Multi-Zone Audio Systems are similar to most stereo systems. They need a pre-amplifier and a power amplifier to process the audio.
The pre-amps stage can be divided into three parts:
1. An input selector – for selecting the component you wish to listen to
2. A pre-amplifier to adjust volume
3. An equalizer to provide tone controls (from bass to treble)
When wiring speakers to the amplifier, two ways are available to wire multiple speaker pairs that are dedicated to one zone. They are “parallel” or “series”.
When you plan to place your speakers throughout your home, the best wiring strategy should be to wire the speaker pair in “parallel”. If a speaker is damaged, the remaining speakers would still continue to function.
On another note, if you wired your speakers in “series”, a damaged speaker would interrupt the signal path and thereby cause other speakers on that line to stop playing.
Most stereo amplifier is stable between 8 Ohms and 4 Ohms. This stability range is also known as the amplifier's impedance level. “Impedance” refers to the resistance in which the amplifier can bear.
Most speakers have an impedance of 8 Ohms, 6 Ohms, or 4 Ohms. If your amplifier is stable to an impedance level of 4 Ohms, you could connect one pair of 4 Ohms speakers to it or two pairs of 8 Ohms speaker in parallel.
As speakers are added to parallel wiring schemes, the impedance on the amplifier drops. The more speakers connected, the lower the impedance.
If the speaker's impedance load is below that of the power amplifiers, the amplifier will suffer damage over time.
1/(Total Impedance) = 1/(Speaker 1's Ohm) + 1/(Speaker 2's Ohm) +…+ 1/(Speaker's r's Ohm)
an example below:
1/(6 Ohms) + 1/(6 Ohms) = 1/6 + 1/6 = 2/6 = 1/3 (3 Ohms is the total impedance)