Along the same lines of the house system for bar bands

[motleylorca]

Hi,

I'm in a metal band and we're figuring out what to get for a PA system. The truth is, I don't know anything about it and for some reason it seems a thousand times more complicated to me than dealing with guitar racks. Anyway, I read the entire post regarding the house system for bar bands and looked at the recommendations there, but a 4000 power amp seemed a bit excessive to me for what we want, which is a PA system for rehearsals and maybe small clubs (the clubs where we live tend to have their own house systems, so there's no point in shelling out that much cash for something we're never gonna need anyway). A friend recommended the Yamaha EMX5000 powered mixer and a couple of Peavey PR-15 Speaker Cabs, but you guys sure as hell seem to know your stuff, so I'd rather ask you.
Also, here go a couple of stupid questions, 'cause I'm really confused. 1) Say that I were to get the EMX5000 and the Peavey cabs. The EMX5000 is a 1000W powered mixer, and the cabs are each 400W. It sounds obvious, but just to make sure...does that mean that I'm going to be asking 800W from the mixer (or power amp if we get a power amp instead?). 2) If a power amp says 2X600W, what the hell does that mean? Am I getting 1200 W or what? 3) What's wattage-per-channel? If the thing says, i.e., 300 Watts-per-channel, what exactly am I getting (I told you I was confused)?
We're not worried about mikes, cables, etc., just about the mixer, power amp, cabinet deal...and maybe a monitor or two (I'm getting a headache from thinking about this). Anyway, if you guys can help I'll be eternally grateful!

[boingoman]

Originally Posted by motleylorca

1) Say that I were to get the EMX5000 and the Peavey cabs. The EMX5000 is a 1000W powered mixer, and the cabs are each 400W. It sounds obvious, but just to make sure...does that mean that I'm going to be asking 800W from the mixer (or power amp if we get a power amp instead?).

No. The rating on the speaker is how much power it can handle, not how much it draws. Speakers don't draw power from an amp like an amp does from the wall. They react to how much power is given to them.

Speakers usually have at least three ratings. The important ones are RMS or continuous, program, and peak. Peak is the max the speaker will take without burning up. Continuous/RMS is the long-term continuous power handling of the speaker, like running a sine wave into it. It is a standardized AES (Adio Engineeering Society) measurement. Good speakers will provide this number, as it is a good indicator of the quality of the speaker.

Program or music is the amount of power you can throw at the thing long-term with most music going into it, like in a live sound situation or recorded music.

So when you say you have 400W speakers, it pays to know what 400W means. Those PR15 boxes are 400W program, 800W peak. They can handle a good amount of power. I have actually heard these boxes. Not bad for $200 apiece. A bit honky and plasticky sounding, but they are plastic, after all.

Originally Posted by motleylorca

2) If a power amp says 2X600W, what the hell does that mean? Am I getting 1200 W or what? 3) What's wattage-per-channel? If the thing says, i.e., 300 Watts-per-channel, what exactly am I getting (I told you I was confused)?

OK.

The amount of power an amp can deliver depends on the impedance that it is hooked to. The amount of power goes up as impedance goes down. Hooking PA speakers together drops the impedance.

So, that Yamaha mixer puts 500W per channel into 4ohms, 325W into 8ohms.

That means that each side, left and right, have a separate amp channel that will put 500W into a 4ohm load, 325W into an 8ohm load.

Most PA boxes are 8ohms. So if you hook one speaker to each side, each box will get 325W max, for a total of 650W. If you hook two to each side, the load drops to 4ohms per channel, the amp puts 500W per channel, both speakers on each side will get 250W, for a total of 1000W max available.

A practice PA is for different things than a performance PA, for the most part. All you are really looking for is vocals, as with metal, most everything else is loud enough in the practice space. It will also let you do small shows, where again, the vocals need the most reinforcement. You won't get the kick in the chest kick drum, but it will do.

Personally, I would get some better speakers, if this thing is gonna be used for gigs, and if you can afford it. Those things aren't bad, but I would move up to the SP series, like the SP-5, or the JBL MPro 415. Used SP-5s can be had pretty cheap, make sure they are from within the last seven or so years, Peavey made some major improvements to the SP line around then.

[Cave Dweller]

yes, what he said.

and to answer to a few of your questions:
if is says 300watts x 2, that means the unit has 2 amplifiers, each capable of 300watts. watts per channel is the exact same, 300 watts per channel is 300watts X 2.

as with speakers, it certainly pays to find out what exactly they are measuring...be it peak, RMS, or program. also handy to know is the distortion at that measurment, or THD, which will help you to compare amplifiers more effectively.

[Tim Brown]

On top of all that, you need to learn to read specs....espeiocally the SPL level.
Why?
Well, if a speaker is rated at 90 db's at 1 watt @ 1 meter, and a speaker is rated at 98db's @ 1 Watt @ 1 Meter, the one that is 98 Db's is going to be louder.

watts decibels

1 90-(2)-93 98-(2)-101
2 93 96 101 104
4 96 99 104 107
8 99 102 107 110
16 102 105 110 113
32 105 108 113 116
64 108 111 116 119
128 111 114 119 122
256 114 117 122 125
512 117 120 125 128
1024 120 123 128 131


Now, this first series of numbers down the left hand side is amplifier power. Every time you have a doubling of Power - you add 3 decibels of output.
200 Watts is NOT "twice as loud" as 100 Watts. In ordewr to be twice as loud as 100 watts, you have to have TEN TIMES the Power - or 1,000 Watts.

The spl ratings here are for a 90 db speaker (the na pair of 90 db speakers) then a 98 decibel speaker, then a pair of them.

with the 90 db speaker - you have to have 1,024 watts of power to reach the average legal limit.
with the 98 db speaker, you only need 128 watts.

Why? Because a higher SPL (or Sound Pressure Level) reading means that the speaker is more efficient, and therefore LOUDER.

So, always look for speakers that have a higher SPL level.
Also, keep in mind that most professional grade speakers are generall right around 98 Db.

Also, every time you DOUBLE the number of speakers, you add 3 db's to the output... so one speaker would be 90, two speakers would be 93 db's, and four speakers would be 96 db's.


I hope this helps a little.


Tim

[Tim Brown]

Crap! It didn't keep them in the neat order that I had them.

That is really annoying.


Tim

[motleylorca]

Thanks for all the help. I'm actually aware of power-dB relationships and stuff like that; it's just audio equipment that gets me confused because I never learnt how specs were laid out...for instance, I know that dB are ruled by logarithmic proportions, so that just doubling the power won't double tHe decibel rating, but I didn't know jack about SPL. All this is REALLY REALLY helpful...thanks a million guys

[Garak]

For a rehearsal system I'd get something that makes a good monitor rig, cause monitors are all you need right

Anyway I'd look at a pair of yorkville NX-550p or JBL eon's or some other powered cabinet that works well as a wedge. With most powered cabinets you don't even really need a mixer, they have mic inputs and really basic eq on the back of the cabinet. Need alittle more control and eq you can get a cheap behringer mixer. For around $2000 you should be able to get 2 great montiors.

Beyond that I'd get one for each member of the band and an allen & heath mixwizard and your own mic splitter. That way you can take your own montiors to a gig and do your own mix right on stage and let the sound guy focus on the room sound.(Just keep in mind that if your loud on stage you will make the sound guys job hell)