MBL 101 E Radialstrahler Omnidirectional Loudspeaker

The very first thing HP told me when I started writing for this magazine ten years ago was never to paint myself in a corner with a rave. “Always leave room for the next great thing that comes your way,” said he, “because sooner or later it will.”

In this instance, it’s come far too soon for comfort. Just as I finished my, uh, rave of the Kharma Midi-Exquisite/CeSb 1.0 loudspeaker system in Issue 151, these space-age contraptions from Meletzky Berlin Loudspeaker (MBL) showed up to make me eat my words.

Well, “eat” is too strong a word. Perhaps “rechew” is better. The Kharma Midi-Exquisites will remain in my listening room for the reasons outlined in Issue 151. But the MBL 101 Es have now joined them—and in several ways superseded them—as my references.

Before I start singing the 101 E’s praises (and pointing out its peculiarities), let me talk a little about how the speakers work, since they work differently than just about every other loudspeaker I’ve auditioned. The MBL 101 Es are omnidirectional speakers, meaning they radiate sound throughout a true 360 degrees. The folks at MBL like to point out that musical instruments are also omnidirectional radiators, which is true, although unlike the 101 Es musical instruments do not radiate equal energy in all directions.

The way MBL gets its speakers to radialstrahl (emit a circular signal) involves a nifty bit of thinking from MBL founder Wolfgang Meletzky (in cooperation with Professors Josef Sternberg and Herbert Fritz of the Institute for Aeronautics and Aerospace at the Technical University of Berlin), and a just as nifty bit of execution by MBL’s resident engineering genius, Juergen Reis. To take the Radialstrahlers’ tweeter as an example, the driver’s “motor”—a fairly conventional magnet and voice coil—is seated horizontally on the chassis, like a dynamic speaker sitting face-up on a stand. Instead of being attached to a paper or plastic cone, however, this magnet/voice coil is wired to a sheaf of slightly bent, carbon-fiber petals (what MBL calls “lamellas”) that are arrayed vertically in a circle, rather like a segmented orange standing on its stem, and then glued at their tops into a thrust bearing. As the voice-coil moves up and down, the lamellas of the spherical driver are driven, accordion-like, in and out, producing sound throughout 360 degrees. A true—dare I say it?—pulsating sphere.

The tweeter and midrange Radialstrahlers use carbonfiber lamellas; the big tulipbulb woofer uses aluminum/ magnesium ones. Other than these material differences, they work in exactly the same ingenious way. Each is bolted atop the other—tweeter, midrange, woofer—with no box surrounding them.

The only conventional dynamic driver in the four-way 101 E is the 12" cone “subwoofer” (a proprietary MBL design), located immediately beneath the tulipbulb woofer. It does have a box—a beautifully finished, high-gloss, piano-black enclosure, with two front-facing ports near its bottom—into which it fires downward. (Though it is called a “subwoofer,” the cone woofer is actually just a very good low-bass driver, with a LF cutoff of about 25Hz and HF cutoff of 105Hz; like all low-bass drivers it, too, radiates sound omnidirectionally.)

Wearing their optional, tall, “pagoda- like,” mesh grilles, the 101 Es are stunning-looking, avant-garde objets d’art; unfortunately, these grilles cause all sorts of audible diffraction problems and simply cannot be left in place for critical listening. Stripped of them, the 101 Es look rather like, well, Star Wars’ C-3PO sitting in a hot tub. (Our CEO, Tom Martin, who came to Cincy to audition the 101 Es, said that he kept expecting them to get up and start moving toward him.) I love their vaguely android looks, but even if you don’t, the 101 Es are certainly going to be conversation- starters—grilled or grilleless. Outside of the Avantgarde Trios, I can’t think of another loudspeaker that makes this much of a design statement.

So what does C-3PO-in-a-hot-tub sound like?

First, as you might expect, because they radiate sound through 360 degrees the 101 Es make your room an even bigger factor than usual. Unless you have a very large space or a very well-damped one, the MBLs are going to require you to pay careful attention to: 1) room treatment (behind the speakers, to the sides of the speakers, and on the wall behind the listener); 2) listener height (for the very best balance, the Radialstrahlers prefer you to be seated with your ear roughly parallel to the midrange driver—sit lower than this and you begin to hear too much woofer; higher, too much tweet); and 3) listener distance from the speakers, and the speakers’ distance from the back and sidewalls and from one another. Although all speakers require careful attention be paid to these matters, they become considerably more critical with the omnidirectional Radialstrahlers. (I should note that 101 Es allow you to better accommodate room acoustics by giving you the choice of quite-different- sounding silver, silver alloy, or copper wiring from the crossovers to each of the radial drivers. You can experiement with the three kinds of wire via large, easy-to-set jumpers on the backs of the speakers.)