If you have a surround sound home theater system, you may be considering running 4 ohm and 8 ohm speakers together. For example, you may want to run 4 ohm speakers at the front, center and sides with 8 ohm speakers at the rear. Is this a good idea? In this article, we will answer the question – can I run 4 ohm and 8 ohm speakers together?
So, can can I run 4 ohm and 8 ohm speakers together? Yes you can run 4 ohm and 8 ohm speakers together as long as the AV receiver or amplifier is 4 ohm capable, you run the speakers in series, not parallel and don’t use both A/B speakers.
Here are the scenarios quickly:
If you wire the speakers in series: Then the amp or receiver will see a 12 ohm load and that would be OK.
If you wire the speakers in parallel: Then the amp will see a load of 2.67 ohm which is a very low impedance and can damage the amp or receiver.
If you use the A/B terminals on the back of the receivers: Then the amp will see a load of 2.67 ohms because the A/B terminals are wired in parallel. Again this is a very low impedance that can damage the receiver.
4 Ohm vs 8 Ohm Speakers
Before we talk about 4 ohms vs 8 ohms speakers, what are ohms anyway? Ohms is a measure of electrical resistance and is related to ohms law.
Ohms law describes the relationship between voltage, current, and resistance. This is described in a mathematical equation:
I (current) = V (voltage) / R (resistance)
According to ohms law, the value of the resistance of a conductor is a ratio of the potential difference or voltage between the ends of the conductor to the amount of current passing through it.
Now a 4 ohms resistance is much lower than 8 ohms. Because just like water only flows to the direction it finds it easier to, electrical current prefers to flow through conductors with lower electrical resistance.
As a result, if two speakers of 4 ohms and 8 ohms are wired to two different current sources of the same value, more current will flow through the 4 ohms speaker while less current will flow through the 8 ohms one.
This means that much more power is required to drive speaker systems with lower ohms ratings because they pull more current. In other words, a 4 ohm speaker will pull more current than a 8 ohm speaker.
This is because the smaller impedance allows more current to flow through it easier. It therefore means that a 4 ohms speaker requires more power to operate compared to a 8 ohms speaker.
Connecting the 8-ohm speaker with a 4-ohm speaker to the same stereo will therefore alter the load line depending on how they are connected. If the overall impedance is too low, this can become dangerous and increases the chances of you blowing up the system.
How To Wire 4 Ohms Speaker And 8 Ohm Speaker Together
You can still wire the two speakers with different impedance ratings together without harming your amplifier.
Before we look at the steps, take note that there are two modes in which the two speakers can be connected:
1. Series Connection
In this mode of connection, the total impedance level increases because the speakers are connected end to end.
In general, if you have two speakers with impedance levels less than 8 ohms, it is best to wire them in series because this will create a total impedance level great enough to not overpower the amp.
For this scenario, connecting the two speakers will yield a total impedance of 12 ohms, since the formula for total impedance in any series connection of resistors is simply the sum of the two resistors.
The 12-ohm total impedance is in the range of 6 – 16 ohms within which most amplifiers work best. Therefore, performing a series connection for the two speakers on a single amplifier will not be harmful.
Wiring The Speakers In Series
Wiring speakers in series is an easy process as you can see in the illustration above. In any case, follow the procedure below.
Join the positive polarity of the amplifier to the positive terminal of the 4-ohm speaker. Then, join the negative polarity of the amplifier to the negative terminal of the 8-ohm speaker. Once this is done, the remaining two opposite polarities from the speaker cables are conjoined together.
2. Parallel Connection
Parallel connection is the other mode of connection that can be used to have your 4 ohms speaker and 8 ohms speaker connected together.
When connected in parallel, the total impedance reduces. For parallel connections, multiply the two resistors and divide by the sum of the two resistors.
In this case:
(8 * 4) / (8 + 4) = 2.667 ohm
So, when connected in parallel, the 4ohm speaker and the 8-ohm speaker will produce an effective total load of 2.667 ohms, which is very low.
This mode of connection is preferred for speakers which have an impedance value of more than 8 ohms. This is because they yield a total impedance greater than 4 ohms.
For this reason, most hi-fi systems are designed to have a total impedance of 4 ohms or higher. And, the quality of the sound is well maintained at its maximum level.
Therefore, based on the speakers onboard (4 ohm and 8-ohm speaker), this type of connection is not the best to consider. This is because the total impedance will go way below 4 ohms.
Wiring The Speakers In Parallel
If for whatever reason you still proceed with the wiring design of the two speakers in parallel even though the speakers are incompatible in this connection mode, check the steps below:
Because we only have one amplifier for the two speakers, we will connect the amps outputs directly top the speakers. There are two polarities a + sign and the other a – sign.
- Case 1 (both speaker cables are connected directly to the amplifier ports)
Your amplifier has two wires emerging from the two ports, two positives and two negatives. One of the positive wires is connected to the positive polarity of the speaker port and the other positive wire to the next positive port of the next speaker. The same is replicated to the negative ports.
- Case 2 (joining cables of the second speaker to the first speaker/ looping mode)
A single positive and negative speaker cable are connected to the amplifier then directly looped from the first speaker polarities to the next speaker, positive for positive and negative for negative.
- Case 3 (joining the cables from both speakers to the cable from the amplifier/ cable division)
Single paired cable from the amplifier is conjoined to the cables from the two speakers with their polarities well considered
Can I Run 4-Ohm And 8-Ohm Speakers On A/B Terminals?
It’s a good idea to get a receiver or amplifier that has A and B capability. For example, you can use the Bs to play music in a different room. It is generally easier to do that than say using zone 2 connections.
You can generally use the speaker pair A + B to run speaker pairs together. However, it is generally recommended that both speakers have a minimum impedance of 8 ohms or higher.
Well, the channels are parallel.
Since the channels are parallel in nature, wiring a 4-ohm speaker and an 8-ohm speaker to the A/B terminal contributes a total of 2.67-ohm load. This is too low for the receiver to handle and will most likely blow the amp.
It is therefore not recommended that the speakers be wired to the A/B terminals.
Yes, running the two types of speakers with different impedance ratings is possible. However, the connection should be done in series. This is to safeguard the amplifier or receiver from blowing as a result of parallel connectivity.