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Product Review - Kellerschon Akustik Bookshelf Speakers - June, 1995

By Jeanne Fairbrook

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Kellerschon Akustik Bookshelf Speakers. IDEAL. One 6" rubber impregnated low frequency driver, one 1" high frequency driver (dome), frequency response 40 Hz - 22 kHz, sensitivity 87 dB/W/M, power handling 110 watts, size 13 7/8"H x 8 7/8"W x 11 1/4"D, weight 12 pounds, $540/pair (black oak); PRIMUS. One 6" translucent plastic low frequency driver, one 1" high frequency driver (dome), frequency response 40 Hz - 22 kHz, sensitivity 85 dB/W/M, power handling 140 watts, size 13 7/8"H x 8 7/8"W x 11 1/4"D, weight 13 pounds, $950/pair (black oak, rustic oak, nutwood, cherry, mahogany); MAXIMUS. One 6" plastic impregnated cloth low frequency driver with phase plug, one 1" high frequency driver (dome), frequency response 35 Hz - 25 kHz, sensitivity 85 dB, power handling 150 watts, size 13 7/8"H x 8 7/8"W x 11 1/4"D, weight 15 pounds, $1,475/pair (ruby, azure, graphite, maroon, natural). All speakers have one 7" passive radiator on top. North American Distributor: 53 Thornhill Road, Stratham, New Hampshire 03885, Phone (603) 772-3662.

Kellerschon Akustik is a name that probably does not ring a bell with American consumers. It is a small manufacturer in Germany that has received big praise in Europe, but only recently have they grown large enough to introduce their line on another continent. We first heard them at the CES in Las Vegas, and because of the unusual configuration of their drivers, we felt that they might be interesting to test in a home theater environment. They also have an extraordinarily beautiful finish, which is what attracted us into the doorway of their exhibit.

There are two design characteristics that make the Kellerschons unique. One is that there is a passive radiator on top of the enclosures, covered with a grille cloth, and the second is the lack of any acoustic damping material inside. The passive radiator acts to reduce box resonances, and the technique appears to work.

The drivers are the same size in all three models that we auditioned, but their quality increases with each step up the scale, from the Ideal to the Primus, to the Maximus. The passive radiators (cone shaped rather than flat membrane) are all 7", while the active low frequency drivers are 6". The crossover networks are of high quality components, placed on a PCB attached to the binding post plate. Mr. Kellerschon explained to us that each speaker design is tuned by ear (adjusting the crossover components) to achieve a natural sound quality. The binding posts (gold plated on the Primus and Maximus) are set up for bi-wiring on the Maximus.

The finish on all the speaker enclosures is wood veneer. The most unusual of these is the birdseye maple (simulated). I had never seen a finish like this before and did not know what it was. If you purchase a pair of Kellerschons with this finish (it comes in several colors), you are guaranteed to receive comments and compliments from everyone who sees them in your home. I would say that they have a very high spouse acceptance factor (my husband loved them). It is not real birdseye maple, but a facsimile made from wood and epoxy resins, and has a very glossy surface, almost like glass.

Now to the sound. We tested all three models with several amplifiers, including surround sound equipment. One of our reference speaker systems is planar-magnetic, so we like the large sound stage produced by the signal emanating from more than one surface. In the case of the Kellerschons, the passive radiator on top of the enclosure radiates sound in the lower frequencies at various angles of phase with respect to the active driver, depending on the frequency. The result of this particular configuration is quite startling. It is very difficult to localize the sound as coming from the enclosure, and the sound stage is, thus, very large compared to speakers with all drivers on the front. Obviously, there is some reflection from the ceiling which adds to this effect. Although some listeners might not like this, we found it to be a very attractive feature of a bookshelf sized speaker. We enjoyed the sound when listening to CDs, but we particularly liked it when we connected them to our surround sound system.

Although these speakers appear to have a nice bass extension, they all benefited from a good subwoofer to handle the lowest octave. The sensitivity of the Kellerschons was too low to make satisfactory use of our 7 watt single ended triode, so if you like tube amplifiers, plan on higher power.

Like most women, my high frequency hearing is a bit more sensitive than men. So, when I listened to the speakers connected to surround sound coming from cable television, I preferred the Ideal model, since the Maximus was better at reproducing the high frequency distortion present in the TV signal. We performed this study single blind, and both women (myself and one of the other referees, Ms. Tricia Ogden) came to this same conclusion. However, the guys (editor John Johnson, and referee Alex Samet) preferred the Primus and Maximus. For CD listening, we all liked the Maximus for its high end detail and tight bass, and the Ideal for its full bodied mid-range. The Primus was somewhere in between, but none of the speakers sounded harsh or thin. For overall listening to several sources, my money would be on a set of the Ideals in the front and rear in a home theater setup, particularly with the advent of AC-3. Now all Kellerschon Akustik needs to do is make a matching center channel speaker.

Jeanne Fairbrook
Staff Writer

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Biography of Klaus Kellerschon
Our speakers are manufactured by Klaus Kellerschon of Ostfriesen, a small town in Germany. Klaus was a former Dusseldorf radio station disc jockey who opened a night club in the same city. He became unsatisfied with the quality of his sound equipment and started experimenting with speaker design. After a number of years, he found great success at creating speakers for his own night club.

Around 1985 he got out of the night club business and started making and selling his own line of speakers. His design was unique and his methods unconventional. He used a passive radiator affixed to the top of the speakers and used no damping material in the enclosures. He tuned the crossovers by ear in his own living room and developed what is today one of the most respected lines of speakers in Germany.

Klaus has received innumerable praises in reviews from European audio magazines. These reviews placed him in head-to-head competition against many of the worlds leading loudspeaker manufacturers, and Kellerschon Akustik came out with a very high ranking. We believe that the pattern of success achieved in Europe can be repeated in the United States.

In January of 1995 we exhibited at the Consumer Electronics Show in Las Vegas where our reception was tremendous. Our first orders came at the show from three members of a company exhibiting across the hall. Their company manufactures electrostatic loudspeakers. When the owner of their company wanted a pair of our small box speakers, for they were the best thing he had heard in that size, we knew then we had something very good to offer fine audio enthusiasts. When you hear them, we think you will agree.

Oliver Robinson
Kellerschon Akustik


Copyright 1995, 1996, 1997 Secrets of Home Theater & High Fidelity
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