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Soccer World Cup – Then and Now

June 10th, 2010 Posted in worth knowing Tags: , ,

It’s kick-off time for the 19th FIFA World Cup in South Africa. A lot has happened in the past 80 years of World Cup history: there were winners and losers, enthusiastic and disappointed fans, festivals of goals and goalless draws.

Do you remember the pictures of the 2006 World Cup in Germany? Waving flags in black-red-gold throughout the whole country. Millions of spectators watching the games on public viewing screens or in front of the TV at home cheer for the teams and celebrate the winners on the “Fan Miles” – for example in front of the Brandenburg Gate in Berlin. Over three million people watched the matches of the participating 32 nations live in the stadiums. But if you turn to the beginnings of FIFA World Cup, you’ll get a rather different picture: Only 13 nations entered the first tournament in Uruguay in 1930. Many European teams didn’t participate, due to the duration and cost of travel – South America wasn’t accessible by plane yet. Only Belgium, France, Yugoslavia and Romania made the long journey, crossing the Atlantic Ocean by ship within two or three weeks – of course, they also had training on deck.

In Uruguay, the teams were not welcomed by millions of fans: Only 300 followed the match between Romania and Peru, the lowest attendance in a World Cup game. Although there were 70,000 spectators at the Uruguay versus Argentina final, the popularity of the first competitions cannot be compared with today’s tournaments. An important milestone was the 1950 World Cup held in Brazil: The world’s biggest arena, the “Maracanã Stadium” with a capacity of 200,000 was built. For the first time, the million mark had been cracked – around 1.34 million fans watched the games live in the stadiums. With 170.000 spectators the match Uruguay versus Brazil holds the record for the highest attendance in World Cup history. Until then, the football experience had been reserved for the fans in the stadiums, because there was no television coverage yet. This changed in 1954 at the World Cup in Switzerland: for the first time the matches were broadcasted on television. Around 90 million people watched the tournament. They often watched together in bars, because only few households had their own TV – “Public Viewing” was born and has been growing ever since.

The latest World Cup has shown how football can move and enthuse the masses.

It will be interesting to see what the upcoming competition in South Africa will bring. This tournament will be the first FIFA World Cup to take place on the African continent. The preparation involved great efforts and costly investments in the infrastructure during the last years: with six new stadiums, the expansion of the international airports in Cape Town and Johannesburg as well as a new airport in Durban and numerous hotels, South Africa is prepared. Nevertheless, the country will have to face some challenges in the area of security, owing to the high crime rate. Fans, football teams as well as journalists are urged to consider special precautions. Yet one thing is certain: in June 2010, the football world will again turn its full attention to the World Cup, to South Africa.

Did you know…

…the first goal in World Cup history was scored by Lucien Laurent of France.

in the 1934 World Cup, both the Italian and German teams played in uniforms consisting of white jerseys and black shorts. As Italian fans protested, the German team had to change their dress.

…Hakan Sükür from Turkey holds the record for scoring the fastest ever World Cup goal in 11 seconds at the 2002 FIFA World Cup.

…in the 1974 World Cup in Germany, for the first time, the final did not take place in the host-country’s capital for the first time but at the Munich Olympic Stadium.

…in 1958 Pelé from Brazil became the youngest player to play in a World Cup final match at 17 years.

…Roger Milla from Cameroon is the oldest player to have scored a goal in the World Cup at the age of 42 (1994).

…the 1994 World Cup in the United States holds the record for the highest attendance in World Cup history with over 3.5 million spectators.

…with 15 goals, Brazilian Ronaldo is the most successful World Cup scorer, followed by Gerd Müller from Germany with 14 goals and Just Fontaine from France with 13 goals.

The stadiums of the World Cup 2010

Moses Mabhida stadium in Durban
Capacity: 69.957
Built: 2009

Street View


Soccer City in Johannesburg
Capacity: 94.700
Built: 1987

Street View


Free-State stadium in Bloemfontein
Capacity: 37.160
Built: 1952

Street View

Mbombela stadium in Nelspruit

Capacity: 43.589

Built: 2009

Street View


Royal Bafokeng stadium in Rustenburg
Capacity: 44.530
Built: 1999

Street View

Ellis Park stadium in Johannesburg
Capacity: 61.639
Built: 1982

Street View

Green Point stadium in Kapstadt
Capacity: 66.005
Built: 2009

Street View

Nelson Mandela Bay stadium in Port Elizabeth
Capacity: 46.082
Built: 2009

Street View

Peter Mokaba stadium in Polokwane
Capacity: 45.264
Built: 2010

Street View

Loftus Versfeld-stadium in Pretoria
Capacity: 49.365
Built: 1906

Street View


A class of its Own – PA Amplifiers

April 19th, 2010 Posted in worth knowing Tags: , , , , , ,

In the following basic article we would like to discuss the distinctive criteria of PA amplifiers. An important factor of modern power amplifiers is not least the weight. In the past, power amplifiers were often reviewed according to the factor watt per kilogram. In times of line arrays and other actively separated speaker systems even in the semi-professional sector, attributes like handiness and compactness became more and more important for power amplifiers. Now, frequently terms like “class H” or “class D” and “switch-mode power supply” can be read in article descriptions, which often are confusing or have no informative value for outsiders. We have prepared a short introduction for you in order to change that as fast as possible.

Power Supply Unit

As a main component of the power supply unit, conventional power amplifiers possess a large toroidal transformer which converts the 230 V power tension into several low tensions. These are necessary to supply power to the individual components such as pre-amplifier and power amplifier of a PA amplifier. As the transistors of the power amplifier blocks require direct current, large rectifiers and several electrolytic capacitors are located behind the toroidal transformer for grading. A conventional power supply unit sometimes takes up more than half the volume and mass of an amplifier. The advantage of this technique is that it is fairly simple, inexpensive and stable during operation. Moreover the technique is known for its pulse strength in terms of the amplification of low frequencies. And although there are amplifiers weighing 30 to 35 kilograms they have their right to exist. The press-praised* Omnitronic B-3600, which draws its maximum output power of 3,600 watts from a mass of 32 kilograms, can serve as an example.

Switch-mode power supply units (abbr. SNT or SMPS) work far more efficiently than their conventional counterparts and are much smaller in size. Optically, they almost cannot be distinguished from a power amplifier block but they only account for a third of an amplifier’s mass and volume. Switch-mode power supply units make use of the advantage that a significantly smaller transformer can be used with higher transmission frequencies. With a mains frequency of 50 hertz, for example, you would need a 25-kilogram copper transformer for transforming 4,000 watts whereas with a frequency of 125 kilohertz a 500-gram transformer would do. The disadvantage of SMPS is the occurring signal interference which must be filtered out and only gradually made the technique affordable.

With the sophisticated SMA series, Omnitronic offers inexpensive PA amplifiers with SMPS technology, which are both convincing by their cost/performance ratio and their outstanding performance/weight ratio. The top model SMA-2000 is rated at 2,000 watts power, yet weighs a mere 9 kilograms. In comparison: The popular Omnitronic P-2000 weighed more than twice as much and was rated at the same power.

Switch Concepts

Class A

The technically easiest method to amplify a signal electronically is to use a class A amplifier. Here an active component (transistor or electronic tube) takes over both the positive and negative half-wave of the incoming alternating current signal. The advantages of this technique are the extremely simple structure and the superb sound. However, as the active component must be constantly kept in the center of the linear part of its characteristic line, class A amplifiers require a very high standby current and thus have a very bad degree of efficiency, which ideally is at 50 percent but often is even less than 25 percent. For the high output power that the modern PA technique is calling for, class A amplifiers are certainly out of the question. However, they have earned themselves a permanent place for applications which demand lower output power. Hi-fi aficionados, for example, use them in their home stereo systems. In the professional stage sector class A circuits rather than anywhere else can be found as pre-amplifiers in premium mixing consoles and external channel strips. Today, almost every guitar amplifier is still equipped with a class A amplifier as an output power over 200 watts is rarely needed.

Class B

Far more efficient than class A amplifiers are class B amplifiers with a theoretical efficiency of almost 80 percent. Here two separate active components each take up a half-wave of the incoming alternating current signal. During each half-wave the other components are switched off which cuts the high standby current. The disadvantage of the circuit is, however, that during the transition of positive to negative half-wave of the amplified signal a distinct transfer distortion is can be heard, which renders the use of class B amplifiers impossible in the professional audio sector. Class B is used in the radio technique but even there has become almost completely displaced by the even more effective class C (with up to 90 percent degree of efficiency).

Class AB

Class AB combines the major advantages of class A and B, i.e. the professionally usable sound quality with a high degree of efficiency, which is still acceptable even at high output. For this class AB also uses separate components for both half-waves. Yet contrary to class B they are not constantly turned on and off but are steadily supplied with mains power. Thus far less distortion takes place in the transmission area of the alternating current signal. The degree of efficiency still is substantially higher than with class A and usually is at 40 to 60 percent. Most audio amplifiers available on the market work according this basic principle.

With the P series, Omnitronic offered a successful AB power amplifier for years. In mid 2009 this popular series was replaced by the new E series, which features pretty much the same circuitry, is available with power ratings ranging between 200 and 1,300 watts, and is particularly designed for beginners. The smaller models of the lines SMA (including the SMA-1000) and B (through B-1300) also operate with class AB circuits.

Class G/H

A further development from class AB to even more efficient power amplifiers are circuits with graded supply voltage. While the basic structure corresponds to class AB power amplifiers, here the transistors are not supplied with a fixed tension but with varying tensions depending on the momentarily required output power. For this grading the degree of efficiency can be increased compared to a class AB power amplifier (in the ideal case up to 85 percent) without a loss in sound quality. The classification is not standardized which is the reason why class G can mean both, graded and steady supply voltage.

With Omnitronic class H stands for graded supply voltage. The most important amplifiers of this class are the top models of the lines SMA (SMA-1500 and SMA-2000) and the press-praised* B-2000 and B-3600.

Class D

Class D amplifiers, which are colloquially called “digital amps”, are different from all concepts mentioned so far as they do not directly process the waveform of the signal which is to be amplified but rather a “digitized” version of the signal. The input signal is scanned with a frequency far above the audio range and thus is converted to a square wave via pulse-width modulation (PMW). As these amplifiers only have the condition on or off they are also known as switching amplifiers. With class D amplifiers an efficiency of more than 90 percent can be achieved which is why they are getting more and more popular in the professional PA sector. First examples of this class had to fight with audible distortions particularly in the high frequency range. But these problems were eliminated by further development in the past few years. Due to the high efficiency very compact modules can also be implemented in active speaker boxes.

Class D amplifiers can be found in Omnitronic’s new, very compact EDP series rated at 300 to 1,000 watts output power while requiring only one rack unit, and in the upgraded versions of the active systems AS-900 and AS-1500.

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*tools4music issue 5&6.2009
figures: Wikipedia

Line array in theory & practice – part II

February 17th, 2010 Posted in PSSO, worth knowing Tags: , ,

11040900gThis second part of our line array series deals with the physical aspects of such sound systems. Quite a complex subject yet we have tried to give you a comprehensible access.

The basic problem of every sound reinforcement system for large venues is the fact that an individual speaker cabinet cannot supply the complete audience with the required sound pressure level. Even if the audible transmission range between 20 Hz and 20 kHz is separated into five or more different speaker sizes, the necessary characteristics required for audiences with thousands or even a hundred thousands of people cannot be produced – even with the latest technology.

Furthermore, destructive interference occurs even when using only two speakers at once. Interference occurs when sound waves from two different sources overlap and lead to undesired amplification or elimination of parts of the frequency range. The aim of every sound reinforcement system is to minimize destructive interference and to provide the desired signal level at every position in the audience are.

For reaching this aim, speaker clusters were used for a long period of time where several technically identical speaker systems are horizontally and vertically grouped together. Due to sophisticated cabinet constructions and the use of horns in front of the individual drivers, the efficiency, i.e. the realistic electric power converted into sound pressure level, could be increased while reducing the interference areas within the crossover areas between the individual speaker systems to an acceptable level and thus getting closer to a physically ideal point source.

The sound pressure level is reduced by 6 dB for every doubling of the distance from the speaker system, although this only applies to ball waves, i.e. undirected sound sources. Especially in closed rooms, a point is very fast reached where the diffuse sound, i.e. the sound reflecting from the walls and ceiling, reaches the same level as the direct sound from the speaker system. From this point on, the destructive interference is so strong that the acoustic performance can only be recognized in a strongly falsified manner. This distance is referred to as critical distance. One solution is applying delay lines where the transmitted signal is “refreshed” before the critical distance, thus enabling a large or longer audience area at large venues. Nevertheless, the delay speakers must reproduce the signal with a delay as the speed difference between acoustic and electric signal transmission is already audible from only 20 meters away. This is where the name “delay line” comes from.

Another disadvantage of this procedure is the significant sound level loss even among the first meters of the audience area. According to the already cited formula, the sound pressure level at eight meters distance is only one eighth of the level in one meter distance from the speaker system clusters. Often, this problem was solved by more volume which is not only a health hazard in the stage area, but may also have a negative effect on the sound quality and sound level on the stage and which can no longer be recommended with today’s emission guidelines.

linearray1Line arrays are the next logical step in this chain of cause and consequence. With line arrays, it is possible to minimize the basic problems of conventional cluster systems. With line arrays, it is possible to minimize interference between the vertically aligned speaker systems by a vertical dispersion of less than 15°, to increase the coverage and to keep the sound pressure level constant for the maximum number of people in the audience by curving the system, i.e. setting the individual components at a specified inclination angle. Furthermore, line arrays can realize a larger horizontal dispersion angle than horn systems.

In order to realize this, some physical problems need to be solved. While the vertical alignment of several low speakers or mid speakers is easy and already applied in the column speakers as described above, more problems occur with higher frequencies. Thus it is not possible to realize the necessary, very low distance between high speakers via standard horn speakers or cone speakers. This distance between the speakers and the number of signal sources in vertical alignment and the curving angle is very important for the acoustic aim of the line array technology: the production of a coherent wave front.

In order to reach this aim nevertheless, so-called wave guides are used. They enlarge the output of the individual sound source which makes a very low distance between several vertically aligned sound sources possible. Additionally, these wave guides modify the delays of the sound waves in the transmission area of the hi speaker in a way that building a coherent wave front is possible.

With an ideal line array, a sound pressure level loss of only 3 dB for doubling the distance could be realized, in reality and depending on the system and the number of elements used, this value lies somewhere between the ideal 3 dB and the 6 dB of a cluster system. Thus using delay lines is still necessary especially for larger venues, but within a higher distance to the main PA. The reason is the improved directivity of the systems in comparison to conventional horn speakers.

linearray2Introducing line arrays led to a reduction of individual speakers up to one quarter which provided additional resources for lighting and video technology. With the introduction of the DMX protocol in 1990, it was especially the concurrent digitization of the lighting technology that considerably benefited from the smaller and lighter sound reinforcement systems.

IP Code – what does IP stand for?

August 13th, 2009 Posted in worth knowing Tags: ,

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What does the IP in several product names stand for? A question many may ask, especially while flipping through our outdoor illumination chapter. To put it simple: The digits show how suitable spots and the like are for outdoor use – it is about the device being protected from water. Now more detailed information:

IP stands for International Protection, sometimes also named Ingress Protection. This is the degree of protection which provides information about the use of electrical equipment under various environmental conditions – in our case this means the protection from dust and water. Additionally, it comprises the hazard protection for persons during use. Read more »