button and an eleven LED output display with a 13th clip LED. There is no input clip light, but you'll probably have problems downstream of the output before the input clips. To the right of these two sections; the Midside Stereophony controls include a M/S mode switch, width control and center gain control. Standard gain settings range from 20dB to 65dB. The circuit is designed for 23dB to 25dB above 0dB before clipping the output. There's also a high-gain button on each preamp that adds another 10dB, making the range 20dB to 75dB. The 20dB pad before the preamp is designed not to changed the 1.2k Ohm input impedance of the preamps. Impedance-altering pads usually change the sound of the mic because they alter the impedance relationship of the mic and preamp input. The channel I/O button operates silently, muting each channel. As long as the filter section buttons are engaged or disengaged quickly, they are also silent. The high-pass filter is adjustable from 35Hz to 65Hz. The low-pass filter goes from 1kHz to 20kHz. Maximum output is +27.5dB. Frequency response is listed at 10Hz to 25.3 kHz (-1dB) and 7Hz to 50kHz (-3dB). Mic amp noise is listed as -52.2dB @200 Ohms (22Hz-22kHz) at 75.5dB gain. EIN is -127.8dB, 131 dB shorted. The back panel features two XLR mic inputs, three line level outputs (M-S, M+S, Mono), a TRS jack for an external mute switch for the two channels and a jack for a 10-pin HE10 cable for consoles with logic circuits for operating the channel mutes. This simple but useful feature can be used to mute the monitors in studios with mics and monitors in the same room. There's also a standard IEC power jack on the back. HOW DOES IT SOUND In the noise test with the RCA 77DX, the LP-21 did as well as most good preamps with transformerless inputs. For quiet sources, especially with low level ribbon mics, you will hear preamp noise. The low-pass and high-pass filters did come in handy for taming unwanted frequencies without noticeable phase smearing. I compared for sound, the LP-21 preamps with my GML preamps and those in the new Mackie VLZ/XDR, through a 1604 VLZ/XDR mixer. The XDR preamps sound darker and smoother than all previous Mackie preamps I've heard. The GML was the most natural sounding, the LP-21 a bit more bright, and the XDR brighter still. In the quiet of the studio I plugged in a set of Sony 7506 phones and cranked up a new pair of Neumann TLM 103s with Gotham GAC-3 mic cable in search of preamp noise. In order to hear the noise, the gain was loud for the Neumann's to plainly pick up the sound of my lunch of leftover Indian food making its way through my upper intestines from a distance of about two feet. At that level, both the GML and XDR preamps appeared to have similar amounts of noise, which was slightly less than that of the LP-21. I switched mics, re-balanced gains and tried different inputs, but the noise differences remained the same on both channels of the LP-21. I set up for M/S using a Neumann U 89 and a TLM 103 and connected the three outputs of the LP-21 to the VLZ/XDR, panning both side channels to their extremes, and bringing all faders up to unity gain. Because the side mic is 90 degrees off axis from the sound, thereby only getting sound as it skips across the diaphragm, you'll want to use the quietest and best figure of eight you can get. Otherwise, as you increase the stereo spread, you'll begin to hear the self noise of the mic. I positioned the mics to keep the figure of eight from nearby reflective surfaces to keep it from hearing bounced sound that would mess with the stereo spectrum. I recorded acoustic guitar at different distances; three feet , two feet and a foot or less. As I got closer I realized that I could "center" the guitar so that it nulled out much of the proximity effect caused by having a guitar sound hole within a foot of the mid TLM 103. When I moved the guitar slightly to the left or right, the proximity effect started to emerge on the respective side. Using the width control on the LP-21, I was able to go from mono to a very wide guitar, filling both speakers. When I pushed the width control to extremes, I got V e r y W i d e S o u n d and, finally, an increase in noise. The next application was to try to record a guitar duo. The thought being, making a simple stereo recording of two acoustic guitars sometimes gets really complicated and "phasey" when multiple mics are used on each guitar. Guitarist Bob Showacre and I formed a more or less equilateral triangle with the M/S mic array, each of us from about 18 inches to over several feet from the mics. Placement and movement have a major bearing on where the sound ends up on the stereo spectrum. At one point, the midrange tones of my D28S Martin came from more or less the center of the stereo spectrum, while the higher notes came more from the right side. And that was without moving the body. I was very pleased with how quiet the recordings were and how natural they sounded; just a couple of guitars in a nice space. Summing the channels to mono revealed that the phase anomalies were not great enough to compromise the high-frequency response. Summing did seem to cause a very slight increase in upper bass or lower midrange. I decided to push the envelope a bit by adding a third guitar; a Telecaster played by my wife Bette. It was plugged into a Fender Super Reverb a good seven or eight feet to one side of the M/S array. Bob moved slightly more on-center to allow the Telecaster to fill up the right side. The Tele sounded "in the room and over to the side somewhere". The hazard of this approach is that you do lock yourself into the placement on the stereo spectrum and that everyone playing must be very conscious of the dynamics and levels of everyone else. If you get it right, it sounds pretty sweet. IN CONCLUSION Although the LP-21 was not designed for the music studio, it performed rather well. If stereo Foley is your bag, the LP-21 is a natural; that's what it was designed for. Regardless of its minor noise, which I had to dig deeply to find, it offers two nice sounding preamps, filters, and the all important M/S matrix controls. It'd be nice to have a line level input to matrix M/S recordings, but you can do that with three inputs and one polarity-reverse switch or cord. I wanted to record a drum kit, thinking M/S would sound great on the right drums with the right player in the right room, but I ran out time and words. Hey, make that your next project. Technique, Inc. (C) Copyright 1999. Ty Ford may be reached at http://www.tyford.com PRO: M/S matrix and filters are a plus. CON: Slightly more expensive due to added features. APP: Foley and other stereo or two channel recording. __________________ Ty Ford's Audio Bootcamp Field Guide Ty Ford's Audio Video Blog

November 10th, 2006, 08:56 AM	#7
Ty Ford Inner Circle Join Date: Nov 2004 Location: Baltimore, MD USA Posts: 2,337	Hey George, That would be stereo/shotgun, not stereo shotgun. ;) The weird sound you're hearing in the 835ST is what happens when sound gets around the rear of the mic on either side. I talk about it in my review of the mic which is in my online archive. It's what happens when you have an M/S array with the mic elements not in the same vertical space. I can't remember whether the figure of eight capsule is in front of or behind the cardioid in the 835ST, but as the sound source swings around the side, at some point the arrival of sound doesn't get to the front capsule first. At that point, there's a little flip flop in the stereo image.You get the same thing as the sound source continues around back and comes back around front on the other side. If you don't have a lot of sound coming in behind the mic, you'll never hear this. Regards, Ty Ford __________________ Ty Ford's Audio Bootcamp Field Guide Ty Ford's Audio Video Blog

October 28th, 2006, 07:30 AM	#2
Bill Southworth Regular Crew Join Date: Dec 2005 Posts: 37	I use a booomed Sanken CMS-10 M-S microphone and sometimes a Sennheiser 418. I prefer the Sanken. A bit warmer sound. I put these either into a Sound Devices 744T recorder or 422 mixer, both of which have M-S decoding. I monitor as de-muxed stereo so I can narrow or widen the stereo imaging to get more or less shotgun.

November 8th, 2006, 02:31 AM	#4
Seun Osewa Major Player Join Date: Oct 2006 Location: West Africa Posts: 255	Shouldn't the dialogue go into a central sound channel?

November 10th, 2006, 06:51 AM	#6
George Ellis Trustee Join Date: Feb 2004 Location: Suwanee, GA Posts: 1,241	Ty hates the term stereo shotgun if you have not figured it out :P I have an A-T 835ST. I find it very versatile and easy to use. On narrow, rear and side rejection are good (I had a band director drop the F bomb standing next to me during a performance and it was not in the audio.) While never as good as a set of crossed over and split pairs, it does give me enough seperation to hear the left and right side of the fields. It is portable and does give the audio some depth. BUT, it can at times seem to cross the audio over (left is right, but when I have heard that, it could be echo delay - I am in a football stadium with a set of reflectors, err opposing team stands, on the other side.) Footnote that has nothing to do with this - I just finished a 17 band video. While working through it, I realized I had this slight hmm which sounded like 60 cycle humm. What the!!!... I am DC. Where is this coming from? I had my wife listen to it. She said, "Oh, it was nothing you did. It was the stadium." All of the empty aluminium seats in the stadium would resonate when the bands were playing. The louder they were, the louder it got. It got better as the day went on because more people were sitting on the seats. It explains something I always heard and never processed. When a band marches on or off, somethings a snare will beat a single hit cadence. The echo has a buzz to it. All those empty seats singing along.

November 10th, 2006, 10:41 AM	#8
George Ellis Trustee Join Date: Feb 2004 Location: Suwanee, GA Posts: 1,241	That explains it. I suspect it happens when the crowd cheers which seems to make sense.