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 feel
confident you're making the right decision. Speaker spec sheets can be difficult to navigate,
especially if you're not used to looking at them. You've got to be careful, because some
specifications might actually mislead you into thinking that a speaker is much more
powerful than it actually is. You'll learn how you can find and understand some of the key
specifications that you should be considering when choosing your speakers. It's best if you can
start the process of designing a sound system with a clear understanding of the goal. Here are the
three questions to ask before getting started. Where will the audience be located? I think this
question is the best place to start. Is this a listening system for one person, 50 people, or
a thousand people? If there's only one listening position, you know where the listener will be at
all times and that means that you can optimize the system to sound best at that exact position,
maybe even employing a stereo or surround setup to make the experience even more immersive for
that 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 a speaker's technical specifications, you might find a coverage angle that describes
the vertical and horizontal angle that sound disperses from the speaker. There's only one angle
listed for this particular speaker - 75 degrees. That means that both 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 steps outside of the speaker's
coverage pattern, it will start to sound dull to that listener 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'll usually be aiming 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'll also cancel out at some
frequencies because of phase interference. I've got another post that goes into much more
depth on why this happens, but the result is 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 a single listener. While
addressing larger groups, the approach as a whole might change to groups of distributed speakers
that address smaller portions of the audience. 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 a 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 really 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 and, in most situations, you won't be able
to place the speakers in the absolutely ideal position. Paying attention to the coverage pattern
of the speakers not only helps to provide sound where it is 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 a speaker
and the placement of a speaker. Naturally, the coverage area becomes larger at
longer distances from the speaker. While a ceiling speaker with a 135-degree coverage
pattern might cover a 14-foot diameter from 8-foot ceiling height, that same speaker could cover a
24-foot diameter from a 10-foot ceiling height, because there's more distance for the sound
to spread out before reaching the listener. That means more speakers are required
to cover the same listening area when the ceiling height is lowered. The same goes
for surface mounted speakers. A 75-degree 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. Often fill speakers will be used to cover the
areas not fully covered by the main speakers. 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, let's take a look at this chart. I usually aim
for a music system target between 80 and 100 dB SPL at the listing 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 to 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. Most often, you'll see something like this.
When one watt of power is applied to this speaker, you can expect 97 dB SPL measured
from one meter away from the speaker. 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 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
in almost every case. Let's take a look at how sensitivity and power capacity are related. If
this speaker is capable of producing 97 dB SPL at one meter away with one watt of power from the
amplifier, how loud will it be when supplied with 500 watts (its continuous power capacity)? This
formula will help us to answer this question. By the way, many of the formulas and charts
you'll see 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 using a scientific calculator like this one. I'll leave
a link to this one in the description below. The formula tells us that 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 dB SPL at one meter. With this information,
we can determine if a speaker is capable of achieving our target level at the listening
position. The inverse distance law states that, with every doubling of distance, there's 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 we plan for the speaker to be placed about 10 meters
away from the listener. This time, we're going to use the non-power decibel formula, because
we're comparing distance rather than power. Distance 1 is our starting distance that we
found in the sensitivity specification - one meter. Distance 2 is the distance between the
speaker and the listening position. This formula tells us that there will be about a 20 dB loss
over that distance. So, subtracting 20 from 124 tells us that the speaker will produce
104 dB SPL at the listing position. That means that the speaker is certainly capable of
providing adequate level to listening position. If the speaker couldn't get loud enough at
its continuous power capacity, you'd need to choose either a more sensitive speaker or a
speaker with a greater power handling capacity. 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 video that's on your screen now. I
provide you with a simple guideline for choosing an amplifier and explain why it's so important to
match your amplifier to your speakers properly. If you found this video helpful, hit
the "Like" button and share it so the video can reach more viewers.
I'll see you in the next video.
