Which frequency response is better?

AJ Soundfield

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"What were the results of the double blind listening tests for the two single spatial pressure points measurements above, using human binaural hearing? Which did 2 ears/no eyes-beliefs prefer?
In anticipation I had pointed out the differences between the 2 "sides" to these discussions previously."

What gibberish. Those graphs are for multiple measurement points averaged. I cannot imagine that anyone competent in reading those graphs would suggest that some psycho surveys are needed to tell which one is technically superior.
Listening tests are neither "gibberish" nor "psycho surveys". They are the ultimate arbiter for sound. regardless of baseless beliefs about "technical superiority" of single pressure points uncorrelated to binaural hearing. That's the whole reason Toole got involved, if you've ever read his work and the countless others he cites. Listening/what people hear is actually the most, not least important.

Ditto Miro's graphs and his question. i.e. The Topic here.
I am trying to find the best soundstage. I have a problem with finding the best listening position..
Like Sonnie, it's pretty clear to me Miro is trying to find optimal sound but is confused as how to do so, quite common on forums. He may actually believe the measurement(s) is a substitute, rather than a compliment to actual listening.
All my advice, links, etc. are related to him getting better sound. My advice to you would be to read the links I provided Miro as well, since they are relevant to the discussion.

What exactly are you trying to do here?
Give Miro an alternative view based on over a hundred years of sound science. Ultimately, he should trust neither your or my "authority", but instead trust what his ears tell him is best for him. Maybe it is your studiophile near wall "technical" based approach, or maybe he'll opt for what "Pyscho surveys" have found, including those of many studiophiles, as linked.
We'll see. :)
No hurt feeling either way, it's his ears he has to satisfy.

cheers
 

Miro

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"What were the results of the double blind listening tests for the two single spatial pressure points measurements above, using human binaural hearing? Which did 2 ears/no eyes-beliefs prefer?
In anticipation I had pointed out the differences between the 2 "sides" to these discussions previously."


What gibberish. Those graphs are for multiple measurement points averaged. I cannot imagine that anyone competent in reading those graphs would suggest that some psycho surveys are needed to tell which one is technically superior. Ditto Miro's graphs and his question. i.e. The Topic here.
As I said, my input here is acoustics. It is of professional level acoustically but also informed by decades of creating the source material to a sometimes reference level.
What exactly are you trying to do here? All I can see is repeated advice to the point of annoying insistence that Miro's speakers MUST be distant from his Front Wall. Irrespective of his own evidence posted and completey ignoring his glass walls and dissing qualified advice.
The problem in my LIVING room (as you can see in the picture) is that I have on one side a huge glass wall and on the other side is the open space with 10m deep. So I have reflections from the left side wall and no reflections from the right side. Further, I am also not able to place the speakers deep into the room like in the picture, this is only for the measurements. In practice my speakers can not be placed further than the front of the TV cabinet and that is 70cm from the front wall to the front of the speakers. But I have a lot of freedom to place my listening position.

With this in mind I am looking for the best frequency response. As I understand, it's better to have peaks in the response because they can be better managed by miniDSP and Dirac Live?

best regards, Miro

34712
 

Miro

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Listening tests are neither "gibberish" nor "psycho surveys". They are the ultimate arbiter for sound. regardless of baseless beliefs about "technical superiority" of single pressure points uncorrelated to binaural hearing. That's the whole reason Toole got involved, if you've ever read his work and the countless others he cites. Listening/what people hear is actually the most, not least important.



Like Sonnie, it's pretty clear to me Miro is trying to find optimal sound but is confused as how to do so, quite common on forums. He may actually believe the measurement(s) is a substitute, rather than a compliment to actual listening.
All my advice, links, etc. are related to him getting better sound. My advice to you would be to read the links I provided Miro as well, since they are relevant to the discussion.


Give Miro an alternative view based on over a hundred years of sound science. Ultimately, he should trust neither your or my "authority", but instead trust what his ears tell him is best for him. Maybe it is your studiophile near wall "technical" based approach, or maybe he'll opt for what "Pyscho surveys" have found, including those of many studiophiles, as linked.
We'll see. :)
No hurt feeling either way, it's his ears he has to satisfy.

cheers
I am a guitar player with over 35 years of experience and I know how instruments should sound. Regarding my audio reproduction and equipment I can clearly hear the soundstage with all instruments between the speakers. But I still think that I miss clarity, the sound coming from my speakers is effected by maybe to much reflected sound or a kind of echo. I will discribe the sound as too "wet" or something. I read something about a critical distance and withing this distance I can hear more direct sound and less reflected sound. Maybe this is something to consider in finding the best listening position.

best regards, Miro
 

AJ Soundfield

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The problem in my LIVING room (as you can see in the picture) is that I have on one side a huge glass wall and on the other side is the open space with 10m deep. So I have reflections from the left side wall and no reflections from the right side.
That can be somewhat mitigated by toeing in the speakers and pulling the curtains closed. However, all that relates mostly to imaging, whereas you are also trying to solve possible bass issues. You have yet to say what "problems" you are hearing.

Further, I am also not able to place the speakers deep into the room like in the picture, this is only for the measurements. In practice my speakers can not be placed further than the front of the TV cabinet and that is 70cm from the front wall to the front of the speakers. But I have a lot of freedom to place my listening position.
Then it makes zero sense to measure with speakers not at 70cm. Nor measure in places where you don't sit..unless you normally sit on floor and your one ear is where the mic is in picture???

With this in mind I am looking for the best frequency response.

best regards, Miro
My mistake for misinterpreting you wanting best sound. Dan is correct, you want "best" microphone measurement, so I will cede to his authority there.

cheers
 

AJ Soundfield

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Regarding my audio reproduction and equipment I can clearly hear the soundstage with all instruments between the speakers. But I still think that I miss clarity, the sound coming from my speakers is effected by maybe to much reflected sound or a kind of echo. I will discribe the sound as too "wet" or something. I read something about a critical distance and withing this distance I can hear more direct sound and less reflected sound. Maybe this is something to consider in finding the best listening position.

best regards, Miro
Well, put a nice sofa underneath where the mic is in picture. Put a rug on the floor. Toe in the speakers where they cross at the tip of your nose. Listen. Place the mic at approximate location of your head and take 3-4 measurements. Cut any peaks in the bass, gently at first...listening each change.

cheers
 

Miro

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That can be somewhat mitigated by toeing in the speakers and pulling the curtains closed. However, all that relates mostly to imaging, whereas you are also trying to solve possible bass issues. You have yet to say what "problems" you are hearing.


Then it makes zero sense to measure with speakers not at 70cm. Nor measure in places where you don't sit..unless you normally sit on floor and your one ear is where the mic is in picture???


My mistake for misinterpreting you wanting best sound. Dan is correct, you want "best" microphone measurement, so I will cede to his authority there.

cheers
Now, I measure response hoping to find the best sound. At the end the sound is what matters. And I thought that a good frequency response is a precondition for a good sound.
 

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Again the graphs are multiple measurement locations averaged. Miro asked a question, I answered. His OP suggests that ears alone are not answering his question. i.e. Which of those responses is better?
Perhaps he wants actual fidelity as well as ear candy?
Here's a shocker..... I have been a Sound Engineer for decades. Although I always had an interest I took up Acoustics formally around 2007.
As one gets more into it, more and more counter intuition proves itself. In the Celestion graphs, the red one was an early attempt. Done by ear alone. This is where they sounded 'best' to me. But my work kept coming out as Bass Heavy.
Moving the speakers to the FW and relocating my seat to optimise resulted in the obviously flatter Blue curve. Since then I have moved to modern speakers and Dirac Live.
I work to the B&K, Harmon Target. The sound in The White Room is fabulous and the lack of tonal change on several different systems throughout the house is truly remarkable.
Ultimately it is so much more fun than where the 'ear candy' initially located me.

I have presented the full science at all times. i.e. Best response is as close as possible to or as far as possible from the Front Wall, with exceptions for in between placement which positions the null to counter an unwelcome peak.
I do not believe the widely accepted preferred tonality varies from Control Room to Cinema, to Gig, to Home Theatre, to Home Hi Fi.
This is from personal experience where the ultimate success in Mixing and Mastering is to have as similar a sound as possible everywhere.
I will back that with the fact that the best and most popular high end headphones have this tonality built in.
 
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AJ Soundfield

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Now, I measure response hoping to find the best sound. At the end the sound is what matters. And I thought that a good frequency response is a precondition for a good sound.
They are related and in many ways correlated. But you cannot determine "sound" as heard by your 2 ears and a single frequency response at a pressure microphone somewhere. Things are far more complex with our binaural hearing.
I suspect much of your lack of "clarity" is related to the fact your speaker must be close to front wall (behind speaker). But you indicated they must be that distance, so that is what you must work with. hence me suggesting toeing in and also mitigating any bass peaking..carefully. If you measure a 6db peak at 55hz, move the mic 15cm left or right and 10cm up/down and repeat measurements. Cut the peak first by 3db, not 6...and listen to bass in music. If it sounds right, don't cut another 3db, start enjoying some music.

cheers
 

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AJ- But you cannot determine "sound" as heard by your 2 ears and a single frequency response at a pressure microphone somewhere.

You keep saying that, seemingly obvious to my repeating statements that the graphs presented are not single point measurements but were an average of multiple measurement points, as is done by Dirac, Sonarworks, or any Acoustician measuring a space or zone. Given head movement there is no significant advantage to binaural measurement over other multiple points. It is just twice as fast.
Miro's two single point but two speaker measures indicate a fully predictable change in the frequency of the SBIR Null. Perfectly credible and a valid platform to ask the question IMO.
I find the Spectrum Analyser and Pink Noise, zoomed to LF only, invaluable for quickly scanning. e.g. Place the speakers kissing the FW, Pink Noise zoomed to say 20-300. Move the mic around to find the flattest spot.
Label the speaker and listener spots on the floor, take a screenshot or save. Move out 50cm repeat. If the optimum listening spot remains static great, it may or may not, but one will never know without checking it.
Using this fast moving methodology, it is very quickly and easy to see trends, particularly the No Fly zones.....It is in fact multiple measure points with simultaneous evaluation. The optimums are often quite obvious.

Miro Now, I measure response hoping to find the best sound. At the end the sound is what matters. And I thought that a good frequency response is a precondition for a good sound.

Frequency Response remains the most telling and easy to understand technical reliable repeatable assessment of sound quality. Something following the slope of B&K or Harman with as few peaks and nulls as possible sounds good without question.
I have been making preference sound choices all my life. Tweaking individual sounds to full mixes. But this involves all sorts of comparison and analysis techniques and preknowledge of what will fit will with what. e.g. Pairing a Kick Drum and Bass Guitar.....
When it comes to getting best response from Speakers in a Room, I find measurement way more reliable, repeatable, quicker, more accurate and in every way better, than ear guessing.
 
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DanDan

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The problem in my LIVING room (as you can see in the picture) is that I have on one side a huge glass wall and on the other side is the open space with 10m deep. So I have reflections from the left side wall and no reflections from the right side. Further, I am also not able to place the speakers deep into the room like in the picture, this is only for the measurements. In practice my speakers can not be placed further than the front of the TV cabinet and that is 70cm from the front wall to the front of the speakers. But I have a lot of freedom to place my listening position.
With this in mind I am looking for the best frequency response. As I understand, it's better to have peaks in the response because they can be better managed by miniDSP and Dirac Live?
best regards, Miro

Yes, clearly it is a place where AV is enjoyed, but acoustically.... the elephant in the room is the glass. This is bound to be a very lively room as it has lots of reflective surfaces. Glass absorbs LF and allows it to pass through. So your tonality of both direct and reverberant will be lacking in Bass. So..... as your measurements show go for the better LF response at 46cm or even closer if you can. Find your optimum listening position as described. If there are options, go for the one nearest the speakers which will increase the direct sound vs the room tone, more clarity. As AJ says, soft furnishing like a couch, wall hangings, pictures without glass, rugs, will all help the HF clutter a bit. But overall absorption on the ceiling would be more effective and less obtrusive. Perhaps go for a bit of both. Thin curtains do little but thicker ones, pleated to simulate thickness should easily match your absorbent opposite wall treatment.
 
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Adhoc

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@Miro; You mentioned critcal distance and having listening position there = higher ratio of direct sound.The more live the room is (reflective) the more it diminishes. The more absorbtive it is, the more critcal distance increases, -as you are damping otherwise noticable reflections. From the pictures of your room it is short, around or less than 1 m or so. Enclosed is some text from ”Acoustics of Small Rooms” by Kleiner and Tichy. As you see in the diagram, comparing 1 m and more typical 3 m listening distance, you are more sensitive to noticing reflections at 3 m compared to 1 m. A 3 dB difference is clearly noticeable, a 10 dB ”appears” like twice / half as loud.

Localization of sound source / phantom image along the baseline between the speakers is determined in about 0,8 ms = very short time, corresponding to the circumference of your head / width between ears, Reflections thereafter tends to widen the apparent source width and possibly its depth (depending on frequency) which may sound just nice and enjoyable, like what is written in Tool’s book. They blurry what is actually in the recording though, -as each speaker has 7 mirror sources / reflections. So enjoyment is not necessarily equivalent to accuracy. Pick your poision …

To find out how ”bad” your reflections are, you need to check out the ETC-diagrams in REW. A goal in control rooms is not stronger than -20dB within 20 ms. Hard to impossible to reach in your room but aim for as low as possible in combination with symmetry between listening position and speakers. As you have the glass doors nearby and 10 m of empty space in opposite direction, symmetry sounds impossible unless you put a sh-tload of absorbers in front of the glass doors. Something which may sound stupid but can be worth a quick check: If the glass doors opens towards the TV wall, open them up and you have a 100% perfect absorber. Depending on speaker directivity and toe in, you may end up with killing reflections from the nearby speaker which should be placed close up to the TV wall (in my opinion). If the neighbourhood is quiet and you don’t disturb any other people, it could be worth a try.

By the way, your mic is pointing straight at the speaker ( = 0 degree). You are interested in the response of speaker + room interaction, not the speaker alone. All the large peaks and dips in your frequency curves come from room interaction, not the speaker. Point the mic at about 70 degrees upwards. Good post for mic direction when measuring speaker + room combination: https://www.gearslutz.com/board/showpost.php?p=12067922&postcount=32
 

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Hi Adhoc, nice to see you here. Small detail, literally, hard to see. Miro used a Mic Cal File, so the best way to point the mic would correspond with that Cal File.
 

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Well, as I see it if speaker + room interaction is of interest: Load the 90 degree calibration file when REW is opened up, then aim the mic at around 70 degrees.
 

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AJ- But you cannot determine "sound" as heard by your 2 ears and a single frequency response at a pressure microphone somewhere.

You keep saying that, seemingly obvious to my repeating statements that the graphs presented are not single point measurements but were an average of multiple measurement points, as is done by Dirac, Sonarworks, or any Acoustician measuring a space or zone.
I'm far from oblivious to multi-point averaging, whereas you have made clear you are oblivious to perceptual science, not "psycho tests".
Your posted measurements, like Miros, say near zero about sound perceived. There is no information on the directions of all the sounds averaing to those pressures. The mic can't tell, but 2 ears and a brain can. Have you ever read any of Tooles books or even the 2 links I provided? Your measurements are not indicative of SQ whatsoever. Doesn't matter which you might have preferred under whatever conditions they were made.

Frequency Response remains the most telling and easy to understand technical reliable repeatable assessment of sound quality. Something following the slope of B&K or Harman with as few peaks and nulls as possible sounds good without question.
Wow, that is completely false and badly misinformed. The B&K and "Harman" curves are steady state room responses and thus cannot be used as SQ references, regardless of this extremely common misconception.
What is preferred by 2 ears is a speaker with anechoic smooth on and off axis. When such as speaker is placed in "typical" bounded space/reflective room, the summed total pressures at a mic placed mid-far field/typical listening distance, will have a slope similar to the Harman curve, but not a straight line. Real rooms/speakers cannot have such uniform polars/reflectivity to produce a straight line.
The reverse is false. The "Harman curve" can be any speaker EQ's to that elixir slope, but that does not determine preferred SQ!
What I'm posting here should be a sticky for every single "acoustics" thread.
Dan, Miro, everyone, which frequency response is better?
34761

Dan, all 3 are the same speaker, 6 points averaged frequency responses at listener position. First is no correction. Second is some manual correction. The last is an example of "Room Correction" optimized for flattened sloping in room response.
Which of those 3 would 2 ears prefer?
Btw, a great deal of the confusion regarding "Room Correction" comes from badly misreading this study:http://seanolive.blogspot.com/2009/11/subjective-and-objective-evaluation-of.html
Olives very first comment:
In truth, the optimal in-room target curve may depend on the loudspeaker directivity and reflectivity of the listening room. If the room is acoustically dead with few reflections and/or the directivity of the loudspeaker is quite high, the in-room response will represent a higher proportion of the direct sound, which should be flat. Using a target curve with large downward tilt will make the loudspeaker sound too dull.
 
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AJ Soundfield

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Well, as I see it if speaker + room interaction is of interest: Load the 90 degree calibration file when REW is opened up, then aim the mic at around 70 degrees.
What would that show?
I had suggested to Miro earlier to do a 1m measurement of the speaker itself, best pulled well out in room, to get an idea of the "speaker" response, since it does not appear available on web.
I curious as to what you are suggesting.

cheers
 

AJ Soundfield

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They blurry what is actually in the recording though, -as each speaker has 7 mirror sources / reflections. So enjoyment is not necessarily equivalent to accuracy. Pick your poision …
How do you know perceptually what is "in the recording" being "blurry"? What is your "accurate" perceptual reference of a fabricated stereo construct?
 

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From @AJ Soundfield ’s link in post #41

“2.4 “Room Equalization” Is a Misnomer
It is a bold assertion that a single steady-state measure- ment in a room—a room curve—can reliably anticipate human response to a complex sound field. Such measure- ments take no account of the direction or timing of reflec- tions within the sound field. Time-windowing the measure- ment is useful to separate events in the time domain, but these too ignore the directions from which sounds arrive. Human listeners respond to these cues, in some detail, and they exhibit skills in separating room sound from the tim- bral identity of loudspeakers, and in adapting to different circumstances. This is, after all, what happens at live, un- amplified, musical events. This means that not everything measured is perceptually important, nor can our reaction to such sound fields be constant, we adapt (see [1] chapters 5–11, and section 11.3.1, and [2] section 2.5). The simple measurements therefore cannot be definitive”
Author: Dr. Floyd Toole

Always made sense to me if for no other reason than I’m not great with math, but this I can grasp. :)

So enjoyment is not necessarily equivalent to accuracy. Pick your poision …
The distilled version. Thanks!

Welcome to AV NIRVANA. Frequency response doesn't always tell the story initially. The first thing I usually do is get the placement setup where I get the best imaging and sound stage, then I let my processor with Dirac Live take care of the frequency response to improve on the imaging and sound stage.
I always have credited @AudiocRaver (Who’s enlightening posts I miss, by the way) for my personal adoption of this. Have never looked back.

@DanDan thanks also for your insight. To me speakers have always sounded better away from the walls even when afflicted by SBIR cancellations. I can see why as a sound engineer you’d have to opt for smoothest response when mixing. Can’t build a bad response into a mix and no way to know in advance how every room is going to alter your work.
 

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@DanDan thanks also for your insight. To me speakers have always sounded better away from the walls even when afflicted by SBIR cancellations. I can see why as a sound engineer you’d have to opt for smoothest response when mixing. Can’t build a bad response into a mix and no way to know in advance how every room is going to alter your work.
You are welcome. Me Too! but not always. Sometimes, often actually, a serious speaker in an untreated hard boundary room can deliver just, well, too much bass. But the huge areas of glass and the measured response in the OP's room concur in my opinion, i.e. a bit light in the loafers, but also confusingly way too much HF room reflections. The Harman and B&K curves are derived from musical preference, in the latter case with separate data for Pro listeners. Hen and egg here, but all people prefer a tilted response. Steady state is the measurement after the listening. Egg, not Hen.

Adhoc- Well, as I see it if speaker + room interaction is of interest: Load the 90 degree calibration file when REW is opened up, then aim the mic at around 70 degrees.

You have a point. If UMIK and Dayton etc. would provide a 70 degree Cal file, we would have best of all worlds, recognising the imperfection and optimum OMNI behaviour of such mics. But vertical would make more sense for surround of course. I think most of the Mic makers supply 0 and 90 degreee Cal Files these days. I seem to remember seeing a 45 degree too somewhere, which seems odd!
 
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AJ Soundfield

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From @AJ Soundfield ’s link in post #41
Always made sense to me if for no other reason than I’m not great with math, but this I can grasp. :)
Well, we can only hope Miro (et al) also reads that AES link (and the 2 previous AH ones):
For decades it has been widely accepted that a steady state amplitude response measured with an omnidirectional microphone at the listening location in a room is an important indicator of how an audio system will sound. Such measurements have come to be known as generic “room curves,” (aka B&K, Harman, etc) or more specific “house curves.” That belief has a long history in professional audio, and now it has penetrated consumer audio with stand-alone products and receivers incorporating automated measurement and equalization capabilities. The implication is that by making in-situ measurements and manipulating the input signal so that the room curve matches a predetermined target shape, imperfections in (unspecified) loudspeakers and (unspecified) rooms are measured and repaired. It is an enticing marketing story..
I fear Miro, like 98% of audio forum folks, has fallen for this story.

The distilled version. Thanks!
Unfortunately this "accuracy" to made by others/you weren't there/echoic memory limits/etc, etc, etc stereo constructs, exist only in the minds of audiophiles/studiophiles. :)
Part of the Circle of Confusion!
Now binaural or better yet PSR, maybe...

@DanDan thanks also for your insight. To me speakers have always sounded better away from the walls even when afflicted by SBIR cancellations. I can see why as a sound engineer you’d have to opt for smoothest response when mixing. Can’t build a bad response into a mix and no way to know in advance how every room is going to alter your work.
No reason not to have both. Think I may have demo'd that for you. My methods being hardly unique.

cheers,

AJ
 
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AJ Soundfield

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Enclosed is some text from ”Acoustics of Small Rooms” by Kleiner and Tichy. As you see in the diagram, comparing 1 m and more typical 3 m listening distance, you are more sensitive to noticing reflections at 3 m compared to 1 m. A 3 dB difference is clearly noticeable, a 10 dB ”appears” like twice / half as loud.

Localization of sound source / phantom image along the baseline between the speakers is determined in about 0,8 ms = very short time, corresponding to the circumference of your head / width between ears, Reflections thereafter tends to widen the apparent source width and possibly its depth (depending on frequency) which may sound just nice and enjoyable, like what is written in Tool’s book. They blurry what is actually in the recording though,

34764
Whoa, how did you get from reflection JNDs to "blurry" with what you cited? Did you see it's referencing "speech"? You seem to be suggesting that speech (strong) first reflections should be absorbed. That would be a big mistake. First reflections with speech don't "blurry" them at all!

To find out how ”bad” your reflections are, you need to check out the ETC-diagrams in REW. A goal in control rooms is not stronger than -20dB within 20 ms.
What does the often misguided practices of studiophile control rooms have to do with someone like Miro's stereo at home listening room? You cited Toole, who repeatedly and clearly differentiates between "home" and studiophile listening. Including what studiophiles 2 ears actually prefer in controlled/blind listening tests, often the opposite of their beliefs! (Some of the McGill studies etc were quite funny). An ETC is going to tell him what his 2 ears can't? Can you cite some double blind listening tests correlated to ETC's for clarification?
I would certainly be interested. Thanks.

cheers,

AJ
 

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'Often misguided' 'fallen for a story' 'exists only in the imagination' 'that would be a big mistake' 'badly misreading' AJ I don't have the time or interest to go through your posts deleting such negative pejorative nonsense. Please take this opportunity to do so yourself. Please also consider and respect the OP, the technical level of his question, and repeated declaration of lack of knowledge. Toole is like the Bible, one can read almost anything into it. And what in the world is a 'studiophile'?
 
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AJ Soundfield

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'Misguided' 'Fooled' 'Exists only in the imagination' AJ I don't have the time or interest to go through your posts deleting such negative pejorative nonsense. Please take this opportunity to do so yourself. Please also consider and respect the OP, the technical level of his question, and repeated declaration of lack of knowledge. Toole is like the Bible, one can read almost anything into it. And what in the world is a 'studiophile'?
Hey wait a second, where did I say "fooled"? :)
Dan, the fact is, many if not most audio related people come in already believing that these EQ+ products will magically make the sound better, since this is such a widely accepted view. This thread is symptomatic of that.
No, Toole isn't at all like the Bible at all. As I stated very early, there will be 2 "sides" in these discussions. The one with scientific/listening test evidence (aka "Toole") and the other without. That's exactly how this has played out.
Miro, like I'm sure most adults, seems perfectly capable of deciding which path he should follow. I make my case based on where all the science points, including listening test references, he can decide whether he does as well. He's of to a good start by including measurements, hopefully, as a compliment to what his ears tell him.

cheers,

AJ
 

Miro

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Jul 2, 2020
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@DanDan thanks also for your insight. To me speakers have always sounded better away from the walls even when afflicted by SBIR cancellations. I can see why as a sound engineer you’d have to opt for smoothest response when mixing. Can’t build a bad response into a mix and no way to know in advance how every room is going to alter your work.
You are welcome. Me Too! but not always. Sometimes, often actually, a serious speaker in an untreated hard boundary room can deliver just, well, too much bass. But the huge areas of glass and the measured response in the OP's room concur in my opinion, i.e. a bit light in the loafers, but also confusingly way too much HF room reflections. The Harman and B&K curves are derived from musical preference, in the latter case with separate data for Pro listeners. Hen and egg here, but all people prefer a tilted response. Steady state is the measurement after the listening. Egg, not Hen.

Adhoc- Well, as I see it if speaker + room interaction is of interest: Load the 90 degree calibration file when REW is opened up, then aim the mic at around 70 degrees.

You have a point. If UMIK and Dayton etc. would provide a 70 degree Cal file, we would have best of all worlds, recognising the imperfection and optimum OMNI behaviour of such mics. But vertical would make more sense for surround of course. I think most of the Mic makers supply 0 and 90 degreee Cal Files these days. I seem to remember seeing a 45 degree too somewhere, which seems odd!
Hi M,
I use a 0-degree calibration file from UMIK-1 which is advised for stereo measurements. Are you saying that 90 degree is a better and that UMIK-1 should point at the ceiling?
best regards, Miro
 

Adhoc

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Jan 7, 2018
Messages
25
Cool down AJ.There’s a lot of unnecessary aggesive attitude from you, when you try to make your point. Problems also arise when you seem not to notice or comprehend what other people are actually writing and what that (can) mean in a further discussion or mental process figuring out solutions to problems.

To your questions:
Microphone position; what is actually of interest here? If you wish to know how good your speaker is in reproducing the recorded sound, make a sweep and aim it straight at the speaker / driver at driver height from a very close range, a cm or so (Or do it outside far away from any borders). But, the speaker response itself should not be the main interest here. As a listener it is of interest to include room interaction. After all, that will influencea lot more of what you hear. To pick up more of room interaction (random incoming reflections), angle the mic at around 70 degrees or so at listening position, so it picks up more of the room influence. Aim the mic straight towards the speaker and it will pick up less of room influences. Response changes should show up mostly at high frequencies but why settle for a worse mic angle than necessary …?

In enclosed diagram there are 3 curves. All 3 curves are REW sweeps for 5,5 seconds / 512 k with 48 th smoothing applied. Red is with mic 1 cm from a mid bass driver at 61 cm above floor. At 1 cm range the mic picks up just about only direct sound = what is actually recorded / swept. Frequency response is +/- 1,5 dB within the range it shall play and is OK to me.

Green curve with the deep dip is with mic 75 cm away = 3 cone diameters. Here the 1st and closest mirror source shows itself big time = a floor reflection with destructive interference at 230 Hz and 670 Hz and corresponding constructive interference (peak) at 460 Hz. Blue curve is with insulation on the floor, extending from speaker to behind the mic, 20 cm / 8” thick with a gas flow resistivity of 5000 Pa.s/ m². Not enough to completely damp out the interferences but quite efficient. If the speaker manufacturer hasn’t proposed a certain distance from the wall behind the speaker and taken that into account in the construction, there will be a similar dip at another frequency if the speaker is placed away from the wall. That dip cannot be EQ:ed up. Placing the speaker baffle flush with the wall / close to it will give some bass boost which can be EQ;ed down in frequency. Flush mounting = no back wall dip. Close at wall and the dip goes up in frequency, requiring a thinner absorber say 2-4” to effectively dampen the destructive interference. (The green curve type of measurement is what you propose to Miro to use. At 1 m he is not measuring the speaker itself as you wrote. -Quite evident from my curves.)

230 Hz corresponds to a wave length of 1,5 m. Width between the ears is close to 0,15 m. A ratio of 10:1 means the SPL at both ears will be the same as the bass wave doesn’t ”see” the head. With 1/6 octave smoothing corresponding roughly to what we can notice, the dip ranging from 125 to about 250 Hz is 5 dB deep. Speaker response from the red curve = direct sound is +/- 0,3 dB from 125-250 Hz. Will a dip of 5 dB due to the mirror source be noticeable at listening position? Yes. Can it be resolved with EQ? No, -as it is a SBIR, speaker boundary interference response. Does the dip corrupt / change perception of the recorded sound and its timbre at listening position? I would say yes. At listening there are also 6 more major mirror sources to have in mind. Will they influence too (?), sure they will. If one prefers accuracy, truthfulness to the recorded sound, one can try fix those reflections. If one doesn’t, timbre will change, apparent source width will increase, phantom image may change, details in the recording might not be heard due to masking.This doesn’t mean the reproduced sound is not nice and enjoyable. But perceived sound deviates from what was recorded.

Regarding the diagram from ”Acoustics of Small Rooms”. Speech is often used checking detection of reflections as it contains a lot of consonants = transients and we are sensive to transients. Music usually have less transients and is more ”forgiving”, and reflections are less noticeable compared to speech. My goal for ”accuracy” would be a flat speaker response of the direct sound within the first 15-20 ms or so, with reflections damped -15 to -20 dB within that time period. Thereafter diffuse reflections coming in from backwall => sidewall at an angle slightly behind listening position. A steady state, with flowing music, can result in a slope in the frequency curve from low to high with quite normal furniture, curtains, carpets etc. Something along the Harman curves or Brüel & Kjaer’s curve. Otherwise prominent bass modes damped with passive fixes as far as possible, EQ for the severest. Decay time, T60, as even as possible from bass to treble, about 300 ms (bass) to 175 ms (treble) at listening position in a 72 m³ / 2540 ft³ concrete room.
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