Microphones are obviously needed to record your podcast - and just like everything else this is or can be a complex area. The more you get into it, the more you realise you don't know. The good news is you don't need to be an audio engineer to make a podcast, but it's worthwhile knowing some basic information so you can make the right choice of mic. 

The right mic will help your podcast be the best it can be for both your audience and any sponsors that you might have. Fortunately you don’t need to spend thousands of pounds on equipment to get listenable quality but it will help to have an appreciation of some of the theory.

The two main items of equipment you’ll need for audio podcasts are some form of microphone and some form of recording device to which the microphones are connected.

Many, if not all laptops come equipped with a microphone these days for use with applications such as Skype but unless you have a particularly good laptop these mics will be cheap and nasty affairs and in any event will limit the content of your podcast.

So not only is the quality of the mic important but so are the acoustic properties of the mic as well. There are different types of acoustic “pick up” and you need to have an appreciation of these designs so that you can position the microphones in your recording environment for the best possible audio capture.

The basic types of mic acoustic characteristics are illustrated in this diag.

Omnidirectional, as the name implies, has no selective sensitivity, it will capture sound equally from all directions. The mic used in your smartphone is an omnidirectional one. At the other extreme are “shotgun” mics that are far less sensitive to audio from either side or behind, and much more sensitive to sound from in front. They are very “directional” and are ideal for capturing the sound of a bird singing for example.

The best mics to use for your podcasts are “cardioid” mics. These are somewhat less sensitive to sounds from behind the mic than they are to sounds forwards of the mic; in other words sounds coming from behind the mic will be suppressed by about 25dB, technically known as the “rear projection”.

Now you have to give some thought to the nature of your podcast content as this will determine the physical design of cardioid mic that you will end up buying. For example if your podcasts are entirely studio-based there is no need to use a wireless “tie” mic, a static studio mic will be perfect. On the other hand if you wanted to capture the audio of a speaker at a conference, then a wireless tie mic would be ideal.

If your podcast is a single presenter narrating a documentary, linking all the supporting material and media, then at a pinch you could use the inbuilt mic of your smartphone, but it’s not really designed for this type of audio work so the result won’t be great. The next stage up might be to use the external mic supplied with your cellphone - the one you use to make telephone calls with.

These two options have the merit of being free :)

Better still would be a specialist “USB mic”, which connects to your laptop by the USB port (adaptors may be necessary). These range in price from relatively cheap such as the Samson Q2U, to quite expensive such as the Blue Yeti. Buy the best you can afford - it's your show and you want it to be good, right?

USB mics connect directly to the laptop you’re using to record your podcast using software such as Garageband (Mac only) or Audacity (Mac and PC).

For many of the podcasts I produce which are more interview-based, I use at least one pair of small “tie” mics (AKG C 417 PP Lavalier microphones) that are wired directly to the recording device, whether that’s a digital audio recorder or a broadcast quality video camera. The advantage of this approach is that there is a good “signal to noise” ratio between the speakers’ voices (i.e. the mic is close to the sound source, the human voice) and the surrounding sounds (a noisy café perhaps) without the risk of “audio drop out” which you sometimes get with wireless mics. 

Both my guest(s) and I wear one each and with my set up I can accommodate 3 guests, so I have 4 mics. The benefit of this approach is that each person in the podcast is treated fairly and equally by the mics and recording kit. With just one central USB mic, it would be hard to balance things so everyone sounds recorded at the same level. It's tricky to use more than one USB mic at a time, and probably not worth the hassle of trying.

These tie mics and associated recording kit also mean I'm fully portable and can record anywhere - an important consideration if asking guests to appear in your show. The first podcast I recorded for the SafeToNet Foundation was recorded in my guest's office in Cambridge, the second was recorded at the SafeToNet Foundation's HQ in Southwark.

The drawback of wired mics is that there are a pair of wires trailing along the floor which may not be acceptable in some situations. For example I used to make some video podcasts about cooking, featuring chefs working in their live restaurant kitchens, it would clearly be a risk to have trailing wires so I used these wireless mics from Sennheiser with the “receiving station” mounted on the camera.

Whilst not cheap, these provide excellent sound. The wireless tie mic is connected to a transmitter (a body pack) which transmits the audio to a receiving station which in turn connects to the recoding device by an “XLR” port. What's an XLR port?

XLR is an audio industry standard port, or plug and socket, in the same way that USB or Ethernet ports are standard on laptops. If you have an XLR mic, unlike a USB mic, it won’t plug directly into a laptop, so what do you plug it into?

I’ll cover that off in the next blog entry.

As usual, any questions, pop them in the comments section :)