# Which graph does the human ear hear



## Phillips (Aug 12, 2011)

Hi

Which particular graph do we hear. 

Thank you


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## Kal Rubinson (Aug 3, 2006)

Phillips said:


> Hi
> 
> Which particular graph do we hear.
> 
> Thank you


How old are you? lddude:


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## JohnM (Apr 11, 2006)

If you are referring to the graphs in REW, all show things that have an effect on what is heard, and there is no single graph that is able to capture 'what we hear'. The frequency response graph is closest, with some smoothing (around 1/6th to 1/3rd octave, varies somewhat with frequency) but there are various characteristics that the frequency response graph does not show which also have audible effects, such as distortion, decay time and group delay (but there are plenty of others).


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## Phillips (Aug 12, 2011)

Kal Rubinson said:


> How old are you? lddude:



Thanks Kal not that old, 48.

Thank you


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## Phillips (Aug 12, 2011)

JohnM said:


> If you are referring to the graphs in REW, all show things that have an effect on what is heard, and there is no single graph that is able to capture 'what we hear'. The frequency response graph is closest, with some smoothing (around 1/6th to 1/3rd octave, varies somewhat with frequency) but there are various characteristics that the frequency response graph does not show which also have audible effects, such as distortion, decay time and group delay (but there are plenty of others).



If i use the frequency response graph 1/6th or 1/3th smoothing that will be a general idea?

Which RTA noise generator test tone is best for EQ? 

Is RTA just a guideline then fine tune with the frequency graph?

With the RT60 tab there are several different measurements (T30,T20, EDT, TOPT) which is the RT60?

The group delay what does this do?

Thank you


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## JohnM (Apr 11, 2006)

Phillips said:


> If i use the frequency response graph 1/6th or 1/3th smoothing that will be a general idea?


Yes



> Which RTA noise generator test tone is best for EQ?


Pink PN, with the RTA set to use a rectangular window, averaging is not needed with Pink PN. 



> Is RTA just a guideline then fine tune with the frequency graph?


They both show the frequency response, but the frequency response obtained with the sweep measurement is higher resolution and more accurate and allows other properties to be examined.



> With the RT60 tab there are several different measurements (T30,T20, EDT, TOPT) which is the RT60?


All of them are RT60 times, calculated over different portions of the impulse response. There is more information in the REW RT60 graph help and here is an article on EDT and RT60: http://www.synaudcon.com/site/author/pat-brown/early-decay-time-as-a-system-performance-benchmark/



> The group delay what does this do?


http://en.wikipedia.org/wiki/Group_delay_and_phase_delay

It would be worth doing some background reading on acoustics, there is more to the topic than can be covered in a few lines of forum postings. F. Alton Everest's Master Handbook of Acoustics is a good introductory text, http://www.amazon.com/Master-Handbook-Acoustics-Alton-Everest/dp/0071360972


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## Phillips (Aug 12, 2011)

Please can someone confirm the right/correct process for equalising full range (20 - 20000 Hz?)

I understand not to over EQ.

What I have seen:

1.	EQ both speakers combined (share the same filters)
2.	EQ individual from 20 – 250 Hz then combined from 250 – 20000 Hz
3.	EQ combined from 20 – 250 Hz then individual from 250 – 20000 Hz

Thank you


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## Kal Rubinson (Aug 3, 2006)

Of the three offered options, definitely 3. However, I would reserve judgement on the 250Hz transition point until I knew lots more information about the room, the speaker design and the uncorrected performance.


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## Phillips (Aug 12, 2011)

Kal Rubinson said:


> Of the three offered options, definitely 3. However, I would reserve judgement on the 250Hz transition point until I knew lots more information about the room, the speaker design and the uncorrected performance.



Hi Kal thank you.

Attached are the graphs, if you need more, no problems.

The receiver is a Yamaha Z9, speakers Energy Verita's 2.3i (floor standers).
The room has a lot of soft furnishes, big windows with curtains. Measurements are 5.8 meters (L) 3.7 meters (W) 2.8 meters (H). The left side has a slight slope downwards. 
Moving the speakers closer or further away can only be slight. I can move them closer together.
The right speakers port fire into the lounge suite arm (about 200 mm away).

People say e.g. from the sidewall & from the wall behind the speaker. Is this considered to be from the middle of the driver & front of the speaker?

Thanks again


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## Kal Rubinson (Aug 3, 2006)

The graphs are a bit too smoothed to see detail, especially in the bass but, off the top of my head, I would do the mono EQ only from 100Hz down. The profiles from 100-200Hz are quite different.


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## Phillips (Aug 12, 2011)

Kal Rubinson said:


> The graphs are a bit too smoothed to see detail, especially in the bass but, off the top of my head, I would do the mono EQ only from 100Hz down. The profiles from 100-200Hz are quite different.


Hi Kal thank you. Attached are some better graphs including a adjusted Tone Bass -6 Graph.

The GEQ on the Yamaha are 63hz,125,250,500,1000,2000,4000,8000,16000.

Thanks again


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## Barleywater (Dec 11, 2011)

An overlay view of left and right speaker with 1/12 or 1/6 octave smoothing makes comparison much easier. Views do show the complex nature of sound. Concentrating on the individual 1/12 octave views, first big response dips are at 50Hz for right, and 70Hz for left. Assuming measurement is made from listening position, these reveal different relative placements from boundaries, and may well be influenced by proximity to furnishings as previously described. 

Your receiver has an octave EQ, each band is doubling in frequency, so coverage for each band is very wide. Good comparison would be looking at your measurements with 1 octave smoothing. Thus your EQ can't do much to the real peaks and dips, it mostly moves peaks and dips together within each of its bands.

Before and after pics for EQ reveal its broad effects. Here is picture overlay:









Looks like you have good grasp of this. You haven't gone wild. Visually it looks better, and may be more correct, but comes down to personal preference.

Peak around 16kHz is ringing of tweeter. I'd like to see pic at 1/48 octave smoothing, or better the mdat of measurement to see how sharp peak is. I've got tweeters with very sharp ringing about 16kHz too, and use DSP with very sharp filter to tame them. I can't hear 16kHz well at all (ah, youth), but with mine, ringing modulates onto whole midrange, impacting sound stage detail.

Regards,

Andrew


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## Kal Rubinson (Aug 3, 2006)

The low dips may be impervious to EQ if they are real nulls. The L/R peaks are fairly consistent across most of the sub-100Hz range and that suggests that mono-EQ would be the way to go there. Above 100Hz, the peaks/nulls become less congruent (try L/R overlays) and independent EQ might be the way to go there but be gentle.


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## Phillips (Aug 12, 2011)

Barleywater said:


> An overlay view of left and right speaker with 1/12 or 1/6 octave smoothing makes comparison much easier. Views do show the complex nature of sound. Concentrating on the individual 1/12 octave views, first big response dips are at 50Hz for right, and 70Hz for left. Assuming measurement is made from listening position, these reveal different relative placements from boundaries, and may well be influenced by proximity to furnishings as previously described.
> 
> Your receiver has an octave EQ, each band is doubling in frequency, so coverage for each band is very wide. Good comparison would be looking at your measurements with 1 octave smoothing. Thus your EQ can't do much to the real peaks and dips, it mostly moves peaks and dips together within each of its bands.
> 
> ...




Hi Andrew thank you.

Attached is the mdat file (Zip).

All measurements are taken at the main listening position

Thanks again.

I am using the Omnimic microphone + laptop sound card (which i can't measure). The mic has it's individual calibration file which is loaded. The laptop only has a mic input, no line input.


View attachment Veritas.zip


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## Phillips (Aug 12, 2011)

Kal Rubinson said:


> The low dips may be impervious to EQ if they are real nulls. The L/R peaks are fairly consistent across most of the sub-100Hz range and that suggests that mono-EQ would be the way to go there. Above 100Hz, the peaks/nulls become less congruent (try L/R overlays) and independent EQ might be the way to go there but be gentle.



Hi Kal thank you.

I have attached a mdat zip file in the above post if that helps.

Where you say if they are *real nulls*, can there be false readings?

So i learn, if the peaks are reasonably consistent on both speakers sub 100hz then mono EQ as a rule of thumb, and if not, stereo EQ? 

Also the same goes for above 100hz, but normally stereo EQ.

Can you do from 100hz up, EQ mono on some and stereo on the rest, or is this not recommended? 

As you can see i have attached a graph for Tone Bass -6 which is effectively a shelf filter, is the way to go first before EQ?

Thanks again


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## Barleywater (Dec 11, 2011)

The microphone measures what is really happening. And this is very sensitive both to placement of speakers and placement of microphone.

The real dips in this case are impervious to equalization using the EQ on your receiver, because it is an octave EQ.

The superposition principle for wave behavior tells us that what microphone "sees" with both speakers playing is the sum of what the microphone sees with each individual speaker playing. This is why a speaker can have woofer, midrange, and tweeter too. So when possible, EQ each speaker.

The EQ feature of REW allows you to model fairly well what your EQ does, and what other EQs with narrower bands might do.

Once again the 1 octave smoothing provides good overview of what 1 octave EQ does. When 1 octave EQ is applied to 1 octave smoothed plot, and then smoothing is changed to 1/6th octave, you see that underlying narrow band behavior continues to exist. If you switch to narrow band EQ, you will see that narrower peaks/dips may be individually modified. EQ with higher Q is essentially same as EQ with narrower bandwidth (inverse relationship) some EQs display as BW, some as Q for filter width.

Here are some REW EQ pics working with your response with your EQ defeated:

EQs are all setup with Q=1 or BW=1

FBQ2496:









and with display at 1/6th octave smoothing narrow peaks and dips are still there, but moved according to EQ settings:









DCX2496 flavor:









And DSP-30









I recommend finding settings that you like the sound of with a wide selection of listening material.

Tweeter peak is actually at about 14.3kHz. Based on above models, your 16kHz EQ control in conjunction with 8kHz EQ control may be used effectively to pull this down. I would pull it down to at least theoretical flat, listen for a while to music, and then keep on going down until it just becomes apparent that something is missing from brass, cymbals, rim shots, etc. and then bring it back up a touch.

The signal to noise ratio in your measurements is very good.

Regards,

Andrew


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## Phillips (Aug 12, 2011)

Barleywater said:


> The microphone measures what is really happening. And this is very sensitive both to placement of speakers and placement of microphone.
> 
> The real dips in this case are impervious to equalization using the EQ on your receiver, because it is an octave EQ.
> 
> ...



Thank you very much.

I will try these and remeasure and post the results later, over the next few days

With the Omnimic mic + laptop sound card, does the laptop sound card have a big influence on the measurement? Unfortunately the laptop doesn't have a line input (only mic in) so i can't measure it, any ideas how i could?

Thanks again


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## Barleywater (Dec 11, 2011)

Some stock soundcards are horrible, but most are typically surprisingly flat from at least 30Hz to 15kHz. Above and below the range they roll off faster than higher quality soundcards. Since lowest EQ on your receiver is 63Hz and highest is 16kHz, in my opinion their isn't going to be much impact from your lapstop's stock soundcard. As seen you've captured sharp peak at 30Hz, which is gain fromboundary effects/room mode behavior.

Calibrating soundcards without line in, and using microphone in seems problematic for forum members. That you aren't working with a sub, or an EQ that can effectively do that, I wouldn't worry about this for now.

Looking over your posted mdat I see you have selected soundcard calibration files: Omnifix.txt.txt for measurement of Veritas EQ Defeat, Right Defeat, and Tone Bass -6 500hz, and Omnifix.txt - Copy (2).txt for measurement of Left Defeat:

















Both of these curves have a mathematically smooth curve below 600Hz with effect of boosting the displayed bass. Omnifix.txt - Copy (2).txt shelves flat above 600Hz, and Omnifix.txt.txt additional effects from above 3kHz, which also look mathematical in nature. These are not soundcard calibration files, but look like artificial target curves.

Can you tell me about these?

Removing them from results, and leaving Mic/Meter cal file in place results in following comparisons:

















In each case the responses look better without the Omnifix files. Comparison is made by opening second copy of mdat and removing soundcard calibrations.

Regards,

Andrew


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## Phillips (Aug 12, 2011)

Barleywater said:


> Some stock soundcards are horrible, but most are typically surprisingly flat from at least 30Hz to 15kHz. Above and below the range they roll off faster than higher quality soundcards. Since lowest EQ on your receiver is 63Hz and highest is 16kHz, in my opinion their isn't going to be much impact from your lapstop's stock soundcard. As seen you've captured sharp peak at 30Hz, which is gain fromboundary effects/room mode behavior.
> 
> Calibrating soundcards without line in, and using microphone in seems problematic for forum members. That you aren't working with a sub, or an EQ that can effectively do that, I wouldn't worry about this for now.
> 
> ...



Hi Andrew thank you.

I have attached the mdat file with the corrected file.

The sound card (omnifix) file was made up by JohnM (REW) from a measurement i made from Omnimic software. The Omni V1 calibrated file is what came with the mic.

I can get my hands on another mic (XTZ V1) to compare. What would be the best process / way to compare mics?

Thanks again

View attachment Veritas.zip


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## Barleywater (Dec 11, 2011)

I search and follow in:

Mic Thoughts post 89

Eventually thread dies without response from JohnM on comparing microphones.

I've looked at post 89 mdat. Omnimic software appears to be using some manner of 1/3 Octave smoothing. Results indeed look different from Omnimic used with cal file and REW. This is very disconcerting. Which if either measurement is correct?

JohnM in Mic Thoughts #90 tempers validity of Omnifix approach:



> That should make the measurements correspond more closely, but whether the measurements are then more correct or not I can't tell - there's no way to know the actual response of your omnimic without getting it independently calibrated or making comparison measurements against a calibrated mic.




XTZ V1 appears to be microphone/soundcard combo with calibration file. So all depends on calibration file. Certainly would be interesting to see results using it.

Further searching seems to indicate that nobody has sent Cross-Spectrum an Omnimic for calibration.


Regards,

Andrew


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## Phillips (Aug 12, 2011)

Barleywater said:


> I search and follow in:
> 
> Mic Thoughts post 89
> 
> ...



Thank you

You are right, would be interesting to do a test against the XTZ.

What would be the correct process for measuring / comparing mics, i suppose near field? If so how is the best way to measure near field? 

Thanks again


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## lcaillo (May 2, 2006)

Phillips said:


> Thank you
> 
> You are right, would be interesting to do a test against the XTZ.
> 
> ...


Whether one agrees with the methodology or it is practical to apply or not, this may be informative.
http://www.nist.gov/calibrations/upload/aip-ch8.pdf


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## Phillips (Aug 12, 2011)

lcaillo said:


> Whether one agrees with the methodology or it is practical to apply or not, this may be informative.
> http://www.nist.gov/calibrations/upload/aip-ch8.pdf


Thank you, i will take a look at it.


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## Phillips (Aug 12, 2011)

When i do the comparisons what smoothing should i use, I will make a sound card calibration file to compensate.


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