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SPL for critical listening

Blumlein 88

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As I recall Katz's thinking was Dolby had shown wide range material was considered not too loud and not too soft by nearly everyone around 83 db SPL. Most mainstream music was going to be compressed. He was hoping not master in a way that would result in ridiculous compression. When you compress music and adjust volume to suit the average SPL goes up. His experienced opinion was if you are working as a mastering guy, reduce levels by 6 db from that 83 db reference level. And DO NOT CHANGE THE VOLUME. Then your mastering will more or less naturally cause you to pick an amount of compression and levels that result in music near that 83 db level. So he was attempting to adhere to the standard in a way mastering guys could just listen and get a good result.

You can buy some current music and see his attempt was unsuccessful.

I seem to recall he used pink noise set to -20 db at 83 db SPL C-wtd slow response for reference and reduced his amp volume by 6 db at that point for one channel.

Regarding my comment above about hearing acuity. We listen for enjoyment, so a little louder than optimum acuity is not far fetched.
 
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RayDunzl

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Phase at the listening position as reported by REW:

Blue - both speakers, red - left, green - right. I don't see how the left and right make the pair response, so ???

This graph is aligned at low frequencies to show the phase difference at 48Hz that I think creates the cancellation at that frequency.

1550954844227.png
 

Krunok

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I have a miniDSP OpenDRC-DI (digital in and out) with 6144 taps on each channel available for FIR, and 14 slots for IIR.

For filter construction, AcourateDRC (think Acourate Lite set up to easly build filters for that miniDSP.

At top is the current FIR setting, the bottom is the IIR> Phase correction is not displayed.

View attachment 22449

Well, I managed to solve similar problem by lowering the phase of my problematic right speaker by 90-100 degs at the frequency of the center of the dip. Initially I tried to fight that dip with amplitude correction but when I reached the 12dB limit without significant results I switched to phase correction and it worked. You may want to try the same, hopefully it will help.
 

Krunok

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Phase at the listening position as reported by REW:

Blue - both speakers, red - left, green - right. I don't see how the left and right make the paired response, so ???

View attachment 22452


When you say paired you mean how the green and red phase make blue one? Me neither but it is still worth a shot, nothing to loose and much to gain. :D
 

RayDunzl

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Unfortunately, I don't have enough taps to create an FIR filter that would make much of a dent in the phase at 48Hz.

What's a cheap box with lots of taps and S/PDIF in/out, preferably at least four channels, six better?

I don't want it in my PC.
 

RayDunzl

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When you say paired you mean how the green and red phase make blue one?

It's three measurements:

Red - Left speaker only
Green - Right speaker only
Blue - test tone playing simultaneously through left and right.
 

Krunok

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Phase at the listening position as reported by REW:

Blue - both speakers, red - left, green - right. I don't see how the left and right make the pair response, so ???

This graph is aligned at low frequencies to show the phase difference at 48Hz that I think creates the cancellation at that frequency.

View attachment 22452

Left:


Right:


I hope you see what I mean. Amplitude of right speaker couldn't be pushed further so I corrected phase, and it worked!
 

flipflop

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I don't know that the web blog is on the web anymore, but I've seen a pro amplifier company which at one time did in house blind testing of their amps. The guy running that said an RMS SPL of about 75 db gave the most discerning results. He said there was some deterioration in their experience going up to 80 db SPL. He said as soon as people insisted on going higher then 80 db their ability to hear differences was drastically reduced.
Sounds contradictory to the testing done by Zwicker and Fastl with pure tones where just-noticeable level differences became smaller as the the SPL increased.
dfgdfgdg.PNG


As I recall Katz's thinking was Dolby had shown wide range material was considered not too loud and not too soft by nearly everyone around 82 db SPL. Most mainstream music was going to be compressed. He was hoping not master in a way that would result in ridiculous compression. When you compress music and adjust volume to suit the average SPL goes up. His experienced opinion was if you are working as a mastering guy, reduce levels by 6 db from that 82 db reference level. And DO NOT CHANGE THE VOLUME. Then your mastering will more or less naturally cause you to pick an amount of compression and levels that result in music near that 82 db level. So he was attempting to adhere to the standard in a way mastering guys could just listen and get a good result.

I seem to recall he used pink noise and set a -20 db pink noise signal at 78 db SPL.
I assume you're talking about this part from the article I linked:
In 1983, as workshops chairman of the AES Convention, I invited Tomlinson Holman of Lucasfilm to demonstrate the sound techniques used in creating the Star Wars films. Dolby systems engineers labored for two days to calibrate the reproduction system in New York's flagship Ziegfeld theatre. Over 1000 convention attendees filled the theatre center section. At the end of the demonstration, Tom asked for a show of hands. “How many of you thought the sound was too loud?” About 4 hands were raised. “How many thought it was too soft?” No hands. “How many thought it was just right?” At least 996 audio engineers raised their hands.This is an incredible testament to the effectiveness of the 85 dB at 0 VU standard originally proposed by Dolby's Ioan Allen in the mid-70's. It’s stood the test of time. Dialogue, music and effects fall into a natural perspective with an excellent signal-to-noise ratio and headroom. A good film mix engineer can work without a meter and do it all by the monitor. The meter becomes simply a guide. In fact, working with a fixed monitor gain is liberating, not limiting. When digital technology reached the large theatre, Dolby attached the 85 dB calibration to a point 20 dB below full digital scale (abbreviated -20 dBFS, referred to as the standard Dolby Calpoint in this document). This calibration must be measured with pink noise, with an averaging meter (not a peak meter), playing one channel (loudspeaker) at a time, and the SPL meter set to slow, C weighting. Tom Holman has recently proposed more refined ways of making this measurement, but the basic principle remains. The 85 dB SPL/0 VU/-20 dBFS standard has also stood the test of time, as digital productions can be created with excellent headroom.

When AC-3 and DTS became available for home theatre, Dolby recommended that the monitor calibration standard be lowered by 6 dB to 79 dB SPL (at -20 dBFS average). This is because mixes originally geared for large theatres do not totally translate to the small venue. There is often so much dynamic range and impact from loudspeakers in a small space, that even high-powered home theatre systems (and tolerant listeners) have trouble bearing the loudness if reproduced at the Dolby 85 monitor calibration. It’s admirable that certain program producers are preserving the original 85 dB large theatre mix for posterity, but many home listeners may complain that “this DVD is too loud”, or “I lose some of the dialogue when things are soft”. This is because they turn down their monitor gains without the mix being changed, and soft passages may become too soft. To make the 85 dB-calibrated presentation palatable for such listeners, the dynamic range may have to be reduced by 6 dB (6 dB upward compression) in order to be reproduced at a Dolby cal of 79.
79+6=85, not 82 :)
 

RayDunzl

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I hope you see what I mean. Amplitude of right speaker couldn't be pushed further so I corrected phase, and it worked!

I understand, just unable.
 

Blumlein 88

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Sounds contradictory to the testing done by Zwicker and Fastl with pure tones where just-noticeable level differences became smaller as the the SPL increased.
View attachment 22451


I assume you're talking about this part from the article I linked:
In 1983, as workshops chairman of the AES Convention, I invited Tomlinson Holman of Lucasfilm to demonstrate the sound techniques used in creating the Star Wars films. Dolby systems engineers labored for two days to calibrate the reproduction system in New York's flagship Ziegfeld theatre. Over 1000 convention attendees filled the theatre center section. At the end of the demonstration, Tom asked for a show of hands. “How many of you thought the sound was too loud?” About 4 hands were raised. “How many thought it was too soft?” No hands. “How many thought it was just right?” At least 996 audio engineers raised their hands.This is an incredible testament to the effectiveness of the 85 dB at 0 VU standard originally proposed by Dolby's Ioan Allen in the mid-70's. It’s stood the test of time. Dialogue, music and effects fall into a natural perspective with an excellent signal-to-noise ratio and headroom. A good film mix engineer can work without a meter and do it all by the monitor. The meter becomes simply a guide. In fact, working with a fixed monitor gain is liberating, not limiting. When digital technology reached the large theatre, Dolby attached the 85 dB calibration to a point 20 dB below full digital scale (abbreviated -20 dBFS, referred to as the standard Dolby Calpoint in this document). This calibration must be measured with pink noise, with an averaging meter (not a peak meter), playing one channel (loudspeaker) at a time, and the SPL meter set to slow, C weighting. Tom Holman has recently proposed more refined ways of making this measurement, but the basic principle remains. The 85 dB SPL/0 VU/-20 dBFS standard has also stood the test of time, as digital productions can be created with excellent headroom.

When AC-3 and DTS became available for home theatre, Dolby recommended that the monitor calibration standard be lowered by 6 dB to 79 dB SPL (at -20 dBFS average). This is because mixes originally geared for large theatres do not totally translate to the small venue. There is often so much dynamic range and impact from loudspeakers in a small space, that even high-powered home theatre systems (and tolerant listeners) have trouble bearing the loudness if reproduced at the Dolby 85 monitor calibration. It’s admirable that certain program producers are preserving the original 85 dB large theatre mix for posterity, but many home listeners may complain that “this DVD is too loud”, or “I lose some of the dialogue when things are soft”. This is because they turn down their monitor gains without the mix being changed, and soft passages may become too soft. To make the 85 dB-calibrated presentation palatable for such listeners, the dynamic range may have to be reduced by 6 dB (6 dB upward compression) in order to be reproduced at a Dolby cal of 79.
79+6=85, not 82 :)
Yep that is it. And it reminds me that Bob Katz lowered the 85 to 82 or 83 for the same reasons in the last paragraph. Most home music listening is in a smaller room.
 

Krunok

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Unfortunately, I don't have enough taps to create an FIR filter that would make much of a dent in the phase at 48Hz.

What's a cheap box with lots of taps and S/PDIF in/out, preferably at least four channels, six better?

I don't want it in my PC.

Huh.. I don't know any such device. :(
 

Blumlein 88

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Sounds contradictory to the testing done by Zwicker and Fastl with pure tones where just-noticeable level differences became smaller as the the SPL increased.
View attachment 22451

I have no doubt that is true. But listening to music and tones is different, and involves more than just level differences. I've no way to confirm what the fellow said. I do know listening to music at even 95 db SPL with higher peaks will obviously blunt your hearing after just a minute.

I also find using 82 db SPL reference levels minus 6 db just about right for the mixing/mastering I done of music I recorded. I'm no pro and only done a little, but it works to be at least near that range.
 

flipflop

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I do know listening to music at even 95 db SPL with higher peaks will obviously blunt your hearing after just a minute.
Isn't it fair to assume the same goes for sine waves?
I think the different outcomes of the tests are more likely to be a consequence of listener fatigue than source material.
EDIT: I'm talking about listener fatigue in the subjects of the amp test, in case it wasn't clear.
 
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Krunok

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Unfortunately, I don't have enough taps to create an FIR filter that would make much of a dent in the phase at 48Hz.

What's a cheap box with lots of taps and S/PDIF in/out, preferably at least four channels, six better?

I don't want it in my PC.

In theory you can use $100 fanless PC with BruteFIR convolver combined with this cute device.
 

Krunok

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In theory you can use $100 fanless PC with BruteFIR convolver combined with this cute device.

@March Audio - if you now decide to put fanless PC and Motu 8A in some fancy aluminum box with BruteFIR installed and sell it as your product it would only be fair that I get 3% of royalty fee from each sell! :D :D
 

Blumlein 88

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Isn't it fair to assume the same goes for sine waves?
I think the different outcomes of the tests are more likely to be a consequence of listener fatigue than source material.
EDIT: I'm talking about listener fatigue in the subjects of the amp test, in case it wasn't clear.
I don't know how the test was conducted. I doubt they let you listen to a sine wave for 60 seconds at a time. My guess would be it was a few seconds.
 

Blumlein 88

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https://www.digido.com/portfolio-item/level-practices-part-2/

I mis-remembered part of this from Bob Katz. He didn't adjust to 82 db for home use. He said 83 db, and quotes the Dolby presentation as having said 83 db. He does mention - 6db for home use.

So @flipflop your quote of the AES presentation is identical to Katz quoting it at the digido link. Except everywhere your quote has 85 db, Katz has 83 db. I wonder which it was? And where did you grab your quote from?

EDIT: here is another difference. Tomlin Holman at Dolby began using 85 db SPL with pink noise that had been filtered to have 500 hz to 2000 hz. I wonder if he added 3 db for the reduced bandwidth. His reasoning was you had results more consistent without the uneven lower frequencies in rooms (theaters) and the different absorption in theaters for frequencies above 2 khz. I think Toole suggests matching speakers for testing with the same signal with 2nd order slopes above and below.
 
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flipflop

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I don't know how the test was conducted. I doubt they let you listen to a sine wave for 60 seconds at a time. My guess would be it was a few seconds.
Much shorter than that, actually. Only the subjects in the amp test could have developed listener fatigue.
dfgdfgdfg.PNG
So @flipflop your quote of the AES presentation is identical to Katz quoting it at the digido link. Except everywhere your quote has 85 db, Katz has 83 db. I wonder which it was? And where did you grab your quote from?
I'm a little confused at this point o_O I'll give you the source and leave it at that:
III. The Magic of 85 with Film Mixes (p. 4) - again, same article
http://www.aes.org/technical/documentDownloads.cfm?docID=65
 

SIY

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Assuming these are musical selections rather than test tones, I use the Peter Walker criterion: for any given recording, there is one correct playback level. If I'm listening to an acoustic recording of a singer with a guitar, the level will be quite different than if I'm listening to a jazz quartet, and that level will be quite different than listening to an amplified rock band.
 
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