So After doing even MORE looking around. Sleeping a bit. THE SHORT answer is that at 1-Khz, was agreed upon
was...
CUZ MAGAZINES MADE IT POPULAR.
Here is
Gene From Audioholics take on it.
Covid-19 Edition.
1kHz Power Sweep vs Distortion
(1kHz PSweep) - popularized by the print magazines, this is an instantaneous power vs distortion test at 1kHz. This is the test most manufacturers (and many print publications) do when rating their amplifiers " Continuous All Channels Driven". The problem with this test is it often masks slew related and or frequency response problems some amplifiers exhibit at the frequency extremes, and thus inflates the measured power results. It does provide an instant gratification number for consumers to argue over on the forums so we are now incorporating this test to please the masses. It also gives the consumers an apples to apples comparison between our ACD measurements and the measurements that the major print magazines do.
Now WHY would a Magazine do that? Would it just be Monkey see Monkey do? Or was it something that was repeatable? Something easy? The truth is, that it was the most Simple error free way to do it.
You have to think back to back in the day when getting a
reference grade signal generator cost more then some homes. Getting one that was based on the Audio band was not that much cheaper. Sure you could Build one. But then you have
all these other things to think about. Such has line level out, Impedance mismatch etc.
From INFOCOM:
There are two methods for setting system gain: Unity and Optimized. Both methods are relatively simple and neither requires expensive equipment. For a typical presentation/conference room/boardroom type environment, Unity Gain will provide an adequate system signal-to noise ratio – around 60 dB using professional audio components. If the first device shows a signal level output of 1.23 V, you should be able to measure a 1.23 V signal all the way to the power amplifier inputs. For a more critical listening environment such as a small studio, broadcast facility, performing arts center, lecture hall, etc., the System Optimization Method will provide the optimal signal-to-noise ratio allowed by the equipment in the signal path. This method takes more time and skill to complete than the unity gain method.
So if you think about it, testing something like an amplifier is easy if you are just doing one thing. POWER OUTPUT. But Amplifiers are not Linear output devices that perform one function so to speak. Unlike a Power Invertor that we want a set mode of parameters, (50-60hz, (cycles per second at the Zero Cross point of an Alternating current output?) @ 120-240 VAC at 15-20-30 or 50 Amps Rated Load; Audio amplifiers have to do the min of 20hz to 20 Khz at any level demanded at any power level from a Micro volt to 1000 watts; And do it with the least amount of distortion of the signal possible.
Now if you remember back in the day, how much gear could really do 20hz-20Khz FLAT White noise? Sure you could make electroinics that could do that. But did you have Playback gear that could? The Answer to that is No.
Heck your Tape decks can BARELY do this out of the box. Let alone FLAT. Let alone without adding anything else to signal (Distortion or extra noise) Let alone your Phono machines of the day.
But? You could build a Signal Generator that put out one tone at the time. And do it reasonably well for a modest cost that could be used as a reference. Then you run into another problem.
Audio Unity.
Andrei Martinez Agras:
Unity Gain, also called Unity Volume or volume at unity, is when the bypassed output level of a device that can be a guitar pedal, a studio hardware unit or a plugin is the same as when the device is engaged. Typically this can be achieved by using the output level control of the device or the auto gain function if its included. The importance of using unity gain levels when applying a process or effect is that a positive difference in volume can be perceived by our ears as an increase in fidelity and sound quality tricking us to believe the effect makes our tracks sound better even when the only change is volume. In this example we used a Maxon SD9 distortion pedal and Audified U73b v.2 compressor plugin on guitars and drum loop respectively.
This
link goes into Audio Unity and the white paper by AES. Thanks to Amrim for sharing this.
Amirm
Staff Member CFO (Chief Fun Officer)
Founder/Admin · From
Seattle Area
Basically, It ain't easy getting a solid reference grade signal from one device to another. And make it repeatable.
Things such as Gain from one Makers device to another can be different from brands etc. This is important as when you are trying to get the S/n (Signal to noise ratio, and Noise floor, & Dynamic range, this all plays into how you measure power.
And of course, there is another thing. Bass Frequencies from an electronic perspective require more power reproduce then High Frequencies. (Generally speaking) AKA why
Avionics use 400hz power vs 60hz. like you have at your wall outlet.
Here is a good Visual on that from the Big-Dummy Lord Supreme Mystro of OldSkool !
As you can see from these tests, the amp gives you different power levels of output on the dyno resistive load.
in practice? Unless you run magnepans or Ribbons? You will never see that power. And there is the whole
Amp stability thing as well. (second modern reference
here) And if you want to get your AES Inviite one day? Look
here.
With all these variables, you start to see the reason and logic of the 1 KHz Standard used for gain and power testing. It just makes things simple & repeatable. Not to mention it is a heck of a lot simpler for any human to hear it, and see it on an O-scope.
Remember, computers were not really common place in the 90's. Even worse still was that the know how on how to get your computer to take in a signal and then write the software on looking for a Distortion or un-lineratity in just the 20-20Khz bandwidth for just one second Stereo would be about 288 kB (kilobytes) for a 24 bit 48 khz sample rate. But say we just want to look at what they had back in the day. PCM @ 16 Bits @44.1 Khz---That would be 176.4 kB (kilobytes) a second sample with a data Bit rate of Bit Rate: 1411.2 kbps (CD RedBook audio)
So, with that in mind, we know have a screaming fast 286 CPU. Well. Hold on here. It still can't PLAY BACK PCM by itself.
Not in real time with everything else it has to do.
So you are in the Pentium Area. That was the late 90's. If you got the hardware to do it, then you could. But then again, just doing the Data calculations would have taken the machine at least a gigabyte of data. More then the CD at the time to do a Full analysis. Let alone the RAM needed. And Custom hardware.
It would have taken you for just that ONE second of audio? about a day or two if you wrote that program in C. More like a Week if we are being honest.
If you did do this kind of work? You had one of these.
Or an SGI workstation.
And a few of these:
But most likely, you had this to work with:
And just Writing the program to do this would have cost you upwards of maybe a Million dollars. Lets not forget the hardware you need to make it work all custom built.
Or you Went to HP and got a turn Key solution. If you were lucky, You could get a GREAT deal on a Vacuum Tube Frequency counter.
And you need all this too.
For a Magazine? Or for anyone else? Using the 1Khz method sure is a LOT simpler and a O scope.
The other thing to take into account is that what you get from the LAB is not going to be what the End user gets.
This is more of a Problem with Car Audio. As you can tell, we have all sorts of Standards that are used for gain. Its my opinion that its the reason why the Optical Output or Digital output is the perfered method and why it sounds so good as you get bar none the FULL output of any gear. Its all to a standard already (SPDIF/Toslink)
So from your source, (Car Radio) to your Amplifiers, if you can take it all the way to the last item in the chain, then you get that full dynamic rage possible. Hence, at that point, you don't even need to bother with gain settings. Its all done for you. (See Rockford Fosgate's/ Stillwater Designs Link Above and other links to point out gain vs Dynamic range and Loudness levels)
When you do all the Math, and calculations of all the variables? You get the magic 1 Khz to set gains that works across all gear. And Anyone with Basic tools can do this and get the same results. (Mostly)
Some Reference Points.
Amplifiers, explained with the minimum of maths. Amplifier design, Amplifier Classes A to H, NFB, Circuits, Power Amplifiers, Op amps.
learnabout-electronics.org
Amplifiers, explained with the minimum of maths. Amplifier design, Amplifier Classes A to H, NFB, Circuits, Power Amplifiers, Op amps.
learnabout-electronics.org
Guys, I need help with direction on how to measure my 4ch car amp for crossover point, gain and response. Channels 1&2 are bridged to drive left speakers and channels 3&4 are bridged to drive the other side. Now on with my problems: 1. Gain setting: with this setup the left and right...
www.diyaudio.com
I'm pretty new to car audio but am an electrical engineer so I have some background in gains and filters and such. I've recently upgraded the sound system in my 2012 Hyundai Elantra. I have an Alpine MRP-F300 driving Infinity Reference 6030cs in the front and 6032cf in the rear. Also an...
www.diymobileaudio.com
Okay, here's a write-up based on the notes I took while Mark Eldridge was setting gains on ItalynStalyn's car. I'm sure there are some errors here and there. Please point them out, so i can edit this. I plan on adding pics when I can get them. By properly adjusting gain setting in an audio...
www.diymobileaudio.com
Tests your audio equipment, speakers, room acoustics and hearing. Audio signals and test tones playable online. High resolution sound test files available for free download.
www.audiocheck.net
Moving the discussion to a new thread. Don't want a specific issue cluttering up the in house random thread:biggrin:. 1. Yes 53/63
forum.polkaudio.com
This guide covers how to simulate the gain margin and phase margin to assess stability in an LM3886-based chipamp. The impact of the Zobel/Thiele/Boucherot Networks on stability in audio power amplifiers is simulated in TINA-TI.
neurochrome.com
www.psaudio.com
WAY more then you need to know. But Hey, I had time on my hands. I hope you find all this Info Useful.