Setting Up a Small PA System ???

[musicworld]

Hi

With regard to a small PA System what exactly goes in to what ? I'm a singer performing to backing tracks, and my rig consists of two Speakers, Mixer, Amp and Mic. Being new to the set up process I'm unsure as to what should go where and how everything should be connected, example: should everything be connected to the mixer ? Sorry to sound dumb! but I'm a newbie.

 

[Armistice]

Not quite...

 

[Bob F.]

Plain vanilla set up:

Mic and playback source for your tracks get plugged into the mixer using the appropriate cables. The "main outs" L/R of the mixer go into power amp, and the power amp L/R goes out to the main monitors (speakers).

Make your connections. Keep your volume on the mixer as low as it can go until the mixer is turned on. ALWAYS power up your monitors LAST and THEN bring up the levels on the mixer. While talking into the mic, use the input gain control to get a signal (you should have some kind of "peak" indicators like a red light on each channel.) You should basically be just a little south of that peaking light. Raise the main volume on the mixer THEN use the channel volume to bring up the level in the monitors--talk into the mic while you bring up the level on the channel.

Break it down in reverse; bring the levels down on the mixer, shut the monitors off first, and then turn off the mixer/peripherals.

 

[AbuseTheMuses]

what he said.

 

[musicworld]

Mic and playback source for your tracks get plugged into the mixer using the appropriate cables. The "main outs" L/R of the mixer go into power amp, and the power amp L/R goes out to the main monitors (speakers).

Hi Bob

Could you break that down as to why that is ? as I'm not sure what powers what and for what reason.

 

[Bob F.]

I don't know what gear you have, and while some things are usually similar, some things may be different. I don't know what you're using to play your tracks back with, or necessarily what cables you would use to make that connection. Some monitors are self-powered (you plug them straight into an outlet), others are used with a power amp.

Follow the bouncing mic signal:
You say something something into the microphone, which basically converts your voice (the original "source" or 'audio signal') into an electric "signal". The microphone isn't making your voice any louder (or necessarily softer)--you do that physically yourself.

Technically, you could then plug the mic cable into an amplifier (to make the signal stronger), and a then speaker, and that would work to make the sound of your voice louder.

But you're going to to plug the microphone into the mixer, which basically offers more control as to where in the mix you want your voice to be heard (left, center, right), and how loud you want that sound to be, among other things.

The electric signal then goes out of the mixer, to an amplifier to make it stronger. That now-stronger signal leaves the amp through the speaker cables (they're not the same as instrument cables!), and it goes out to the monitors (speakers). The speakers then convert the electric signal back into a physical sound wave by vibrating. The vibrations cause the sound wave which is usually louder than the original sound that you made with your voice, without having to actually physically raise your voice.

Basically.

 

[gcolbert]

This is not technically accurate, but an analogy:

You have two sources of sound that you want to make loud so they can be heard clearly over a large area. Starting at the end you have speakers that put out the final sound. The speakers are driven by an amplifier (although there are 'powered' speakers that have built in amplifiers there is still a speaker and an amplifier).

Think of the amplifier as a sound multiplier. Let's just think of some silly numbers here, and think of an amplifier being able to multiply sound by 1 to 10 depending on where you set the volume. The amplifier takes the signal that you want to amplify and multiplies it by (1 to 10) and sends that power to the speaker.

So lets think about your CD (or whereever you have your backing tracks). It puts out sound at a power between 0 and 1 (so half loud would be .5). So if we feed your CD into the amp at full power with the amp turned all the way up we would get a power 10 sound ( 1 X 10 = 10) to the speakers.

Your microphone generates its own power from a small coil of wire and a magnet. It puts out a power between 0 and .1 (much less than the CD Player). If you fed full signal from the microphone to the amp you would only get a power of 1 to the speakers ( .1 X 10 = 1) even with the amplifier turned all the way up. If you connect the CD and the mike to the amp, you would have to turn down the CD output to .1 to match the microphone and the combined signal would result in the amp only putting a power of 1 to the speakers.

Your mixer most likely has another amplifier inside it designed specifically for microphones to amplify the microphones puny 0 to .1 power level to the same 0 to 1 level that your CD player produces. The final output from all of the sources on your mixer provides a power of 0 to 1 to your amplifier. By making the microphone as powerful as the CD player, the mixer can now allow you to fine tune which is louder or quieter - the mike or the CD player without compromising the final power that is sent to the speakers.

The only what powers what in this scheme is the amplifier powering the speakers.

If your amplifier has an internal microphone pre-amp and a line level input you could concievably (don't do this) just plug them both into the amplifier and not use the mixer at all. Mixers usually have better quality microphone preamps than power amplifiers, and the purpose of the mixer is to let you match the levels of all of your inputs easily (in theory anyhow).

The sound quality and clarity that you end up with is dependant on the power outputs of a connected device closely matching the designed power handling of the device it is fed into. Knowing what to do here involves learning a little bit about line level inputs and outputs (there are two of these by the way). Impedance matching (as important with microphones as it is in speakers), balanced vs. unbalanced wiring and a bunch of other things that you learn along the way if you pay attention.

There are several postings on the forum with painfully accurate technical and scientific explanations of matching, but it sounded from your question like you needed the mud-map version. Hope you don't take offence.

 

[Armistice]

If you want more help I suggest you post the actual make/model numbers of your "rig".... then people will know what they're dealing with.

And what manner of device is playing your backing tracks?

 

[musicworld]

Thanks guys for all your advice, I'm in the process of purchasing a new rig so I'll get back to you with the specs. Whilst on the subject of gear I'm also looking to purchase a Shure PG58 wireless mic and was wondering if anyone had any experience using this model? I wanted to go for the SM58 wireless but it was out of my budget.

 

[bouldersoundguy]

Cheap wireless sounds crappy. Wired mics sound better than all but the very best wireless. A standard SM58 will sound much better than a wireless PG58.

 

[bruiser1964]

I agree with that don't go wireless unless it's top of the range (ULX or SX for Shure) cheap wireless = cheap sound.

 

[musicworld]

I'll heed your advice guys, but have you seen the price for the Shure SM58 wireless. My retailers asking ?450 which I'd love to pay but haven't got the notty, thats why i was considering the PG58.

 

[moresound]

Well save up for a bit then go for the gold.

 

[buzzard bass]

The suggestion was for a wired SM58, which I'd second, why does it have to be wireless?

 

[musicworld]

The suggestion was for a wired SM58, which I'd second, why does it have to be wireless?

My act consists of a lot of moving round as i like to mingle with the crowd, not to mention tripping up over the damn things. I'll go with moresound, wait and save a ilttle then go for gold.