Long after some Einstein engineer figured out that music sounds better coming out of two speakers rather than one, and someone else discovered the pan pot, the dinosaur known as ‘mono’ insists on existing. Virtually all the blame for this can be placed on A.M. radio, Ford half-tons, and television, with their shitty litle 3″ speakers. As a result, engineers still have to ensure that their mixes are mono-compatible and that half of the instrumentation doesn’t fall out when mono is pressed.
I have always found the biggest culprit to be multiple miking techniques on pianos, guitar cabinets, and the like. Although it is virtually impossible to determine if your mic placement is phase coherent before actually listening to it, a little planning and common sense can go a long way towards minimizing Tylenol intake.
If, for example, the idea is to produce a stereo image from a single guitar cabinet, a pair of mics is obviously required. since increaded distance from the edge of the speaker cone decreases bass response, setting up a stereo configuration in the middle of the front of the cone isn’t going to do it, unless the desired sound is thin. If one micgets moved to a placement, say 2″ in from the edge of the cabinet, 1/2″ away from the grille, and a foot above the floor, set the other mic up as a mirror image on the other edge of the cabinet. Instant Phase-Coherent Microphone Placement, Just Add Level. At such close distances to a source, a small movement results in a largephase shift. If one microphone is 1″ away and the other is 2″, it takes the sound twice as long to reach the second mic as it does the first, and there is a 180 degree phase shift – perfect cancellation – at 6600 Hz, the frequencywhose wavelength is 2″. This should also be remembered for subsequent overdubs. If the original bed track guitar was done with the two mics 2″ away from the speaker, and, at a later time, the guitarist doubled his rhythm part but the pair of mics was 4″ away this time, each of the stereo guitars on tape will be phase-coherent within themselves but not together. This time, the problem will occur at about 3300 Hz., a 4″ wave-length. Isn’t modern technology wonderful? Engineers will be haunted with this until mono is abolished and North America catches up with Japan in the TV department. Pray it will happen soon.
Wouldn’t mixing be so much easier if we ahd just one ear in the middle of our foreheads? But, then again, we’d look pretty silly talking on the phone.
Eric Abrahams – Head Engineer, Cherry Beach Sound, Toronto, ON. (Credits include: Kim Mitchell, Trash Gallery, Roxy Lane, Russian Blue, Dreamer, Nicola Vaughan, Angel Marr.)