For most engineers and sound companies, microphones represent a substantial investment, and they are a crucial set of tools for getting the job done. Yet they get abused, left out in the rain, dropped, carelessly tossed into cases, stored under poor conditions and largely ignored until something malfunctions. There aren’t a lot of things you can do once a microphone capsule gives up, but there is plenty you can do to prevent damage and ensure it performs up to spec over the long haul.
The Scope of the Problem
Let’s start with the obvious: keep the grills clean. Microphone grills and windscreens pick up all sorts of foul particles such as food (yuck!), lipstick, lip balm, saliva, cigarette smoke and nicotine deposits (albeit less of a problem these days). It should be obvious that a clogged grill will change the frequency response of the mic. What’s not so obvious is that when dust or dirt blocks the ports or vents on directional mics, the microphone’s directionality can be compromised, increasing the possibility of feedback.
Periodically, grills should be removed and washed with mild soap and warm water. If the windscreen inside the grill can be removed, do so and soak it until it is clean, or replace it. An old toothbrush can work wonders on a metal grill, and you might be surprised to find that the frequency response of your mic “comes back” after you’re done. The foam windscreen liners on any mic will decompose over time, becoming crumbly and powdery. Even if the grill looks clean, remove it and examine the foam shield underneath to ensure it hasn’t disintegrated. Check that the grill has dried thoroughly before you put it back on the mic. When you’re providing PA for multiple acts that are sharing microphones, wipe the grill of each vocal mic with an alcohol prep pad or a clean cloth doused with mouthwash.
Round grills that have been banged around and are no longer in shape should be repaired or replaced. Sometimes you can restore the shape of a dented grill by removing it and using either your fingers or the back end of a fat drumstick to gently push out the dents. These dents don’t really affect the sound, so why bother? It’s an image thing. If people perceive that your gear is junk, then they’ll treat it as such. If the grill is smashed up badly, get a replacement.
If the grill cannot be removed, you can still get some of the crud out of it. Start with a clean, dry paintbrush and then use a damp (not wet) toothbrush to remove some of the offending debris. I’ve heard stories of people who will turn a microphone upside down and use a wet brush to clean a non-removable grill, then keep the mic upside down until the grill has dried, but this sounds risky to me. Microphones don’t really like water, especially condenser models. Any moisture collecting between the backplate and the diaphragm of a condenser mic capsule can cause electrical shorting, causing more Snap, Crackle and Pop than a bowl of Rice Krispies. And even if you take pristine care of your mics, be aware that this same condition can occur when performing in humid conditions.
In the unfortunate event that your gear is exposed to rain, do not store the mics until they have dried out in a warm, dry room for a day or two. Speaking of storage and transport, the ideal arrangement is a case where each mic lives in an isolated compartment. If you’re a fanatic with your mics like I am, place the mic in a plastic bag with a packet of silica gel to absorb moisture (don’t forget that silica gel packs have a finite ability to absorb moisture and need to be “recharged” — typically by placing them in a slightly warm oven for a few hours). Road case foam is notorious for adhering to just about anything once it gets damp, and the plastic bag will prevent this from happening.
Prevention is Everything
Much of any microphone maintenance regimen is preventative, so let’s look at a common problem that can be easily avoided. Just about every handheld mic (and many non-handhelds) has an XLR male connector at the bottom. Examine the pins of this connector. They should be straight. There should not be any oxidation on the pins. Not only does oxidation contribute to loss of signal, it can hinder the transfer of phantom power on condenser microphones. There’s usually a screw set into the body of the mic, holding the XLR connector in place (see Fig. 1). Make sure that this screw is tight (many manufacturers use a reverse thread). Once it works loose, it’s only a matter of time before someone yanks on the mic cable attached to it, pulling the connector out of the body of the mic and breaking the very fine wires that attach the connector to the output circuitry of the mic (see Fig. 2). If you find that a mic suddenly fails, check these wires — it could be an easy fix.
Certain condenser microphones provide the option of operating via battery as well as phantom power. When was the last time you checked the battery? You may not care if that battery actually works or not, but you certainly don’t want it leaking chemicals into the mic body where they can eat away at circuitry. The same can also apply to some direct boxes.
General Hints for Mic Health
Test a mic by scratching the grill with your fingernail, not blowing into it or tapping the grill. Blowing into a mic can permanently damage the diaphragm, especially if it is a ribbon.
Choose a mic appropriate for the job. If a mic is not designed to handle high SPLs, don’t place it in front of a raging Mesa Boogie or a kick drum.
If the sound quality of a condenser mic has deteriorated over time, it may be possible to have the diaphragm cleaned. Don’t try this at home; check with the manufacturer and send it back for service if necessary.
Avoid leaving microphones on the floor where they can be stepped on, kicked (duh) and where they will probably be picking up a multitude of dust particles. This is particularly critical with condenser mics where the electrical charge between the diaphragm and backplate attracts dust particles. Eventually, that dust will adhere to the diaphragm. If mics are left set up on stands overnight for long run shows, cover them with a plastic bag.
This may seem obvious, but try to avoid dropping microphones. When mounting a mic on the stand, try getting into the habit of doing it in this order: 1) Screw the mic clip onto the stand. 2) Wrap the cable around the stand once and plug the cable into the mic. 3) Then place the mic into the holder. If it slips, at least there’s a chance the cable could save the mic from hitting the floor.
