If you’re building an audio system, I’ve got three questions you can ask that will help you to choose the perfect speakers.
The answers to these three questions will be your guide to understanding the features and specifications so that you’ll feel confident you’re making the right decision.
Speaker specifications sheets can be difficult to navigate if you’re not used to looking at them. You’ve got to be careful, because some specifications might actually mislead you into thinking a speaker is much more powerful than it actually is!
Throughout the post, you’ll see how you can find and understand the key specifications that you should consider when choosing speakers.
3 Questions To Ask When Choosing Speakers
It’s best if you can start the process of designing a sound system with an understanding of the goal.
Here are the 3 questions to ask before getting started…
Where Will The Listener(s) Be Located?
I think this question is the best place to start. Is this a listening system for one person, 50 people, or 1000 people?
If there is only one listening position, you know where the listener will be at all times. That means you can optimize the system to sound best at that exact position, maybe even employing a stereo or surround setup to make the experience more immersive for the listener.
When designing a sound system for a larger audience, just providing even coverage can be a challenge. A sound system can really only be optimized for one point in space, so you’ll have to make some sacrifices when optimizing the system to sound good throughout a larger audience area.
In your speaker’s technical specifications, you may find a coverage angle that describes the vertical and horizontal angles that sound disperses from the speaker.
In the following image, you’ll see that there is only one angle listed for this particular speaker – 75-degrees. That means the vertical and horizontal coverage angles are 75-degrees, but the vertical and horizontal angles aren’t always the same. Some speakers even have variable coverage angles.
If a listener goes outside of the speaker’s coverage pattern, it will start to sound dull, because high frequencies are more directional than low frequencies.
It might seem like the wider the coverage angle, the better… However, there are several reasons why this isn’t necessarily true.
One reason is that you will usually aim for a consistent level throughout the listening area and the sound from overlapping speakers will add together at the point where they overlap. The areas where the speakers overlap will be louder and the areas covered by just one speaker will be quieter.
Not only will the speakers add together, but they will also cancel out at some frequencies because of phase interference. I’ve got a post about comb filtering that goes into more depth on why this happens, but it results in a change in the frequency response of the system.
Obviously, designing a home theater system is much different from designing a PA system for a music festival or a paging system for a building…
In a surround sound system, the goal might be for the various speakers to work together to create an immersive experience for the listener.
When addressing larger groups, the approach as a whole might change to groups of distributed speakers that address smaller portions of the audience.
Where Can The Speakers Be Located?
The second question should be “Where should the speakers be located?”. Unfortunately, the question is most often “Where can the speakers be located?”.
The best location for the speaker, in terms of sound quality, might be directly in front of the audience. However, if the speaker obstructs the view of the audience, it doesn’t matter how good it sounds – the speaker will need to be placed somewhere else where it won’t obstruct any important sightlines.
The reality is that it’s commonplace for visual aesthetics to be prioritized over sound quality. In most situations, you won’t be able to place the speakers in the ideal position.
Paying attention to the coverage pattern of the speakers not only helps to provide sound where it’s needed, but it also helps to reduce sound levels outside of the listening area. This could be used to prevent sound from leaking into nearby areas or to prevent unnecessary reflections off of nearby walls.
It’s important to understand the relationship between the coverage pattern of the speaker and placement of the speaker. Naturally, the coverage area becomes larger at longer distances from the speaker.
While a ceiling speaker with a 135-degree coverage angle might cover a 14-foot diameter from an 8-foot ceiling height, that same speaker will cover a 24-foot diameter from a 10-foot ceiling height, because there is more distance for the sound to spread out before reaching the listener. That means more ceiling speakers are needed to cover the same listening area when the ceiling height is lower.
The same goes for surface-mounted speakers. A 75-degree coverage pattern might seem narrow at short distances, but a 75-degree speaker on each side of the stage might cover the entire audience if there’s enough distance between the speaker and the audience.
How Loud Does The System Need To Be?
The third question to ask is, “How loud does the system need to be?”.
If you know the location of the listeners, the location of the speakers, and you have a target level for the listening position, you’re off to a great start.
To give you an idea of what the target level should be, take a look at this chart.
|Reference Point||Sound Pressure Level|
|Threshold of Hearing (Quietest Sound)||0 dB SPL|
|Speech||60 dB SPL|
|Music||80 dB SPL|
|Threshold of Pain (Extremely Loud)||120 dB SPL|
I usually aim for a music system target between 80 and 100 dBSPL at the listening position. Having that extra headroom is unnecessary in many situations, but I’ll leave that up to you to decide.
This is a good time to mention a pair of specifications that help us understand how loud a speaker can get: sensitivity and continuous power capacity.
The speaker’s sensitivity tells us how loud the speaker will be if supplied with a given amount of power. When 1 Watt of power is applied to the above speaker, you can expect 97dB Sound Pressure Level, measured at 1 meter away from the speaker.
97 dB, 1 W @ 1 m
The speaker’s continuous power capacity describes how much power can be supplied to the speaker consistently over time without causing damage or permanent change.
Speaker companies will often boast about the much higher peak power capacity, which merely describes the maximum momentary power that can be supplied to the speaker without damage. I think comparing speakers based on continuous power capacity is much more useful.
Let’s look at how sensitivity and power capacity are related.
If this speaker is capable of producing 97 dBSPL at 1 meter away with 1 watt of power from the amplifier, how loud would it be when supplied with 500 watts, its continuous power rating?
This formula will help us answer this question…
By the way, many of the formulas and charts in this video can be found in the Audio University article on decibels.
Power 1 is our wattage from the sensitivity specification. Power 2 is the continuous power capacity, 500 watts.
This formula can be solved with a scientific calculator online.
The difference between 1 watt and 500 watts is nearly 27 decibels. So, by adding 27 to the 97 from the specs, we can calculate that the speaker is capable of producing 124 dBSPL at 1 meter. Remember – every doubling of power only gives us a 3 dB increase!
With this information, we can determine if the speaker is capable of achieving our target level at the listening position.
We just need a simple formula that describes the inverse distance law. The inverse distance law states that with every doubling of distance, there is a 6 dB loss in level. This is another reason why it’s so important to know where the speaker will be in relation to the listening position.
Let’s say the speaker is placed 10 meters away from the listener.
This time, we will use the non-power decibel formula because we are comparing distance rather than power…
Distance 1 is our starting distance, 1 meter. Distance 2 is the distance between the speaker and the listening position.
This tells us that there will be about a 20 dB loss over that distance. Subtracting 20 from 124 tells us that the speaker will produce 104 dBSPL at the listening position.
That means the speaker is certainly capable of providing adequate level to the listening position from where it will be located at the side of the stage.
If the speaker couldn’t get loud enough at it’s continuous power capacity, you’d need either a more sensitive speaker or a speaker with a greater power handling capacity.
Choosing The Right Amplifier For Your Speakers
I think it’s always best to choose speakers first and then find an amplifier that will provide enough power to those speakers.
If you’re ready to learn how to choose the right amplifier for your speakers, check out the Audio University post on choosing an amplifier.
I provide you with a simple guideline for choosing speakers and explain why it’s important to match your amplifier to your speakers properly.