Mic options for interview using Sony α7 II

Discussion in 'Video' started by Colin O, Apr 12, 2020.

  1. I came across a suggestion by Philip Greenspun on his personal website about Capturing Family History on Video. This seems to me a fantastic idea, and I'm going to give it a go later in the year hopefully. But I want to ask about recording audio, which I don't really have much of a clue about.

    I intend to "interview" my own parents as well as several aunts and uncles. The interviews will probably take place in a living room or kitchen in the respective houses. Each interview will be with 1 or 2 people. I have a Sony α7 II, and I'll set it up on a tripod with a 50mm lens probably. But how should I record audio? I will need to buy some hardware for this, and if possible I'd like to keep my expenses under £100. Where do I start? What are my options even? Philip suggests using lapel microphones, but I am wondering if that's really so essential. I don't want my relatives to feel that it is a "professional" interview - I'd like them to relax. I was wondering about one of those directional mics that slot into the camera's hotshoe. Are they good for recording 2 people, or only 1? Do they offer a significant improvement over the camera's built-in mic? I assume so. What about something like the RØDE VideoMic or the RØDE VideoMicro - would either/both be a reasonable/good option?

    If lapel microphones really are significantly better, what are my options at this kind of budget? Particularly with 2 people. Can I use a simple splitter and input one person's audio to the camera as the left channel, and the other person as the right channel? Is that even a good idea, to have different people on different channels? I probably won't edit the video myself - I was thinking of maybe using an online freelancer to outsource the editing. What about a wireless receiver that can simultaneously connect to 2 transmitters/microphones? Does such a thing exist (at this budget)?

    Thanks for your insight.
  2. The trick to getting good interview audio is to have the mic close enough to exclude most ambient noise and early reflections. Early reflections give the sound a hollow, distant effect. A directional (cardioid) lapel mic is nearly ideal, and presents a relatively innocuous appearance in the video. A conventional microphone should be 1-2 feet from the subject, either hand-held or on a stand. Either way, it will be in the field of view. Professionally, you would use a shotgun microphone 2-4 feet from the subject, usually on an overhead boom just out of camera range.

    These microphones will require a separate preamplifier for use with the camera. Alternately, you can use a hand-held recorder and match up the sound in post.

    The camera should be at least 5 feet from the subject. Any closer, and the facial features are distorted due to perspective. Even the best directional microphone on the camera itself will give marginal performance. Need I describe the poor quality of the built-in microphone, which is useful only for synchronizing sound from a separate recorder.

    I am concerned that the Rode Videomic has a built-in amplifier with a line-level output adjustable from -10 to + 20 dB. This suggests that the microphone and camera levels would be set to the lowest value, which would make the signal noisy and prone to clipping. I minimize clipping with a line-level feed from a Zoom F8 by turning the F8 output to - 20 dB, and recording at -20 dB peak level.

    The best option for a Sony A7ii would be the Sony XLR-K3M (or K2M) digital adapter, which fits in the multi-interface shoe on the camera and bypasses the analog camera preamp altogether. The adapter comes with a Sony short-shotgun microphone, which is probably okay, and has two XLR inputs which can be used with any professional or consumer level microphone. The next step up for your application would be one or two wired lavaliere microphones, which come at various price points.

    Wireless microphones are subject to interference from a wide variety of sources. Good ones, with frequency hopping UHF, cost $1000/channel or more. Bluetooth incurs a built-in delay of up to 1/4 second - 1960 Japanese movie dub quality. I'm about to drop the hammer on a Sony dual-channel receiver which mounts in the Multi-Interface shoe, plus a pair of matching transmitters. That will give me a stereo feed from my audio mixer, which is usually 60 feet from the camera on a different floor.
    Last edited: Apr 12, 2020
  3. Thanks a lot Ed for the characteristically knowledgeable advice.

    I'm still a bit unsure though. I get the impression that really lavalier microphones would be a better option? Interviewing one person, what would the lavalier microphone plug into? I get that one option would be a standalone recording device, and the sound would be matched with the video in post-production, but what kind of device would I be shopping for? I mean, what is it called, or what are the absolute baseline features it has to have?

    I guess I would have to rule out wireless solutions because it sounds like the price for this kind of option is way out of my budget.

    Excuse the naivety of the question, but is it possible to just have a long (extension) cable that connects the lavalier microphone directly to the camera? I don't really understand about preamplifiers, amplifiers, decibel levels...

    How exactly would these setups have to change when interviewing two people?

    As for the Sony XLR-K3M option, it's obviously more than I wanted to spend, but if it's a good option, maybe I'll just buy one, use it, and sell it second-hand after the project is done, and just take the hit on whatever I lose on the transaction.
  4. I can suggest something which would come at a reasonable cost and be nearly future-proof.

    You could use a hand-held sized recorder, like a Zoom H4n or Zoom H6. Both have a built-in stereo microphone nearly ideal for interviews and conferences, and 2 or 4 XLR inputs (respectively) for use with conventional microphones. In addition to digital recording, they have a 3.5 mm TRS line output which could be run directly to the A7iii camera. The output level can be turned down at least 20 dB, and is very quiet (90+ dB S/N). They have a 1/4"-20 socket, and could be mounted on the flash shoe or microphone stand, or even placed on a table top. They work best at 1-3 feet distance for spoken word.

    Their performance is as good or better than anything I've seen specifically for camera use, and much more flexible. They are a little large for mounting on a camera, unless you use a cage or bracket. Even so, they would be too far from the subject for good pickup. In addition to a line output, they record to a single SD card, and use AA batteries. Even in the larger H6, a set of batteries will last at least 6 hours.

    I carry an H6 as part of my regular kit, but I don't use it as much as I should. The H6 is more flexible than the H4n, but costs more. It has interchangeable microphones and separate line and headphone outputs, plus two more XLR mic/line inputs than the H4. That said, the H4 would do everything you need, with room to grow. It's built like a rock.
    Jochen likes this.
  5. Lavaliere microphones are nearly all condenser microphones, which require external power with specialized connectors. I had to shop around to find wired versions which would feed a standard XLR preamp, much less a camera.
  6. I thought it would be helpful to put some numbers to normalization of analog audio inputs to the 3.5 mm jack of a Sony A7iii, using a professional grade audio interface, a Sound Devices MixPre 10ii. For a source, I used the MixPre test oscillator set to -20 dB at 1000 Hz, which is the target recording level I use in the field. The analog output is adjustable over a range of +20 dBV to -40 dBV. For the purpose of this test, I adjusted the MicPre output and A7iii input to a record level of -20 dB.

    At the lowest setting of the A7iii, the MixPre could be set to no higher than -26 dB. With the MixPre set to -40 dB, the record level of the A7iii was 11 (out of 31). At -40 dB, the output of the MixPre is roughly that of a condensor microphone. At that setting, the end-to-end S/N ratio was 68.32 dB. While not great by digital standards, It is comparable to my old Ampex 351-2 studio recorder. A lot of vinyl and CD recordings still in circulation were recorded on machines like that.

    My takeaway is that the Rode Videomic Pro, which is adjustable between -10 db and +20 db is probably too hot for the 3.5 mm input, precluding normalization. A Zoom H6 has a line output range of -30 to 0 db, which places it just inside the allowable range for a Sony A7iii or A7Riii.

    (I published an earlier version of this response in DPReview)
  7. I have been experimenting with the use of MS stereo microphone techniques. MS stands for Mid-Side, where the main microphone has any pattern, from omnidirectional to cardioid (directional) or even a shotgun. The side microphone is always a figure-8 (or cosine) pattern, held at right angles to the main mic. The lobes of a cosine mic are 180 degrees out of phase. This signal added to the main mic generates the right and left channels by interference. The amount of stereo separation depends on the balance of the Mid and Side microphone levels.

    The advantage of MS miking is that the signal is highly compatible with mono transmission, which makes it popular for radio work. It is not always desirable to have the maximum stereo separation, which is easily adjusted with this technique. For me the most important attribute is the ability to use a highly directional (e.g., hypercardioid and shotgun) microphone to minimize the hollow sound in small rooms due to reflections from the walls and ceiling. I can get a clean spoken sound at a distance of 5 feet, that would require about 1 foot with a conventional microphone. The composite sound is more "natural" than from the shotgun mic alone. The MS stereo effect can be generated in real time, or in post by mixing the raw outputs.

    Working from a distance keeps the microphone from being "in the face" of the talent, and makes it easy to keep it out of the field of view.

    Ideally you should use matched microphones, positioned as close as possible to each other. In practice, they don't have to be matched, just reasonably phase-accurate, and 1-2 inches is close enough. MS is commonly used in sidecar microphones for video, as well as hand-held interview recorders.
  8. For those not familiar with stereo recording, the usual combinations are XY (crossed) or ORTF (together, pointed outwards 90-105 deg) or spaced (any pattern, 4-8 feet apart). XY microphones have excellent mono compatibility, ORTF has the best stereo imaging, with reasonable mono performance, and spaced mics sound good over speakers, but the stereo imaging is poor and phase relationships are confused.

    Stereo imaging is mostly in the brain, and depends on frequency. Below about 1000 Hz, stereo image is based on phase difference between the ears. Above 3000 Hz, it is almost totally based on intensity, where the head shadows sound from the opposite side of the ear.

    None of these traditional methods have microphones pointed directly at the subject, rather toward the reflecting surfaces that are so problematic in small rooms. That is where MS recording excels.

    There are other microphone strategies. If you ask any two engineers, you will get five answers.
    Last edited: Apr 30, 2020
  9. If you want to take a minimalist approach, I have had very good luck using an iPhone or iPad with a Zoom 1Q6 stereo microphone, which attaches to an Apple Lightning power/data port. The microphone attaches directly to the end of the phone, but since it cannot be turned, you need a Lightning-Lightning female extension cable to video at the same time. A similar attachment is the 1Q7, which is an MS array which can be rotated 90 degrees toward the subject. The 1Q6 is US$99 and the extension cable is about US$10.

    Both mics are directional, and have a much clearer sound than the omni mic built into the iOS device. Similar mics can be used with Android devices. I find that a stereo pickup is superior to a mono microphone, clearer and better suited to a two person interview. I like lapel mics too, but only one can be used at a time with an iOS device

Share This Page