Behind The Scenes (Feb. 1975)

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LATE LAST SUMMER, the great Philips company of Eindhoven, Holland, and the AKG company in Vienna invited members of the hi-fi press corps to inspect their audio manufacturing facilities in their respective countries ... and needless to say, do some sightseeing and "live it up a bit." Understandably, these press junkets are very popular (even if you do have to do some fast "hustling around," and in this respect our Dutch and Viennese friends are as expert as their Japanese counterparts), so in addition to yours truly there were such well-known hi-fi personalities as ... Larry Zide, Julian Hirsch, Norman Eisenberg, Martin Clifford, Harry Maynard, and Ivan Berger. A number of wives were along to "keep the boys in line" (and to spend their money), and we were accompanied by George Garnes, Advertising Director of North American Philips Co., and the grey-haired, grey-bearded, distinguished national sales manager of Norelco, Robert Miller. We were to be joined in Eindhoven by the genial general manager of Norelco, Andy Brakhan. It should be noted here that Norelco distributes AKG products in America, thus the Norelco people were acting as dual hosts until we reached Vienna.

We deplaned from our 747 in Amsterdam, and were then flown to Eindhoven in Philips' private prop jet.

As you might expect, as headquarters for the Philips vast, globe-girdling industrial empire, Eindhoven is very much a "company city." There are many electronic and other types of manufacturing plants in Eindhoven, which employ some 45,000 people.

Ensconced in our hotel and having recovered from "jet lag," we were given an elaborate "Welcome" dinner, (suitably lubricated with plenty of the famous Heineken and Amstel beer) and met many of the Philips executives who would be our hosts for the next several days.

Bright and early the next morning, we began our visit to the Philips electronics laboratory, which is indeed an extensive facility. Of course our main interest was in the audio lab and demonstration room, and our hosts were eager to give us an elaborate presentation of their new 22RH532 Motional Feedback (hereinafter known as the MFB) loudspeaker system. The demo room was roughly 20 by 40 ft. with about a 9 ft. ceiling.

Along one wall they had arrayed six well-known U.S. and European loudspeakers. I won't name names, but the speakers represented both ends of the price scale in popular acoustic suspension models. I should note that all the speakers were in stereo pairs.

Interspersed among these speakers, and in general dwarfed by them, were stereo pairs of the tiny 15 x 11 1/4 x 8 3/4 in. MFB speaker.

An elaborate A/B switching set-up was provided to check the MFB against the other speakers. Peter Gouw, the head of the audio labs and an engineer of immense talent who aided his presentations by his obviously sincere and enthusiastic love of music and audio, had provided every possible kind of source material, including open-reel tape with Dolby A. Records were played over their new 209S turntable (about which more later on), and since the MFB has its own internal amplifier, to allay any fear of under-powering the other speakers, those were driven by Bose's huge 1801 250-watt amplifiers.

Before we go on with the tests, here is a description of the MFB. In the approximately 15 liter enclosure is an 8-in. woofer, 5-in. mid-range, and 1 in. dome tweeter, all made by Philips.

Two output amplifiers are also contained in each enclosure. The woofer amplifier is terminated with a 4-ohm speaker, and with one-volt input can deliver up to 40 watts. The other amplifier is similar, except that it delivers up to 20 watts. Connected to the output of this amplifier are a highpass and a low-pass filter with a crossover at 3500 Hz. All frequencies above 3500 Hz are fed to the dome tweeter, while frequencies between 500 and 3500 Hz are fed to the mid-range driver. The woofer is crossed over at 500 Hz through an electronic crossover ahead of the two amplifiers. In other words we have a bi-amplified speaker system in this small enclosure with an output total of 60 watts.

The heart of the MFB is a piezoelectric crystal acceleration transducer attached to the cone of the woofer, just outward of the voice coil.

This PXE sensing element, as Philips calls it, measures the acoustic acceleration (movement) of the cone and converts it into an electrical signal. This signal is proportional to the cone motion and is fed to a comparator which compares it with the original incoming signal supplied to the woofer amplifier. As differences are detected by the comparator, corrective signals are fed back to the speaker via the built-in amplifier.

Thus, we have a motional feedback system. The objective of this system is the reduction of bass distortion and since the resonance of the woofer is treated by the MFB as an anomaly, it is "corrected" so that in essence the 8 in. woofer has a resonant frequency of 35 Hz.

Let's get back to the A/B tests. Peter Gouw started off with a superb recording of Oscar Peterson, in which Oscar's piano was accompanied by a string bass played arco (with a bow). The bass is playing a descending figure and the sound is very "open" and revealing. Switching between the various speakers and the MFB, it was apparent that all the speakers could reproduce the lowest note played, about 45-50 Hz. However, it was equally apparent that there were considerable differences in the quality of the sound among the conventional speakers as well as that of the MFB. To be perfectly candid, we were as much interested in the quality of sound of the popular U.S. speakers under these finely controlled A/B conditions, as we were with the MFB. Most noticeable, once we had become acclimated to the acoustic qualities of the room, was the degree of coloration exhibited by these speakers, mostly in the form of an emphasis in the 100 to 200 Hz range which gave the bass a "voomy" over resonant quality adversely affecting the timbre and cleanness of the sound. In contrast, the MFB was free of the coloration and was singularly clean in its bass reproduction. Most impressive was that this tiny enclosure could actually reproduce such low frequencies. Claimed response is to 35 Hz, and with source material which actually contains such frequencies, the MFB does a very creditable job, but in my opinion, I would say that at 35 Hz, it was down about 5 dB or so.

While the reduction of bass distortion and the freedom from mid-bass coloration are among the most important features of the MFB, equally important are the advantages of its bi amplification.

We auditioned the MFB with a wide variety of pop and classical music and were impressed with the general cleanness of the mid-range and highs, and with the extended high end response. In summing up the sound quality of the MFB, it impresses most with its exceptionally smooth overall response and neutral character. I should mention that these little MFB speakers can play at quite a high level, with a claimed SPL of 106 dB at 1 meter.

Among other advantages Philips claim for the MFB, is that if they are used with receivers or integrated amplifiers of less than 60 watts per channel, the output power of the receiver/amplifier will be upgraded to 60 watts per channel. There are input connections on the rear of the MFB enclosure, to accept the signal from a pre-amplifier, etc., and there is also an output jack which can be used to connect other MFB units in series for greater power output. Carried to the ultimate extension of this idea, as many as 15 MFB units could be connected to each channel of a preamplifier, and assuming a four-channel system, you could wind up with 3600 watts of power! Peter Gouw and his cohorts showed us other audio items, including a prototype "big brother" of the MFB with a 15-in. woofer. Late in the afternoon, Peter asked us to take a break for refreshments, and to come back in half an hour, when he would have a special treat for us. When we returned to the sound room, a bar had been set up, and everything was very festive, with a 5-man jazz combo, of piano, bass, drums, saxophone, and trumpet, furnishing live music for our pleasure.

After a while, as we were watching and listening to the band, the drummer put down his sticks, casually lit a cigarette and walked over to the bar ... but the sound of the drums was still neatly accompanying the rest of the players! Then the piano man left, and subsequently the trumpeter and the rest of the band headed for the bar, and the music played on! I had noted a few clues that tipped me off to what was happening, but we all agreed that we had heard the best "live versus loudspeaker" demonstration in our experience. The players and the Philips recording engineers had done an outstanding job of recording without introducing the obtrusive acoustical qualities of the room that usually betray these demonstrations. Everything was beautifully synchronized, and then the background drape opened, revealing two pairs of the little MFB speakers on each side of the orchestra. Truly impressive, and all of us gave the Philips people a well-deserved round of applause. There is no doubt in my mind that in the MFB loudspeaker, Philips has come up with a unique new product which should find a wide and appreciative audience.

While we were in Eindhoven, we visited the audio research labs, where after a general overview of their facilities and activities, we were given a look and a listen to what could be a very significant advance in magnetic tape. The Philips scientists have come up with a tape coated with iron powder, rather than iron oxide. One of the principal virtues of this new tape is said to be in the improvement of signal-to-noise ratio. We listened to a triple pianissimo section in the finale of Respighi's Pines of Rome, recorded on chromium dioxide and on the iron powder tape. An A/B comparison between them dramatically substantiated their claims of a 6-dB improvement in the S/N, as that amount of tape hiss became obtrusive on the CrO2 tape. Because of its higher coercivity, thinner coatings with the same relative output as conventional tape are possible. Higher bias drive is necessary, somewhat more than for CrO2.

After a evening of wining and dining, the next morning we were off for Hasselt, Belgium, where the Philips plant that manufactures the new 209S electronic turntable is located. Hundreds of girls are employed here on the assembly lines, where every part and then the subassemblies go through quality-control checkpoints located at various intervals on the lines. Finally, the completed units are tested in a glass-enclosed "clean room." The 209S turntable is one of the most automatic units yet devised.

There are three motors in each; one for turntable drive, one for pick-up arm movement, and one for cueing.

On the top right of the turntable base is a panel with controls for manual operation, if desired, plus a 33 1/3 / 45 rpm speed adjustment control and an anti-skating force adjustment control. When the sliding smoked-plexiglass panel is pulled over the control panel, the turntable is in AUTO mode.

Now dig this, fellas ... you place a record on the turntable platter, and whether you have put on a 7-in. 45 rpm single, or a 10-in. (I suppose some people still have some of these) or 12 in. 33 1/3 LP, the turntable begins to revolve at the correct speed, the pickup arm lifts up and contacts the lead-in groove at the correct diameter, the record is played to conclusion, then the arm lifts off the record and returns to the arm rest. If you wish you can interrupt the playback at any point with a mere finger touch on a capacitor-type button which controls the arm lift. To return the arm to PLAY position, you touch another button. If you would like a repeat play of the entire recording, just leave the sliding panel in place and the unit will go through the whole cycle again.

Should have mentioned that a muting circuit goes into operation before and after pick-up arm set down and lift off, so you never hear anything from this turntable except the program.

The whole system operates electronically, with three sensors in the turntable to "recognize" record size and speed, and pass this information to a so-called mini-computer. The arm has an accurate built-in stylus pressure gauge, and the arm lift has viscous damping. The 209S turntable drive motor is of the d.c. type with a tacho-generator. The generator produces a frequency signal which is fed to another mini-computer (probably the usual comparator/feedback correction scheme) to correct any speed variations. There is a sub-chassis under the turntable base which provides considerable damping for reduction of acoustic feedback. The 209S certainly must be regarded as one of the most sophisticated pieces of record playing equipment yet offered to the public.

After returning from Belgium, we all were treated to a most memorable and delicious farewell dinner at our hotel. I can't praise too highly the very efficient job the Philips people did in providing us with every possible and technical support in this presentation of their new products, and their open-handed, generous hospitality which made our visit so pleasant. Next month .... to Vienna and AKG.

(Source: Audio magazine, Feb. 1975; Bert Whyte)

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