Are the speakers sensitive to polarity?

In the following, we answer frequently asked questions, you will find out everything you need to know about lighting and sound technology, and in the glossary you will find explanations of industry-specific terms.

Why does a sound system hum sometimes and what can I do about it?
What are the differences between speaker and microphone cables?
Why is correct polarity of speakers important?
What does PAR 64 mean?
Why do some white objects not glow under UV light ("black light")?
Why is fog used in conjunction with light?
What is fog fluid made of?
What does DMX-512 mean?
What does phantom power / phantom power mean?
What does cardioid microphone mean?
What is a DI box?
Power connections and services
What do "daylight" and "artificial light" mean?
What is a delay line and what do you need it for?
Why aren't 1000 watts twice as loud as 500 watts?
What is parametric tone control?
What is a “dichroic filter”?
How is ground fog generated?
What does RMS, sine, nominal, music power mean?

Why does a sound system hum sometimes and what can I do about it?

If it is a low-frequency, saturated hum, the reason is usually a so-called “hum” or “earth loop”.
This occurs when two devices are connected to ground via two different points. The classic case: a lighting control desk is connected to the sound mixer on the same power line, i.e. the same phase. A control cable leads from the lighting desk through the hall to the dimmer, which is located on the stage and is connected to another phase of the power supply. One mass is the protective conductor (“earth”) of the power supply, the other mass is the result of the connection of the control cable between the lighting console and the dimmer. The potential differences that occur here are noticeable in the loudspeaker as "mains hum".
To rectify this, one of the two ground connections must be avoided; either by connecting the lighting desk together with the dimmer to a phase, i.e. a common power supply, or by disconnecting the ground connection of the control cable by means of a ground lift adapter.
On the other hand, masking the protective earth in the socket is prohibited and DANGEROUS TO LIFE!

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What are the differences between speaker and microphone cables?

A fundamental difference between loudspeaker and microphone cables is the lack of shielding on the loudspeaker cable. For this reason, speaker cables cannot be used as microphone cables.
Another difference is the number and thickness of the wires and their assignment on the connector.
Loudspeaker cable has 2 wires (plus phase & minus phase) which are connected to pin 1 (-) and pin 2 (+) on an XLR connector. Pin 3 remains unused.
Microphone cables have 3 wires (2 x conductors + 1 x shield), which are assigned to the following pins on the XLR connector: pin 1 (shield), pin 2 (+), pin 3 (-).
From this it follows that microphone cables can be "misused" as speaker cables, but this should be avoided because of the insufficient conductor cross-section and the associated loss of performance. In addition, the cable heats up and becomes unusable in the medium term.

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Why is the correct polarity of speakers important?

Although the signals to the loudspeaker are alternating voltage, the polarity must be observed: both loudspeakers must move synchronously with a mono signal, otherwise the membrane and thus the air movements cancel each other out. The result is a cancellation of low frequencies and a distorted impression of the room without a stereo sound image.

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What does PAR 64 mean?


PAR stands for the parabolic shape of the reflector.
The following number indicates the diameter of the light exit in inches.
A PAR 64 spotlight has a diameter of 64/8 = 8 inches (20.32 cm),
a PAR 56 on the other hand 56/8 = 7 inches (17.78cm).

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Why do some white objects not glow under UV light ("black light")?
Not all white materials "glow" with UV light, only those that contain fluorine or phosphorus compounds, e.g. teeth, light-colored clothing (if appropriate materials are available), some types of paper, etc.

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Why is fog used in conjunction with light?
There are two main reasons for using fog machines and hazers: on the one hand, as scenic fog (mostly in theaters, TV), on the other hand, to make light and laser beams visible as lighting effects in the room

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What is fog fluid made of?
The fluids mainly consist of distilled water and propylene glycol, which is approved as a food additive in the EU (E 1520). There are also special mist systems that work with anhydrous oils. Composition and chemicals used vary from manufacturer to manufacturer. Specially coordinated fog fluids provide a choice of light, hazy or long-lasting fog.

Fluids should be accompanied by a TÜV certificate / clearance certificate and DIN safety data sheet or the purity of the ingredients according to DAB (German Pharmacopoeia) and / or USP (United States Pharma) should be guaranteed. Fog fluids are completely water-dilutable, biodegradable and non-flammable.

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What does DMX-512 mean?
DMX-512 (Digital MultipleX) is a standardized, digital transmission method for control signals. Up to 512 control channels, so-called addresses, are available that control appropriately equipped dimmers, switch packs or lighting effects.

In contrast to analog control cables in which each control channel is assigned a separate wire in the cable, only a 2-wire, shielded cable is required for DMX-512, which is connected through from one DMX device to the other. Each device can now be configured in such a way that it taps off certain required control signals (-> addresses). In this way, complex systems can also be implemented with little cable expenditure.

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What does phantom power / phantom power mean?
In sound technology, phantom power is a special type of power supply that supplies condenser microphones or active DI boxes with the required DC voltage (usually 9-48 volts) via the microphone cable. A supply voltage of 48 V ± 4 V is widely used in practice.

Almost all microphone mixing consoles now have (switchable) phantom power.

Phantom power means that the + voltage in the XLR cable is applied to pins 2 and 3 with the same potential, i.e. no voltage can be measured in between and therefore the microphone capsule cannot be dangerous. Therefore dynamic microphones can also be connected without danger, provided they are connected symmetrically.
The voltage can only be measured opposite pin 1, but this also means that a symmetrically wired cable must be used.

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What does cardioid microphone mean?)
The terms cardioid, hypercardioid, omnidirectional, figure eight and lobe denote the directional effect of a microphone, i.e. the angle at which a microphone picks up the strength of the sound.

The required directional characteristic can vary depending on the intended use.
In the following (simplified) some types:

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What is a DI box?)
DI (Direct Injection) boxes are required when a signal source with an asymmetrical output (usually coming from a jack or cinch connector) is to be connected to a device with a symmetrical input (usually an XLR connector).

Typical examples of asymmetrical signal sources are electric guitars,
Keyboards and other electric instruments or compact disc players; Common balanced inputs are found on mixers or audio interfaces. The symmetrical signal routing enables an effective reduction of interfering signals, especially with long cable lengths. The ground connection can also be separated, for example to interrupt hum loops. In addition, DI boxes can adapt the impedances and levels of signal sources to those of the subsequent inputs. In practice, DI boxes are often fed into the signal path via a multicore.

A distinction is made between passive and active DI boxes. The former achieve balancing solely through a broadband low-frequency transformer, the latter contain active amplifier electronics. The power supply then required is provided by batteries or phantom power.

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Power connections and services
The following table shows the power connections commonly used in event technology and their distribution options.

The two most common connectors of the connector system are colloquially referred to as CEE three-phase plug connectors, CEE plug devices or CEKON:
1.) the red so-called CEE 5-pole three-phase connection, often incorrectly called high-voltage connection, which carries the neutral conductor (N), the protective conductor (earth = PE) and the 3 phases (L1, L2, L3). 3-phase alternating current connections can be found e.g. on dimmers or switch packs whose total output exceeds 3.5 KW and for which a normal 230 volt / 16 ampere connection is no longer sufficient. 3-phase CEE can be switched to normal Schuko-

(= Earthing contact) sockets.

2.) the blue CEE 3-pin connector with only one phase, neutral and protective conductor for a voltage of 230V, which is sometimes used in power amplifier racks or ACL headlights as well as in camping areas.
CEE-5-pole 3 × 125 amps / 400 volts -> total output max.approx .: 86.6 kW
CEE-5-pole 3 × 63 amps / 400 volts -> total output max.approx .: 43.6 kW
CEE-5-pole 3 × 32 amps / 400 volts -> total output max.approx .: 22.1 kW
CEE-5-pole 3 × 16 amps / 400 volts -> total output max.approx .: 11.0 kW
CEE-3-pole 1 × 16 amps / 230 volts -> total output max.approx .: 3.5 kW
Schuko-3-pole 1 × 16 amps / 230 volts -> total output max. Approx .: 3.5 kW

Sub-distribution options for 3-phase CEE connections:
1 x 125 A = 2 x 63 A or 4 x 32 A or 8 x 16 A

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What do "daylight" and "artificial light" mean?
The terms "daylight" and "artificial light" refer to the color temperature of the light source. This is measured in Kelvin and provides information about the color spectrum emitted. For example, sunlight has a color temperature of 5,000 to 15,000 Kelvin, depending on the time of day and cloud cover. "Daylight lamps" (HQI, HMI, HTI ...) are in the range up to 7,000 Kelvin and are therefore closer to "real" daylight than the "artificial light lamps" (Tungsten) with the usual 3,200 Kelvin. Due to the different color spectrum, daylight appears bluish to white, while artificial light appears yellowish.

Daylight is used, among other things, for neutral object lighting (shop windows, trade fairs) or for film + TV (outdoor shots to avoid creating a mixed light between sunlight and artificial light).

Artificial light is used wherever softer colors are to be achieved.

Special correction filters can also be used to change the color temperature (blue or red filters) in order to convert a daylight lamp to artificial light or vice versa.

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What is a delay line and what do you need it for?
A delay line is used in the sound system to adjust the transit times of the sound. In contrast to light, sound is quite slow, namely just 331.5 m / s at 0 ° C or 343 m / s at 20 ° C in air.

If loudspeakers are at different distances from a listener, the sound needs different (running) times to get there.

There are echoes; the sound becomes indirect. The result is a certain amount of confusion as the human brain places the sound source where the sound comes from first (direct sound). Although delays in the millisecond range are involved, the use of a line delay brings clear advantages for speech intelligibility and music from a distance of approx. 10 m. However, the prerequisite for the calculation of sensible delay times is that the sound reinforcement is directed (e.g. stage -> audience).

Special line delays, in which the distance can usually be entered in meters, or high-quality multi-effects devices that have a corresponding delay program are suitable as delay devices. The delay is set here according to the rule of thumb 3.4ms per meter.

A fine adjustment should still be made by ear, as the temperature influences the speed of sound.

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Why aren't 1000 watts twice as loud as 500 watts?
The term watt is a quantity that relates to an output or required power. In sound engineering, it usually refers to amplifier performance or (loudspeaker) load capacities. However, a watt specification says very little about volume levels.

For example, in order to achieve an increase in volume that is just noticeable to a listener, an amplifier that previously "played" with 100 watts must already deliver twice the power - 200 watts. A doubling of the volume, subjectively perceived by the listener, on the other hand, requires ten times the power from the same amplifier, i.e. 1000 watts. The required power in relation to the volume does not increase linearly.

In practice this means: Whether an amplifier has 500 watts or 600 watts of power is not nearly as important as the quality of the loudspeaker that is operated on it. High-quality loudspeakers are very "economical" and therefore another value is much more important in connection with power and volume: the so-called sensitivity or "sensitivity", which is specified for loudspeakers in dB / watt / 1m.

A speaker A, the z. B. has a sensitivity of 102 dB is with the same amplifier power
twice as loud as a loudspeaker B with 96 dB, or in other words: loudspeaker B only reaches the same volume as loudspeaker A with ten times the amplifier output

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What is parametric tone control?
The usual mixing consoles for disco applications, as well as some live mixing consoles, mostly have a 2 or 3-band tone control in the individual channels; One controller each for bass, middle and treble. These controllers can be used to generate a change in a frequency range previously specified by the manufacturer, namely a lowering or raising of the specific frequency.

This type of tone control is usually sufficient for disco consoles, as "canned music" is mostly used here. However, in order to equalize a (vocal) microphone in live sound reinforcement, for example, and if necessary to filter unwanted feedback or characteristics of the voice, a (semi-) parametric tone control is necessary: ​​here there are the parameters frequency (f) and gain (g ) with the semi-parametric or the filter quality (Q-factor) with the fully parametric tone control. A controller determines the frequency to be processed and the gain controller determines whether this frequency should be increased or decreased. With the Q-factor it is finally determined to what extent neighboring frequencies should be raised or lowered with the setting.

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What is a “dichroic filter”?
The simplest and cheapest way to color light is to use commercially available filter foils made of special plastic, which are placed in front of the headlights using a filter frame. However, these foils have the disadvantage that a lot of (light) power is lost, especially with darker colors, and the filters quickly “burn through”.

A “dichroic” (dichroic) color filter, on the other hand, consists of a special glass that refracts the light like a prism and only lets through certain color components. The result is intense, rich colors - even with dark tones. The disadvantage of dichroic filters is the high price (PAR-64 dichro approx. 45 EUR) and compared to plastic filters they are easily breakable. This is why dichroic filters are mostly only used in scanners, moving lights or projectors.

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How is ground fog generated?
In principle, fog must be heavier than air or colder than the ambient air in order to remain close to the ground.

There are various alternatives to this:

1. Dry ice
Dry ice has the disadvantage that the ice can only be stored for a short time and its productivity is low. 10 kilograms of dry ice are only enough for about 5 minutes of fogging time.
In addition, the evaporation creates carbon dioxide, which can be a problem in closed rooms.

2. nitrogen
Nitrogen mist machines are very expensive and need liquid nitrogen in the form of pressure bottles to operate (costly procurement / transport).

3. Conventional chemical mist is cooled down considerably after it has been generated and thus sinks to the ground. Conventional evaporator fog machines can be used, which can be turned into "ground fog machines" by means of an air conditioning attachment.However, since the fog lasts longer, part of the fog will rise again after it has been warmed up and the effect is therefore not as spectacular as with dry ice or nitrogen fog.

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What does RMS, sine, nominal, music power mean?
RMS power: The specification of a power in watts (RMS) is the official, international and only meaningful statement. RMS stands for Root Mean Square and is a complex measuring method that records the power over the entire relevant frequency range by means of pink noise. Compared to white noise, pink noise has a level drop of 3 dB / octave upwards, which ensures that the energy content of the signal is constant at any frequency.

Continuous sine tone power: This measuring method is out of date and can only be used on power amplifiers. Loudspeakers would easily be destroyed when measuring the maximum load capacity with sine tones. Because of the great popularity of the term "sine continuous tone power" it is still used occasionally. The values ​​are close to those that result from the RMS method.

Nominal power: the term actually comes from heavy current engineering. In connection with power amplifiers, it corresponds roughly to the RMS output. However, it is not certain that the standardized measuring method was used.

Music performance (also often referred to as "maximum performance"): This is an outdated measurement method, which is based on the idea that music does not have a constant level and therefore the performance of a system can be significantly higher than after measuring with sine tones . The actual background, however, is likely to be the advertising effectiveness of the values ​​that are about twice as high compared to the sine continuous tone performance.

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