DiyMobileAudio.com Car Stereo Forum banner

1 - 13 of 13 Posts

·
Registered
2013 VW CC
Joined
·
114 Posts
Discussion Starter #1
I’m wondering does anyone actually know why when setting gains everyone says use 40 or 1000hz?
I can’t comprehend why I would want to set the gains of a amp running tweeters with 1000hz because the amp is ever even going to see 1000hz. It is only going to be amplifying whatever frequency range I send it. NOT THE ENTIRE SPECTRUM.
So how does that make any sense at all?
I can understand it if running passive system. But active it make zero sense.
Say i run my tweets from 3000-20k. It doesn’t matter when the amp clips at 1000hz.
Same thing for setting midrange and midbass. It makes more sense to use tones within the givin signal the amp will be seeing.

And another thing, who chose these couple tones 40 and 1000. Why would we set the gains to not clip at 1 frequency instead of playing pink noose or something playing the whole spectrum?
Yeah it may not clip at 1000hz but what about the other 19999 frequencies?
 

·
Registered
Joined
·
11,974 Posts
you will want to set the gains in the range that they will be playing. setting sub gains at 1khz is pointless as setting tweeter gains there. they wont play it.

personally, set the gains with your ears. if it is too bright turn down tweeters. etc
 

·
Registered
2013 VW CC
Joined
·
114 Posts
Discussion Starter #3
THats what I did. Lol
 

·
Registered
Joined
·
1,837 Posts
Some background is that amp power is universally specified using 1,000 Hz since it is unknown what speaker will be playing. Actually, I can’t find where it says amp power is taken at 1,000Hz but the Texas Instruments paper below mentions the FTC requires 1/8th power preconditioning at 1,000Hz so maybe that has something to do with the 1,000Hz “standard”. I also looked at CEA power guidelines but while it covers power and S/N, it doesn’t specify at what frequency power should be rated, at least not that I could find in a quick search.


However, if you want to set your gain via a test signal, pick a set and play a tone in that range. So for the 1,000Hz test tone, you’d be setting the baseline gain of your system to the mids. Then you wouldn’t use any other test tones, you’d level set the gain on the other channels (subs and tweets) based on the output level of the mids. So your mids at that point would drive the gain structure for the other channels.
 

·
Registered
2013 VW CC
Joined
·
114 Posts
Discussion Starter #5
Dgage thanks for the info.
 

·
Registered
Joined
·
11 Posts
Setting the gains with tones is mostly about having as much SPL available as possible without clipping.
For subs 40Hz makes sense. And for mids 1000Hz makes sense. I think most people still sets tweeter level to sound good with the mids, by ear.

I would think that setting it all by ear would make the most sense, and so do many others...
 

·
Registered
Joined
·
204 Posts
I went looking. Here is what I found.

Audio frog

Points to Harvey Fletcher. (Dutch?) Na.. BRITISH!
263817
Harvey Fletcher’s study of acoustics led to many innovations, and he continued learning and teaching about his field throughout his life.


From BYU:
Sound Science - BYU Magazine




THIS DUDE WAS THE TESLA OF AUDIO! And he even had time for 7 kids!
263818





Article BYU
The Father of Stereophonic sound.

Something else you should hear. This man did this. Please read and listen. AMAZING

From this 1923 Edison cylinders:
<iframe width="100%" height="166" scrolling="no" frameborder="no" src=" https://soundcloud.com/player "></iframe>

To this 1932 FLETHERFIED!:


Fletcher and Munson curves

WILDEN MUNSON, BELL LABS
263821




263822


LINK:

ISO Standard both developed



Human response curve with loudspeakers


Specifically on Audio level measurements
Audio system measurements - Wikipedia

Output powerOutput power for amplifiers is ideally measured and quoted as maximum Root Mean Square (RMS) power output per channel, at a specified distortion level at a particular load, which, by convention and government regulation, is considered the most meaningful measure of power available on music signals, though real, non-clipping music has a high peak-to-average ratio, and usually averages well below the maximum possible.

The commonly given measurement of PMPO (peak music power out) is largely meaningless and often used in marketing literature; in the late 1960s there was much controversy over this point and the US Government (FTA) required that RMS figures be quoted for all high fidelity equipment.

Music power has been making a comeback in recent years. See also Audio power.Power specifications require the load impedance to be specified, and in some cases two figures will be given (for instance, the output power of a power amplifier for loudspeakers will be typically measured at 4 and 8 ohms). To deliver maximum power to the load, the impedance of the driver should be the complex conjugate of the impedance of the load. In the case of a purely resistive load, the resistance of the driver should be equal to the resistance of the load to achieve maximum output power. This is referred to as impedance matching.


RMS or Root mean square
Root mean square - Wikipedia

In frequency domain
The RMS can be computed in the frequency domain, using Parseval's theorem.




ITUR-56

The origin of the current ITU-R 468 weighting curve can be traced to 1956. The 1968 BBC EL-17 report discusses several weighting curves, including one identified as D.P.B. which was chosen as superior to the alternatives: A.S.A, C.C.I.F and O.I.R.T. The report's graph of the DPB curve is identical to that of the ITU-R 486 curve, except that the latter extends to slightly lower and higher frequencies. The BBC report states that this curve was given in a "contribution by the D.B.P. (The Telephone Administration of the Federal German Republic) in the Red Book Vol. 1 1957 covering the first plenary assembly of the CCITT (Geneva 1956)". D.B.P. is Deutsche Bundespost, the German post office which provides telephone service in Germany as the GPO does in the UK. The BBC report states "this characteristic is based on subjective tests described by Belger." and cites a 1953 paper by E. Belger.



i-TUR56


DIYMA GAINS



RF Tech

still no real answer....
 

Attachments

·
Registered
Joined
·
204 Posts
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.

263844
Covid-19 Edition.
263845


(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.
263850


263851
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.
263859


Or an SGI workstation.
263860



And a few of these:
263861


But most likely, you had this to work with:
263863



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.
263866




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.


















WAY more then you need to know. But Hey, I had time on my hands. I hope you find all this Info Useful.
 

·
Registered
Joined
·
511 Posts
Sooo ... setting gains with pink noise is a bad idea ? What if you do it with crossovers applied but an otherwise flat signal ?
 

·
Registered
Joined
·
7,873 Posts
Sooo ... setting gains with pink noise is a bad idea ? What if you do it with crossovers applied but an otherwise flat signal ?
Pink noise isn't very good for setting gains. You can use tones and a meter, or just do it by ear (my preferred method).
 

·
Registered
2013 VW CC
Joined
·
114 Posts
Discussion Starter #13
I have a dd1. When I am using it, say I’m using 1000hz tone. The 1000hz led comes on, then as I increase the gain on the amp or output power from the helix there is a point where he 1000hz light goes out. About two clicks on my B2 audio amps. Then the distortion led will come on and sometimes with no 1000hz led lit. Sometimes the 1000hz led and distortion led will light.
Is my dd1 faulty?
 
1 - 13 of 13 Posts
Top