Basic SR systemBasically, a SR system is very similar to your guitar amp. The basic SR components are
There are more things than that you can have and do with SR systems but these are basics you need to get heard. The good thing is several of these are often offered as package deals so you have options to combine them. They also match the basic system of your guitar rig. Guitar=Source and your Amp provides the rest. On your guitar amps you often have a knob labeled as “Pre”, ”Gain”, or maybe ”Drive” as one of the first knobs on a given channel. This is your Pre-Amp. Its job is to bring the signal from the guitar up to a basic level the amp can work with. On guitar we often use this on purpose to get distortion by various methods. However on SR system usually you want to avoid distortion at all cost. EQ is easy and familiar one (Low, mid and High). Guitar amps don’t have a “mix” as you only have one source so nothing to “mix” together. The power amp, master volume on a guitar amp, and speaker or speaker cab is pretty obvious as well. Really a SR system is just the same.
SourcesA source is anything you want to come out the SR system’s speakers. For most bands just starting out the source will be a microphone or two just for vocals. Just having the vocals come over the PA can be workable solution starting out as your other instruments can be mixed just using volume controls on their amps, especially in smaller venues. And the acoustic drums are often loud enough without amplification. There are lots and lots of options but it’s hard to go wrong with the basic Shure SM58. You can pick these up around $100 anywhere. They sound good and are built to take about an any abuse you can put them through. Plenty of other microphones for live use at various price points you can find with a bit research.
Pre-Amp>EQ>MixThese 3 components are almost always combined into one unit, your basic mixer. Many mixers also have a lot of other useful extras as well, such multiple output paths so you can have different mix for saying your stage monitors or some even come with built-in effects units. On any mixer, digital or analog you will have channel strips for each input where you plug the source (mic) with the various controls running physically straight down the strip. The first knob, often labeled “Pre” or “Gain” controls the pre-amp. Basically, you want to set this to get a decent level on the mic. The more Pre-Amp level you apply to the mic the more sensitive, further away, the mic will pick up. That sounds good but in reality, you likely want to keep this as low as you can but still getting a stong signal. The reason is the mic will also pick up everything around it (Drums, Guitar Amps, Bass Amps, etc…) All those things coming over the mic can make the vocals muddy and contribute to feedback (that awful squeal that will send your audience out the door). Unless you have a vocalist that is just loud naturally, having them sing closer the mic is preferable. The “mix” is the mix of volume between the multiple sources. On better mixers the fader (slider on the bottom of the channel) controls the volume level going to the mixer's main output. The main output will also have a fader so set the overall output level. So you adjust the volume between each source until you have “Mix” that is pleasing to the audience.
Power Amp>SpeakersI put these two together as it is one of the most logical thing for a live sound situation for someone starting out. This combination is sold as “Active” speakers. You get both together and you don’t have to be concerned with matching the power amp to the speaker. Plus it’s less to have to connect and carry around. You will likely need one each for left and right side of your stage and maybe one or two more for monitors so the band can hear the singer on stage. Although I’ve played plenty of shows with just a vocal and acoustic guitar with no monitors and it’s not an issue. But if you have a full band with an acoustic drum set, you will likely need monitors.
On stage monitors, you could just take the main output from your mixer and send it to your monitors and well as the “main” speakers, the audience hears. This can work but you might find you want to hear a slightly different mix than the audience. Also maybe you don’t want to go around and adjust the volume on each of active monitors one at a time. On most mixers along with the main output, you might also have one or more auxiliary outputs. Each of these signal paths are often called a “Buss”, like public transportation in cities, except you can send the signal on multiple buses at once. So you can use an Auxiliary, often labeled “Aux”, as a way to create a separate mix. Hook you monitors to the “Aux” output from the mixer and you have different mix with different master output level than your main for monitors.
TIP: except for some systems specifically designed for it, you want your mains in front of the band. Putting them behind the band, the band could then hear them but the system will likely feedback like crazy. Monitors are designed to point up away from the microphone's pickup pattern thus reducing the possibility of feedback.
TIP for the cheapskates: If you have only one or two sources you might be able to get away with not having a dedicated mixer. Some active monitors have a small mixer on the side of them with 1 or maybe 2 microphone inputs. Most also have an output so you could use the small mixer mounted directly on speaker and connect it to another active speaker. While it’s very limited in capability, if you have one vocalist and little budget, this can get them heard.
Other componentsWhat about effects? Crossovers? Subwoofers? 31/15 band EQs, gates, compressors, Anti-feedback, etc… Many mixers come with digital effects built in these days, and the digital boards come with a huge host of digital versions of these various components. All of those devices might find a useful place in your SR system, however, none of them are necessary to get heard.
Get out of the house and be heard.