Why is there a difference between internally generated test tones and Disk based tones levels? - AVS Forum
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post #1 of 16 Old 11-27-2012, 03:29 PM - Thread Starter
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I was redoing the setup on my small bedroom system and used the tones internal to the Insignia 511 and my RS audio level meter to set levels. I had all 5 speakers matched pretty closely using the internal tone, then I checked it using the AVIA test disk that I ripped to my computer, and the levels varied quite a bit. I noticed a similar thing with my Onkyo system set up using Adussey. I have a hunch the Insignia is an Onkyo based receiver, wondering if it's peculiar to that manufacturer or is it common.

Which is more accurate? There was a significant variation using the AVIA tones.
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post #2 of 16 Old 11-27-2012, 03:34 PM
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Can't speak for the AVIA disk or the Insignia AVR, but the Onkyo uses a 75db test tone to calibrate the unit to reference level of 85db.

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post #3 of 16 Old 11-27-2012, 06:47 PM
 
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there is a difference there because there really isnt a reference level to speak of when you put a level on the chip or disc with an adjustable volume knob.

see..
if it was all done in organized fashion, then there wouldnt be a volume knob on the receiver .. it would be a gain knob to get you at the reference level.

there isnt really a reference level either though.
because reference level is what lets 10,000 people listen to something and hear it exactly the same as if you were the microphone standing there listening.
it means the recording would need to be raised or boosted to meet the reference line.


yes..
it would help a tremendous deal to get in there and look at the compiler for the sample conversion, and then pick something as the reference 0dB to allow every single thing after that to go back to that 0dB
everything .
from amplifier's with 100 watts to amplifiers with 500 watts
to dvd's and blu-ray movies .. to concerts on disc .. to music on disc or computer file .. to preamps .. to turntables .. to speaker resistance.



i did say the reference doesnt exist ... but is it because of different sound levels you found, or is it because the audio track simply hasnt been loaded into a program that will tell you how loud or soft the audio is compared to the reference 0dB

truth is..
anybody can go in there into the compiler and say what is 0dB
but that doesnt mean people will work together as a team and keep the same line used time after time again.

no matter how ugly things get..
when your listening room is setup, you will find out if the audio is working with the 'normal' reference 0dB or if it is using one of it's own.
sometimes they turn down an audio track below 0dB to get all of the dynamic peaks to fit into the digital domain.
if your limit is 110dB and you peaked at 112dB .. then simply turn it down 2dB and you get the full signal without over-processing the sound and ruining the raw content.
..and when that happens, it is up to you to bring the volume up 2dB

some people use pure decibel level
some use barometer pressure.
it helps to know what microphone was used to learn the relationship between barometer pressure and decibel level.
knowing the gap will help anybody dial in the reference level.


the hobby has shown once again that it is better to be aware.
and once again, they give us some tools to help ourselves remain stable.. specifically speaking about the reference 0dB
because if you dont believe one piece of software, you could try half a dozen audio analyzer programs and if they all say 0dB .. you could feel a bit more confident about what a reference level is.

if the receiver's test tone isnt at reference level.. it could simply be because they didnt engineer a circuit to boost the signal.
the signal probably comes as audio data on a chip sent to the digital to analog convertor? or did the chip send the audio to the amplifier on the side?

maybe they told you what the maximum volume level with the test signal.
maybe they told you more than the maximum.
maybe that maximum is what they recorded the total harmonic distortion number at .. and the volume is up higher than it ever needs to be, so turning it down gets you less distortion but it also turns down the dB level of the test tone.


my two guesses:
1. the chip sent the audio to the amplifier with less voltage .. less voltage = lower dB level
2. the chip is really cheap junk and couldnt hold a 0dB signal (kinda like saying the data on the chip wouldnt stay there at 0dB because the data would be corrupted .. so they used a lower dB to keep the data from corruption)

i've heard the test tone from my receiver and it doesnt even sound the same as the pink noise from a test disc or audio software.. and that is before noting anything about it being louder or quieter.
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post #4 of 16 Old 11-27-2012, 07:50 PM
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nonsense of course. the usual thought around here, AFAIK, is that receivers' internal test tones for speaker level checking bypass whatever room correction software is in place. An uncorrected peak or two in room for particular speakers would make those results look different from the results you'd get using a test disc, which would run through whatever room correction is in place.
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post #5 of 16 Old 11-27-2012, 10:25 PM - Thread Starter
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What I'm talking about is the fact I had ALL the levels equaled out L-C-R-LR-RR all hit the same point of the SPL meter using the test tone generated internally. However if I did the same test using the tones on AVIA regardless of the point I pick the levels are all over the place -- some speakers are higher, others lower none are equal. It does not matter what the main volume control is set at, I pick a point and adjust to that.

My point is if I set all levels to "0" on the SPL meter via the internal tone, it should not vary by 2-3 dB from speaker to speaker when using other tones.
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post #6 of 16 Old 11-27-2012, 10:53 PM
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Well, 2-3 dB is really about the measurement error range. I'll hazard a guess your internal tone is a single wavelength (1 or 2k Hz) while you are using a pink noise disk. How your room and speakers behave in different wavelengths can give more than a 3 dB difference if that is the case.
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post #7 of 16 Old 11-27-2012, 11:30 PM - Thread Starter
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I think you identified the problem, tone vs. pink noise.

I guess the final question is which is more accurate. I think the pink noise is more reflective of real world audio whether it's music or TV/movies.
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post #8 of 16 Old 11-28-2012, 05:54 AM
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Quote:
Originally Posted by Matt L View Post

I think you identified the problem, tone vs. pink noise.
I guess the final question is which is more accurate. I think the pink noise is more reflective of real world audio whether it's music or TV/movies.

This. Plus or minus two dB in room would be amazing performance, certainly better than I have in my room. That's at least a 4 dB spread between different frequencies. with a broad spectrum pink noise tone, no single frequency can dominate the reading like a sine wave can. In general, they reason they calibrate multimillion dollar movie mixing stages with pink noise is to have a more representative and accurate level.
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post #9 of 16 Old 11-28-2012, 06:46 AM
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Quote:
Originally Posted by jdsmoothie View Post

Can't speak for the AVIA disk or the Insignia AVR, but the Onkyo uses a 75db test tone to calibrate the unit to reference level of 85db.

Without doubt jd, I think you wanted to say: "The Onkyo uses a -30 dBfs band limited (500 Hz-2kHz) pink noise test tone signal level to calibrate the unit to reference SPL of 75 dB at the MLP." smile.gif
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post #10 of 16 Old 11-28-2012, 07:22 PM
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Nope .. Feri ... meant what I said. Reference level starts at 85db; however, as that is too loud for most home environments, the AVR mfr's use a 75db test tone which is much more tolerable.

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post #11 of 16 Old 11-29-2012, 05:33 AM
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I agree...

You set the receiver's volume at 0 dB, and you get a 75 dB SPL test signal rather than the expected 85 dB signal, because the test signal is 10 dB below full scale.

It still serves the purpose of calibration, but is less painful. Who wants to hear white noise (or whatever colour it is,) at 85 dB SPL ? smile.gif

That's all there is to it, IMO.

"But this one goes up to 11"
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post #12 of 16 Old 11-29-2012, 05:41 AM
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Quote:
Originally Posted by Matt L View Post

I was redoing the setup on my small bedroom system and used the tones internal to the Insignia 511 and my RS audio level meter to set levels. I had all 5 speakers matched pretty closely using the internal tone, then I checked it using the AVIA test disk that I ripped to my computer, and the levels varied quite a bit. I noticed a similar thing with my Onkyo system set up using Adussey. I have a hunch the Insignia is an Onkyo based receiver, wondering if it's peculiar to that manufacturer or is it common.

Which is more accurate? There was a significant variation using the AVIA tones.

I don't know what the reference tones that your receiver are, and I don't know what the reference tones on the AVIA disc are, but the odds that they are different at some level of detail is close to 100%.

Did they sound the same to you in terms of pitch and intensity?

You hold all the cards and I can't read them because you are holding them away from me, and you should be the one reading them anyway.
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post #13 of 16 Old 11-29-2012, 06:03 AM
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Quote:
Originally Posted by MichaelJHuman View Post

I agree...

You set the receiver's volume at 0 dB, and you get a 75 dB SPL test signal rather than the expected 85 dB signal, because the test signal is 10 dB below full scale.

It still serves the purpose of calibration, but is less painful. Who wants to hear white noise (or whatever colour it is,) at 85 dB SPL ? smile.gif

That's all there is to it, IMO.


Consumer AVR's use a -30 dB FS test signal, so you calibrate speakers to 75 dB SPL.

I think that the standard test signal is -20 dB FS in the professional world, so you calibrate speakers to 85 dB SPL.

Regardless, both calibration methods will produce speaker levels of 105 dB SPL if the input signal is 0 dB FS.

This assumes that your master volume is set to the number that you want to use for "reference level". Calibrated reference level is -22 dB on my master volume control, and 0 dB is when the volume is "all the way up". My AVR will not permit 0 dB to be the calibrated reference level number, while other units require that the master volume be set to 0 dB for reference level.
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post #14 of 16 Old 11-29-2012, 06:08 AM
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Below is an RTA made of my receiver's internal test tones for the mains and for the subwoofer with various LFE filters in place. Bandwidth limited pink noise.


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post #15 of 16 Old 11-29-2012, 06:10 AM
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Quote:
Originally Posted by Matt L View Post

I was redoing the setup on my small bedroom system and used the tones internal to the Insignia 511 and my RS audio level meter to set levels. I had all 5 speakers matched pretty closely using the internal tone, then I checked it using the AVIA test disk that I ripped to my computer, and the levels varied quite a bit. I noticed a similar thing with my Onkyo system set up using Adussey. I have a hunch the Insignia is an Onkyo based receiver, wondering if it's peculiar to that manufacturer or is it common.

Which is more accurate? There was a significant variation using the AVIA tones.


Use your ears to adjust for the final trim settings.
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post #16 of 16 Old 11-29-2012, 10:13 AM - Thread Starter
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This one is just a bedroom system, so I am in no way looking for absolute reference signals. All I am attempting to do is balance the 5 speaker levels as close as possible for best imaging. I opted for the pink noise on the AVIA since this is more real world than a test tone.

The front speakers are classic AR 4xs and only about 6' apart and I may opt for a phantom center speaker, I had been using a small speaker that tonally was close but not a perfect match, I'm using some Missions for the surrounds. For an inexpensive system the sound is quite good.
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