Wednesday, October 04, 2006
Polar Response of the Naked Eye Ribbon Mic and what it means
I'm re-posting Herb Singleton's measurements of the Naked Eye since there have been so many comments and questions about this unique microphone.
What you are looking at is a figure 8 polar response pattern that is plotted with various colors according to frequency. It is like you are looking down on the top of the mic from the ceiling, assuming the mic is set straight upright. Imagine yourself standing where the top of the image is and assume that is the front, or emblem side. You will notice right off that the large dashed white/light colored lines are quite different from the opposite side of the figure 8 pattern. Note that the rear lobe is 180 degrees out of phase with the front lobe - very important to remember when doing A-B comparisons.
At the lower left of the image there is a legend that tells you what frequencies the different lines correspond to, and you have to look pretty closely so I have a zoom function set if you just click on the image. If you are in Firefox you can click it twice and really zoom it to fill your whole screen. The 8000 Hz (Chladnis) dashed line is one that is very different. The others are too, just less so.
What is happening
The different responses on each side are very different, not subtly different, from each other. This is not due to any offsetting (phase shifting) of the ribbon or by placing cloth in front of the ribbon to deaden it. That would lead to loss of definition, something we don't want. Instead, the local field around the ribbon is adjusted using transmission line physics to selectively match the acoustic impedance of the soundwave to the ribbon itself. Sound can be reflected, absorbed, and reradiated from materials such as condenser membranes, ribbons, and virtually everything else, so knowing how the sound energy interacts with the "sensor" is the key to engineering in a desired response or tone. Then it is up to the ear/brain to determine if that tone is a keeper.
Naked Eye is unlike the other ribbon mics that are out in the realm, and was created in response to the Frugal Yankee in us that said people would go for a mic that one one side has a sound somewhat like the Studio Vocalist, which has caused quite a stir, won an award, and ended up on the cover of Recording magazine, and then on the other side, the Proscenium, the mic that has caused its own fervor among the very particular.
What it means
Naked Eye configured this way allows the user to select two different "voices" depending upon application. If you need a rising response, such as for some vocals and acoustic guitars, for example, try the side with the highest response in the upper ranges, easily seen in the graph, or better yet, easily heard. Other apps such as loud electric guitar might sound better with the dark side. You decide. Use your ears! (but protect them for later use) Simply rotate the mic in its mount to change it.
Posted by Bob Crowley at 2:50 PM