Home Studio Helpline: A Brief Guide to Microphones (Part 1)

Or should this article be called 'The Mysteries of Mics'?

I'm assuming readers will know what a microphone is... but the likely burning questions on your mind will be:

How do they work?

Why are there so many different types?

Why can't one mic do everything?

Why are the best mics so flippin' expensive?

Whew! I can tell you, it's way beyond the scope of this one article and it won't give you all the answers. But this and my next three articles (mic jargon and techniques; miking-up instruments; recording vocals) will give you a good basic understanding to get you started. There's a lot more to this topic than most people realise. Some good advice to people who use mics is to do some thorough homework about the mics you use, it will help.

First up a simplistic explanation of what a mic is and does.

A microphone is a device used to convert varying pressure waves (vibrations mon!) into varying electrical/digital/audio signals we can record, amplify, transmit or otherwise mess with. The amazing thing is that the air transmits those pressure changes so well and so accurately, over relatively long distances. Amazingly with the help of a diaphragm and a few other snazzy bits and pieces along the way a good mic can help reproduce those 'sounds'.

Beyond the obvious, there are a couple of things you should know about microphone design.

It is notoriously difficult to design a device that accurately converts acoustic energy to corresponding electrical voltages. They are designed by human beings who start out with a subjective idea of how they want them to sound and how they want them to operate.

Because of these two factors, very few mics are physically or sonically alike, they each have their own set of strengths, characteristics and quirks. And that's one of the many reasons why one magic mic can't do everything. (But saying that, some make a pretty good attempt).

Now is a good time to drop-in some simple rules about mics.

Rule #1. There are no rules, only guidelines.

Rule #2. My own golden rule is that good source and good placement and good mic equals good sound.

Rule #3. Don't try to 'fix it in the mix'.

Let's talk about some different types of microphones now.

Dynamic Mics.

Common examples are Shure SM58, AKG D112, etc. Generally more robust than some other types, that's why you see dynamics a lot on stage, but reputably not as sensitive as the delicate (read: expensive) studio types that exhibit clean, pin-sharp clarity. They are usually more affordable, often have a 'fatter' sound and can handle more 'stress' than other types.

Condenser Mics.

Some examples are Neumann 87, Rode NTK, AKG C4000, etc. This is where the fun really starts. You can get small, medium and large diaphragm type condensers. And to make it even more interesting, they often have different polar-response switches, pads and filters (bass roll-off etc). Basically a condenser mic is a capacitor, with one plate of the capacitor moving in response to sound waves. These mics usually require a voltage to get them going, ie; phantom power (typically 48 volts DC) or battery power. They are the mainstay of studio recording, and popular because of their ability to 'grab' a detailed flattering sound. They are as unique as you and I. Used well they can produce superb results however the best ones don't come cheap.

Ribbon Mics.

Some examples are RCA 44 and 77 models, Royer R-122, etc. Generally they are very sensitive to shock, large sound volumes and incorrect use, especially older models. Used correctly they can produce a rich warm, yet detailed sound (check some Sinatra LPs), most don't like phantom power and become a big fuse (expensive again) if not designed to operate that way. Some newer ribbon mics such as the new Royer models can accept phantom power and can take a bit of rough use - and sound as gorgeous as the revered classics do.

Electret Mics.

Examples are everywhere, cellphones, walkmans, etc. Electret microphones are a variant of condenser mics that mostly utilise a permanently charged diaphragm. More responsive in the range of mids to higher frequencies. Not good in kick drums.

PZM (Pressure Zone Microphone) Mics.

For example the Crown PZM 30D, Audio Technica ATA49, etc. Sometimes called boundary mics, these unique mics are basically a miniature condenser mic mounted face down next to a sound-reflecting plate/boundary. These were developed especially for on-surface mounting to avoid the tonal colouration of other types of mics when placed close to a surface. They usually exhibit a wide, smooth frequency response, excellent clarity, and little off-axis colouration.

There are other types of mics such as Digital, Carbon Granule, Plaintalk, Focusing, Crystal, Measurement and so on. The most expensive microphones are usually the large diaphragm condensers. They are expensive because of the R&D involved in making them, and the need for high quality parts with fine accurate tolerances so they are often made in far away countries.

A good studio mic is worth its weight in gold, and you can pay plenty of that for a top of the line model. Fifteen grand is not blinked at for the big toys. The good news is you can get some very decent mics for a fraction of that nowadays.

Next article we'll explore what to look for in microphones, common characteristics and techniques.

This is one area of the sound chain where I believe you get what you pay for, and as it's the critical first stage it's important to get it right (especially if you only get one take!).

Microphones are a sensitive (no pun) subjective matter, but hey, so is music and that's what makes the world go round (apart from love that is). Until next time... record ya later.

Brian Hodges runs Creative Digital Audio & Visual in Christchurch. Contact him at 027 417-7024 or creativedigital@paradise.net.nz