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Verschiedene Artikel in de US-AUDIO sind dermaßen langweilig geschrieben, daß die hier nicht mehr erscheinen. Andere Artikel sind eigentlich nur fachlich falsch, die sind aber auch nicht dabei. - Ein für Vinyl-Fans interessanter Artikel über das "Schmieren" von Vinylplatten - Record Lubrication Has Considerable Effect! - steht hier.
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One of the many installations created by Allied Radio Corpooration in the Chicago area. The system shown incorporates a Fisher Model 80T AM/FM tuner and preamplifier, a Mcintosh MC-30 amplifier, James B. Lansing 001 speaker system, Garrard RC-88 record changer, and the Conrac Fleetwood 24" television receiver. Picturing as it does considerable charm in a monophonie setting, we look forward to learning how it will be converted to stereo.

AUDIO (title registered U. S. Pat. Off.) is published monthly by Radio Magazines, Inc., Henry A. Schober, President; C. G. McProud, Secretary. Executive and Editorial Offices, 204 Front St., Mineola, N. Y. Subscription rates - U. S. Possessions, Canada and Mexico, $4.00 for one year, $7.00 for two years, all other countries, $5.00 per year. Single copies 50£. Printed in U.S.A. at Lancaster, Pa. All rights reserved. Entire contents copyrighted 1958 by Radio Magazines, Inc. Entered as Second Class Matter February 9, 1950 at the Post Office, Lancaster, Pa. under the act of March 3, 1879.
RADIO MAGAZINES, INC., P. O. Box 629, MINEOLA, N. Y.
Postmaster: Send Form 3579 to AUDIO, P. O. Box 629, Mineola, N. Y.
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Note
Occasionally, letters intended for Audioclinic are sent to the magazine. While such letters are forwarded to me, they obviously cannot receive the prompt attention they would have received had they been directed to me, rather than to the magazine. When writing, always enclose a stamped, self-addressed envelope. This will facilitate a reply.


For the benefit of those not familiar with this column, I would like to state here that, regardless of the suitability of the material for inclusion in Audioclinic, your letters are answered personally.

I indicate in each letter whether the material will appear in the column, and when possible, try to indicate the issue wherein your question will appear. Some of you do not wish your names used, in which event we use the question but with a different name and city. In no instance, do I print a complete address.

Some of you who live near this address have occasionally telephoned me for information. I would appreciate it if you would write your questions and submit them to me in that form. This will allow me to give them more consideration, and thereby en sure a more complete accurate answer.

I have received one or two letters in which the writers fear that, because of my interest in loudspeaker manufacturing, I can no longer be objective in discussing loudspeakers. You need not worry on this account. This is based partly on the fact that I am probably more critical of my own work than of anyone else's, and partly on the fact that the nature of the questions makes it hard to bias the answers.

For example, if I were asked what speaker would be suitable for a "Super Blaster" type enclosure, there would be no reason for me to recommend an Audio-Tech woofer, for we don't sell our woofers separate from our complete system.
On this note, I wish you a Very Happy New Year! !

Die jetzt gedruckten Tips und Ratschläge der AUDIOCLINIC zu den Leseranfragen sind fast alle dermaßen primitiv und dazu auch noch falsch, daß ich hier absolut drauf verzichten muß. Die Verwirrung wäre zu groß.

Hier nur ein Beispiel :

Q: I have been a record collector for a good many years, and, as you can imagine, have a great number of monophonic discs, in addition to a few of the new stereophonic discs. Because this stereo system is compatible, I use my stereo cartridge to play both types of discs.

However, many of the monophonic discs are heard with a surprising amount of distortion as contrasted to their sound when a conventional, monophonic cartridge is used. What is causing this distortion and what can I do about it ?

A: There are several possible causes for the distortion of which you speak. One is that you are using insufficient tracking force. Some stereo cartridges are constructed in such a manner that they must track at or slightly above the prescribed force in order for the stylus to be properly oriented with respect to magnetic pole pieces. Failure to observe this precaution means that the cartridge will be too compliant, and the stylus will ride out of the grooves, rather than tracing them faithfully.

The second cause of distortion is a function of the monophonic discs themselves. Many of them are greatly overcut, especially at the high end of the audio spectrum. This will result in the inability of the stylus to stay in the groove properly. It tends to ride up out of the groove, regardless of tracking force. Any time that the stylus rides upward some vertical signal will be produced.

Because of the nature of the system, this vertical component will transmit it to the loudspeaker. Most monophonic cartridges were specially designed to eliminate as much vertical output as possible, and for this reason, little, if any, of this form of distortion was detectable with your monophonic cartridge.

This trouble can be minimized by connecting the two sections of your cartridge in parallel, phased in such a way that the vertical output is cancelled. Most instruction sheets supplied with these stereo cartridges show a wiring configuration which will bring about this end.

Naturally, if you wire this cartridge in this manner, you cannot achieve the stereophonic effect. What you will have to do is to wire a switch and mount it in some convenient place. This will enable you to switch from stereophonic sound to monophonic sound. If there is sufficient interest, such a switching circuit will appear in a future column.

• Anmerkung : In 1959 gab es bei auch in den US-Magazinen ganz offensichtlich eine Menge "Experten", die einfach zu wenig Ahnung hatten, was sie da empfehlen bzw. die sich technisch physikalisch einfach nicht auskannten.
  Es ist schlichtweg falsch, bei Mono-Platten die beiden Stereo-Kanäle einfach kurz zu schliessen. Das ergibt Phasenauslöschungen bei den unterschiedlichsten Frequenezen. Es sei denn, die ganze Anlage ist qualitativ derart "unterbelichtet", daß es sowieso nicht auffällt. Trotzdem ist der Tip mangelhaft.

Also dieser Rat ist absolut unqualifiziert und falsch.
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• • Newark Electric Company, 223W. Madison St., Chicago 6, I11., is now distributing its 1959 catalog No. 69. Covering thousands of industrial- electronic, amateur, radio, television, and high-fidelity items, this new 388-page buying reference features extensive quantity price breakdown listings which are competitive with manufacturers' price schedules. Fully illustrated and replete with comprehensive descriptions, the catalog also contains a convenient products and manufacturers index to facilitate reference to specific items. Your copy will be mailed free upon written request.
• • CBS-Hytron Advertising Service, Parker St., Newburyport, Mass., is now distributing "An Introduction to Stereophonic-Sound," the first of a series of "Stereo-Talk" bulletins, which tells what stereo is and how it works. The four-page publication describes how a stereo record is produced using the 45/45 Westrex system, and illustrates how the playback stylus motion is converted into separate signals for each channel. Components needed for a disc stereo system are listed and some typical questions on stereo are answered. Requests for copies should specify Bulletin E-305.
• • Argos Products Company, Genoa, 111., announces Catalog No. C-58, a complete listing of the company's wall and corner baffles and high-fidelity speaker enclosures. This is an excellent publication for custom builders, irrespective of whether their work involves commercial installations or equipment for the home. The new Argos "Californian" series of pre-finished kits will be of exceptional interest to the hi-fi hobbyist. Your copy of Catalog C-58 will be mailed upon written request.
• • Commercial Engineering Department, RCA Electronic Tube Division, Harrison, X.J., has just issued a colorful 137-page book, the "Designer's Guide" to "Preferred Tube Types", covering entertainment receiving tubes. Format of the handsomely-bound volume presents technical data in easy-to-read fashion. Color is widely used throughout the book to enhance readability and to highlight graphs and curves. Specially prepared for the men who design high-fidelity audio equipment, phonographs, radio receivers and TV sets, the book contains tube characteristics, dimensions, and base diagrams. Requests for copies of the "Designer's Guide" must be written on company letterhead.
• • United Catalog Publishers, 60 Madison Ave., Hempstead, N.Y., is now releasing a 24-page industry-wide booklet which provides listings of all available panel, flashlight, neon-glow, automotive and multipurpose lamps. Incorporated in the booklet is a composite listing, arranged numerically, of lamps manufactured by Chicago Miniature Lamp Works, General Electric, National Carbon, Oxford Components, Radio Corporation of America, Raytheon, Tung-Sol and Westinghouse. Simply by checking the lamp number the user can determine at a glance the manufacturer, bulb type, base, voltage, current, and bead color. All bulb types are illustrated with physical dimensions. Requests for copies should be addressed to The Radio-Electronic MASTER at the address shown above, and must include a remittance of ten cents to cover handling costs.
• • David Bogen Company, P.O. Box 500, Paramus, N.J., includes its complete new line of high-fidelity equipment in Catalog 510 which is just off the press. Among new units listed are the Model DR230 stereo control center and dual 30-watt amplifier, Model ST662 FM/AM stereo tuner, and Model DB130A preamplifier-amplifier. Requests for copies should be addressed to the Advertising Department.

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Sir:
Lack of reaction to the article on improvement in "Air suspension" speakers by tube venting (November 1958) would be disappointing. It was expected that the main theme might cause controversy. But Mr. Edgar Villchur's challenge (Letters, December 1958) on another subject gives welcomed opportunity to explain our statement that "A large box always allows more and cleaner bass than does a small box." His thesis is that box air stiffness must greatly exceed speaker suspension stiffness, implying lower harmonic distortion, as air stiffness is more linear. We feel the whole story should also consider transient response and amplifier problems.

Curves here show how the smaller air stiffness of the large box allows lower system resonance. The inevitable 6db-per-octave dropoff below resonance can be then set below the listening region instead of in it. Thus amplifier power or distortion will not increase to maintain flat output over the entire listening region.

He states that the cone sees the same impedance and elastic restraint whether with acoustic or mechanical suspension predominant, assuming final resonance the same. The point is that final resonance is not the same, the larger box giving lower resonance and lower cutoff. His and our speakers use linear, highly compliant suspensions.

It cannot be called an advantage to have speaker resonance in the listening range, as happens when high box stiffness runs resonance up to, say, 45 to 60 cps. Resonance is not noticeable if damping is critical or better. Here the small box again runs afoul of the laws of physics.

If a requirement is flat response to resonance, or a little below (and who claims anything else ?) the Q of the small-box system must be made considerably higher than 0.5, the figure for critical damping. In commercial low-efficiency small closed-box systems we observe a Q between 1 and 2, high enough to give detectable hangover. As pointed out in the November 1958 article, tube venting would improve damping by transfer of the vent radiation load to the cone.

For given sound output and frequency, the cone must move a certain distance. Assuming the same speaker suspension linearity, the small box cannot give less harmonic distortion. The cone still has to move the same distance, so distortion arising from the suspension cannot be lower.

On the other hand, with a vented box the radiation from the vent contributes to the total so that cone movement is much less
than in the closed box for the same sound output. Distortion from suspension non-linearities then is at a minimum.

A more analytical paper on this subject by J. F. Novak was given at the AES Convention in New York in October, 1958.

Philip B. Williams and James F. Novak,
Jensen Manufacturing Company,
6601 S. Laramie Ave.,
Chicago 38, 111.
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* U. S. Patent 2,810,448.
** The Hague, Netherlands

A modification of the "organ pipe" type of radiator results in wide-band performance and good low-frequency reproduction from 8-inch speakers without the resonant peaks which usually accompany this type of enclosure.

IT IS GENERALLY KNOWN that a good loudspeaker enclosure must enable the speaker to radiate sound energy equally well over the whole audio-frequency range. This implies that the enclosure be so designed that it has several particular properties: the enclosure should depress the natural resonant frequency of the speaker which exists, usually, at about 50 or 60 cps, in order to remove the "boomy" low-frequency response and the consequent deterioration of the transient response of the speaker; the enclosure should handle the back radiation from the speaker cone in a manner which avoids destructive interference with the forward radiation, especially at the lower frequencies; and the enclosure should add no resonances of its own in the audio-frequency range.

It is also known that a more realistic concert-hall effect will result if the reproduced sound is made to approach the listener from a broad front, as in the original concert performance. This effect can be obtained by using two or more spaced loudspeakers, driven in phase with each other. What is not so well-known, however, is that the sound wave should approach the listener as if it emanated from a slightly elevated source.

In a concert hall the normal to the sound front tends to dip into the absorbing audience, so that the sound emanates from an elevated virtual source, and this effect is usually enhanced by the reflection characteristics of the back wall of the concert stage. To obtain this effect in a home, therefore, the loudspeaker should be mounted at a moderate elevation above the listener's level, with the speaker axis tilted downwards slightly. A further benefit from this type of mounting is that there will be no obstructions between the loudspeaker and the listener, hence the high frequencies which radiate as straight beams from the speaker cannot be blocked by furniture or by other listeners; in many installations where the loudspeaker is placed near the floor, shadow zones for the high frequencies exist which make the high-frequency performance of otherwise high-fidelity equipment completely illusory.

Fig. 1. Two of the author's enclosures mounted on a wall in a position which would be suitable for stereo.

Fig. 2. Electrical impedance of the enclosure with a ty pfca I 8-inch speaker.

The conventional type of loudspeaker enclosure would be too large and too disfiguring to the average room if it were used in a manner which would satisfy all of these conditions, especially if the feature of multiple sources were desired. A study was therefore made of the possible types of smaller enclosures which would be satisfactory, and which could, in addition, be inexpensively and easily constructed. This study revealed that a small enclosure, whose fundamental resonance could be made to coincide with that of the loudspeaker cone, a radiating cross section about the same as the loudspeaker and whose volume could be closely coupled acoustically to the speaker, appeared to be the straight closed organ pipe. Although the general mathematical problem of computing the minimum volume for an enclosure of specified properties is extremely difficult, calculations made for different constructions of same resonant frequency and radiating cross section indicated that the closed organ pipe is the smallest enclosure or, at least, very close to the smallest enclosure possible.

The straight organ pipe requires some (Continued on page 69)

JOHN E. TURNER (* Box 513, Boise, Idaho.)
(Hier nur die Einleitung, der Rest ist viel zu alt.)

Although somewhat more complicated than the use of a simple elapsed-time meter, many constructors will have many of the parts for this type of device in the "junk box" and will enjoy working out the details of construction indicated by the author.

Serious audiofans almost invariably employ diamond styli in their music systems and, although their longevity is far greater than that of any other material known to the art, diamond needles do eventually develop flats which can damage the intricate pattern of grooves on LP records.

The life of a diamond stylus is variable, depending on the quality of the material and the degree to which it has been polished. Estimates vary from 800 to 2000 hours; however, 1000 hours seems to be a good average.

It is recommended that styli be examined at approximately half-life and again at expected time of replacement. This, at once, presents the formidable problem of knowing just how long the stylus has been used. Most persons cannot rely on their memories to maintain a cumulative record of playing time, hence the need arises for the development of a suitable mechanical system to record this data.

The primary requisites of such a mechanism are: 1) accuracy, 2) reliability, 3) convenience, and 4) no effect on the normal function of the music system.

The counter described below is the culmination of nearly two-years' development and testing and incorporates all the aforementioned requirements. The unit counts each record side as it is played and cumulative playing time is calculated by simply assigning an arbitrary value, 30 minutes, to each side. The playing time of most discs is well within the 30-minute period, thus allowing a safety factor.

Fig. 1. Complete schematic of photo-relay circuit.
Fig. 2. Top view of turntable showing flush mounting of counter.

Der Betriebs-Stunden Zähler für den Plattenspieler an sich ist zu ausschweifend beschrieben und daher nicht sinnvoll.
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