A few well-planned and well-researched hardware purchases can really make a difference in your podcast's sound.
To this point in the “Attack of the Pod Penguins” series, we’ve covered much in the way of software and licensing. Those are the things you think of first when considering all the pieces of your open source podcast. They’re important pieces, to be sure, but they may not be quite enough to deliver your podcast with the top-notch sound quality you’re looking for.
Take a closer look at the hardware in our slideshow
Whether your podcast is primarily spoken word or focused more on music, it’s likely that, at some point, you’ll realize that the sound quality is just not what you were hoping for.
That’s especially true if you’re regularly listening to other podcasts. Many of the most popular podcasts are recorded and produced by radio pros, using great hardware as well as software. There’s a lot to be said for the convenience of this hardware/software approach, and the resulting sound quality can be very, very high. If you get beyond the point of “podfade” (the point in the life of a podcast, usually about 10 editions in, at which the podcaster realizes how much work a regular podcast can be, and just fades away), it’s likely that you’ll start looking to improve the overall sound quality of your podcast.
A few well-planned and well-researched hardware purchases can really make a difference. So, in this installment of “Attack of the Pod Penguins,” we’ll diverge a bit from licensing and software to look at hardware. These items are no less critical to the quality of your podcast than choosing the right software.
Microphones
It almost goes without saying that your choice of microphone is very important to the quality of your podcast. It’s the hardware bridge between your voice and your recording. In the past few years, the quality of microphones has continued to increase as prices have come down. It’s possible today to purchase a mic for less than $200 that captures sound more accurately than mics costing upwards of $1,000 just a few years ago.
When considering your microphone purchase, two items are of primary importance:: interface and recording pattern. Mics are generally available in one of three interface types: USB, unbalanced and balanced. USB mics offer some real convenience in that they’ll interface directly to your computer system. That’s an important convenience if you’ve chosen not to add any additional interface between the the mic and the computer – you’re recording directly from the mic to the hard drive.
USB mics draw any necessary power from the computer. However, they do trade off some sound quality for convenience. As USB is a subsystem in the architecture of a computer, they’re much more susceptible to the vagaries of CPU load on your system than the other interface types. In other words, the ability to connect directly to the USB subsystem on your computer may be an advantage that’s outweighed by a slight loss of sound quality and by greater sensitivity to what other software you’re running. USB mics are generally at the lower end of the price range.
Unbalanced mics interface with a single connection to computer systems or to other devices external to the computer. You’ll recognize an unbalanced mic by its 1/4-inch or 1/8-inch connector. These mics can also be connected directly to your computer. If the connector is of the 1/4-inch size, you’ll generally need to purchase an adapter to step it down to 1/8-inch.
In general, unbalanced mics have a higher resistance value. Wikipedia defines resistance as the ” … measure of the degree to which an object opposes the passage of an electric current.” Put a bit more simply, the higher the resistance, the tougher it is to pass an electrical current along a line.
In the end, that’s what every mic does – convert a sound wave to an electrical signal and deliver that signal along a line to another device. The higher resistance offered by most unbalance mics means that you may have to spend a bit more time “punching up” the sound of the vocals in your podcast.
With the increasing popularity of USB mics at the low end of the price range, unbalanced mic prices have stayed fairly stable over the past few years. They’re holding pretty firmly in the middle of the price range. Most professional audio recording uses balanced mics. These mics offer low electrical resistance and very high resolution sound reproduction.
The most common interface for a balanced mic is the XLR connection, a large round connector containing three discrete lines. Because unbalanced mics offer lower electrical resistance, the signal can be carried across much longer distances than either unbalanced or USB. Balanced mics also most often require external power, generally 48 volts DC, often referred to as phantom power. The current from the phantom bus is delivered to the mic by the XLR cable itself.
“Phantom,” in fact, refers to the absence of a visible power source to the mic, and that the power is not apparent in the audio signal. If you’re looking to capture the highest possible sound quality, a balanced mic is the place to start. (What’s described is actually a combination of the most common balanced mic configuration elements. The power requirement shouldn’t be confused with the balanced nature of the mic itself. The power requirement arises in condenser mics, which are most often balanced mics. In reality, balancing a mic line has nothing to do with phantom power, though a combination of the two is easily the most common configuration for balanced mics.)
Mics are available in several common recording patterns. The cardioid pattern, or some variation, offers the most flexibility for voice recording. A cardioid recording pattern, as its name implies, is approximately heart-shaped, with the top of the heart at the back of the mic when viewed from above. Cardioid mics capture most audio from the front and sides, while ignoring much of the audio from behind – the top of the heart pattern.
The cleanest sound capture with a cardioid-pattern mic occurs directly in front, with sound scaling away as the source moves around the mic. There’s one other quick note regarding mics that has little to do with the interface or the recording pattern. The highest resolution mics are condenser mics (as mentioned above). Condenser mics contain an electrically-charged diaphragm and a conductive back plate. These two pieces are separated by a thin layer of air. The vibration of the diaphragm changes the voltage between the diaphragm and the conductive plate, a change that is further amplified by a circuit built into the mic.
A good rule of thumb for condenser mics is “the bigger the diaphragm, the better the resolution,” though diaphragm sizes larger than 2 inches really become pretty impractical. So, if you’re looking for convenience, a USB mic will serve the purpose well. If you’re looking for higher sound quality, both unbalanced and balanced mics will deliver much higher resolution. For the best possible sound quality, it’s best to spend the extra bucks for a powered cardioid-pattern condenser mic.
Processing units
As noted in an earlier installment of the “Attack of the Pod Penguins” series, digital recording can, in many cases, create a somewhat “sterile” sound. The conversion from an analog sound wave to a series of bits just loses something in the translation that’s difficult to describe.
You can, however, sweeten the source sound quite a bit using a tube-based mic preamp. Yes, that’s “tube” as in vacuum tube – the precursor to today’s modern digital circuitry. Sometimes you really have to step back in time in order to step forward. Tubes have the effect of “warming” sound; exciting the lows and midrange while knocking off some of the sharp edges of the upper frequencies. They tend to add presence that feels more real than simple straight to digital recording.
This is all done prior to the amplification stage in your sound chain – thus, the name “preamp.” These preamps also offer phantom power for use with condenser mics. This fact alone will tell you that the preamp will be the first stop in your podcast audio chain. Some tube preamps also offer a combination of solid state and tube circuitry. As pure tube preamps are expensive to manufacture (and maintain), this combination allows for somewhat lower prices.
In all configurations, increasing the gain levels serves to “open” the tubes, increasing the amount of output from the tubes. Many of the tube mic preamps on the market also offer additional features, such as equalization. If you’re looking to warm the sound of your podcast voices, to make them feel more natural, a tube mic preamp will be essential.
Of course, you can choose to run directly from a preamp into a mixer or your computer, but you may find that some additional sound tweaking is necessary to achieve the sound you’re looking for. Background noise, for example, can be a real problem in home recording. It’s tough and expensive to completely soundproof a room specifically for the purposes of podcast recording.
You may also find that the fans on your computer are louder than you realize. Or, perhaps a wall clock ticks just loudly enough to be captured by a sensitive condenser mic. Or that ambient sounds tend to leak through a window in the room, even when closed. They’re all sounds that buzz right past your consciousness unnoticed from one day to the next, but that become a distraction when captured in a podcast.
A useful piece of hardware to acquire for these situations is a noise gate. Using hardware, it’s possible to set a noise threshold, normally in decibels, below which all sound is ignored. In many cases, that will kill the fan noise or the ticking clock or the neighborhood kids outside the window when no other sound above the threshold is present. You may still hear those sounds faintly in the background when speaking, for example, but they’ll be completely ignored when no other sound source is present.
Noise gates can also be a bit finicky. If the threshold is set too high, you may clip the beginning of words as the gate waits for higher levels to release from silence. The same will be true of the end of words or phrases, as well. It’s always a matter of trial and error to find the correct levels for your noise gate. But, in most cases, the result is well worth the effort – a relatively noise-free podcast.
In addition to gating, you may also want to use hardware for compression. Compression is an important element of all podcasts, but it’s especially critical when using a variety of source audio material. The sourced material will, most likely, vary widely in gain levels. Compression is a great way to bring out the lower volume elements by knocking down – compressing – the higher volume pieces.
As you’ve seen, this can be accomplished in Audacity quite nicely. However, hardware has an advantage in that it’s real time. You can save a great deal of time in post-production by performing the compression tasks on the fly. If time is of the essence and you’re utilizing a variety of sound sources in your podcast, you’ll definitely want to consider the purchase of a compressor unit.
Hand-in-hand with compression is expansion. This is a process of taking that compressed sound material and bringing it all, as a whole, to a nominal level, usually -3 Db or 0 Db. In fact, expansion is so tightly tied to compression that most compression units also contain expansion features. So, with a single unit, you can completely optimize the sound levels of all your diverse source files, on the fly. That’s a considerable savings in time and effort over manually working these processes in software.
It’s also useful to use hardware for limiting. There’s no real mystery in limiting. It’s a process of reacting to sound that falls beyond the upper limit of a defined range, and preventing that sound from clipping. While there are several methods of knocking down those peaks, the purpose is the same: to prevent such unanticipated sounds as hand-claps and coughs, for example, from blowing out your listeners’ ears.
Like most other hardware, audio hardware tends to handle all these tasks best – gating, compression, expansion and limiting – when it has no other tasks to perform. That is, the Cadillac audio recording setup utilizes individual units for these elements of audio processing.
But, you’ll find that purchasing these individual items can be quite a bite on the wallet. They don’t come cheap. For that reason, the market has recently embraced several all-in-one units, companders, that combine gate/compression/expansion/limiting into a single box. In a typical podcast audio chain, such a unit would live after a mixer, with its output sent directly to the computer.
Aside from the mic, the mixer is, perhaps, the most important piece of your podcast audio chain. It’s where you capture all your input, set levels, adjust panning as necessary for imaging and, in some cases, perform some rudimentary equalization. And, along with mics, mixers are the audio recording gear that has seen the most significant price reductions in the past few years. It’s now possible to purchase mixers with as many as ten discrete input channels for less than $75.
That’s more inputs than most podcasters will ever require. Many mixers also offer phantom power to balanced line inputs, should you choose to forego a mic preamp. In order to draw the podcast hardware picture more into focus, let me pass along the layout of my audio chain.
This is how I use hardware and software for production of The Roadhouse, IndieFeed Blues, The ClarkCast, and the other podcasts for which I’m involved in production. Mic -> tube preamp -> mixer input Various audio sources (post-preamp mics, computer, Sirius receiver, iPod) -> mixer inputs Mixer output -> compander input Compander output -> computer line in With this setup, all the audio tweaking has been accomplished by the time Audacity receives the signal from the line input. All that’s left is just to capture and save what’s coming in.
It’s true that hardware discussions might not be quite as sexy in a series of open source podcasting articles as talk of licensing and software. However, the value of some additional hardware to your podcast setup can be huge, both in overall sound quality and time-savings.
In some cases – tube processing, for example – it’s nearly impossible to accurately reproduce the effect and sound of hardware in software alone. If you’ve got a few extra bucks to spare, or plan on settling in for the long haul with your podcast, a moderate investment in this additional hardware will pay huge dividends over time.
We’ll return next month to the sexier issues in open source podcasting, or any podcasting, for that matter. As nearly every podcast will utilize music in one form or another (as a feature of the podcast or a transition between segments, for example), I’ll pass along my own experience in securing permissions to use music in the podcast medium. I’ll attempt to unravel the process of securing permissions, where necessary, and put to rest some of the commonly-held beliefs about music licensing. It’s a discussion that strikes close to the heart of any open source-based podcaster. See you then.
Whether your podcast is primarily spoken word or focused more on music, it’s likely that, at some point, you’ll realize that the sound quality is just not what you were hoping for.
