Yamaha MA2120 MA2120 Setup Guide - Page 18
High-Impedance and Low-Impedance Connections, Multiple Speaker System Drive Capability
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Appendix High-Impedance and Low-Impedance Connections For a high-impedance connection, a speaker transformer that raises the impedance to several hundred or thousand ohms is added to the speaker system. This allows the speaker system to be effectively driven with much lower current than is required for a low-impedance connection. Therefore, a large number of speaker systems can be connected. Even over long distances, there is very little transmission loss due to the cable resistance being negligible in relation to the impedance of the speaker system. High-impedance speaker connections usually operate at a specific maximum power amplifier voltage of 100 or 70 volts. The more orthodox low-impedance connection does not use a speaker transformer. The speaker systems are directly connected to the power amplifier with a rated impedance generally around 4 - 16 ohms. For short distances over which cable resistance is insignificant, low-impedance connections deliver a sound quality that is superior to high-impedance connections. The differences between connection methods are explained as follows. Multiple Speaker System Drive Capability High-Impedance Connections As long as the total nominal power input rating for all speakers is within the power output capability of the amplifier, any number of speaker systems can be connected in parallel. The power input rating is determined by the speaker systems and speaker transformers used. It is also possible to connect speaker systems that have different input power ratings. In the case of speaker systems that are capable of changing their input power rating (Yamaha VXC and VXS series, etc.), this can be utilized to vary the volume of each speaker. 70V/100V Speaker transformer 10W 10W 10W 10W 10W Low-Impedance Connections When connecting multiple low-impedance speaker systems to a single channel, the following methods are possible. Parallel Connection When multiple speaker systems having the same impedance are connected in parallel, the total impedance becomes the individual speaker system impedance divided by the number of systems connected. 4Ω Cannot be connected 8Ω 8Ω 8Ω Total impedance = 4Ω Serial Connection When connected in series, the total impedance is simply the sum of the impedances of the speaker systems connected. However, if one speaker system happens to fail, the electrical signal will not be passed on and subsequent speaker systems will be affected. Interruption 4Ω Failure 4Ω No sound Total impedance = 8Ω 18 MA2120 Setup Guide