A guide to series and parallel wiring for speaker systems.
A guide to typical types of series and parallel wiring types for speaker systems. Plus 70/100V line wiring for PA systems.
There are a few different ways to wire up speakers depending on your chosen application. This article discusses three types of wiring for low impedance type speakers (series, parallel and series-parallel), typically 4-8 Ohm speakers. These circuits essentially allow you to present the amplifier with a suitable load for the speakers to be powered. Without the correct total impedance of the circuit, the speakers can cause damage to the amplifier, so it is always important to consider the total impedance of a given speaker circuit. Many consumer amplifiers will become unstable or excessively hot when driving circuits lower than 4 Ohms, some will go as low as 2 Ohms. So it is important to check your amplifier specification when designing a speaker circuit for it to power.
Also covered below are the basics of 70/100V line speaker circuits. These speakers feature their own power transformer on the rear of the speaker allowing many speakers to be connected together in a string and connected to a single amplifier. These are commonly found in commercial audio systems where many speakers are to be distributed throughout a building.
Series Wiring
Speakers in series double the nominal speaker impedance, ie. two 8 Ohm speakers become 16 Ohm. The diagram below shows how series wiring is connected:
Parallel Wiring
Speakers in parallel halve the nominal speaker impedance, ie. two 8 Ohm speakers become 4 Ohm. The diagram below shows how parallel wiring is connected:
Series-Parallel Wiring
Speakers wired in series parallel are used to maintain the same impedance as a single driver. ie four 8 Ohm speakers wired in this configuration represents an 8 Ohm load to the amplifier. This arrangement substantially increases the total SPL of the system compared to one single driver. The diagram below shows how series-parallel wiring is connected:
70V/100V Line Speaker Circuits
Wiring speakers in parallel for 100V line: Where several speakers are to be used at one time, on one circuit, it becomes necessary to use speakers fitted with line-matching transformers. This is to overcome the effects of connecting speakers in parallel and cable losses. The amplifier generally has an output voltage of 100 Volts. In this configuration the total Wattage load on the amplifier is derived from adding all the line transformer primary tap ratings together. For example, 70 one Watt speakers will have a total speaker load of 70 Watts. Or alternatively, it is conceivable to connect 100 one Watt speakers to a 100 Watt, 100 Volt line amplifier. The diagram below shows how a typical 100V line circuit is connected:
Measuring 100V Line Speaker Impedance
To measure amplifier system load, you must use an impedance meter in order to measure the AC resistance of the connected speaker network. Impedance cannot be measured with a standard multimeter, as this measures the DC resistance. Use the Q 2004 impedance meter or similar.