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"off duty" 1970 - 1997 - eine Werbezeitung für's US Militär

Die in diesem amerikanischen (Freizeit-) Shopping-Magazin angeprie- senen Produkte waren auschließlich amerikanischen und kanadischen Militärangehörigen ausserhalb der USA zugänglich - also zu kaufen - vor allem zu ganz ungewöhnlich (verblüffend) niedrigen US $ Military-Preisen. Zu der einführenden "off duty" Seite geht es hier lang.


Das Angebot an Lautsprechern wuchs unaufhaltsam

Den Leidensdruck konnte man fast schon riechen, wenn Tonbandgeräte- Hersteller auf einmal Electronik anboten, wie es bei TEAC und AKAI der Fall war oder bestens bekannte Receiver- und Verstärker- Hersteller Bandgeräte konstruierten wie PIONEER und SANSUI und TOSHIBA und andere. Auch McIntosh brauchte auf einmal Lautsprecher im Programm ?? Und kurz darauf versuchte sich sogar KOSS mit Lautsprechern, als die Kopfhörer nicht mehr gewünscht wurden.

Wenn man die Lautsprecher-Preisliste im 3. Teil ansieht, findet man die Großen der Branche und auch viele Kleine, aber noch lange nicht alle, die auf dem Weltmarkt ihre Produkte anboten. Hier in off-duty wurden fast nur Produkte aufgeführt, die im military Bereich verkauft wurden. Auf dem US Markt waren es viel viel mehr Anbieter.

Am Ende waren sogar Edelhersteller wie Kensonic/Accuphase, McIntosh und SAE samt OHM und Infinity "gezwungen", hier mit extremen Discount- Preisen mitzumachen.


Getting a Hearful

How to choose loudspeakers - By LARRY MYERS - Off Duty / Europe / October 1975

Lautsprecher in so vielen Designs fast wie Krawatten

LOUDSPEAKERS, LIKE NECKTIES, are available in an almost mind-boggling variety of designs. And, like neckties, the ones that suit you best are entirely a matter of taste. It isn't that the technical side of loudspeaker design and construction isn't important, it is just that your criteria in choosing a speaker that sounds best to you are uniquely your own.

If you are new to the high-fidelity scene or if you've just become accustomed to something less than quality sound, you may well be satisfied with relatively inexpensive speakers — at first. But no doubt as your interest grows and you listen to other systems, you will become a more demanding, more sophisticated listener.

By studying this OFF DUTY Shopper you will learn some of the things to look and listen for when you go speaker shopping.

The procedure.

When you're finally ready to start hunting a new set of speakers, you'll need a program to follow so you can come as close as possible to finding the speakers you want. There are several ways to go about this, but in the next few paragraphs we've outlined a procedure which works well for most people.

First, figure out the size and general price range of speaker system you want. For the price range, consult your pocketbook; for the size, see our comments further on.

Next, consider the power requirements of the speakers. If you already have an amplifier or receiver, you'll need to match the power handling ability of your new speakers to your amp. If you're starting from scratch, remember that low-efficiency speaker systems require high-output amplifiers and that means more money!

After this, read our comments on specifications and start digging into the speakers' performances. Keep in mind that not all manufacturers give performance specifications and only a few give complete, referenced specs. You may not get far in this step but it will give you a good overall view of what's available.

The final step is to audition the speakers themselves. Don't rush this! Go to several speaker showrooms, if you can, and take your own records. Take records that you've listened to over and over, so you know every little scrape and squawk on them and be sure it's the
type of music you like to listen to. If you enjoy symphonic recordings, don't take rock records.

Go to your friends' homes and listen to their speaker systems (yes, take your records along). Ask around to find people who may have systems you're interested in. (You'll find that audiophiles love to demonstrate their systems - even to complete strangers.)

Try to take notes when you audition speakers. This will help you avoid confusing the many similar-sounding brand and model designations. It's also a good idea to make notes about how well speakers reproduce particularly difficult musical passages. Such impressions will go a long way toward resolving your confusion about what to buy.

Frequency response.

There are three types of speaker manufacturers when it comes to frequency response; those who give no frequency response, those who give unreferenced frequency responses and those who give complete frequency response figures.

All of this is a reflection of the many loudspeaker theories which exist today - every manufacturer seems to have his own. Granted, with the many different designs, it is difficult to produce a standard method of measuring loudspeaker frequency response but a good system has to at least start by producing the full range of audio frequencies.

Especially in the case of regular, front-firing systems, there is a little reason why a standardized measuring method can't be found. Likewise, distortion measurements are often not provided or are so involved that they are not given in the following listings.

Frequency response statements which are unreferenced (do not give variance limits, such as ±4dB) tell you, at best, what frequency range the speaker is supposed to cover. Very often, these types of speakers will lose over 20dB of output by the time they reach their stated end frequencies.

Keep in mind, too, that the room where you place your speakers will have an effect on the apparent frequency response - this is where you can use the treble and bass controls on your amplifier and speakers to good advantage.


The impedance of the speaker system should match the output of your amplifier for best performance. Actually, the impedance of most speaker units varies considerably according to the frequency they are reproducing. This variance in impedance is reflected back to the amplifier which may reduce its output power by a considerable amount.

Remember, impedance is just a way of describing an electrical characteristic of a speaker. It in no way reflects on speaker quality or lack of it.

Power rating.

The maximum power rating of a loudspeaker tells you the highest amount of power you should allow to be put into the speaker system. In some cases you may burn out the speaker elements if you exceed this limit. In other cases the manufacturer has found that driving the system above a certain limit seriously distorts the output of the system and makes any further power increases useless. In stating power ratings, however, manufacturers may use any of several methods including rms, program and peak.

Continuous or rms.

Many manufacturers give their speakers an "rms" maximum power rating meaning that a loudspeaker system can stand a certain amount of power if it is driven by an amplifier delivering a steady tone. While this rating is the most scientifically accurate, it is difficult for the average audiophile to use because very few people listen to steady tones with their systems.

Nevertheless, the rms rating is generally considered to be the most conservative method of rating speaker systems. If you connect your speaker system to an amplifier which has an rms power rating at least 20 per cent less than the rms power rating of the loudspeaker, you should rarely have trouble with overloading.

Also,thanks to a new Federal Trade Commission (FTC) rule, the power output of receivers and amplifiers must now be stated in continuous watts, which means you will have an easier time determining amplifier / speaker power compatability.


When a loudspeaker is rated in "program" watts, it means that the system can withstand the stated amount of power when driven by an amplifier delivering musical program material. This is the easiest rating for the audiophile to understand because he will most likely be using his system to reproduce music.

When matching a speaker system rated in program watts to an amplifier rated in rms watts, you can make direct comparisons of the figures with no conversions necessary. Again, however, give yourself a 20 per cent margin in the speaker rating just to be safe.


This rating generally means that a speaker system can withstand only extremely short bursts of the stated power. It is one of the least conservative ratings and should be reduced considerably when choosing a matching amplifier. As a general rule, one should discount peak ratings by 50 per cent to be safe. In cases where no power method is stated, consider the rating to be the program method.

Number of speakers (gemeint sind die Chassis) and ranges.

Most speaker systems have some means of splitting the audio spectrum into two or more parts each of which is then fed to speaker elements especially designed to reproduce a particular range of frequencies. The result is lower distortion and better frequency response even though there is some loss of energy in the frequency dividing network.

Trying to relate the number of frequency ranges and transducers to the overall performance of a loudspeaker, however, is difficult. A unit which splits the spectrum into two parts might, in fact, give better performance than a unit that splits the spectrum into five parts. Likewise, the number of speaker elements in an enclosure is little guarantee of overall performance. The frequency ranges and number of speaker elements are given so that you will have some idea of what is in a particular unit and the design concept of the manufacturer.


There may be as many as three types of components inside your speaker cabinet although sometimes functions are combined in two units or even one to save space and money. If you have three types of components in your system, you will most likely have a woofer to cover the low frequencies, a midrange unit to reproduce midrange frequencies, and a tweeter to take care of the high frequencies.

Most woofers are of the cone-type design. They usually reproduce the bass frequencies from 20 Hz up to 500 or 1,000 Hz, at which point the mid-range and/or tweeter takes over. Sometimes woofers are used along with a "drone cone" or passive bass radiatior to improve response. The drone cone is not electrically coupled to the amplifier or the other transducers, it simply vibrates in response to the woofer.

Midrange and tweeter

Midrange and tweeter units are usually of the cone, dome or horn design. The latter two generally offer better treble dispersion than cone units although they, too, perform satisfactorily if well designed. Many multi-driver speaker systems use a cone speaker for low-midrange reproduction and a dome or horn unitforthe higherfrequen-cies. Some also incorporate features to further improve dispersion, such as "diffusers" and "lenses."

Another type of transducer, particularly well-suited for higher frequencies, operates on the electrostatic principle, its sound generated by the motion of a very light diaphragm suspended in an electrostaticfield. In some instances relatively large electrostatic transducers are used as full-range speakers, reproducing the bass frequencies as well as the higher ones.

Hier ein Verweis auf die Wirkung des Gehäuses

Also influencing the dispersion characteristics of a speaker system is the design of the enclosure. The various approaches taken in recent years, with the aim of broadening the stereo (or quadraphonic) sound field, include positioning the tweeters and midrange drivers at various angles, reflecting part of the sound off nearby walls or mounting speakers on several sides of the enclosure.

The designer's objective is to permit all frequencies reproduced by the speaker system to be heard equally well regardless of the listener's position relative to the speaker. Those who favor this omnidirectional approach claim the sound more closely resembles that of live music, other feel instead that it results in an exaggerated sound, particularly when reproducing a soloistorsmall group. The best way for you to decide is to listen to several speaker systems of each type and draw your own conclusions.


There are many different types of enclosures, each with different advantages and drawbacks.

Sealed enclosures.

These units are completely enclosed with only the fronts of the speaker elements exposed. The idea is to prevent radiation from the rear of the elements from reaching the front side of the unit where it could interfere with the overall sound quality. In some cases this is called an "infinite baffle"
arrangement and absorbing material is placed in the cabinet to soak up the rear radiations.

Many "air-suspension" systems are not acoustic-suspension systems, as you may be led to believe, but simple sealed enclosures. A few of the current sealed enclosures are special in that they have a "terminated line" - a tube-like structure - behind the woofer in order to smooth out the low-end frequency response. In any case, sealed enclosures can offer excellent sound and are usually medium-efficiency systems requiring medium-size amplifiers.

Acoustic-suspension enclosures.

These systems are a type of sealed enclosure but they must have specially designed speaker elements to work. In principle, they utilize the air trapped inside the speaker cabinet to modify the characteristics of the speaker elements. They offer extremely clean bass response but are notoriously power hungry and inefficient. Plan on a large amplifier.

Bass-reflex enclosures.

Put a hole in an enclosure so that the bass frequencies from the back of the woofer can come out the front and reinforce the front radiations and you have a bass-reflex enclosure. Such a system has a fair amount of efficiency and can be driven with a smaller amplifier.

A number of refinements or variations of the basic bass-reflex principle are now available, including enclosures with special ports, ducts, drone cones and transmission lines. In each of these cases, the purpose is to give smoother frequency response by affecting the response of the bass speaker
elements. Modified bass-reflex systems will usually have reduced efficiency.

Tower enclosures are becoming increasingly popular of late, with many manufacturers producing a wide range of models. These tall, slim units take up relatively little floor space - an important consideration if you need a four speaker quad set-up - yet offer good sound. Here again, there are a number of designs, but most are based on the folded horn principle which allows a small speaker enclosure to efficiently reproduce the lower frequencies.


In our listings we've classified speakers as small, medium or large. If you share a room with three other people, you aren't likely to have room for a giant, floor-standing speaker system. On the other hand, if you live in a 30-room mansion, you'd probably not be interested in something tiny. Most speakers are medium-size and will perform satisfactorily in just about any room of reasonable size. If you have some very exacting requirements as to size, for example, if you want speakers that will fit onto existing bookshelves, then refer to the dimensions given at the bottom of the listings.

Virtually all the speakers in the listings that follow are speaker systems. That is, they consist of two or moreindividual speakers (sometimes called "drivers" or "transducers") housed in an enclosure of some sort. The listings also contain a few models that consist of two or more speaker enclosures (or systems) that are sold as a unit.

- Werbung Dezent -
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