THE NEW PHASE-LINK SPEAKERS BY BANG & OLUFSEN PUT MUSICIANS IN THEIR PLACE.
When music is well-recorded, it is not too much to expect that, during playback, your loudspeakers will reflect the same dynamics and ambience that were present at the original event. Re-creating the placement of instruments as well as they re-create the character of each note.
If your loudspeakers can't do all that, there's a very legitimate reason: audible phase distortion.
After years of research, Bang & Olufsen has created a speaker system that provides the missing link in speaker engineering by virtually eliminating audible phase distortion.
The Beovox Phase-Link loudspeaker.
Now you can hear musicians on your stereo sound stage (your listening area) as they were recorded: from front to back, as well as from side to side. With excellent transient response, definition and clarity.
But let's backtrack and see exactly how Bang & Olufsen got so far ahead.
The problem of phase distortion.
Phase distortion occurs in multiway conventional speakers at the cross over point when the same note is being reproduced simultaneously by two drivers. It is most noticeable at lower frequencies and during transients (sudden variations in volume).
What you hear is a blurred sound picture, lacking definition.
There are two characteristics to phase distortion: one is fixed, the other is variable. In conventional crossover filters, alternating driver units are fixed mechanically and electrically 180 degrees out-of-phase (to compensate for amplitude "suck out"). (See Diagram A.) Variables in phase shift are due to passive filter components.
Today's high-quality loudspeakers have virtually solved the problems of frequency response, as well as harmonic and intermodulation distortion.
Diagram A: Conventional 12dB/oct. cross over filter.
Which makes the study and correction of phase distortion, the final hurdle in speaker perfection, all the more important and meaningful.
A discovery we really listened to.
At the 1973 AES convention in Rotterdam, two Bang & Olufsen engineers, Madsen and Hansen presented a paper on audible phase distortion that represented three years of research.
They had created an electronic crossover, tri-amplified speaker which totally eliminated phase distortion. From it, they concluded that phase distortion is the remaining main source for sound coloration in conventional speakers.
That it is, indeed, audible at lower frequencies and higher volume levels.
The solution: the Phase-Link method.
Madsen and Hansen's electronic crossover speaker was, of course, ost-prohibitive to the consumer. So Bang & Olufsen set about creating a practical solution.
E. Baekgaard, head of the Bang & Olufsen electrical engineering department, developed a mathematical computer simulation of the loudspeaker's electro-acoustic transfer function. And he began experimenting.
Instead of placing alternating drivers 180 degrees out of phase, he put them all in the same phase, "curing" the fixed phase shift. This created an audible amplitude "suck out7(See Diagram B) which led to the discovery of the missing link:
An additional narrow band filler driver at the crossover point. It "cured" both the amplitude "suck out" and the variable phase shift by providing a compensating signal between the woofer and midrange.
Diagram B.
Diagram C: The Bang & Olufsen new dynamic filler driver eliminates
phase distortion.
And it made the audible output identical to the electrical input. (See Diagram C.) Today, our Beovox Phase-Link loudspeakers have even further refinements. The drivers are mounted to form a common, angled baffle, acoustic axis to ensure that the sound generated from each driver will reach the ear simultaneously.
Acoustic Axis
Diagram D.
(See Diagram D.) These speakers are so acoustically accurate, they can re produce p an electronic square wave signal. Proof that they have excellent frequency response, low distortion, and are free of audible phase distortion as well.
(See Diagram E.)
Diagram E: 1. A good conventional speaker with wide, flat frequency response
and low distortion still cannot reproduce the original square wave signal
2. Beovox Phase-Link loudspeakers can reproduce square wave accurately by
virtually eliminating phase distortion.
Your Stereo Sound Stage.
More than stereo separation, Beovox Phase-Link loudspeakers produce a total stereo sound picture.
With notes retaining their clarity, free from hangover because of excel lent transient response. Which means that in a fine recording, you'll be able to sense where every instrument and section is located.
Now you need real proof. So take a favorite recording to your authorized Bang & Olufsen dealer.
He'll be happy to put your musicians in their place.
Because the ear is sensitive to phase distortion mainly in the lower frequencies, phase link is only used between the low-frequency driver and the midrange unit in the high-power.
Bang & Olufsen--Narrowing the gap between man and music.
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(High Fidelity, 1976)
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