I have 6 pair of in-ceiling speakers mounted throughout my house. each pair of speakers is on a separate circuit of an ADC speaker selector switch which is connected to a 200w per channel Yamaha receiver. All are 6 or 8 inch JBL speakers. I want to add one more pair of speakers in the ceiling of the outside gazebo. The easiest way is to run wires from the existing covered patio speakers about 20 meters to the gazebo ceiling. If I do this each circuit will have one pair of speakers on it, except the outside circuit which will have 2 pair. The question is, should the new speakers be installed in series or in parallel with the existing speakers? There is no separate volume control on each circuit, so ideally, the circuit with 4 speakers should not be significantly louder or quieter than the other circuits. I do not run all of the curcuits at the same time, but often the living room and patio speakers are on at the same time. I know that mounting them in series will increase (double) the impedence and mounting them in parallel will half it. They are 8 Ohm speakers, so in series the circuit will have 16 Ohms and in parallel the circuit will have 4 Ohms, which is nice to know, but I am not sure what difference it makes in relation to the sound and the volume. Both are within the recommenced range of impedence, 2 to 16 Ohms.

I just finished the installation of the new pair of speakers. Information on the internet said that the volume would not be different as between in parallel or in series installation, which does not suggest that it would not be different in either case from a circuit with only 2 speakers rather than 4. Serveral writers did say that the sound of the speakers would be different when installed in series from speakers installed in parallel. Several writers said that they preferred the sound of speakers in series. Another said that in parallel installation is a bit safer. Many writers said that the biggest factor is using adequate sized wire so as not to add to the impedence. I used 10 AWG wire for a 10 meter run, which is I think more than adequate. I tested both in series and in parallel installations after I had the wires in and the holes cut. I could hear no noticeable difference in the sound quality or volume between in series and in parallel installation. I decided to install the speakes in parallel, but I had no strong reason for doing so other than I had to make a choice and the ladder was getting uncomfortable. The new speakes sound good and not significantly less volume than the speakers on other circuits, so I am satisfied with the choices all around.

As long as your amp is rated for/can handle the 4 ohm load, parallel is the way to go.