P.a. System Questions

[All of Me]

I know this might not be the right question for this site but I always get good info here so I am gonna ask anyway.lol I am a guitar player and vocalist. I use distortion and effects through my guitar and reverb on my vocals. I will be playing with a drummer, bass player and another guitarist.
How many watts will it take minimum for me to be heard and still sound good?
I use a digitech gsp-2101 for guitar effects and that would run through the p.a. with my vocals.
Is it worth it to buy a powered mixer or seperate p.a. and mixer?
I was looking at carvin equipment, mostly cause of great quality and price.
Would there 2oo watt head with speakers work for me or am I dreaming?
I figured that the 1000 watt p.a. would definetly do the job but would like to spend 1/2 the price on the 200 watt system
Any help or guidance would be greatly appreciated

www.mp3.com/all_of_me

[Joe E]

Best purchase would be a seperate Mixer, EQ, power amp.

With that being said the: PA's like the Mackie 800 (something or another) are very popular in small clubs. 400 watts stereo or 400 watts for Monitors and 400 for Mains.

As for wattage: In the old days we could use 100 watts for Monitors and 200 watts for mains pushing a pair of 12" spkr and a horn. Today things are more power hungry. As a rule I use this: aprox 250-300 watts per 15" speaker 75-100 watts per horn if seperate from speakers. 150-200 watts per 12".

The reason: well as you turn up the volume on a power amp the signal shape starts changing (voltage increases as well I think). If using 90 % of the amps power,the amp starts to clip and the signal can damage a speaker. So by using a more power full amp you will hitting the same volume with a lower percent of the total amps power. THe signal is cleaner and less likely to damage the speaker.

With a 3 piece band mic'ing vocals and guitars I use a QSC MX 700 for mains and the same for monitors (15" speakers in each)

If you add subs you will need around 500 watts per 15 or 18" speaker to help maintain clean articulate low end.

[All of Me]

wow, thanks. I appreciate your time a lot!!!!

[All of Me]

I am just a little confused on the ohm thing. Does it matter if say your speakers are 8 0hm but your amp is 2 ohm. Also is 8 ohm better than 2 ohm or is 2 ohm better?

[detuned6]

2 8 ohm speakers would be 4 ohms
4 8 ohm speakers-> 2 ohms
2 4 ohms-> 2 ohms

2 16 ohm-> 8 ohms
etc.....
theres a good article on the carvin website under Dr. sound about ohms, speakers an shit (this was last yeaR . but it might still be there)you should plan out your speakers an amp selection first before buying. You dont whant to under power your speakers.

[Tom Hicks]

Ohms is the resistance of the copper wire to having the electricity pushed through it.8 ohms is more resistance than 2 ohms.If your amp is rated (for example) at 800 watts at 2 ohms,it would put out 400 watts at 4 ohms and 200 watts at 8 ohms.See?The resistance reduces the power that gets through.
Now,a 2 ohm load is pretty uncommon in actual practice,although certainly possible.Most amp mfgs. will give you an ohm rating at their theoretical best case scenario in order to boost the apparant power rating of their amp.Most speaker systems are wired to be 16,8 and 4 ohms.
Multiple 8 ohm speakers can be wired to be any of the above resistances depending on whether the wires are series,parallel,etc.
You really need to take a bit of expert guidance here to make sure everything will get wired up correctly.I'm a guitar player who has wired up a few cabinets and I like to consult my electrical engineer brother to back me up on things like this.Bottom line,don't take a chance frying your gear.Make sure of all the details first with a knowledgeble person.

[All of Me]

ahhhhhhhhh, thank you thank you!!!!!!

[White Trash]

The rule of thumb (in general) is have twice the amp as what your speakers will need.
Got a pair of 500W mains? Get a 1000W/ch. power amp.
Not that you'll be cranking that much juice, but it's the "clean headroom" concept. Clipping is very very bad, and that's what we're avoiding by having the extra ponies on tap for signal peaks, etc.
Today's speakers can handle lots of clean power. Underpowering them will do damage quicker than overpowering (unless it's just waaayyyy too much power going in, of course)
If you have 8 ohm speakers, your amp should produce an 8 ohm load if wired correctly to the speakers.
When parrellel wiring, as in hooking more cabinets up, then the load drops as detuned6 stated.
Your amp will probably go "safely" down to a 2 ohm load, but will push whatever it "sees"
If the maximum power is rated at 250W/ch. @ 8 ohms, it will be more, maybe 325W (I don't have the formula handy) @ 4 ohms, and again more @ 2 ohms.
Conversely, @ 16 ohms it may be 175W/ch.

[ausrock]

As has been said, it is good insurance to have a power amp rated somewhat higher than the speakers capabilities............the alternative is to have QUALITY components which are closely matched BUT which are rated above what you are ever likely to need.

The last PA rig I had was a QSC mx3000 amp (1200-1300 watts a side into 4 ohms) powering 2 single 15 and horn boxes (600 watts at 8 ohms). The beauty of this rig was that I had the choices of;...... running one box per side with shitloads of headroom/ combining both boxes off one side of the amp which immediately made them a 1200w@4ohm load and then running subs off the other side/ or adding a stereo active cross-over, with the boxes, one each side but with a sub added each side controlled by the cross-over.

My point is that if you research things and plan accordingly, it is possible to have a system that can be adapted to the needs of each individual gig.

[TexRoadkill]

You can never have too much power.

[Special K]

definitely have seperate mixer/amp etc. Don't buy bricks cos they are a waste of time...especially if they fail on you, it is very hard to determine the problem without taking it back to the manufacturer.

In terms of wattage...get the most power you are willing to spend money on. It really depends what type of rooms you will be playing in - 200 watts would do the trick in some, but you might have to push it and really strain the system to get some volume in some larger rooms. Do yourself a favour and get a big rig, with lots of nice comforting headroom.

You never can have too much power!


K

[drstawl]

>You never can have too much power!

True enough in most cases but:

When you put an amp with more power (potentially) to deliver than your speakers can handle without melting, it becomes a serious user responsibility to use this power wisely.

It's not a very common event for a signal input (fed live in real-time to your amp/speaker system) to be come horribly overloaded due to a loss of shielding- like the sound of a guitar amp with the input cable connected to the amp and the other end in your hand. But it does happen.

[Special K]

very true...but when I say "you can never have too much power" I meant in the sense that if you buy a 1000 watt amp, you buy speakers that are capable of being driven at this power loading.

There is no point having a 3000 watt set of speakers with a 60 watt amp! or vice versa.

If you do have the money, buy a SET of components that can run TOGETHER at their specified maximum wattage, maximising the potential of both speakers and amps.


K

[Matt303]

Its worth remembering when we talk about how many Watts that twice the Wattage is not twice the volume. What sounds loud (pardon the pun) is based upon a lot of things not least the frequency ranges you are trying to amplify. Anyone who has stood close to a fire alarm siren will know that with a relatively small power rating the volume is high over a small frequency range. All keyboard players will know that they need far more powerful amplification to match a guitarist volume even if the guitarist is playing though a low rated power amp the VOX AC30 is icredibly loud for the rating. This is because the keyboard is amplifying over a far greater range. Higher Wattage equipment will tend to give better transient response and better quality.
I agree with most of what has been said, in general, if you are not asking your vocal PA to do anything but amplify vocals and you dont want to spend a lot of money then the 'all in one' PA systems with built in pre amp, power amp and effects are a good enough. I have used the Peavey 200W per channel system into 4ohm cabinets to great success. If you choose your speakers carefully you can graduate to bigger systems. One thing nobody has mentioned is the microphones, better to spend some of your savings on good quality microphones. If the sound source is poor the PA is irrelevent it will always sound nasty