The first part of that sentence references this specific thread because the stated speaker specs are not legitmate, you referenced the powered version to demonstrate that and I agree.
The second part of the sentence references powering speakers in general where a 1000w amp would be a legitimate option to power a 250w RMS speaker. That ratio(2x Program) is often recommended in pro applications as it allows the system to attain maximum performance from the speakers without ever clipping the amplifier, and in my own experience has proven to produce excellent results.
This arrangement gets “maximum performance” out of speakers because it is where both the amplifier and speaker are intended to be run. 500W program, 250 RMS (or AES) really means that the long term thermal capacity of the speaker is 125 watts. AES rating is a 3dB crest factor, program typically 6. Amplifiers are intended to be used around 1/8 of rated RMS (or maximum average) power. That amp rating on the back by the IEC connector is the number of amps it draws off the wall socket with a noise signal (similar to music) run up to produce 1/8 of rated power on average. Look it up in the spec manual (which may also indicate amp draw at full rated power, which is typically FAR above 15 amps). If you look at this waveform on an oscilloscope you will see *clipping*. Usually not enough to be audible or objectionable. That 1000 watt amp, putting out a long term thermal average of 125 watts, which EXACTLY matches the speaker. This is as loud as it should be run - if it needs to be played louder, you REALLY need bigger speakers (and the proper amp for them).
That powered version probably had some abuse margin built into it - with the amplifier intentionally made much smaller. Low end gear sometimes (but not always) does, because users often try to get too much out of them. This is somewhat aligned with amp sizing for systems which get intentional abuse. Every DJ has found themselves in situations where no matter how loud it is, it’s not loud enough unless it sounds like the rig is fixing to explode. When I run a gig in those conditions, I use mid/hi speakers with an AES rating at least as high as the amp, and subs at least double. And run the amps 8 ohms per channel to keep the heat down and keep from tripping breakers in the main panel. The amps are simply too small to do damage.
That powered version probably had some abuse margin built into it - with the amplifier intentionally made much smaller. Low end gear sometimes (but not always) does, because users often try to get too much out of them. This is somewhat aligned with amp sizing for systems which get intentional abuse. Every DJ has found themselves in situations where no matter how loud it is, it’s not loud enough unless it sounds like the rig is fixing to explode. When I run a gig in those conditions, I use mid/hi speakers with an AES rating at least as high as the amp, and subs at least double. And run the amps 8 ohms per channel to keep the heat down and keep from tripping breakers in the main panel. The amps are simply too small to do damage.
Your statements are absolutely correct. I can only add to them a little. The amplifier-loudspeaker pair chosen must match the crest-factor of the musical signal, and they were chosen for a fairly large crest-factor, which is more appropriate for jazz music, not just vocals, where it is not very big, no more than 3dB and the smaller it is, the maximum power is closer to the thermal limit
ANY “real” music has a crest factor of 10+ dB, not just jazz. Anything played live with actual instruments will be higher, but usually the mix is compressed or the amps are run a bit into clipping until the crest factor IS about 10 dB when the music is at its loudest. At that point, the sound quality is generally acceptable. A DJ creating distortion for effect has the same crest factor as a guitar amp - between zero and 3dB. Some “ghetto bass” can stay near zero dB, because it literally sounds like someone thumbing the end of an RCA cable, with an occasional interruption. Close enough to zero dB crest factor, and when you drive the amp into clipping you certainly get it to zero dB. But sound systems are NOT intended to be used that way, and because of the gross distortion produced. Anybody in the trade making a living off it will not run the equipment that hard unless they are specifically rigging it for battle (and most real professionals will just refuse that kind of work). Even then it requires a substantial investment in speakers because they have to handle the average power produced.
If a rock band is playing live, and their PA is only running a crest factor of 3 to 6 dB, where the speakers are likely in danger - it probably sounds like HELL. And should be either turned down, or get bigger speakers (and amps) until the distortion goes away.
If a rock band is playing live, and their PA is only running a crest factor of 3 to 6 dB, where the speakers are likely in danger - it probably sounds like HELL. And should be either turned down, or get bigger speakers (and amps) until the distortion goes away.
It does not work that way. [2]
In a real world situation, doubly so in the hands of inexperienced operators such as here, power amps are GUARANTEED to be driven into clipping.
The nice theory of "use a bigger amp so it never clips" simply does not happen.
THAT, + 1000
OF COURSE it will sound like Hell.
Will an operator turn it down?
Of course not!!!!
We are not talking a World Touring Band setup in a Stadium , with lots of roadies and operators, 2 days to setup everything, equipment driven in with 18 wheelers, but a quick and dirty local Club, Hi School Gym type situation, hastily set up by amateurs.
Shock of reality: 500/8 amp, NO LIMITERS, driving a 170/8 cabinet (manufacturers themselves use them that way, they "should" know), passive crossovers , loud backline .... a perfect storm waiting to happen.
I know there are many high level Pros around ... but situation here is more greasy joint $2 burger than $170 Filet Mignon dinner
If an operator doesn’t turn it down and it blows up its on him. Bottom line is many amateurs run their rigs too hard because they don’t have enough MONEY to buy what is REQUIRED.
People think an amateur like me is crazy building a DIY rig the size of what I have, but at least it *can* sound like a professional did it. And if they want it to sound like it’s being run within an inch of its life I can do that too - without blowing anything up.
People think an amateur like me is crazy building a DIY rig the size of what I have, but at least it *can* sound like a professional did it. And if they want it to sound like it’s being run within an inch of its life I can do that too - without blowing anything up.
Except that it does, my own passive rig includes amplifiers that are capable of up to 4x the drivers rms power ratings. The difference is these are all high quality B&C and RCF drivers and the amp rack has custom dsp processing and limiting.
Yes.. but as I stated above SEVERAL TIMES.. adequate speaker protection is NOT OPTIONAL!! No professional equipment provider in business today utilizes a passive PA system without DSP processing, all powered speakers made today include extensive DSP speaker protection specifically because the product wouldn't make it through a single event without it.
Tell THAT to the OP
And thousands others
It simply happens very often.
Tell me something I/we/they don´t know
Good for you, congratulations.
No doubt bout that .... but then you "know".
Average unknown Rock band operator dialogue:
"How did you set up the limiters?"
"Limiter? ... what´s a limiter?"
Of course we are not here to shame the OP, but to give him sensible answers for the next time.
Thanks for agreeing and proving my point
IF I wanted to nitpick, and going even further:
If OP has a 500W amp , but 170W *real* capacity speakers , and sets Limiters and Processing so it never ever goes beyond 170W RMS so it never clips , then in practice (and measurements will back that) he has a 170W RMS amp, by definition.
Which is exactly my point.
Even more, and to address the opposite situation: if he has same setup, and a power amp built-in limiter (very common feature) which is not adjustable (almost none is, only ON-OFF at best) but detects clipping or reaching within 5V of rails so maximum possible output is, say, 499 unclipped W RMS, he will still blow mid/highs driver, given time (as in on the first feedback squeal).
I know you are a seasoned PRO and know how to do things right ... simply you are not a representative sample and this is the best of compliments.
Me?
I have worked with the best, including Luis Miguel, Paco de Lucia, Zubin Mehta, BB King, Megadeth, and most Blues and Jazz celebrities visiting Buenos Aires ... including local Stadium filling acts, of course, for over 50 years now, but the customers who put most of the beans in the pot are smallish Rock bands, think neighborhood or High School known bands, similar to the OP Daughter´s one.
I could fill pages with "horror stories"
Oh well, nobody is born knowing, practice makes perfect.
PS: the trivial solution, which is both simple, cheap, and requires no sophisticated adjustments or Operator input, is what the Cabinet manufacturers did: they fit a plain 170W amp (I bet they determined by test and error that´s what it safely handles) with a simple fixed Limiter, nothing further, and it becomes a saleable product.
Just for reference, check our friend APEX "500W amp with limiter" : robust and simple, and Limiter is self triggered on getting within 5V of positive rail.
Very simple and efficient and requires NO adjustments whatsoever.
It´s an "universal" type and can easily be added to other power amps ... including OP´s
(hint hint)Personally I LOVE minimalistic but efficient solutions
The “sensible answer” is the original speakers were too small. You ought to have seen what one of those girl bands did to a pair of Pioneer monkey coffins with an old QSC - it was *hilarious* (and 30 years ago).
Most PA amps have those automatic clip limiters, which do work for the most part. The time constants are set to preserve most of the dynamic range of the music - which normally prevents you from turning it up too loud and putting out excessive average power. Doesn't mean you can’t blow up a cheap $10 tweeter (it’s just too easy) - but will usually save the woofer and any real compression driver. You can always drive them hard enough that at maximum gain reduction you’re still clipping, but usually pretty hard to do with a run of the mill mixing board unless you clip that too. And if you overcompress ahead of them, they can’t tell and the crest factor can get excessive. And of course they can usually be disengaged. They *can’t* on my CA18’s, but why would I want to? No help at all for feedback at mid/hi frequency where you send full power to the compression driver, or for one note hold your finger on the RCA cord bass. Can’t have everything, especially considering the cost of a couple of transistors and an OTA.
If the OP had been running with limiters on those speakers, it probably wouldn’t have been “loud enough”.
Most PA amps have those automatic clip limiters, which do work for the most part. The time constants are set to preserve most of the dynamic range of the music - which normally prevents you from turning it up too loud and putting out excessive average power. Doesn't mean you can’t blow up a cheap $10 tweeter (it’s just too easy) - but will usually save the woofer and any real compression driver. You can always drive them hard enough that at maximum gain reduction you’re still clipping, but usually pretty hard to do with a run of the mill mixing board unless you clip that too. And if you overcompress ahead of them, they can’t tell and the crest factor can get excessive. And of course they can usually be disengaged. They *can’t* on my CA18’s, but why would I want to? No help at all for feedback at mid/hi frequency where you send full power to the compression driver, or for one note hold your finger on the RCA cord bass. Can’t have everything, especially considering the cost of a couple of transistors and an OTA.
If the OP had been running with limiters on those speakers, it probably wouldn’t have been “loud enough”.