100 V speakers: For decades indispensable for Public Address

That is why 100V line technique is so interesting for planners and electricians


A resourceful electrician designed the 100V line technique decades ago to transmit sound over long distances. The term 'PA technology', i.e. technology to operate a Public Address system, and the term '100V line technique' are mostly used synonymously. Today we apply this technology in schools, supermarkets and for voice alarms. We briefly outlined in which aspects the 100V line technique is so efficient and attractive. Although they have heard of 100V line technique, many craftspeople forget about it because they work with the technology so infrequently. In our opinion that is a shame, since the 100V line technique solves many problems and makes things easier.

These are the advantages of 100V line technique: a quick overview

  • Smaller cable diameters and therefore higher economic efficiency of the system
  • Simple cabling due to parallel connection
  • Higher cable lengths are possible than with low-impedance systems
  • Significantly lower voltage losses on cables compared to low-impedance systems

 


What is 100 V line technique and which problem does it solve?

DIY stores, hotels, big offices and department stores all have one thing in common: they are extensive and therefore require many speakers. For a system with one or more amplifiers and many speakers, though, you would need a high intensity of current. However, this means thick cables with cabling distances as short as possible. Laying cables like these requires great effort and expense, a problem solved by the 100V line technique.

In the 100V line technique, a transformer used to be integrated between PA amplifier and 100 V speaker. Today, this transformer is already built into the PA amplifier. It raises the output voltage of the amplifier to 100 V. An additional transformer, which transforms the 100 V current to a level suited for the speaker, precedes the speaker or is built into it. Due to the high voltage, audio signals can be transmitted via thin cables for hundreds of metres without great losses.

The 100 V (PA) line technique is the solution for long cabling distances and many speakers

100 V line technique provides the option to add speakers as needed at a later date by connecting them to the cable, which is already laid. Thus, you are able to 'clip' speaker after speaker to the connection. The result is a simple parallel connection in which you only have to take the total power capability of the amplifier into account.


100V line technique prevents cable chaos and complicated calculations

Raison d'être and another great advantage of the 100V line technique is the following:

No more impedance problems.

You can simply connect the speakers in parallel and if you keep in mind the total power capability of the PA amplifier you do not run the risk to overload the device by too low load impedance. Without 100 V line technique you would always have to consider the connected speaker impedances to avoid an operating status dangerous to the amplifier. For planners it is very convenient to be able to ignore such calculations sometimes. You do not have to be an expert to distribute 100 V speakers throughout a room.

Another advantage is the easy laying of cables. There is only one cable with 2 cores which leads into the ceiling and to which all speakers are connected. No more cables that split at some point or run along walls or skirting boards. You only have to take into account the maximum output power of the respective PA amplifier. Yet that will also be easy if you do not have to calculate resistances thanks to the 100V line technique. How many watts are required for the speakers? The simple answer is, you have to add up the power ratings of all speakers and that's it. 10 speakers with 20 W? The amplifier should provide at least 200 W. Another example: 2 column speakers with 20 W + 10 ceiling speakers with 3 W = 70 W. Mind you, you should leave a buffer of 10-20 percent, i.e. you should always allow for a power reserve.


100V line technique does not influence sound quality, but the myth prevails

One part of the myth is that systems with 100 V line technique transmit mainly mono sound, i.e. the merged stereo signal from the left and right channel. Far too frequently we have heard that stereo sound equals good sound. However, stereo sound is only good under certain conditions, namely if the listening position in relation to the speakers is exactly right and as constant as possible. For optimum sound, the listener has to be at the same distance from both stereo speakers. This is almost never the case with PA applications. Mono sound from speakers contains the same audio data as stereo sound from 2 stereo speakers. The audio channels are simply merged. Contrary to widespread belief, there is no loss of sound.


Tip: higher reliability with loop line

If the cabling is implemented only with line A, a disruption at point U leads to the failure of speaker 2 to 4. The solution is a loop line. You simply route the line from the last speaker back to the amplifier and connect it with the right polarity to the output line. This prevents speaker failure at the event of a single line fault.

Tip: higher reliability with loop line

If the cabling is implemented only with line A, a disruption at point U leads to the failure of speaker 2 to 4. The solution is a loop line. You simply route the line from the last speaker back to the amplifier and connect it with the right polarity to the output line. This prevents speaker failure at the event of a single line fault.

You do not specialise in PA projects but would like to get into this field? Your Project is Our Project. Therefore we compiled basic knowledge on planning ceiling speaker systems and PA systems for you.

Image source Headergrafic: Deyan Georgiev – stock.adobe.com

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