Proper PA power?

[bongomania]

I've almost always only ever run my amps at half power (gains say about 12 o clock)

...Except that having the gain knobs at 12:00 is no assurance of half power. It might be close to half gain, depending on the pot taper, but even at half gain your amp can produce its full maximum power, just by feeding it a stronger input signal.

 

[seamonkey]

Get modern power amp with a DSP
They have adjustable limiters
Some brands like Behringer let you dial in the max power the amp will put out. Perfect for horns.

 

[ggunn]

...Except that having the gain knobs at 12:00 is no assurance of half power. It might be close to half gain, depending on the pot taper, but even at half gain your amp can produce its full maximum power, just by feeding it a stronger input signal.

FWIW
I always run my amps wide open and control the system gain/volume at the desk.

 

[bongomania]

The extra power does allow for expansion / adaptation to meet the needs of the venue.

But this assumes more speakers are added for the expansion; so during non-"expanded" times, you're running a grave risk of blowing the smaller number of speakers that are connected. A careful-listening soundman with limiters in the chain can get away with this. That's not the same thing as a soundman just following a "rule of thumb" about 2x or 3x the power.

That's why I keep railing against that method--because it ONLY works if the soundman is very careful and attentive, and knows exactly what to listen for, and is not making any assumptions.

 

[Floyd Eye]

FWIW
I always run my amps wide open and control the system gain/volume at the desk.

I used to do this ( well at the desk and the crossovers) until I noticed that even with the slider all the way down I was still getting a ton of signal from my bass mic. Gain structure. Now I run them at about 3/4.

 

[ggunn]

I used to do this ( well at the desk and the crossovers) until I noticed that even with the slider all the way down I was still getting a ton of signal from my bass mic. Gain structure. Now I run them at about 3/4.

Channel trim?

 

[seanm]

If you really want to guarantee you never blow the speakers, get the new powered speakers. They generally have tons of protection built in. It's going to cost $$$$$$$ though

 

[thumbknuckle]

At least twice the continuous power rating is generally appropriate. Most people I know mixing on anything more involved than a couple two way boxes on sticks are using more than that.

In order to deliver the same SPL with half to a quarter of the power a professional would be using you are going to need to buy twice the PA. Those are some really expensive training wheels.

 

[Joe Louvar]

It's complicated. Yes, you can blow up some speakers/crossovers by driving them with a relatively small amp pushed far into clipping. I have done that and it was expensive. You certainly can blow up speakers by overpowering them as well. Done that, too.

A better answer than saying speakers should be 2X the amp rating or amp 2X the speaker rating IMO is that they should both be capable of producing 2X to 4X the volume you will ever need. If you never push speaker or amp even close to its limit, it doesn't really make all that much difference which is rated higher and your sound will be much cleaner. Headroom is where it's at.

Just like the Boy Scout "Be Prepared" motto.

 

[Joe Louvar]

But this assumes more speakers are added for the expansion; so during non-"expanded" times, you're running a grave risk of blowing the smaller number of speakers that are connected. A careful-listening soundman with limiters in the chain can get away with this. That's not the same thing as a soundman just following a "rule of thumb" about 2x or 3x the power.

That's why I keep railing against that method--because it ONLY works if the soundman is very careful and attentive, and knows exactly what to listen for, and is not making any assumptions.

If they don’t know that - they’re a just hack, NOT a soundman!!!

 

[Floyd Eye]

Channel trim?

If you just barely crack it and it's loud enough, turn your amp down.

 

[Joe Louvar]

Floyd Eye, I think what ggunn was saying is - if you had the channel properly trimmed you shouldn’t of had that problem.

 

[bongomania]

About all this talk of headroom and spl:

If the speakers are hit with more power than they can handle, there is no headroom. If the amp is not EVER using any more power than the speakers can handle, what use is the potential extra power?

If the extra power cannot ever go into the speakers, since we are talking about whatever level of power the speakers cannot handle, then where is this supposed extra spl? Nowhere. It doesn't exist.

Now, some speakers may be able to handle momentary transient spikes far higher than their wattage rating. In those specific cases, the things I said above don't apply, because of specifying that the speakers can handle the power.

It is not smart to assume that all speakers have some magical extra power handling above their ratings.

 

[ggunn]

Floyd Eye, I think what ggunn was saying is - if you had the channel properly trimmed you shouldn’t of had that problem.

That's not quite what I was saying; I was merely raising the question of channel trim. I haven't seen his setup.

 

[Joe Louvar]

That's not quite what I was saying; I was merely raising the question of channel trim. I haven't seen his setup.

Oh, I see - you were just asking if he had channel trim on his mixer - ok, my bad.

 

[Joe Louvar]

About all this talk of headroom and spl:

If the speakers are hit with more power than they can handle, there is no headroom. If the amp is not EVER using any more power than the speakers can handle, what use is the potential extra power?

If the extra power cannot ever go into the speakers, since we are talking about whatever level of power the speakers cannot handle, then where is this supposed extra spl? Nowhere. It doesn't exist.

Now, some speakers may be able to handle momentary transient spikes far higher than their wattage rating. In those specific cases, the things I said above don't apply, because of specifying that the speakers can handle the power.

It is not smart to assume that all speakers have some magical extra power handling above their ratings.

You’re missing the point - headroom as in power to spare so the amps don’t have to run as hard!!!

You can never have to much extra power!!!

 

[Joe Louvar]

If you really want to guarantee you never blow the speakers, get the new powered speakers. They generally have tons of protection built in. It's going to cost $$$$$$$ though

This could be a good way to go seeing as the amps/speakers are well matched. But note - if not careful they too can be damaged.

 

[bongomania]

Amp ratings are given for their normal safe clean operating range. A 1kw amp will not be strained too much by putting out 1kw. A 2kw amp will not have "an easier time" putting out 1kw.

 

[Joe Louvar]

You can never have to much extra power, and it’s much better to have more power than needed than not enough.

EDIT: PS - push amps at their full rated rate show after show, year after year and see how long those amps don’t last.

 

[EastCoastThump]

Can't have too much power? Sure you can.