Understanding Signal Flow in 4 Simple Steps
Understanding signal flow is important to have a nuanced and complete understanding of how audio systems work.
Here’s the basic list:
An input transducer (such as a microphone or pickup) to intercept a sound signal and convert it into an electronic signal.
An amplifier to boost the weak signal produced by the pickup to a level that can power a speaker.
An output transducer (such as a loudspeaker) to convert the electrical impulse from the amplifier back into sound waves that move through the air to the ears of listeners
From this foundation, more complicated PA systems can evolve that include mixers or mixing consoles, extra speakers, preamps, and many other externals. These are the 4 basic components of signal flow.
1. Microphones Translate Sound to Signal
These are the most common type of input transducers, which convert sound to an electronic signal. Mics can be wired or wireless, and are designed with any of a number of different sound pickup patterns.
In general, wireless mics are good for speeches or singing – but potential interference and signal loss problems make them unsuitable for micing up instruments.
Most microphones are low-impedance, which means they’ll require special inputs (usually labeled “mic”) on your amp or mixer. A PA system featuring both low and high impedance inputs is recommended for maximum versatility.
2. Mixers Feed Signals to the Amplifier
This is the hub of the PA system, which sums every audio input including mics, CD players, and direct instrument lines into one signal (or, in the case of stereo systems, a two-channel stereo signal).
This is also where preamps boost low-level signals (such as those from microphones), and sliders or knobs set the relative volume levels.
Mixers can be either rack-mounted units with a few inputs, or full-blown mixing consoles with dozens of separate channels.
When choosing a mixer, think of how your PA system will be used. For amplifying speech and pre-recorded music, you may need only 2-4 channels. But for bands and DJ’s, that number can balloon up to 6, 8, or even dozens of channels.
3. Amplifiers Push Signal to the Speakers
From the mixer, the signal travels to the amplifier. Amplifiers are sometimes integrated into the mixer, mixing console, or into the loudspeakers. They boost incoming signals to a level that can power the speakers.
Unless you assemble a PA system with amplifiers built into powered loudspeakers, matching your amp or powered mixer to your speakers can be a tricky business.
In general, your amp should be loud enough to power a speaker without cranking the volume all the way to the top, which may cause speaker-shredding distortion. Sound professionals often refer to this as leaving plenty of headroom. Your amp should be rated comfortably higher than your speaker’s normal (not peak) rating.
On the other hand, at continuous high-volume operation, a loud amp sometimes can clip if it’s running anywhere close to full throttle. If you’re anticipating long periods of heavy-duty use, make sure your speaker’s peak rating is double the peak power of your amp.
4. Speakers Broadcast Sound to Your Ears
Also known as the output transducer, speakers convert electrical impulses back into sound waves. Speakers usually take the form of multipurpose loudspeaker units that can cover a wide range of frequencies and power levels.
Impedance matching (making sure your amplifier can handle the load of the speaker) is another concern, and is a thorny subject in its own right. Simply put, make sure to get speakers that are at (or above) your amp’s rated impedance.
If you add more speakers, make sure their load never drops below the amp’s impedance rating (usually 4 ohms). Most of the time, if you’re using 8 ohm speakers in a pair, you’re probably within the tolerance of your amp.
Lastly, make sure you’re running the right kind of cable to your speakers. Using anything other than speaker cable with unpowered speakers can reduce the efficiency of your speaker, and in extreme cases, damage your PA system.
Questions? Email or call (1-212-766-0248) AudioLink’s team of experts to help you put together your ideal PA system.
