Speakers (including loudspeakers and studio monitors) are transducers that convert audio signals into sound waves and are often connected to computers (laptops, smartphones, etc.). To fully understand the audio signal flow of speakers in terms of inputs and outputs, we must also comprehend the definitions of input and output devices in computer systems.
Are speakers/studio monitors input or output devices? When speakers are connected to a computer (laptop, smartphone, etc.), the computer outputs information to be received by the speakers. This means that speakers, monitors, and loudspeakers are, by definition, output devices.
In this article, we’ll go through full definitions of input and output devices and address the role of speakers in the greater framework of a computer audio system.
What Are Input And Output Devices?
The terms input device and output device are defined by computer systems.
An input device is a device that inputs information into a computer for processing. An output device, by contrast, is defined as a device that receives and reproduces information from a computer.
Typically these devices are completely digital. In the case of audio/sound transducers such as speakers, which are inherently analog, a digital-to-analog converter (DAC) must be put in place between the computer and the speaker.
With microphones (which are input devices), an analog-to-digital converter (ADC) must be put inline between the mic and computer.
Speakers receive information from computers (think smartphones, laptops, tablets, etc.) and are, therefore, output devices. This information is in the form of digital audio.
As we've discussed, the digital audio must pass through a DAC before it is able to drive the speakers to produce sound. With proper conversion, a quality speaker will accurately reproduce the information from the computer.
The Input And Output Of Speakers As Transducers
Let's discuss speakers as transducers in a bit more detail.
The role of speakers is to convert analog audio signals (electrical energy) into sound waves (mechanical wave energy). If we think of it this way, speakers have audio signals at their “input” and sound waves at their “output”.
Note that the definitions of input and output devices are relative to a computer system. Speakers are output devices!
However, it's worth thinking about how speakers act as transducers and, as a thought experiment, let's consider the energy “input” and energy “output” from the reference point of the speaker.
Speakers, like headphones, use drivers to convert energy. Speaker drivers tend to be larger, though this is not necessarily true.
Typically these drivers are dynamic (moving-coil) drivers that utilize electromagnetic induction to function.
Electrical audio signals (AC voltages) are sent/inputted through a conductive voice coil. This voice coil is connected to a movable diaphragm and is suspended in a magnetic field.
As the signal flows through the coil, the coil moves. This causes the diaphragm to move according to the audio signal. As the diaphragm moves, it pushes and pulls air and produces sound waves that are effectively outputted from the speaker.
Reverse Order: Speakers As Microphones
Electrodynamic (moving-coil) speaker drivers are essentially wired the same way as moving-coil microphone cartridges, only in reverse.
Speakers convert audio into sound, whereas microphones convert sound into audio. However, their design is essentially the same.
By that token, it's possible to turn speakers into microphones and vice versa. Of course, just because it's possible doesn't mean the results will be superb.
Microphones are designed to produce low-level full-range mic signals. Speaker level signals would blow a mic cartridge if the mic were to be wired in reverse.
Speakers are designed to produce high sound pressure levels with high-level signals that have restricted bandwidth. Therefore, even yelling into a speaker setup like a microphone would output a low-level signal with poor frequency response.
Microphones are considered input devices according to computers.
However, like speakers, if we take the mic as our reference point, we see that it has both an input (acoustic waves) and an output (electrical signals).
For more information on the close relationship between microphones and speakers, check out the following My New Microphone articles:
• How To Turn A Loudspeaker Into A Microphone In 2 Easy Steps
• Do Microphones Need Loudspeakers Or Headphones To Work?
• How To Plug A Microphone Into A Speaker
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Let's discuss DACs in a bit more detail here.
As mentioned, computers deal with digital audio while speakers require analog audio to produce sound. Therefore, we need DACs.
Fortunately, computers are built with sound cards that act as DACs (and ADCs). These sound cards allow the computers to have built-in speakers that can effectively produce sound and allow us to connect speakers directly to the computer via the headphone jack.
If we plug in a “digital speaker” like a USB speaker, the speaker itself will have an ADC that will convert the computer's digital audio into analog audio that can drive the speakers.
The Creative Pebble is an excellent example of a pair of USB computer speakers.
There are also plenty of DAC converters available that can connect to a computer's digital output and convert the digital audio signal to analog to drive “analog-only” speakers.
The DACs mentioned above may very well offer better results than the built-in sound cards of our digital audio devices.
Audio interfaces also have built-in DACs and ADCs. This allows them to easily connect many audio transducers to a computer via a single digital connection.
These audio transducer devices can be either input or output devices and include inherently analog devices such as speakers/monitors, headphones, microphones and instruments.
These audio interface I/Os generally have better sound quality and greater versatility than a computer’s built-in sound card.
A common low-end “prosumer” audio interface is the Focusrite Scarlett 2i2:
If we have a look at the rear of the Focusrite Scarlett 2i2 audio interface, we see two 1/4″ TRS line outputs (left channel and right channel audio) that are meant to send audio to our studio monitors.
There are plenty of better professional audio interfaces on the market that feature multiple stereo pairs of monitor (speaker) outputs.
To learn more about audio interfaces, check out my article What Are Audio Interfaces & Why Would A Microphone Need One?
Some power amps connect directly to computers and act as digital-to-analog converters as well.
Is a microphone an input or an output device? Microphones are input devices because they input information into a computer. Note that the mic signal must be converted into digital data before it can be sent to and used by a computer.
To learn more about microphones and their role with computers, check out my articles Are Microphones Input Or Output Devices? and How To Connect A Microphone To A Computer (A Detailed Guide).
What are the parts of a speaker? Speakers are made of several parts. The key component is the transducer element or driver, which may work on either electromagnetic or electrostatic principles. Other key parts include the housing/enclosure, crossover network, damping, and amplifier (active designs).
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With so many loudspeakers on the market, purchasing the best speaker(s) for your applications can be rather daunting. For this reason, I've created My New Microphone's Comprehensive Loudspeaker Buyer's Guide. Check it out for help in determining your next speaker acquisition.
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