Why do I need a speaker selector?
Why do I need a speaker selector when connecting multiple speakers?
If you want to connect several pairs of speakers to the same amplifier, you may need a speaker selector with impedance protection. It allows you to use multiple speaker pairs simultaneously without presenting the amplifier with too low an impedance.
This is particularly important if you want to play music in several rooms or connect two or more pairs of speakers to a normal stereo amplifier.
Can I connect two pairs of speakers directly to the amplifier’s A+B outputs?
It depends on the amplifier and the speakers’ impedance.
Many amplifiers have connections labelled Speaker A and Speaker B, but this does not automatically mean you can use two pairs of speakers simultaneously.
On many amplifiers, the speakers are connected in parallel when A+B is activated. This lowers the combined impedance and requires the amplifier to deliver more current.
If the amplifier is not designed for that load, it may overheat, activate its protection circuit or, in the worst case, be damaged.
What happens to impedance when I connect multiple speakers?
When two speakers with the same impedance are connected in parallel, the combined impedance is halved.
Speakers |
Combined nominal impedance |
|---|---|
Two 8-ohm speakers |
4 ohms |
Two 6-ohm speakers |
3 ohms |
Two 4-ohm speakers |
2 ohms |
It is important to remember that the speakers’ stated impedance is nominal. The actual impedance varies with frequency and may be considerably lower.
For example, a speaker rated at 8 ohms may drop to 3.7 ohms within a certain frequency range. If two identical speakers with the same impedance curve are connected in parallel, the load at that frequency may drop to around 1.85 ohms.
This can be a very demanding load for a normal stereo amplifier.
How does a speaker selector with impedance protection work?
A speaker selector lets you connect multiple speaker pairs to the same amplifier and choose which ones play.
Models with impedance protection, sometimes called impedance matching, are designed to limit how low the load impedance becomes when multiple speakers are used simultaneously.
This reduces the risk of overloading the amplifier.
However, not all speaker selectors have impedance protection. A basic selector may only switch between different speaker pairs without protecting the amplifier when several pairs are used simultaneously.
How do I connect a speaker selector?
In a typical installation, connect:
The amplifier’s Speaker A output to the speaker selector’s input.
Each speaker pair to a separate output on the speaker selector.
The speaker selector’s impedance protection according to the manufacturer’s instructions.
Check that the speaker selector is rated for the amplifier’s power and the number of connected speaker pairs.
Do I always need a speaker selector?
No. Some amplifiers are designed to drive multiple speaker pairs simultaneously and have clear specifications for this.
If the amplifier has A+B outputs, check the minimum speaker impedance the manufacturer permits when both outputs are used.
If you are unsure, a speaker selector with suitable impedance protection is often a good solution.
Can BRL help me choose the right speaker selector?
Yes! Tell us which amplifier you have, which speakers you use and how many speaker pairs you want to connect.
We can then help you check whether the amplifier can handle the load or whether you need a speaker selector with impedance protection.