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Best Practices in Wiring Classroom Audio Systems

 

Wiring speakers to an amplifier completes the audio system and allows the audio to be distributed to students. Careful consideration should be taken when selecting speakers and when wiring the speakers to the amplifier. Improper wiring of a system can result in damage to the equipment or, in the worst case, become a potential fire hazard. Proper wiring provides the best performance from the entire audio system. Speakers should be wired to match the resistance level supported by the amplifier. To match the resistance value of the wired speakers to amplifier, the total resistance of the speakers must be calculated. The following formulas can be used to determine the total resistance of speakers, based on the wiring scheme used.

 

Wiring in Series

 

When wiring speakers in series, the speakers will be "daisy-chained". The positive terminal of the amplifier will be connected to the positive terminal of the first speaker. The negative terminal will be connected to the positive terminal of the second speaker. This pattern will be repeated until reaching the last speaker. The negative terminal of the last speaker will be connected to the negative terminal on the amplifier. If the speakers are wired in a series, then the total resistance is the sum of the resistance value of each speaker wired in series.

 

RTotal = R1 + R2 + … + Rn

 

If two 8Ω speakers are wired in series, then the total resistance of the system would be 16Ω.

 

RTotal = 8Ω + 8Ω RTotal = 16Ω

 

If four 4Ω speakers are wired in series, then the total resistance of the system would be 16Ω.

 

RTotal = 4Ω + 4Ω + 4Ω+ 4Ω RTotal = 16Ω

 

If the resulting resistance is higher than what the amplifier is designed to support, then the system may underperform, and the equipment will eventually be damaged.

 

 

Wiring in Parallel

 

Parallel wiring indicates that the positive and negative terminals of the amplifier will be connected to the positive and negative terminals on the first speaker. The positive and negative terminals of the second speaker will be connected to the positive and negative terminals of the first speaker. This pattern will be repeated until the last speaker is connected. If the speakers are wired in parallel, then the total resistance is reciprocal of the sum of the reciprocals of the resistance value of each speaker wired in parallel.

 

1/RTotal = 1/R1 + 1/R2 + … + 1/Rn

 

If two 8Ω speakers are wired in parallel, then the total resistance of the system would be 4Ω.

 

1/RTotal = 1/8Ω + 1/8Ω
1/RTotal = 0.25
RTotal = 4Ω

 

If four 16Ω speakers are wired in parallel, then the total resistance of the system would be 4Ω.

 

1/RTotal = 1/16Ω + 1/16Ω + 1/16Ω + 1/16Ω
1/RTotal = 0.25
RTotal = 4Ω

 

If the resulting resistance is lower than what the amplifier is designed to support, then the equipment will eventually be damaged, and it is possible that a fire may result.

 

 

It is very important that these wiring schemes are used to match the resistance of the speaker configuration to the resistance of the amplifier that will be supporting the system. Depending upon the design of the system and the number of speakers used, there may be situations where it is required that both wiring schemes be used. Matching the resistance will ensure that the equipment performs to its maximum potential and will help avoid damage to the equipment.

 

​​​​​​​This white paper is for informational purposes only and is subject to change without notice. C2G makes no guarantees, either expressed or implied, concerning the accuracy, completeness or reliability of the information found in this document.