actual power output?

[seamonkey]

There's no "standard" because there's not enough consumers in the MI industries for governments to care, and there's not enough consumers in the industry to demand a standard. Your $$$ matters but you have to insist.

In the case of FOH/PA - yes, there are enough to demand standard of measurement because many shows are bankrolled by investors who care and insist on standards of measurement.

 

[Analogeezer]

I think the biggest clue to how "honest" an amp company specs are is if they label the amp name with the four ohm output (e.g. B600XLX or whatever) but do not provide a spec of the amp's output at 8 ohms.

This kind of rating is known as "marketing watts" LOL

Analogeezer

 

[Al Kraft]

IME many people quite erroneously assume that their ears and the volume or master knob position is an accurate way to compare different amplifier capabilities.

 

[byacey]

IME many people quite erroneously assume that their ears and the volume or master knob position is an accurate way to compare different amplifier capabilities.

If it's brain bursting when the input is at 11 and the master at 2, it must certainly be a powerful amp, no?

 

[Al Kraft]

If it's brain bursting when the input is at 11 and the master at 2, it must certainly be a powerful amp, no?

As all experienced technical people (like yourself) know...it depends!

 

[byacey]

As all experienced technical people (like yourself) know...it depends!

I've witnessed many times someone describing their amp as being "very powerful" because it's loud with the master at a low setting. Of course many of these same people believe they have a genuine Stradivari violin that their grandfather had packed away in the attic!
I found it's best just to nod quietly and agree rather than trying to explain the facts.

 

[Al Kraft]

I've witnessed many times someone describing their amp as being "very powerful" because it's loud with the master at a low setting. Of course many of these same people believe they have a genuine Stradivari violin that their grandfather had packed away in the attic!
I found it's best just to nod quietly and agree rather than trying to explain the facts.

All too frequently people mistake overly simple, easy to understand internet representations from less than credible sources as scientific truth. Of course those of us who practice in scientific and technical fields know these generalizations and folklore explanations almost always have little to no basis in fact. Sadly though, most folks don't want hear the often lengthier "it depends answers" which are the correct ones as context and detail matter when addressing a technical question.

Fortunately, my field of practice keeps me around people who get it and have no tolerance for or patience with those who can't back up their answers with solid science and best practice. I would go insane if I had to work in the regular world where people just want fast, easy, and simple...oh yeah, and cheap or free is simply a given.

 

[Foz]

For every complex problem there is an answer that is clear, simple, and wrong.

Invalid Link Removed

 

[TieDye]

How are you measuring?

At this time i don't own a high power resistive load so I cannot measure maximum output. I looked on Ebay and can get a 1`00 watt load for around 40 bucks. I just posted this here to make sure so one else was already doing

 

[TieDye]

Not sure anyone I know of is claiming to produce 2000 watts from 125 watts, but anyway P=VI is all you need to know.

I bought a Behringer that claims 2000 watts but only draws 125 watts from the power source. It didn't get as loud as my 250 watt practice amp so I returned it.

 

[TieDye]

My 800W labeled Mesa into my 212 produces more measured dB than the 1,000W Crest power amp into a 2-15 (EV) plus 4-12 stack I used to run. It's not the Watts. It's not the Ohms. It's not even the tort. It's the decibels.

Efficiency of the speaker also influences the sound vs power.

 

[TieDye]

There is no difference in how class D amps are rated compared with class AB amps.

The problem is that different manufacturers have in fact rated their amps using different metrics (such as "peak" versus "RMS)", or "burst (20mSec versus continuous (or continuous for amplifier purposes). For bass guitar or guitar purposes, THD is nowhere near as important as for other applications because the instruments themselves generate 10X the THD the amp does under linear operation.

You have to use your brain a little bit to sort through the specs, some manufacturers provide comprehensive specs that clearly state how the power is measured and some manufacturers provide almost no information (or information written by the marketing department without control of the engineering folks). I am strongly in the first camp as a designer.

Regarding power input versus power output, what you may be missing is what the safety and EMC regulators require for how power input is calculated. I have done these calculations here many times yet it still seems to be misunderstood.

Let's say an amp is rated for 1000 watts RMS into 4 ohms. The regulators require that the AC power (or current) draw is printed on the back of the amp and it's based on 1/8 of rated audio power, though it can be more IF the amp is designed and intended to be operated at higher than 12.5% duty cycle. 1/8 of 1000 watts is 125 watts (which is 1/8 of rated audio power). Now, the amp and PSU efficiencies must be factored in, a typical class d amp with SMPS is going to be about 85% efficient so the input power is 125/.85 = 147 watts. This is how the power draw number is arrived at. For a typical class AB amp w/ line frequency power supply, the efficiency number is going to be around 50%, so the power draw would be 125/.5 = 250 watts.

Different designers qualify their amps differently. For example, I have (very) detailed specifications for my products, and they are easily understood by professional engineers who design and test amplifier products. They would look like Greek to an average person however. Like the amps themselves, different designers place different levels of importance on different aspects of their products. As a word of caution, I have seen significant mistakes made by magazines that have attempted to measure things that they did not fully understand. This causes folks who don't understand this to draw incorrect conclusions which get perpetuated like a bad rumor.

I didn't expect standards of measurement to have changed. I do believe that the published numbers today are not comparable to the published numbers from back before class D was a thing. I believe that manufacturers don't often publish real RMS output any

 

[TieDye]

There is no difference in how class D amps are rated compared with class AB amps.

The problem is that different manufacturers have in fact rated their amps using different metrics (such as "peak" versus "RMS)", or "burst (20mSec versus continuous (or continuous for amplifier purposes). For bass guitar or guitar purposes, THD is nowhere near as important as for other applications because the instruments themselves generate 10X the THD the amp does under linear operation.

You have to use your brain a little bit to sort through the specs, some manufacturers provide comprehensive specs that clearly state how the power is measured and some manufacturers provide almost no information (or information written by the marketing department without control of the engineering folks). I am strongly in the first camp as a designer.

Regarding power input versus power output, what you may be missing is what the safety and EMC regulators require for how power input is calculated. I have done these calculations here many times yet it still seems to be misunderstood.

Let's say an amp is rated for 1000 watts RMS into 4 ohms. The regulators require that the AC power (or current) draw is printed on the back of the amp and it's based on 1/8 of rated audio power, though it can be more IF the amp is designed and intended to be operated at higher than 12.5% duty cycle. 1/8 of 1000 watts is 125 watts (which is 1/8 of rated audio power). Now, the amp and PSU efficiencies must be factored in, a typical class d amp with SMPS is going to be about 85% efficient so the input power is 125/.85 = 147 watts. This is how the power draw number is arrived at. For a typical class AB amp w/ line frequency power supply, the efficiency number is going to be around 50%, so the power draw would be 125/.5 = 250 watts.

Different designers qualify their amps differently. For example, I have (very) detailed specifications for my products, and they are easily understood by professional engineers who design and test amplifier products. They would look like Greek to an average person however. Like the amps themselves, different designers place different levels of importance on different aspects of their products. As a word of caution, I have seen significant mistakes made by magazines that have attempted to measure things that they did not fully understand. This causes folks who don't understand this to draw incorrect conclusions which get perpetuated like a bad rumor.

Regarding "The regulators require that the AC power (or current) draw is printed on the back of the amp and it's based on 1/8 of rated audio power," This would make that information useless to a power engineer who was calculating how much power he needed to supply for a rack full of audio amplifiers. It also doesn't take into account the efficiency of the power supply and power amp. I've seen some amps with larger draw from the source ratings than their output ratings, and this makes question whether manufacturers aren't just making that spec up as well. I have asked design engineers about the discrepancy in our products when i worked for a manufacturer. They hemmed and hawed for a few minutes and then referred the question to marketing people who said "Those are different kind of watts". Of course marketing people aren't reliable technical authorities.

 

[agedhorse]

I didn't expect standards of measurement to have changed. I do believe that the published numbers today are not comparable to the published numbers from back before class D was a thing. I believe that manufacturers don't often publish real RMS output any

Not at all true, and has never been true.

There are and have always been honest, up front manufacturers with accurate published specs and those who don’t.

I have used RMS power ratings in all the products I have designed going back 30+ years, others have as well.

Regarding "The regulators require that the AC power (or current) draw is printed on the back of the amp and it's based on 1/8 of rated audio power," This would make that information useless to a power engineer who was calculating how much power he needed to supply for a rack full of audio amplifiers. It also doesn't take into account the efficiency of the power supply and power amp. I've seen some amps with larger draw from the source ratings than their output ratings, and this makes question whether manufacturers aren't just making that spec up as well. I have asked design engineers about the discrepancy in our products when i worked for a manufacturer. They hemmed and hawed for a few minutes and then referred the question to marketing people who said "Those are different kind of watts". Of course marketing people aren't reliable technical authorities.

You are showing that you do not understand the purposes behind these ratings, why and what they are used for.

Different engineering needs use different specifications. For example, for HVAC loading, the power consumption at 1/8 rated power converted to BTU accurately reflects the cooling load required due to the audio equipment. Efficiency IS built into this number as well.

For the EE’s, the 1/8 rated power consumption would be used to calculate feeder ampacity, panel ampacity and service ampacity. It would also be used to calculate unit transformer VA requirements.

For branch circuit calculations, many engineers would use somewhere between 1/4 and 1/3 rated power to account for dynamic load influences and voltage drop calculations.

Efficiency is certainly built into these numbers.

I am both an amplifier design engineer AND a power systems engineer, with a 40 year career.

If you choose to continue down this path, please choose your arguments carefully. Do not call manufacturers dishonest without understanding more than those you challenge. So far, what you have shown of your hand does not support your position one bit.

 

[Al Kraft]

I didn't expect standards of measurement to have changed. I do believe that the published numbers today are not comparable to the published numbers from back before class D was a thing. I believe that manufacturers don't often publish real RMS output any

I can assure that a number of them do and those companies and some of their key people participate in this forum. The actual engineering measurements (in Volts, Watts, Ohms, etc.) and their meanings have remained the same since I started in engineering in the 70's. I do think some of the industry standard measurement protocols/procedures used to create published specs may have changed from ones used years ago. However, all amplifiers regardless class or whether they're tube or SS perform the way the perform and IME no single measurement regardless of how accurate and precise is likely to tell that entire story.

 

[Analogeezer]

I bought a Behringer that claims 2000 watts but only draws 125 watts from the power source. It didn't get as loud as my 250 watt practice amp so I returned it.

Ahhhh yes, Behringer watts LOL.

The last band I was in, when I went to audition it was just a drummer and a guitar player. The drummer had gone on a buying binge and bought some kinda Behringer powered mixer with built in effects and supposedly like 1,000 watts. He also had Behringer speakers.

Well it sounded like ass and the power amp section was clipping just getting over the guitar player, the drummer (he did play loud) and my Ampeg B2-R with a single 2 x 10" cab.

The jam went well and we decided to go ahead and "form a band". I asked the drummer if he minded it I brought over some of my PA stuff the next weekend, he said "great" because he realized the Behringer thing was not getting it.

So I brought over a 12 channel Mackie Onyx mixer, a QSC PLX-1602 and a pair of EV speakers. Oh yeah and an Alesis Wedge for effects. This is what I call my "tiny PA for small gigs" setup.

Even though the PLX was putting out maybe 600 watts total it just mopped the floor with the Behringer. I kind of nicely explained to the drummer the Behringer thing re: watts and all and he sent all the stuff back that week as he had only purchased it a couple of weeks before.

I also explained to him most powered mixers were not sufficient for what we were trying to do (did I mention he played REALLY loud) and what he really needed was a mixer and a dedicated power amp.

Powered speakers with high powered Class D amps were just starting to appear back then and most did not sound that good and a lot of them were rather unreliable. Things are very different with that today of course but I still prefer a dedicated power amp with speaker lines. Running A/C cables to everything all around the place gets old really fast.

But yeah, the formula goes "Behringer watts /4 = actual watts" LOL

Analogeezer

 

[Piper Bob]

I have a Mackie PA speaker that’s marketed as 1500 watts but it only draws about 100 from the outlet.

 

[teemuk]

I have a Mackie PA speaker that’s marketed as 1500 watts but it only draws about 100 from the outlet.

It's an audio amp. It's expected to amplify complex signal with high crest factor. It's not expected to drive a motor with continuos sinusoid output. How come this concept is so hard to grasp?

Being able to deliver momentary burst power is enough to cover short transients of music signal, after which the nominal power output drops to fraction of that. Power supply of the amp has this thing called "capacitance" that allows supplying this much higher peak power than what the amp consumes from the mains nominally.

Works perfectly for audio. Most class-D things would melt - or at least thermally shut down / limit - if expected to deliver the rated high power continuously. And with audio this is not an issue.

Also... speaking of "Behringer watts". I'm not familiar how Behringer or Mackie derive their power ratings but if "they are not as loud as some other amp" is the only reason you think they are being dishonest about them then it really just demonstrates you still have a lot to learn about output power vs. perceived loudness.

 

[agedhorse]

There is nothing that inherently limits the concept of a class D amp delivering power continuously, and in fact that’s exactly what a (modern) AC power inverter is!!!

Most amplifiers (including class AB amps) are not rated for continuous power delivery for several good reasons:

1. Music is not a continuous sine wave, it has dynamics which are reflected in the duty cycle or crest factor of the waveform. Uncompressed, undistorted bass runs around 12.5% duty cycle which equates to 1/8-rated continuous power. Compressed or distorted bass is around 25% duty cycle which equates to 1/4-rated continuous power.

2. Speakers are not designed to handle continuous power either, so the lack of continuous amplifier capability is already limited by the speakers themselves.

3. The unused (and unusable) continuous power doesn’t change performance but would simply add cost, size and weight.

4. The concept of duty cycle is used in many products unrelated to audio as well. For example, car engines and drive trains would quickly fail with operation at rated horsepower if run that way. That’s why 500HP engine and drive train on an over the road truck, used with higher continuous power, is so much more robust (and larger, heavier, more expensive) than the equivalent power in a car that is operated at a fraction of its continuous rated power.

5. I have designed power amps that could deliver rated power for many hours (longer than any gig) but there was no real world advantage to the player. They were also larger and heavier than necessary.

 

[Deleted member 165050]

Also... speaking of "Behringer watts". I'm not familiar how Behringer or Mackie derive their power ratings but if "they are not as loud as some other amp" is the only reason you think they are being dishonest about them then it really just demonstrates you still have a lot to learn about output power vs. perceived loudness.

Not sure about Mackie, but I believe Behringer released a document justifying how they derive their power ratings. I'm sure it's online somewhere.