Poor impedance matching between your amplifier and speakers can cause several problems, including excessive clipping or speaker and amplifier damage. It can also negatively affect the quality of the sound you get.
So, should you be worried if you are running a 4 ohm amplifier with 8 ohm speakers?
Yes, you can use 8 ohm speakers (2 in parallel) with a 4 ohm amplifier. This will not cause clipping, not damage your speakers or amp, but will result in less power output for each speaker and possibly less distortion. Just wire two 8 ohm speakers of the same wattage in parallel. However, wiring more than two 8 ohm speakers in parallel risks damaging the amp.
Please note that reversing this mismatch (4ohm speakers with 8 ohm amp) is a major issue as it will cause excessive heat build-up in the amp’s output, increased distortion, and likely amp damage.
Read on to learn more.
What is Impedance and Why Does it Matter?
To answer the above question on whether you should be worried or not correctly, we need to understand what constitutes impedance.
For every amp and speaker you buy, you will find the impedance indicated in ohms (Ω), and you need to understand the significance of the figure to minimize the risk of damage. For example, you need to understand the difference between 4 ohm and 8 ohms speakers.
What Is Impedance and Impedance Matching?
Impedance refers to the degree of resistance of a circuit or an electronic component in a circuit to electrical current. So, a higher ohm implies the circuit offers more significant opposition to the flow of electric power.
Impedance matching refers to matching the impedance of the amp with the overall impedance of the speakers connected. For maximum wattage or transfer of power to the speakers, the speaker’s resistance must be equal to the amplifier resistance.
Speaker Impedance and Amp Damage
Higher impedance opposing current flow can be good news if your audio system requires little current to function when the circuit impedes the free flow of charge.
On the other hand, if you ignore the basic rules of impedance matching, you may supply inadequate current to your speakers. However, the speakers will still demand the current they require. This can blow out the entire system.
This means that lower speaker impedance will put a heavy load on the amp because the low impedance speakers will demand a lot of power from the amp.
Another essential thing to note is that the indicated ohm is a nominal value, which means the rating is an average of the possible minimum impedance.
We can say that the resistance to the flow of current varies depending on the speaker’s frequencies at different moments. For example, an 8-ohms speaker might operate as a 10-ohms device at one some stage along the frequency spectrum. At other moments, it can be 7 ohms or even 11 ohms.
The best solution to this issue is to use a speaker designed to meet your impedance needs.
Speaker Wiring (Series and Parallel) and Impedance
Wiring also affects speaker impedance. Wiring speakers in series adds up the overall impedance.
On the other hand, wiring speakers in parallel decreases the impedance. For example, wiring two speakers in parallel halves the impedance.
To find the resulting impedance of speakers wired in parallel, simply divide the impedance by the number of speakers in parallel. For example, if you have two 8 ohm speakers in parallel, 8 divided by 2 = 4 ohms.
Can I Hook Up 8-ohm Speakers To A 4-ohm Amplifier?
Yes, a 4 ohm amp can handle 8 ohm speakers once it is a single 8 ohm speaker or the overall impedance of multiple 8 ohm speakers is 4 ohms or more.
If you have multiple 8 ohm speakers, you need to determine what the overall impedance is. While some people manage to wire multiple 8 ohm speakers to equal 8 ohms, in most cases, the overall impedance will be more than 8 ohms if the speakers are connected in series and less than 8 ohms if the speakers are connected in parallel. Some people wire two 8 ohm speaker to equal 4 ohms and so on.
The impedance of your amplifier and the impedance of your speakers are two different things. However, on whether we can use an amp and speakers safely, we need to consider the amount of load that the speakers put on the amp.
Low Amplifier Impedance
Let’s say the amp has a lower impedance than the speakers. This means the amplifier can supply more current than the speakers require.
Given that modern speakers can manage a high supply of power, nothing will likely happen if you run the amp to the speakers. You will get good quality sound.
High Amplifier Impedance
However, that would not be the case if the amp had higher impedance than the speakers.
Remember, we said that the assigned impedance is a nominal value. So, the amp’s ohm can significantly increase.
The same applies to the speakers. Impedance changes as the frequencies increases and drops.
Given that the difference between 4 ohm and 8 ohm is small, you do not need to worry about their maximum sound pressure level (SPL). The chances are that your speaker can cope with the supplied power.
However, since 8 ohm doesn’t fall within the amp’s impedance range, you should exercise caution. Keep the volume low.
In this case, improper impedance can damage the speaker coil or blow the amp, particularly if you fail to control the frequencies. This reminds us why impedance matching is important. Despite the low risk, you need to do the due diligence and not damage the speakers and amp.
What Happens if You Use 8 Ohm Speakers On a 4 Ohm Receiver?
If you use 8-ohm speakers on 4-ohm receivers, you’ll get high-quality audio. The receiver will supply more power than the speaker requires. Since modern speakers are designed to handle excessive power supply, nothing harmful will happen.
However, if you use 4-ohm speakers on an 8-ohm receiver, your receiver might fail to supply adequate power, leading to sound quality issues. In some cases, the shortage of power can damage your speakers and the receiver.
What Amplifier Do I Need For 8 Ohm Speakers?
Speakers with a nominal impedance of 8 ohms and a program power rating of 350 watts require a receiver or amp that produces 700 watts into an 8-ohm load. So, the amp should be rated 700 watts per channel into an impedance of 8 ohms.
Can I Use the Impedance Switch to Match the Impedance?
If your amp features an impedance switch, you may want to use it to adjust the ohm settings to match the eight ohms-speakers. Many manufactures recommend it. Nonetheless, it is not the best solution.
As we have said, impedance is not static. It keeps changing depending on the speakers’ frequency. If you use the switch, you limit the amp’s ability to assign the most suitable impedance.
For example, when the actual impedance needs to be 6 ohms, you will likely switch it to 8 ohms or something closer to that. To learn more, check out this guide on 6 ohm vs 8 ohm speakers. This way, you intentionally cripple the amplifier’s capacity.
The above point is another reason you should not tamper with the speakers’ impedance rating if you want the best performance. Instead, buy amps that match the system’s impedance settings.
Does Impedance Matching Guarantee the Best Experience?
We have seen that you can get excellent quality if you match impedance. Nonetheless, it doesn’t guarantee you the best experience.
Opting for low or high impedance speakers may not serve your needs, especially if you do not understand speaker sensitivity, which many beginners often ignore.
Speaker sensitivity refers to the ability or efficiency of the loudspeaker to convert the amp power to acoustic energy. For that matter, it determines how loud your loudspeaker will be for a specific amp power.
While some people think that speaker sensitivity is a complex concept, but that is not true. Generally, independent consultants and manufacturers will often measure speaker sensitivity. Nonetheless, you can do it.
The primary way to measure it is to use a calibrated sound level meter. To be consistent, you should measure sensitivity 1 meter from the loudspeaker while one watt of power originates from the amp.
Whenever looking for speaker specifications, pay attention to something that looks like this: Sensitivity: 87dB (1w/1m). It shows the loudness level that the speaker can produce when you drive it with 1 watt of power and measure the performance one meter in front.
When comparing sensitivity, remember that different speaker designers and manufacturers may arrive at the figures differently. So, it is best to compare speakers from specific brands differently. You may also need to read the user manuals to determine what makes the speakers’ sensitivity unique.
Overall, speaker sensitivity will help you to know:
- How loud your loudspeaker can be
- The efficiency of the amp that you need
Speaker sensitivity doesn’t determine the quality or lack of quality of your devices. It also doesn’t determine the sound quality, but you must consider it if you are concerned about your speakers’ loudness.
Matching Amplifier to Speakers Wattage
As an unspoken rule of thumb, you should choose an amplifier that can produce double the continuous power rating of a speaker.
This means that a speaker having an 8 ohm “nominal impedance” and a 350-watt program rating will need a 700-watt amplifier to drive this 8-ohm load.
Sometimes, it is even advisable to use an amp that supplies 2 to 4 times the speaker’s continuous power rating per channel.
This leaves 3 to 6 dB of headroom for audio signal peaks. Short-term peaks can be handled by speakers in most designs. The goal is to have enough clean power so the amp can take whatever you throw at it without clipping.
However, if you are limited in terms of budget for availability of powerful amplifiers, you can use an amplifier close to the power resting of the speakers, but ensure that you do not max out the volume. Keep the volume low.
When running a 4-ohm amp to 8-ohm speakers, you should be just fine if you keep the overall impedance of the speakers at least 4 ohms.
However, you should opt for a speaker with the desired sensitivity and match the impedance for the best performance.