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Shoot Expertise: Sound Check

Jan 1, 2007 12:00 PM, By Jan Ozer

Microphone options for better podcasts and voiceovers.

Most videographers know how to choose and use external microphones to maximize the audio quality of their shoots. Although there's some crossover in technologies and equipment, producing narration for voiceovers or screencams is a very different subject. In this article, I'll discuss the various approaches for producing audio for these applications and review several products along the production workflow.

When recording audio with your video, usually you record to either a camcorder or an external device such as a DAT or other recorder. When producing narration, typically it's most efficient to record audio directly to a computer, where you can easily edit and render your audio to the required format. There are multiple workflows for getting there, but before discussing those, let's review the technologies involved to make sure we're all on the same page.

The technologies

Recording audio to a computer involves three separate pieces of equipment: a microphone, a preamp to boost the mic signal to line levels, and a sound board to convert the analog audio to digital for editing on the computer. I'll discuss each category of equipment in turn.

Microphones fall into two categories: dynamic and condenser. At a high level, dynamic microphones are driven by vibration and require no external power. They're typically more rugged than condenser microphones and superior for field use — and they're cheaper. The most significant downside is that they typically don't produce as strong a signal as a condenser microphone, which means more amplification and more noise.

Condenser microphones are driven by internal condensers that require 48V of phantom power, which can be supplied by a battery or preamp. Condenser microphones are more fragile and more expensive than dynamic microphones, but they typically produce higher-quality sound in a controlled environment. Beyond these basics, choosing a microphone is very subjective. For example, our local radio station recently transitioned back to dynamic microphones because condensers were too fragile, and the quality difference was negligible. In contrast, for narration, I prefer condensers because of the additional volume. There is no right or wrong answer here — only preferences.

Another basic characteristic of a microphone is the polar pattern. Omnidirectional microphones, such as those on most camcorders, pick up noise from all directions equally. This can be useful for some stage microphones, such as those shared by multiple singers, but an omnidirectional mic is generally a bad choice for narration. In contrast, a unidirectional microphone rejects most noise from the back and side, with cardioid, supercardioid, and hypercardioid representing increasingly focused patterns. Since most narration occurs in a relatively controlled studio environment, most microphones used for narration have cardioid pickup patterns.

Preamps boost the low-volume input from the microphone (called mic level) to line level, which is the level expected by professional recording devices. The most basic preamp has one input, one output, and a volume dial — although they get much more complicated and expensive. Note that many inexpensive preamps can't supply phantom power, so they won't work with condenser microphones that don't have an alternate power source.

The final component in the traditional analog-to-digital workflow is the sound card that converts the analog signal to digital. Virtually all computers have sound board functions embedded in the motherboard, but you can augment this with a card such as the Creative Labs SoundBlaster X-Fi Elite Pro used in many of our tests.

To summarize, the narration workflow involves three components or processes: the microphone, the preamp, and the analog-to-digital conversion. The microphone captures the audio as accurately as possible, while the preamp boosts the signal from mic level to line level without adding noise. Finally, the sound card converts the analog signal to digital while preserving the original signal quality.

The setup

Our most basic workflow involves all three products in separate forms, with several microphones connected to the SoundBlaster through a Beachtek DXA-10 preamp ($349 MSRP), which has two XLR inputs with phantom power. I tested the Beachtek because its battery operation allows it to serve dual needs, both as a microphone preamp for narration and as a below-the-camera adapter to connect XLR microphones to camcorders with only 1/8in. stereo microphone inputs such as Sony's DCR-VX2000 and HDR-FX1.

The other preamp I tested was a PreSonus Firebox ($499.95), which accepts XLR input, provides phantom power, and converts analog audio to digital internally, sending the digitized audio to the computer via FireWire (hence the name). As a bonus, the unit gets its power from the FireWire connection, eliminating the need for batteries or AC power. Although we tested the Firebox, if you're buying solely for narration, you should consider PreSonus' Inspire 1394, which also has two mic/instrument inputs (XLR or 1/4in.) and phantom power, but lacks the features found on the Firebox — such as MIDI and S/PDIF I/O, which are irrelevant for narration — and is priced more economically at $229.

From here, the products become increasingly integrated. For example, M-Audio's Podcast Factory ($180) combines a USB-based preamp with a dynamic microphone, essentially providing all three functions — microphone/preamp/analog-to-digital conversion — in one SKU, sending digitized audio to the computer over USB. The most integrated product reviewed was Blue Microphones' Snowball for $180, which combines the same three functions into a microphone form factor that connects to your computer via USB. (For more information on the Snowball, see S.D. Katz's review at digitalcontentproducer.com/dcc/blue_snowball.)

The tests

Testing involved three projects. First, I narrated a short segment on all of the microphones, then I acted as sound engineer while a friend (and former DJ and musician) recorded a radio advertisement for my wife's ballet company. Finally, local performer Josh Pickett of No Speed Limit recorded some guitar solos with each of the microphones and gave me his read on their respective performance. He was actually in the market for new guitar microphones for his band, which added a nice bit of synergy.

I recorded the USB microphones on both a MacBook Pro and a Dell Precision 390 workstation, but ran the PreSonus and BeachTek units only on the Dell. Note that I disabled the Dell's onboard sound system in favor of the Creative Labs SoundBlaster X-Fi Elite Pro. I tested the microphones in my office, shutting off all printers, routers, air conditioning, and fluorescent lights — leavingonly the whisper-quiet MacBook Pro and Precision 390 running. We used a pop filter with all microphones, which is a lycra screen that attaches to the microphone stand and screens out pops caused by excessive air blown out with letters such as “p” or “s.” At less than $25 retail, a pop filter is simply the best investment you can make for high-quality narration. Anyway, here's what we found.

USB microphones

To stave off reader hate mail, I choose the products tested as high-quality and credible representatives in their respective classes. I'm not saying these are the best in their class (although results were very impressive), but that they demonstrate performance within the class for comparative purposes. In other words, while you might find a better USB microphone than the Snowball or Podcast Factory, it's highly unlikely that any USB microphone would produce the clarity, warmth, and dynamic range of a separate condenser and preamp system, and so on up the chain. While there are exceptions, you generally get what you pay for in the audio market.

Our most integrated unit, the Snowball, costs about $189 retail and contains two condenser heads, one cardioid, and one omni, so you can podcast and host a campfire sing-along, a versatility unique in this review. The unit is striking in appearance and comes with a useful stand and USB cable, so is very self-contained, which is nice for crowded offices and teens. The only downside was that the sound lacked the dynamic range of the high-end mics, sounding a touch tinny in comparison.

The Podcast Factory produced the highest levels in the group, and as rock bands have known forever, sometimes loud is good. The unit also has an additional input for a guitar or another instrument, and stereo output, which the Snowball lacks. Although it was louder than the Snowball, the sound shared the same lack of dynamic range, and at higher levels, a noticeable clicking noise worked its way into the audio. Also, “s” sounds got a bit muddy in our ballet advertisement (e.g., instead of a “timeless” ballet, a “timelesh” ballet).

High-end condenser microphones

The first high-end condenser microphone tested was the Shure SM89 (about $1,100 retail), a shotgun microphone normally deployed atop a camcorder or on a fish pole. This idea came from the audiobook production world, which often uses shotgun microphones to ease the narration ergonomics. For example, with most other microphones, you have to be 6in. to 8in. from the mic and pop filter, making it tough to read a script, much less create a screencam or page down in Word. In comparison, with the shotgun, you can be about 18in. to 24in. away, allowing you to essentially ignore the microphone.

Working with the SM89 was a dream — a much better experience than working with the other microphones. Audio quality was very good, with good dynamic range and accuracy. It was somewhat lacking in warmth when compared to the KSM27 and Blue Microphones' Mouse. I also noticed a very faint hum, which sounded like echoes from the hard walls in my office. In an acoustically tiled sound booth, this approach might be ideal. In an office setting, it was just one notch short of the top. Overall, I probably wouldn't buy a shotgun for narration work. If I already owned one, I would definitely give it a try before buying a different microphone.

This leaves our two high-end microphones: the Shure KSM27 ($575) and Blue Microphones' Mouse ($1,699). Both are visual works of art — especially the Mouse, which comes in a silk-lined Rosewood case — and both come with their own custom shock mount. Overall, the KSM27 offered the best mix of quality and price performance. Audio quality for narration work was almost indistinguishable from the Mouse. Both produced a rich, warm, and extremely clear and accurate sound that made me recall that old Memorex commercial (“Is it Live, or Memorex?”). Both were totally noise-free during quiet periods, and both produced very good levels.

My guitarist friend, Josh, spent the most time playing and listening to these microphones. In blind trials, he consistently picked out the Blue as producing a slightly superior sound. Specifically, he noted that the Mouse picked up great highs and mid-tones, but was somewhat lacking in the low tones, which made it ideal for acoustic guitar and other instruments, but slightly less so for vocals. The KSM27 was very good at the lows and mid-tones, but somewhat less so at the highs. If he were handed both microphones on a platter, Josh would pick the Blue every time, but factoring in price, the KSM would win out.

The preamps

Both the Beachtek and PreSonus units produced very good quality in our tests. Let your purchase decision be driven by your intended use. If you need XLR connectors for a prosumer camcorder such as the FX1, and want a unit to perform double duty as a narration preamp, the Beachtek DXA-10 is ideal. Otherwise, if camcorder connectivity isn't a requirement, the Firebox (or Inspire 1394) is a lovely bit of integration that eliminates the need for a high-end sound card for analog-to-digital conversion.

Show me the money

So, where do I recommend you spend the money? USB microphones such as the Snowball and Podcast Factory are highly functional and produce very good, but not great, quality audio. If I were producing free podcasts for fun, or audio for internal training materials and similar projects, these would be ideal.

On the other hand, if you're selling your work — either as screencam tutorials or as voiceovers for other videos — or if you need to make a great impression with your audio podcasts, invest in a higher-end system. You can find the KSM27 for around $300 at www.musiciansfriend.com, and if you already have a below-the-camera preamp such as the Beachtek, you're good to go. Or, for an additional $200, you can buy the PreSonus Inspire 1394. That's, at most, $350 more than you'd spend on the Snowball or Podcast Factory, and the results will be noticeably superior.

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Jan Ozer is a writer, consultant, and video producer who lives in Galax, Va.

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© 2008 Penton Media, Inc.