Professional Sound - Indepth

Stereo Imaging by Neil Muncy

Just about everyone uses “nearfield” monitors. While most of these little speakers are amazingly rugged, every so often a problem will develop which affects the stereo image. Good imaging requires matched speakers. If you think you are having imaging problems, or just want to see how well matched your nearfields are, here’s what you can do to test them using only a piece of wire, your ears, and a blanket!

Make a “Y” cable, so that you can feed both speakers from the same power amplifier channel. Connect the speakers, making sure you observe the same polarity for both. Position the speakers on the console so that they form an equilateral triangle with your seated position. Orient the speaker cabinets so that the tweeters are above the woofers. Start the music, and find the centre using your ears. If both speakers are well matched, you should sense that all of the sound is coming from the midpoint between two speakers. Then, to reduce reflections, cover the control surface of the console with a thick blanket. The image should get even tighter and more centred. Next, turn the two speakers so that the drivers are facing each other, and move them together so that they are as close as possible. You should hear a slight increase in sound output. Now reverse the connection to one speaker. There should be a dramatic drop in sound, with all of the low frequencies, and most of the highs, completely missing. If there is any substantial soudn remaining, there is something wrong with one or both speakers. (This test assumes that the drivers are mounted one directly above the other, or that the cabinets are sold in mirror-image pairs).

If your speakers fail these tests, comparing each one individually with another unit which is known to be good shoudl pinpoint the defective unit. If your speakers pass these tests, but the imaging is still “off” under normal conditions, chances are that there is an electrical problem somewhere in the monitor chain, and it may be time to call your maintenance technician.

Neil Muncy – Neil Mancy Associates, Ltd., Consultants in Electroacoustic Systems, Scarborough, ON

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About Andrew King
Andrew King is the Editor-in-Chief at Professional Sound. He is also a co-host of Canadian Musician Radio and NWC Webinars’ series of free music and entertainment industry webinars.
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