Understanding distributed speaker systems – geoff the grey geek kite electricity generation


Distributed speaker systems are also known as “100 volt line” or “70 volt line” speaker systems. They are used extensively where multiple speakers are required. Distributed speaker systems are commonly used in airports, shopping centers, schools, churches, clubs, offices, car-parks, sports grounds and anywhere multiple speakers are required. They can also be used in homes for background music systems. gas and supply Advantages of Distributed Speaker Systems

The basis of distributed speaker systems is similar to the way electricity is distributed. Power stations use step up transformers to distribute power as high voltage, which means low current, and therefore low line losses and thinner cables. Each town and/or street then converts this high voltage/low current down to low voltage/high current (through step down transformers) for use in your home.

Distributed speaker systems use a similar principle. The amplifier normally has a step-up transformer built into it, producing a high voltage/low current output. Then each speaker has its own step down transformer to convert the signal back to low voltage/high current. This allows the cable to be very long without having any significant line losses. 100 Volt Line Speaker System

The most common “high” voltage used in distributed speaker systems is 100 Volts. In many countries distributed speaker systems are known as “100 Volt line” speaker system. In a 100 Volt line speaker system the output of the amplifier is marked “100 volt”. Indeed at full output, the amplifier puts out 100 volts RMS. Each speaker then has a transformer to reduce the 100 volt line level down to normal speaker level. 70 Volt Line Speaker System

In North America the most common “high” voltage for distributed speaker systems is 70 Volts. e85 gas stations in iowa This is because years ago, some states had laws stating that any cable with a maximum voltage greater than 100 Volts peak had to be installed in conduit. This was time consuming and costly to install. So they developed a system where the output voltage of the amplifier was a maximum of 100 Volts peak. This equates to 70.71 Volts RMS. This is commonly known as a “70 Volt line” speaker system. The principle is the same as for 100 volt line systems, but uses a maximum output voltage of 70 Volts. While 70 volt line systems are still the most common in the USA, some 100 volt lines systems are being used. 50 Volt Line and 25 Volt Line Speaker Systems

In practice, many commercial amplifiers have multiple outlets. They may have 100 and 70 Volts, or 70 and 25 Volts, as well as 4 ohm and 8 ohm outputs for normal speakers (without transformers). Normally you should only use one output of a amplifier, that is, either the 100 volt line output, or the 70 volt line output or the 8 ohm output, not all at the same time. static electricity jokes Transformers

Most transformers have a selection of input taps. The example in this picture has taps for 20 Watts, 15 Watts, 10 Watts and 5 Watts. The feed cable is connected to the common and any one of the other taps. This allows the relative volume of the speaker to be set during the installation. For example the speaker in a high noise room might be set on 20 Watts, while the speaker in a small, low noise area might be set on 5 watts.

All amplifiers designed for use with distributed speakers systems have a step-up transformer built-in. It is also possible to add an external transformer to an amplifier without an integrated transformer. Simply use a speaker transformer in reverse – that is, connect the common and 8 ohm transformer connection to the common and 8 ohm speaker output of the amplifier. Just make sure the amplifier and transformer are rated with enough power to drive all the speakers to be connected (see Connecting Multiple Speakers below). Speakers

Ceiling speakers are used in many distributed speaker system installations to cover large areas and/or multiple small rooms or areas. The speaker cable is normally connected directly to the transformer. To change the power settings you need to connect the speaker cable to a different transformer tap. In the speaker pictured, this is a simple matter of moving the speaker wire to a different terminal connector. Cabinet Speakers (Speaker Boxes)

Speaker boxes come in all sorts of shapes and sizes. gas 10 ethanol Many manufactures make a version of their cabinets with an integrated transformer. Connections are often by some form of speaker terminals. To change taps, simply rotate the switch to the desired power setting. Often these switches also have a position for 8 ohms (bypassing the transformer) – this makes them very versatile speakers for the installer. Speaker boxes are used where ceiling speakers aren’t practical, or where higher sound levels are required.

Horn speakers are very efficient, but not very good quality. They are mostly used outdoors when coverage of a large, or high noise, area is required. For example in car parks, sports grounds, school yards and other outdoor areas. electricity in indian villages In the picture shown, the rear of the horn has a selector switch which needs a flat bladed screw-driver to operate. This is useful to reduce the likelihood of inadvertent changing of the settings after the install. Connecting Multiple Speakers

• It is good practice to design distributed speaker systems to use up to only 80% of the amplifier’s total available power. For example, a 120 Watt PA amplifier should only be connected to a maximum of around 100 Watts of speakers. This helps avoid the amplifier’s transformer distorting from saturation (overload), allows for inefficiencies in the system, and allows an extra speaker to be added if required in the future.

• When designing distributed speaker systems, calculate the total watts of the speakers, and select an amplifier larger than required. For example, If an install requires 10 speakers at 5 Watts each (total load of 50 Watts), a 60 Watt amplifier could be used, but selecting a 100 Watt or 120 Watt amplifier will allow speaker taps to be changed or extra speakers added in the future. It is a relative small increase in price to up-size the amplifier before purchase, rather than have to buy a new one later.

• When selecting speakers, chose a higher power one than required. For example: If a 5 Watt ceiling speaker is required, chose a 10 Watt or 15 Watt speaker and use the 5 Watt tap on the transformer. This again reduces the likelihood of overloading cheaper transformers, and gives the ability to increase the power level (volume) if required.

• When connecting many speakers, it is good to have multiple feed cables. For example; if connecting 60 speakers, it is possible to use one speaker cable run and loop in and out of each speaker. gas south However it is better to have several feed cables to smaller groups of speakers. This way if a fault occurs, it is easier to isolate which feed the fault in on.

• Don’t connect a 4 ohm or 8 ohm speaker directly to a 100 volt line or 70 volt line speaker cable. Apart from severely overloading the speaker (and possibly burning it out) a 4-8 ohm speaker effectively puts a short circuit on the speaker line and overloads the amplifier. See the calculations below for the mathematical explanation of this.

Distributed speaker systems are ideal for multiple speaker installations. a gas station They allow long speaker cables and calculation of the total load is easy. Distributed speaker systems are normally mono (not stereo). They are mostly used for paging and background music situations. Although normally used for commercial installations, they can be used in domestic installations for background music systems

In the examples above we saw the speaker impedance of distributed speaker systems is reasonably high. For example a 5 watt speaker on a 100 Volt line has an impedance of 2,000 ohms. Even a 125 Watt load of 100 Volt speakers is 80 ohms. So imagine the load if the total impedance is only 8 ohms. It should be 10 times the load right? This scenario can be calculated: