Technology & Engineering

Klippel Distortion Analyzer


By the time you read this, if you’ve been following along, you’ll probably already feel like an audio engineer. I certainly do, and I’m just writing it. By now you know that a speaker driver produces sound through motion; electrical stimulation tells a magnet when to move the driver up or back. You can probably guess that in order for a driver to reproduce complex sounds accurately, the cone should move exactly the same distance, smoothly, in the same manner, in both directions. What’s important is consistency. And when it comes to speaker drivers, consistency is not as easy as you’d think.

But, as you know, we’re pretty obsessed. Polk engineers searched the high-tech world for a device that would help them better analyze the motion of driver cones in action. We wanted something that looked like a weapon out of a James Cameron movie, with clamps and struts, and lasers, if possible. The state-of-the-art Klippel Distortion Analyzer turned out to be just the thing. It helps us to visualize and optimize the motor structure, voice coil alignment and suspension of our loudspeakers, resulting in much more consistent, and accurate, driver action. 

State of the Art Analysis Spots Weaknesses Before they Become Problems

The Klippel Distortion Analyzer uses a laser (cool!) and sophisticated software to do large-scale analysis of drivers in motion.

The first thing that Klippel analysis reveals is BL product. BL product is (math alert!) the product of the speaker motor’s magnetic flux density times the length of voice coil in the gap at the time. (The gap is the space in which the voice coil moves up and back.) Put simply (with simply being a relative term), BL product is a measure of the motive force applied to the driver cone. The KDA allows us to measure exactly how the motive force moves the cone, helping us pinpoint whether we have the right amount of motive force for the mass of the driver and whether or not it’s applied uniformly. When we can view the motion at this level, we can correct for any performance robbing anomalies.

The graph on the right shows the BL product for our SR6500 speaker driver. In this graph, the center 0.0 vertical line represents the cone at rest. To the left of the center line is forward cone movement; to the right is backward cone movement. A perfect driver would have a straight line graph plot, but in the real world, where drivers have limitations, we look for a symmetrical bell curve, or a broad, flat shape. Using the KDA, motive force can be adjusted and optimized for each driver, guaranteeing smooth, fast, accurate loudspeaker response.

The second thing that the Klippel analyzes is suspension. The KDA gives us a closer look at the tension strength, stiffness or springiness, of a speaker’s suspension. With this kind of analysis, we can ensure more consistent performance over a broad range of cone travel, both up and back. This is an illustration showing the symmetrical and linear suspension stiffness over a broad excursion range of the SR6500 speaker driver. This kind of consistency helps our loudspeakers perform awesomely even at lifelike volume levels. Where other speakers end up banging, booming, and breaking apart from outrageous motion, Polk loudspeakers perform.

We Like it Loud

We say, turn it up! Whether it’s your favorite movie, in digital multichannel sound, or your favorite album, in the vinyl original, we believe you should be able to enjoy your audio entertainment at lifelike volume levels without worrying about your speakers breaking. The Klippel Distortion Analyzer is just another sophisticated tool we’ve put to work to ensure that we have more fun playing.

This article was last modified on Mar 26, 2013

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