Loudspeaker Loops – Keep It Usable

You probably know how to connect a speaker: Simply connect one two-wire cable from the amplifier to the speaker – done.

This is similar with industrial PA/GA systems, however, the approach is quite different here when considering the premise Safety and Reliability.

Cable break – What next?

What happens if the cable from the amplifier cabinet to the speaker lines breaks? The cable could probably be more than 1000 meters long for 100-V speaker systems. If speakers are only connected to just one cable, they may completely fail in the worst case, depending on the location of the failure. The main reasons for cable breaks are wear effects, cable works, or simply carelessness.

If speaker monitoring is available, the failure can be detected and a message is displayed. The failure can be indicated as break, short circuit, ground fault or as general impedance failure.

If cables are laid underground (burried cables), troubleshooting can sometimes be difficult and expensive. During this time, speaker zones may not be addressed and also warnings, alarms, and other information cannot be broadcasted via the PA/GA system, for example.

People are in danger – time is running out!

Here comes the solution!

You can improve the reliability of speaker wiring using the so-called loop wiring of speakers which is required for almost all offshore PA/GA systems today and will probably become the accepted standard in the near future.

Speaker loop wiring provides a second cable which is connected from the amplifier outputs to the speaker lines.

This way, several disadvantages of a single cable can be eliminated:

  • The second cable route is laid separately from the first one to prevent that both cables will be damaged by a single incident.
  • Feeding the speakers from both sides due to the parallel connection has the effect that the cable cross-section doubles and thus also the possible cable length.
  • An interruption of the speaker line, no matter where, will not cause a failure.

CAUTION!

Keep in mind that the speaker loop wiring cannot prevent the following: A short circuit will still lead to a failure of the corresponding speaker line.

16 thoughts to “Loudspeaker Loops – Keep It Usable

  • Beth Walther

    Georg,

    A well written article – very informative

    Reply
  • Beth Walther

    Georg,

    A well written article – very informative

    Reply
  • Mukesh Shah

    Information about the speaker loop monitoring and its concept is very useful. We hope that increasingly it will become a norm to monitor the speaker loops for the safety of people in the plants and to improve the reliability of the system as a whole.

    Reply
  • Mukesh Shah

    Information about the speaker loop monitoring and its concept is very useful. We hope that increasingly it will become a norm to monitor the speaker loops for the safety of people in the plants and to improve the reliability of the system as a whole.

    Reply
  • Bob van Haren

    Loop wiring is already a must in many countrys.
    Also, in case of same wattage for every speaker, you can simply measure where the interruption is by means of impedance measuring. Always liked that. All technicians are awaiting for a reliable speaker isolator, but disadvantage is .that you can’t measure your speaker line as mentioned in above.

    Reply
    • Georg Merkert

      Dear Bob,

      first a ‘Thank You’ for your kind reply and welcome to our INDUSTRONIC Blog.

      You are right with your comment that loop wiring is becoming a standard in countries all over the world.

      We also do the speaker surveillance with an impedance measurement, but you must also
      consider that this kind of measurement has some restrictions.

      I agree with you that it is possible to detect the rough location of a cable break with the impedance
      measuring method, but it is not common with many manufacturers.

      The most reliable method to supervise your speaker network is the use
      of a ‘Multi Function Single Speaker Surveillance System’ (MFS4).

      With this kind of monitoring system you’ll get:
      – Single Speaker Monitoring with exact position and kind of malfunctions
      – Remote Tapping
      – Isolation of defective speakers from network
      – etc.

      …but this is part of another story…

      Many Greetings
      Georg Merkert

      Reply
  • Bob van Haren

    Loop wiring is already a must in many countrys.
    Also, in case of same wattage for every speaker, you can simply measure where the interruption is by means of impedance measuring. Always liked that. All technicians are awaiting for a reliable speaker isolator, but disadvantage is .that you can’t measure your speaker line as mentioned in above.

    Reply
    • Georg Merkert

      Dear Bob,

      first a ‘Thank You’ for your kind reply and welcome to our INDUSTRONIC Blog.

      You are right with your comment that loop wiring is becoming a standard in countries all over the world.

      We also do the speaker surveillance with an impedance measurement, but you must also
      consider that this kind of measurement has some restrictions.

      I agree with you that it is possible to detect the rough location of a cable break with the impedance
      measuring method, but it is not common with many manufacturers.

      The most reliable method to supervise your speaker network is the use
      of a ‘Multi Function Single Speaker Surveillance System’ (MFS4).

      With this kind of monitoring system you’ll get:
      – Single Speaker Monitoring with exact position and kind of malfunctions
      – Remote Tapping
      – Isolation of defective speakers from network
      – etc.

      …but this is part of another story…

      Many Greetings
      Georg Merkert

      Reply
  • Rene Gamurot

    Yes, It is true about that. I have also some inquiries regarding the loop testing while the amplifier and central exchange cabinets are not yet power up. I know that Industronics cabinets are equipped with 6LME devices to monitor and determined its characteristic impedances, and if there are some breakage on the speaker loops and cable. But what if it is not yet power up and I need to consider the speaker loops, I have different types of speakers installed on the entire plant and with different watts and impedance. What should I do to determined that my connection and equipment are in proper termination and connected. Theoretically I know there is a value of the speaker impedance and also the cable as per length resistance of it. Is there any way to determine the continuity of the loop while the systems are not yet powered up. Kindly advised… Thanks…

    Reply
    • Carina Knörzer

      Dear Rene,

      thank you for your comment and the questions.

      Testing of loudspeaker loops without having the PA/GA system powered up can be done by impedance measurement. Therefore, you need an impedance meter to detect impedances between 30 ohms (333 Watts) and 10.000 ohms (1 Watt).

      First, you have to measure the loop from one side and write down the impedance value. After that, please measure from the other side of the loop. The result of both measurements should be approximately the same value. A deviation of about 10 % can be normal dependent on the position of the speakers in the loop.

      To avoid ground leakage it is advisable to measure the impedance with respect to protective ground (PG). The value with respect to ground should be higher than 20 kilo ohms.

      If you need further information or help please contact our Technical Support Center (tsc@industronic.com)

      Kind regards,
      The INDUSTRONIC-Team

      Reply
  • Rene Gamurot

    Yes, It is true about that. I have also some inquiries regarding the loop testing while the amplifier and central exchange cabinets are not yet power up. I know that Industronics cabinets are equipped with 6LME devices to monitor and determined its characteristic impedances, and if there are some breakage on the speaker loops and cable. But what if it is not yet power up and I need to consider the speaker loops, I have different types of speakers installed on the entire plant and with different watts and impedance. What should I do to determined that my connection and equipment are in proper termination and connected. Theoretically I know there is a value of the speaker impedance and also the cable as per length resistance of it. Is there any way to determine the continuity of the loop while the systems are not yet powered up. Kindly advised… Thanks…

    Reply
    • Carina Knörzer

      Dear Rene,

      thank you for your comment and the questions.

      Testing of loudspeaker loops without having the PA/GA system powered up can be done by impedance measurement. Therefore, you need an impedance meter to detect impedances between 30 ohms (333 Watts) and 10.000 ohms (1 Watt).

      First, you have to measure the loop from one side and write down the impedance value. After that, please measure from the other side of the loop. The result of both measurements should be approximately the same value. A deviation of about 10 % can be normal dependent on the position of the speakers in the loop.

      To avoid ground leakage it is advisable to measure the impedance with respect to protective ground (PG). The value with respect to ground should be higher than 20 kilo ohms.

      If you need further information or help please contact our Technical Support Center (tsc@industronic.com)

      Kind regards,
      The INDUSTRONIC-Team

      Reply
  • Abejide Taiwo

    My Loop indicate loop fault and End of line fault, I have check the cabling, no breakage nor partial contacts. Yet the fault remains
    Pls help me

    Reply
    • Carina Knörzer

      Thank you for reading our blog and for your comment.

      For a detailed support we would need more information regarding the loop arrangement. However, we can give you the following tips:

      An indication of a loop fault could be due to a ground leakage fault which has no effect on the function of the speaker loop. In case of a single line break fault all loudspeakers should also still be working. Another possibility is that the fuse of the end of line unit might be blown. If so, you have to check the end of line unit for some defective components.

      If you need further advise please get in contact with our technical support centre via tsc@industronic.de

      Kind regards,
      The INDUSTRONIC Team

      Reply
  • Abejide Taiwo

    My Loop indicate loop fault and End of line fault, I have check the cabling, no breakage nor partial contacts. Yet the fault remains
    Pls help me

    Reply
    • Carina Knörzer

      Thank you for reading our blog and for your comment.

      For a detailed support we would need more information regarding the loop arrangement. However, we can give you the following tips:

      An indication of a loop fault could be due to a ground leakage fault which has no effect on the function of the speaker loop. In case of a single line break fault all loudspeakers should also still be working. Another possibility is that the fuse of the end of line unit might be blown. If so, you have to check the end of line unit for some defective components.

      If you need further advise please get in contact with our technical support centre via tsc@industronic.de

      Kind regards,
      The INDUSTRONIC Team

      Reply

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