Saturday, March 09, 2013

Microphones For Portable Recorders 3: How To Choose?

Capsule

This is the third in a series of articles on choosing external microphones for portable digital recorders. Part one discussed why we might want to improve on the mics that come with our recording devices and part two was an overview of microphones themselves plus power and cabling requirements.

If you have been reading with your own needs in mind, it should be becoming clear which mics you should be looking for. Otherwise, now is the time to fix your objectives in mind. Are you recording lectures or community meetings? Are you gathering dialogue for a video? Are you conducting interviews in the street? Are you recording live concerts or your own band in rehearsal? Are you making nature or soundscape recordings?

These are some of the common tasks people ask me about. So, let me take them one at a time, and discuss what microphones might be best. I'll recommend microphone types (dynamic, condenser, electret, boundary), polar patterns (omni, cardioid, shotgun), and discuss power requirements. I'll even recommend some specific tried-and-true microphone models.

Context and Disclaimers
One big disclaimer. There are hundreds of brands and thousands of makes of microphones on the market. I have used only a fraction of these, and have worked extensively with even fewer. (My goal is recording, not microphone reviewing.) Besides, everyone has their favourites. Though I will mention specific models, there will be other choices that will work just as well for the given application. Despite this, I see no harm in making recommendations based on consensus among recordists, based on my extensive and ongoing readings. Take no offence if I do not mention your specific tools, since this article is only meant as a gentle introduction!

That said, if you have found some great solution you'd like to share, please contribute in the comments.

Another thing to keep in mind is that I am primarily concerned with field recording. To my mind, that's why we use a small portable recorder. If we have the luxury of a studio space or a concert hall, we also generally have access to bulkier and more expensive gear. I will by and large ignore studio equipment in this primer; I won't be recommending ribbon mics, large-diameter condensers, and so on. It's not to say that you absolutely cannot use such equipment in the field, but generally there are more practical choices.

Finally: price. This comes up a lot. You can buy a high quality portable recorder for 200 bucks1, something that blows the lid off anything we could have hoped to record with back when I first started (around 1980). Some people are understandably shocked when recommended microphones that cost 500 or 1000... or more. But good microphones cost money. And in this domain, like many others in audio, small increments in sound quality will cost disproportionately more money to achieve. That extra 5% improvement you are looking for might double the cost. So it helps to be realistic about what quality you need to achieve. And to set a budget that is sufficient to the task.

Like everyone else, I enjoy finding gear that performs better than it should for the price. I don't own any of the truly expensive microphones that top-flight professionals would have in their kit bag. So I have great sympathy for those trying to stretch a modest budget. But sometimes you simply do need to save up for the equipment that is necessary. Or, re-align your priorities.

I will be providing indicative pricing in USA dollars (because that is easiest). Here in Europe things might be rather different.

Of course, if you know a little electronics and are willing to learn more, you can sometimes create your own solutions at a fraction of the price of what is on the market. My own electronic skills are minimal, limited to soldering cables and making contact mics. So instead I will point you to the microphone builders group.

OK, with all of that in mind, let's have a look at each recording task.

Lectures or community meetings
In this situation you might well be seated far away from your source but you can't use any fancy setup that will get in the way of others in the audience. Thus you need to get the mic close -- in the middle of the table, on the podium, or whatever position is nearest to the speaker(s). If you've tried recorded a lecture from the other side of a classroom, or a political meeting from the back of a hall, you realise soon enough that reverberation and crowd noise easily drowns out the speaker. This might be good enough for transcription, but won't be good enough to share playback (for broadcast or other purpose).

The recorder's built-in mics are likely sufficient for this application. You are not concerned with ultimate sound quality; you simply want to document. So, get the appropriate permission ahead of time, set your recorder close to your teacher, the event speaker, or whomever, and press record. Pick it up again after the event. (Er, don't forget. And keep an eye on it in case it goes walkies.)

You likely only need to record in mono. This can save storage space and battery power.

If you do need improved sound quality, a boundary microphone (as discussed in the previous article) can work very well. These are common fixtures in board rooms, churches, and so on. Crown and Shure are the most common makes.

A completely different approach, one that might require more cooperation from the speaker, is to use a lavalier. Read on...

Sennheiser ME66 + K6

Dialogue for video
Entire books have been written about recording sound for video and film work, and there are also dedicated websites like DV Info. My own gloss will cover two methods.

The first method uses a shotgun microphone on a boom, a telescoping pole which enables you to hold the mic over a crowd, avoiding other equipment (for example, the camera and lighting). This method allows an experienced operator to exclude undesirable sounds from off-axis. If you recall from the polar pattern in the last article, a shotgun pattern has a considerable rear lobe (and smaller side lobes), so one must point the microphone directly at the source while avoiding distracting sounds from the other axes. Generally this is accomplished by angling the mic down from above.

The Sennheiser ME66, paired with the K6 power module, is a good mid-price short shotgun (pictured above). The combination is $460. Even cheaper, at $270, is the Rode NTG2. The fact these models run off their own batteries is a bonus, as they do not require any sort of power from the recorder (so even the least expensive devices will do). Be aware, however, that the price of a good shotgun is only a small part of the overall rig, which typically includes the boom, a grip, a blimp to prevent wind noise, plus the necessary cables and interconnects.

Professionals might well be using the Sanken CS-1E ($850), Sennheiser MKH 416 ($1000), Sanken CS-3E ($1450), Sennheiser MKH 70 ($1750), or Schoeps CMC641 ($1920). And these are only mono. Don't say I didn't warn you about prices!

Carrying a boom rig mandates a strong physical presence that may not be suitable for all recordings. The second method involves putting a lavalier mic directly on the subject, either in plain sight, hidden under clothing, hung around the neck, etc. These small condenser microphones are often available in different colours (white, black, flesh) to aid in camouflaging their presence. A good lavalier will resist noise from clothing, the wire itself, and other sources. They are omni or cardioid in pattern.

If the subject needs to be mobile, it is common to run a lavalier to a transmitter pack on their belt. This links up to a receiver at the recorder, so you don't need direct cabling. This solution might require a significant investment and is mono by definition (though multiple channels are often used if there are multiple subjects).

Professionals might use lavs by Audio-Technica, Countryman, Sony, Tram, and several other firms, with prices usually around the $400-600 mark. If you want a cheaper solution the Shure WL183 is $185. But don't forget you still need all the other accessories to form a complete solution.

Each brand seems to have come up with their own proprietary cabling and power systems, so all the standard info I have previously discussed can be thrown out the window! It's an art in itself matching microphone capsules, cabling, interfaces, transmitters, and power sources. (Of course you can simply buy a full kit from one manufacturer.)


Interviews and ENG

ENG (Electronic News Gathering) is one of the more popular applications for portable recorders. Journalists require a microphone that is able to stand up to the rigours of the street, withstand inclement weather, reject plosives and popping, and avoid handling noise. Low self-noise is not a priority since the environment is generally quite loud and the mic will be right up in the subject's face. You also don't want to be messing around with different power systems and, for versatility, would be best off avoiding this requirement entirely. For all of these reasons dynamic microphones fit the bill.

Favoured omnidirectional dynamic microphones include the Electrovoice RE50/B ($180), Sennheiser MD-42 ($200), and Beyerdynamic M58 ($260). The only thing you need to watch out for is that dynamic mics have low sensitivity and thus need a lot more gain to get to a decent signal strength. Unfortunately smaller recorders are often shy on gain, so try to get the "hottest" possible mic. (Of those listed, this would be the Sennheiser MD-42.)

The Sennheiser MD-46 ($200) is a cardioid version of the MD-42. This pick-up pattern will require slightly more care in use, but will capture less of the environmental sound; this might be beneficial depending on your usage. Consider how much control you will have over the interview situation, and if it is indeed desirable to get some environmental sounds for context. You might very well want an omni and a cardioid, so you have the flexibility to use the right tool for the situation.

You can find more advice at Transom, a site focused on the radio community. However I find that their recommendations can be a bit wrong-headed. (For example, they don't seem to recognise the worth of the Olympus recorder line, which I consider to be best-of-breed.)

Music concerts

Gigs are loud, so the number one concern is not overloading your pre-amps or mic capsules. You need a mic with the ability to handle high sound pressure level (SPL) without producing disgusting distortion. Even though acts might well permit concert taping, it often pays to be discreet. Small mics that can be hidden under a hat, on glasses, or disguised as headphones are often just the ticket. Concert tapers often use a stereo pair of electret condensers, also (incorrectly) called binaurals2.

While there is no technical difference between these mics and the lavaliers discussed above, the application is quite different. A mono lav with proprietary power system and transmitter is quite a different setup from a stereo electret pair working off standard PIP. So too the demands are not identical. An interview lav should reproduce the human voice, accurately capturing resonances and inflections. If it rolls off the lower frequencies, so much the better, since these will only be unwanted noises. But if you are recording a rock gig, the last thing you want to do is roll off the bass!

pair of condensers for binaural recording
Pictured above are a pair of electrets, clipped on a baseball cap. This can be worn with the recorder in a pocket, safely out of the way. It won't bring much attention or get in the way of the enjoyment of other punters. This same setup is useful for candid street recordings. Once again, this application is technically quite demanding. Though you can get away with an all-purpose set of mics, recordists with a larger budget might have one set of low sensitivity mics for concerts, plus one set of high sensitivity, for quieter locations.

Discussing which electrets to buy is complicated enough to reserve for another article. You can buy a pair of capsules for $4 and solder up a set yourself that will work with PIP. Or you can purchase a pair of DPA 4060 for $1000 and run them off phantom power. The good folk at Tapers' Section can help you spend your money.

Nature or soundscape recordings

This is a huge subject area as it incorporates divergent recording objectives, which I will discuss separately. What they have in common is a desire for the lowest possible background noise. We need microphones with a low self-noise specification and high efficiency. Furthermore we must pair these with a good pre-amp and use the very best recording techniques. Rarely will the built-in mics be sufficient for this task.

Nature recordists often want to isolate a particular sound (a bird call, for example) from the environment, making it as loud and clear as possible. This means a) getting the microphone very close to the animal, b) using a shotgun microphone, or c) using a parabolic reflector to focus sound from a distance. In the first case almost any mic will do, though you might prefer a dynamic for their robust build. The trick then is in the positioning and having the patience to wait. Shotgun microphones have already been discussed. And I have to say that parabolic reflectors are specialised enough that simply mentioning them is enough for this primer.

Soundscape recordists, on the other hand, usually wish to replicate the entire sonic environment, rather than focus on one specific sound. Since omni-directional microphones are the quietest, the most resistant to wind noise, and colour the sound the least, they are the ideal choice. Various creative techniques involving "dummy heads", Jecklin disks, or boundary layers can be used to further enhance the recording, sculpting it to conform to how we hear. While that's outside the current scope, you might wish to check out the Nature Recordists group for specific recommendations on these techniques.

Unfortunately, answering the question of "which microphone?" becomes as complicated here as in the previous section. So I will not mention specific brands.

Conclusion

I do trust that this series of articles is at least enough to orientate you in the wild and woolly world of microphones. Armed with a basic understanding of microphone terminology, a strong idea of your objectives, knowledge of the abilities and limitations of your recorder, and a budget, you should be able to make headway in the confusing profusion of information out there on the web. I have deliberately kept this as non-technical as possible, though I have dropped in terms like SPL and sensitivity. It would definitely help you to get a more precise idea of what these mean, something easily accomplished through Wikipedia.

In my attempts to be thorough this has turned into a writing marathon. If you appreciate the information I have assembled, please buy me a coffee using the PayPal donation box in the sidebar of this blog. Thank you!

Footnotes

1 A "buck" is a standard monetary measure approximately equal to one American Dollar, British Pound Sterling or Euro. Because generally, more or less, most of the time, give or take 20%, one unit of measure in either of these buys the same audio gear.

2 The term "binaural" actually defines the recording and reproduction methods, not the microphones themselves.

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2 comments:

rudy trubitt said...

Good overview! I would add that for nature soundscape recording, the self-noise of the mic (which you do allude to in your text) is extremely important. The Sennheiser MHK series has very low self-noise and is also very resistant to humidity, also a plus for field work.
cheers,
rudy

robin said...

Thanks for your comments. Given the introductory nature of this article series, mics like the Sennheiser MKH series are likely too expensive for the target reader. Nonetheless I did mention the model 70 above and the entire line is of course excellent. I would own them if I could afford them.

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