Sound System Tips: Speaker Wiring, Power, and Impedance
Power Sharing and Speaker Configuration
When building a sound system, one of the most crucial yet often overlooked aspects is the wiring of speakers. The nuances of speaker wiring can have a significant impact on the sound quality and performance of your set.
In a reggae sound system setup, there are typically multiple speakers wired together within a given frequency range. This can relate to multiple drivers within a single box enclosure, or multiple boxes wired together, or a combination of both.
We’ll take the bass bins as an example: a typical mono sound system will have between two and eight bass bins wired together. A single (mono) cable will run from the sub/bass amp to the first bin and that will be “daisy chained” to the next and next, etc.
The way that the drivers within a box are wired together and the way that multiple boxes are wired together is extremely important. Properly wiring multiple speakers can be a little trickier than one might imagine.
Reviewing the Basics
A proper reggae sound system should have deep bass and crystal-clear tops. To achieve this, it's vital to understand how speakers share power from an amplifier and how different wiring configurations can impact power distribution.
This article will cover speaker power, amplifier power, speaker impedance, and the various wiring configurations, including series, parallel, and series-parallel setups.
Understanding Speaker Ratings
There are a number of speaker specifications that are critical to speaker wiring. These aren’t all of the specs that a speaker manufacturer will provide, but relative to wiring, these are the most critical.
RMS Power
RMS power is the most important and practical measure of a speaker's or amplifier's continuous power handling capability. It represents the amount of continuous power that a speaker can handle without distortion or damage. It's essentially the average power they can handle during normal usage.
Peak Power
This is the maximum power that a speaker can handle in short bursts. It is generally much higher than the RMS power. However, it is not a reliable measure for continuous performance as it doesn’t represent sustained power handling or output.
Program Power
Program power (sometimes called Music Power) is often used to describe speakers, and it represents the power they can handle with real-world music signals. It's typically about twice the RMS rating. It accounts for the fact that music is dynamic and has peaks that are higher than the average level.
Sensitivity
Though not a power rating, sensitivity is related to how loud a speaker will be at a given power. It is measured in decibels (dB) and tells you how loud the speaker will be when fed with 1 watt of power measured at a distance of 1 meter. A higher sensitivity rating means the speaker is more efficient at converting power into sound. I’ll get back to this later.
Impedance
Also not a power rating, but critical to power considerations. It is measured in ohms (Ω) and tells you how much resistance the speaker provides to the current coming from the amplifier. Common impedance values are 4, 6, 8, and 16 ohms (Ω). Matching the impedance of your speakers with the output impedance rating of your amplifier is crucial for both performance and safety. More on this below.
When setting up a sound system, it is best to focus on the RMS power ratings of both the speakers and the amplifier, as this provides the most realistic indication of their continuous power handling capabilities. Additionally, it's important to consider the sensitivity of the speakers and match the impedance of the speakers to the amplifier capability.
However, in terms of loudness, doubling the number of speakers typically results in a 3dB increase in sound output, which is just a slight increase in loudness. This is because loudness is measured in decibels, and the relationship between watts and decibels is logarithmic, not linear.
It is also essential to consider the efficiency or sensitivity of the speakers, which tells you how effectively the speakers convert electrical power into sound. This, along with the amplifier's power, plays a significant role in determining the actual sound output.
In summary, when combining speakers, the total power handling capacity increases, but the increase in loudness is not directly proportional to the increase in power. It's important to take into account both the power ratings of the speakers and their efficiency/sensitivity when setting up a sound system.
Understanding Amplifier Power
The amplifier supplies power to the speakers. The maximum power an amplifier can deliver is influenced by its design and the total impedance of the speakers connected to it. And again, the amp’s RMS power rating is the most important one.
Impedance, measured in ohms (Ω), is essentially the resistance that speakers present to the flow of electrical current. This is also referred to as “load.”
Reducing total impedance (such as wiring in parallel) can increase the power output of an amplifier, but it's important to note that doubling the power doesn't double the volume. The relationship between power and perceived volume is logarithmic, not linear.
Doubling the power increases the sound level by 3 decibels (dB), which is noticeable but not a doubling in loudness. To double the loudness, you would need about ten times the power.
Speaker Impedance and Wiring Configurations
How speakers are wired together affects their total impedance, which in turn influences how much power the amplifier sends to the speakers. This has a direct effect on how loud your sound can be, but also how well your amplifier can tolerate the power running through it. If you run too hard with too low an impedance, you’ll blow up your amp.
Wiring
The essentials of wiring speakers together aren’t difficult, but may not be intuitive. I’ll go over three primary configurations: parallel wiring, series wiring, and series-parallel wiring.
Parallel Wiring
In parallel wiring, the positive terminals of all your speakers are connected to the positive terminal of the amplifier, and the negative terminals to the negative terminal of the amplifier. This configuration reduces the total impedance.
Example: If you have two 8Ω speakers wired in parallel, the total impedance decreases to 4Ω. This would theoretically allow the amplifier to deliver more power, but you must ensure that the amplifier can handle the lower impedance to avoid damage.
Most modern amplifiers will handle a 2Ω load but you should double-check that your amp can run at the required ohms before risking a dead amp.
Series Wiring
In series wiring, the positive terminal of the amplifier is connected to the positive terminal of the first speaker. The negative terminal of the first speaker is then connected to the positive terminal of the second speaker. Finally, the negative terminal of the second speaker is connected to the negative terminal of the amplifier. This configuration increases the total impedance.
Example: If you have two 8Ω speakers wired in series, the total impedance increases to 16Ω. This would result in the amplifier delivering less power than a parallel configuration. However, your amp will have no trouble at all running all day and night at 16Ω.
Series-Parallel Wiring
Series-parallel wiring is a combination of the series and parallel configurations. It’s especially useful when dealing with more than two speakers. If you have, for instance, two boxes with two drivers in each, this will make sense.
Example: If you have four 8Ω speakers, you can wire pairs in series (which gives 16Ω), and wire the two sets in parallel with each other, reducing the total impedance back to 8Ω.
For a mono sound system, a series-parallel wiring configuration may be ideal. This configuration strikes a balance between the number of speakers, the impedance load, and the amplifier's capabilities. It’s crucial to calculate the total impedance of your speaker configuration and confirm that it aligns with what your amplifier can handle.
Wiring Identical Speakers
In most cases, the speakers that you wire together will be of the same design. They will have matched impedance and wattage. In the case of the bass bin example, you might have 4 18” drivers with an impedance of 8Ω each and a wattage of, say, 500w each.
When you wire these speakers together, either in series or in parallel, it affects the total impedance presented to the amplifier, but it does not change the speakers' individual power ratings. In other words, the speakers will receive the same amount of power.
Mixing Speaker Types
Wiring speakers together of different impedance or wattage is sometimes necessary for various reasons and circumstances. Why would you need to wire speakers with different impedance together?
Maximizing Resources: You might have speakers of different impedance or wattage at your disposal. Rather than purchasing new speakers to match the impedance, you can wire what you already have together to make the most out of your existing resources.
Achieving Desired Sound Characteristics: Different speakers have unique sound characteristics. Sometimes, combining speakers of different impedance may achieve a particular sound that you are looking for. This is often done by sound engineers who wish to fine-tune the sound output.
Speaker Replacement or Upgrade: If you're replacing or upgrading a damaged speaker in an existing setup, the replacement speaker might have different specs than the original. In such cases, you may need to wire them together while taking into account the impedance difference.
Cost-Effectiveness: Sometimes it's more cost-effective to combine different speakers that you may already own or can acquire at a lower cost, rather than purchasing new speakers with matching impedance.
Custom Configurations: In a setup with multiple different drivers within the same frequency band (such as different horns and compression drivers), you may have a discrepancy in ohms and or watts between driver types.
When wiring speakers of different impedance together, it’s important to calculate the total load presented to the amplifier and ensure it's within the safe operating range. This prevents damage to both the speakers and the amplifier, and ensures optimal sound quality. Also, understanding how series, parallel, and series-parallel wiring affects impedance and power distribution is critical in such setups.
Wiring speakers with different impedance, but the same wattage
Parallel Wiring
In parallel wiring, once again, all the positive terminals are connected together, and similarly, all the negative terminals are connected together. When speakers with different impedances are wired in parallel, the total impedance is lower than the smallest impedance among the speakers. The formula for total impedance (Zt) in a parallel configuration with two different speakers is:
1/Zt = (1/Z1) + (1/Z2)
Example:
Let’s say you have one 4Ω speaker and one 8Ω speaker, and you want to wire them in parallel:
1/Zt = (1/4) + (1/8) ≈ 0.375 Zt ≈ 2.67Ω
In this example, the total impedance would be approximately 2.67Ω.
Series Wiring
Once again, in series wiring, the positive terminal of the amplifier is connected to the positive terminal of the first speaker, and the negative terminal of the first speaker is connected to the positive terminal of the second speaker. The negative terminal of the second speaker is then connected back to the negative terminal of the amplifier. In a series configuration, the total impedance is the sum of the impedances of the speakers:
Zt = Z1 + Z2
Example:
Using the same 4Ω and 8Ω speakers as before, but this time wired in series:
Zt = 4 + 8 = 12Ω
In this example, the total impedance would be 12Ω.
Series-Parallel Wiring
Remember, this configuration is often used when dealing with more than two speakers. It involves combining speakers in series, and then wiring these series sets in parallel with each other.
Example:
Suppose you have four speakers: two 4Ω speakers and two 8Ω speakers. You could wire the two 4Ω speakers in series (which makes 8Ω), and the two 8Ω speakers in series as well (which makes 16Ω). Now, wire these sets in parallel with each other.
For this series-parallel configuration:
1/Zt = (1/8) + (1/16) ≈ 0.1875 Zt ≈ 5.33Ω
In this example, the total impedance would be approximately 5.33Ω.
When wiring speakers with different impedance, it is crucial to consider the amplifier’s impedance tolerance. Make sure that the total impedance of the speaker configuration is within the range that the amplifier can handle safely to avoid damage or performance issues.
Wiring speakers with different wattages, but the same impedance:
When you wire two speakers of the same impedance but different wattage together, you need to consider how they are wired (in series or parallel) and be aware of the power handling capacities of each speaker.
Wiring in Series
In series wiring, the total impedance is the sum of the impedances of the individual speakers. Since both speakers are 8Ω, the total impedance will be 8Ω + 8Ω = 16Ω.
However, even though the speakers have the same impedance, the one with the lower power rating (250w speaker) will be the limiting factor in terms of how much power it can safely handle. You need to be cautious not to overdrive this speaker.
Wiring in Parallel
In parallel wiring, the total impedance can be calculated using the formula: 1/((1/8)+(1/8)) = 4Ω.
In this configuration, the speakers have equal impedance, so they will share the current equally. However, similar to series wiring, the 250w speaker will be the limiting factor. You need to ensure that it doesn’t receive more power than it can handle.
The main concern when wiring speakers with different wattage but the same impedance is to ensure that the speaker with the lower wattage rating doesn't receive more power than it can handle. This is important to prevent damage to the speaker.
Wiring speakers with different wattages and impedance:
When you wire together speakers with different wattage and impedance, the total impedance and power handling of the system change depending on whether they are wired in series or parallel. Let’s use the 8Ω 500w speaker and 4Ω 250w speaker example:
Wiring in Series
In series wiring, the total impedance is the sum of the impedances of the individual speakers. So, 8Ω + 4Ωs = 12Ω.
However, in the series configuration, the speaker with the lower impedance (4Ω speaker) will draw less power than the 8Ω speaker. Since power distribution in series depends on the impedance, the 8Ω speaker will get more power while the 4Ω speaker gets less.
In series, it is essential to ensure that the power distributed to each speaker does not exceed its rated power handling capacity. For example, if a 500W signal is fed into the series combination, the 8Ω speaker might be okay, but the 4Ω speaker will be overdriven if it's only rated for 250W.
Wiring in Parallel
In parallel wiring, the total impedance can be calculated using the formula: 1/((1/8)+(1/4)) = 2.67Ω (approximately).
In a parallel configuration, the speaker with the lower impedance (4Ω speaker) will draw more power than the 8Ω speaker. This is because, in parallel, the current is divided, and the speaker with the lower impedance will allow more current to flow through it.
In parallel, the lower-impedance speaker will draw more current and may exceed its power rating before the higher-impedance speaker reaches its limit. In this case, it is crucial not to exceed the power rating of the lower-rated speaker to prevent damage.
In both configurations, the total power handling capacity of the system is 500 watts. However, how this power is distributed to each speaker differs in series and parallel configurations. In series, the 8Ω speaker will receive more power, while in parallel, the 4Ω speaker will draw more power.
It's crucial to ensure that the amplifier you are using can handle the total impedance presented by the speakers in the chosen configuration (12Ω for series and 2.67Ω for parallel) to avoid damage to the amplifier or speakers.