Redefine your budget room EQ 'flat' target curve to Harman's pro curve

Apr 19, 2015
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#81
Fascinating thread. Would you mind if I made it a sticky?
How flattering. Are you sure you want to elevate a novice like me to sticky status? Only been at this for two years as solitary practitioner.;)

However the spirit moves you. Your forum. I am just glad to have a place to try out my wacky ideas.:)

Thanks for fixing my account. I have been itching to upload that last graphic all day.:b
 
Apr 3, 2010
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#82
Not exactly. Audyssey curve also sloped down and it did the worst. It may have been flat in the bass but it attenuated the treble.
It did and it scored OK there. Where it failed was in producing anemic bass, a complaint that I hear routinely about Audyssey and matches my own extensive experimentation with different target curves. Harman shows this in a nice graphic which edited later in your post:



Again the dashed line is doing nothing. We see that less performant systems have dropped the bass below that line. The rest of the graph though, looks the same as far as "macro level" picture. Let's pair that with preference scores for each frequency range:



We see that Audyssey did do OK in high frequencies. It was the low frequencies that got it such low scores and mid-range. The mid-range is likely due to mid-range/"BBC dip."

It did worse than the curve that was flat all the way across. At least the other flat curve was deemed as good as no EQ.
The other curve is Anthem's. It did worse than that because didn't screw up the micro picture by inserting a dip in the mid-range. Vocal fidelity is one of the key things tested in Harman listening tests and you better get that right or you get hammered as we see in the pink preference curve above for Audyssey (RC6).

There could have been other reasons why Audyssey performance was undesirable and probably the worst thing about it IMO is how ragged it came out, just as bad as the uncorrected response if not worse plus there is that BBC burble in the midrange too and the bass extension was pulled back by the flat part of the bass curve and the -3dB limit. There were so many things going on it is IMO invalid to point to any one thing and blame it for the poor performance in listening tests.
At the extreme, this problem is not analyzable. You cannot zoom in too much in the data and expect to get anywhere. These are systems which produced very different sounds. With no reference sound that is known to be "correct," we cannot make any absolute judgments.

What we can do, and what the paper does and I and countless others state, is high-level correlations. We know for example from many tests of loudspeakers that have directivity problems, that having a dip in the resulting mid-range, is not going to sound good in proper, blind listening tests. Fortunately there, we can accept that intuitively, Audyssey fanboys who defend anything about it aside (not talking about you Cheryl). The test adds a powerful data point to support this with Audyssey getting such poor results in the mid-range and others not.

The second thing we can extrapolate reasonably is that people like more bass. They just do. This comes out in many tests and we have documented that in this thread. Audyssey goes against that body of knowledge and opts for what one thinks should be done, i.e. flat bass, and as we would predict, gets hammered for anemic bass.

Now, are there other explanations and hence, strategies? Maybe. Until such time that you create controlled tests and extrapolate those insights, and show why the contradictions with other tests makes sense, we have to go by what has been learned over the years here. And that calls for these two strategies in correcting system response:

1. Smooth frequency response (not be confused with "flat" frequency response). This calls for taking out the peaks in bass frequencies.
2. Sloping down response from low to high frequencies. Not just a treble tilt but increase in bass.


We could fight this learning with no alternative listening test data or accept it and optimize from there. I live and breath this stuff and that is where I am.

That certainly works. It might not be optimal though and it also involves a manual step. Auto-manual EQ?
The automatic is good enough for majority of cases. The manual is for someone who wants to experiment. This is only true if you follow the above target curve.
 
Apr 3, 2010
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#83
Look that over and tell me Harman did not just draw a straight line through the in-room response. From my perspective, they did exactly what you are telling me is the wrong approach and at least one person who claimed to know supports that supposition.
I didn't tell you that was wrong. And they didn't just draw a line and call it done. You are misunderstanding what Sanjay said to you. What they did was pick that target, and then spent considerable amount of time performing these double blind tests and found out that their selection worked and worked well. You seem to be saying the results would be more valid if they had picked a bunch of wrong curves first. They didn't make a random selection. They started with body of data and their own experience and intuition and it proved right.

...but it has never been compared to my proposal.
I am sorry and this is my failing but I still don't know your proposal. Hopefully someone else who has followed it better can explain it to me. What I do know is the research and it all points to the simple picture I am painting. And that picture, is one that can be implemented very easily even in manual systems. It does not require for example anechoic spin data that no one has.

I have been making the same claim to support Audyssey in budget systems. It works well enough for the purpose and many people lacking in bottomless pockets agree with me. Does that mean it is time to rest on my laurels?
If it does then fine. My job is to bring research forward, explain what it means and add my own hands-on experience and first-hand knowledge of this work with our membership. What you do with it, is your decision.

If it were me, I would disable Audyssey so it doesn't screw up the mid-range, measure the room with REW. I would then get a subwoofer with a DSP filter or two in it, or cheap little DSP on the path to the sub and take down the peaks. Then set the sub level to be higher than the rest of the range. Yes, this costs a few dollars. If that is too much, then I don't know what to tell you to do when all you have is an all or nothing system. Buy less coffee each day and save up to buy the DSP :). Or decide to not care about the best sound if it is not worth that much to you.

If you only have the choice of turning Audyssey on and off, now that we have discussed the issues with it, my suggestion is to go back and really listen to the system. Play music with some vocals, close your eyes and turn Audyssey on and off and judge which one sounds better. Then open your eyes and see what you selected. Do this with a couple of other loved ones if you can. Make the same honest assessment with bass. If at the end it is all an improvement, then sure, use it.

My proposal would also be a sloping down target curve when a speaker is measured in a room but the slope and curvature would be measured directly off the speaker where it sits.
We are back to me not understanding what you say in this regard :). We always measure the room with the speaker where it sits. :p

Harman speakers with custom EQ is actually a great idea. Any known irregularities in the on-axis response can be EQd out by design. In that respect it has a distinct advantage over my proposal, but I still think there is also value in setting the target or at least tweaking it from the measured in-room response. For all we know maybe that is exactly what that JBL EQ for Harman speaker is already doing. Have you asked them?
Your underlying assumption here is that the speaker response is the right one. That is not the case at all. Vast majority of speakers are sold on basis of what sells in showrooms, and what looks good. An EQ system needs to correct for their response in addition to the room. We are not dealing with idealized transducers in the room. And at any rate, you did not select your speaker based on hearing it in anechoic chamber as to try to extract that sound of them.
 
Apr 3, 2010
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#84
IMO the whole claim that the reason flat room EQ is undesirable is because it does not accurately reflect the original intent in the mixing room is a fallacy. IMO the reason flat room EQ is undesirable is that it violates the intent of the speaker designer who designed the speaker to sound good with a sloping down power response in an enclosed space.
There are thousands and thousands of speakers out there. I assure you that each one makes a different decision in this regard and that is why they all sound different. There is no way you want to base your decision on them having made the right decision here. There is no "there" to try to replicate in all but the best designed speakers.

Besides, Harman did not test the target curves as an independent variable so your statement is only a supposition. For someone who is normally quite specific in demanding science, your implicit assumption that this experiment validated the target curve of the winning system is out of character.
I have been using Auto EQ systems long before Harman's came about, starting with TacT back in year 2000. The first thing I did there was evaluate the target curve. It came with one sloping down and said it was right. I thought, "what idiots." How could that be right? I plug in flat and fell of my chair with it sounded bright and harsh. I spent days trying to figure it out, messing with it just a bit but ultimately had to give up and use their target curve as a much closer one. Prior to that, I kept trying to convince myself that even though my flat response did not sound right, it must have been correct so I should just listen that way. But I could not.

We then built our showroom at work and put in a Wisdom system with Audyssey Pro (stand alone box as tested in Harman's) in there. I did extensive evaluation of it and could not stand what it was doing to the sound. We left it off as it totally screwed up the sound most of the time. As I explain in the story of our system, http://www.madronadigital.com/Showroom/HomeTheater.html, we also had a parallel JBL Synthesis in there. The little horn pro speakers looked cheap, junky and flat out ready to be spanked by the Wisdom system that costs 2X more (the tall planar speakers with line arrays):



My chief designer configured that and I watched over his shoulder as he ran through the program in just a few minutes. We took snapshots of that which I have been sharing:



When it was done, it cleaned the Wisdom clocks. Here I was spending weeks measuring the room with the Wisdom, finding major performance issues, going back and forth with the company, and this other system out of box performed so well. End result was that we ripped out the Wisdom system, licked our wounds there in money and energy lost, and went forward. Speaker designer knowing best? I don't think so.

But my mission did not stop there. I studied the field, went to Harman multiple times, and educated myself and what you see, is what you get now. Meanwhile, my company goes through a ton of AVRs and we are constantly asked to evaluate new lines. So I played with all the other Auto EQ systems from Anthem to Pioneer's and Sony. And of course Audyssey. I have tested these at home and at work.

It is this body of work and experience that I draw upon. It may still be wrong. I don't know everything. But it is no casual observation I am sharing. And certainly is typical of what I do which is read the research, spend time with products and technology, and have real connection to researchers and industry people who bring it to us. If you expected more or different, you are confusing me with someone else :).
 
Apr 3, 2010
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#85
I think you misunderstanding me. I am not proposing to rewrite the book on EQ based on a guess. Only an impulsive idiot does something like that. I am identifying what I perceive as unanswered questions and speculating on a new approach and proposing an experiment like Harman's only more sophisticated in its approach to the problem rather than empirical guess based on listener preference (if that is actually how it happened... really hate all this mindreading).
I will keep repeating this: complexity is not your friend in this regard. Simplest decisions are bound to be more correct in a chaotic system with so many variables you cannot control.

Harman tested EQ systems with widely varying performance (not just widely varying targets) and it did not compare straight line to B&K curved line nor did it attempt to vary the slope or shape of their straight line nor did it attempt to determine if there were any correlations between in-room non-EQd response and the best target across multiple types of speakers in multiple placements in multiple rooms.
The manifestation in their system is the results of years of optimization both in the lab and in countless high-end installations by world-class theater designers. What is there, is what I have beens haring. Don't confuse the data shared in the AES paper we have been discussing which came out before the system even shipped, to nearly 8 years later now. The right decisions have survived the test of time and therefore, require no more answers.

Their justification for not checking on all of this was... mono listening is more accurate? B&W sells the most pro speakers? No, it was probably because they ran out of budget, time, and/or patience.
No, the justification was not mono testing. Where did that come from? As for B&W they sell the most luxury speakers than any other brand. They are as close as you can come to "mass market high-end" as that oxymoron would allow. As such the results do not seem to be corner cases as if they had picked some random high-end speaker few people have heard of.

Or maybe just like already indicated by others on this thread they already knew about everything I am proposing to check into and either quietly slipped it in to the target curve or just ignored it deliberately because of the complexity of getting it to converge reliably. Who knows? I am no mind reader and there are proprietary technologies involved.
The tone of your comments is highly accusatory and inflammatory with respect to work that Harman has done yet you follow with you don't know. Harman uses this research in developing multi-billion dollar business called car OEM audio/infotainment. It is that business that fuels much of this research. There is nothing casual about winning an OEM contract with Toyota to outfit hundreds of thousands of cars. Or BMW. You don't go and confuse yourself with something as opposed what ultimately sounds good, and can outperform lower-end solutions.

So there is no ignorance here. There is nothing deliberately screwed up. It is methodical research and verification through extensive double blind testing that they ultimately and generously share with all of us to use. If you have more reliable research, let's see that. Until then, let's dial back the characterization of intentions behind their work, or lack of implied competence. While you may not know, I do know that neither is the case here even though admittedly, my views are biased based on my personal and business relationship with them.

Do you have the actual Harman EQ they used in that study? Does it automatically adjust the slope of the target based on in-room response?
Of course I do. Do you not read my posts and articles Cheryl??? No, it does not change the target curve based on in-room response. The in-room response is what is being corrected. It is not a variable in itself.

Have you tested it for any changes in target due to measurement? Maybe everyone looks at that study and just guesses that the slope is a fixed target. I do not know, I am not in that league.
Yes, I have tested it, used it. It doesn't do what you say.

I am simply proposing to check into it. I am proposing to finish what Harman started instead of just leaving it status quo because it was good enough last year.
The report came out in 2009, hardly last year's version of the system. I use the current version with all the same characteristics.

Another is the application of the same EQ target curve to all speakers regardless of type and placement when they actually need different target curves to optimize them individually.
We are not optimizing for what a speaker wants to do. We are optimizing for what you and I want to hear. And we are a constant in that equation. We don't bend to the sound of the speaker. We want it to produce what we think is real and pleasing.
 
Apr 3, 2010
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#86
What I am really saying here is why didn't Harman try everything possible to optimize the target? They certainly did a great job with the implementation. That measured response is straight as an arrow. Never seen anything like it anywhere else.
This is why:



RC1 is their system in red. The listening tests said it sounded right, nearly perfect line of preference in "spectral balance" in every frequency band. If you were in their shoes, you would then keep messing with very different curves to get a different answer??? If you designed a system and it worked right, do you go back and design it again six different ways for the sake of it? Based on what reasoning?

Every time I see someone defending that target it is always because Audyssey flat or flattish EQ with its choppy, bandlimited measured result came last in preference. That does not validate Harman's target curve as the optimal approach to room EQ. All it does is make Harman EQ superior to Audyssey under those test conditions.
No, this is not just theory. The system has been deployed in numerous high-end installations. And literally millions of cars. It is that body of experience which says it is right, not some comparison to Audyssey.

If that thought experiment does not at least raise some doubt about the wisdom of always using a fixed target curve as the first approximation and ignoring the actual in-room response, then I might as well check myself into an insane asylum because it means I have totally lost my marbles.
On one hand you say you are novice in this area Cheryl, on the other you say such things with such surety. It has taken me years to get to be in this state I am in this field. The confidence you show in these remarks says you have way passed me with a fraction of research and experimentation. Good for you for being that much smarter than me. But by the same token, don't ask me to agree with you. I can't keep up with you :).
 
Apr 19, 2015
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#87
At the extreme, this problem is not analyzable. You cannot zoom in too much in the data and expect to get anywhere. These are systems which produced very different sounds. With no reference sound that is known to be "correct," we cannot make any absolute judgments.

What we can do, and what the paper does and I and countless others state, is high-level correlations...Until such time that you create controlled tests and extrapolate those insights, and show why the contradictions with other tests makes sense, we have to go by what has been learned over the years here. And that calls for these two strategies in correcting system response:

1. Smooth frequency response (not be confused with "flat" frequency response). This calls for taking out the peaks in bass frequencies.
2. Sloping down response from low to high frequencies. Not just a treble tilt but increase in bass.


We could fight this learning with no alternative listening test data or accept it and optimize from there. I live and breath this stuff and that is where I am.


The automatic is good enough for majority of cases. The manual is for someone who wants to experiment. This is only true if you follow the above target curve.

We appear to be stuck in a cycle. I hope I can end it with this last post.

Harman study concluded that smoothed and extended frequency response is preferable and that the preferred target EQ is not flat. That is direct paraphrase from Dr. Olive's slides.

I am in complete agreement with these conclusions so I am having difficulty understanding why you seem to feel that I question them.:confused:

What I am questioning is the assertion that a straight fixed slope target is optimal starting point for auto EQ by any standard of measure. It may be customary, it may be preferred in the Harman study, it may work well for some people, but as far as I know no one has yet used an EQ with the processing power and tight error limits of the Harman system to compare that target you prefer to the alternative target I proposed.

Also, Dr. Toole apparently disagrees with your assertion, as apparently also Onkyo disagrees.

Toole seems to think that no auto room EQ works well regardless of target curve.

Onkyo design and marketing seems to think that measuring the power response of a speaker in the actual listening room to develop the EQ target provides some benefit.

Onkyo EQ per descriptions I have read anyway seems to measure the front l/r and EQ the rest of the system to the derived target instead of using that target to smooth and extend the frequency response of the speakers they measure, so in that respect their approach also seems questionable to me. I would prefer they apply the derived target to the same speakers they are measuring.

Moreover, I demonstrated that the data presented in Dr. Olive's presentation does not show any change in the global power spectral balance of the equalized speaker system. The preferred targets (RC1-RC3) seem by inspection to closely align with a curve-fit approximation to the unequalized speaker response in that room.

Since your opinion has at least two prominent counter-examples that I can readily point to and visual inspection of the plots in the Harman study seems to support my proposed approach, I have to respectfully disagree (sadly) on a theoretical level and leave it at that. I do not have the funding to provide proof of the validity of my proposal and I never presented it as anything other than a thought experiment, although I did attempt to explain and defend my reasoning in detail. I am sorry if this does not meet the WBF standard for discussion but it is the best that an outsider without funding can do.

You asked me several times to clarify my proposal and indicated that the details are still a mystery to you. In the absence of any funding or time to document and implement it, I have to simply state it in the most concise terms I can and let you make of it what you will.

I hope that some good comes of the following summarized proposal some day, and then, sadly, I will let the matter drop to avoid inflaming the dialog more than it already is.


These are the assumptions I make:

This proposal applies primarily to small listening rooms but could be extended to larger rooms with appropriate measurement definitions that can detect treble attenuation due to distance travelled through air. For very small spaces cabin gain becomes a major factor and I have little knowledge regarding how to handle that so I defer any statements regarding that aspect.

Pro speaker has a mostly flat and extended anechoic on-axis frequency response by design as illustrated in numerous publications. It also has smooth (and smoothly varying) off-axis treble attenuation as a direct consequence of its inherently increasing directivity with increasing frequency. The absolute character and detail of these properties are under the control of the speaker designer and the tradeoffs are made such that a speaker sounds good in appropriate listening room without any outside intervention by room EQ.

Room EQ can only measure power response contaminated by the inevitable room-induced distortions in the spectral balance. The in-room power response integrates the magnitude and phase response of all energy radiated in all directions by the speaker that has not been absorbed on its way to the microphone. The power response is the only remnant of the original intent of the speaker designer that can be objectively determined once a speaker is placed inside the boundaries of an enclosed space.

When placed into a room, the mostly flat on-axis frequency response becomes unavailable to the auto room EQ measurement system due to the reflections off any boundaries and similarly the on-axis response cannot be directly perceived by a human either. Presumably, precedence effect enabled by the head-related transfer function and other psychoacoustic perceptions can provide clues to the on-axis response or else speaker designers would ignore the on-axis response and concentrate entirely on the in-room power response when designing a speaker.

Dr. Toole has referred to this precedence etc. psychoacoustic effect as 'hearing through the room' and it appears to be the primary motivation for purists refusing to EQ the frequency response of a pro system that has been installed in an acoustically controlled environment.

The acoustic characteristics of the room are typically tuned so that the sound of the chosen speakers will be optimized in that room and presumably, pro speakers anticipate the absorptive characteristics of their optimal environment when their response is tuned during the design phase.

It is desirable to EQ out as much of the spectral distortion as possible while preserving as much of the original spectral intent of the speaker designer as possible, and also while extending the frequency response beyond its inherent unequalized bandwidth limitations in such environment.


These are the details of my proposal:

In the absence of any anechoic measurement data, the only way of determining the original intent of the speaker designer is to measure the actual speaker in the actual room so that is what I am proposing to do. I am proposing to replicate the original intent of the speaker designer in the resultant speaker response, smooth that response, and extend its bandwidth based upon a target that is objectively determined via power response measurements with a microphone in the actual listening room.

Moreover, I am proposing to ask the user to identify each channel as belonging to a group of speakers in the system that are all the same model so that their measured response can be averaged or otherwise combined into a more accurate target that more closely resembles the original intent of the speaker designer.

Another aspect is that the derived target for a group can be individually tailored by the auto algorithm to incorporate aspects of in-room response specific to a channel. If no averaging or combining of response is deemed desirable the derived target can be completely specific to a channel. These details remain unknown and I am of course speculating but my suspicion is that subtle differences in the location-specific psychoacoustics could lend themselves to individual tailoring of channels and that the resulting response could provide the listener with a more coherent image if the individual character of the resultant power response of each channel is preserved to some extent.

The inherent frequency response of all speakers tends to have a curved rolloff at the frequency extremes. All room EQ (auto or manual) that I am aware of preserves some semblance of this curved rolloff because to do otherwise would push the equipment beyond its natural limits of operation.

The most appropriate smoothing and extending function for such a system is a second-order function and an appropriate error function to apply smoothing with is least squares. For customization in the event that the resulting slope and curvature is not to preference, or the algorithm has converged on a suboptimal target, two manual control factors can be implemented that will arbitrarily tweak the target to preference in slope and curvature including reversing the slope and curvature if desired, but the countour of the target EQ function will preserve the general natural concavity of the overall power response to preserve the relationship between the on-axis response and the power response particularly at the inflection point in the region where the speaker first starts to become a directional radiator.

The resulting auto EQ target will represent a close approximation of the original intent of the speaker designer because it will directly measure that intent in the only way possible when no anechoic measurements are available. The target will also be customizable so that any second-order fit including a straight line of adjustable slope can be derived. Even an inversion of curvature or slope can be induced.


Disclaimers:

I understand that my suppositions and proposals are speculative and run counter to commonly accepted practices and beliefs. That is the nature of progress. Some ideas pan out and others do not. At this time there is no way to tell but I wanted to share my ideas just in case they hold value for someone of greater means than I to analyze and implement them. I am explicitly giving up my rights to any such invention in publishing here so please consider that what I am presenting is a gift, not an argument.

That is it, Amir. If I made any invalid assumptions or any technical errors due to my lack of experience, I apologize for my limitations. I also apologize for any perceived insult to anyone because there was no such intent. Any appearance of disrespect is likewise a representation of my limitations and I apologize profusely and unreservedly for any perception that my intentions in the course of this debate have been anything but entirely honorable. Any statements I made were intended to illustrate and explain my proposal according to the letter and spirit of the terms of use.
 
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#88
Cheryl, it is because of people like you that we can all advance. You are as dedicated as Amir is in the pursuit of sound excellence.
I can easily see you working alongside the best sound scientists/acousticians on the planet. ...Your drive is impregnating.

It's us who should apologize to not taking the time to read all your analyses. I apologize, ...time is not on my side.
The best is in people first, in you, in your quest. ...And if we aspire to be the best, we do more tests. ...Never rest. ...Only to enjoy the music playing. :b

I would love to see Dr. Toole and Dr. Olive replying to your posts. /// I bet that they are very busy people.
Amir too amazes me, with all the time and dedication he gives to his entire entourage, to you, to all of us.

Thank you, to you both.
 
Nov 3, 2014
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Cheryl -

First, I am in general agreement with Amir as to the theory of this. He really does know what he is talking about. He is also tenacious about getting to the truth.

I think citing what Toole said out of context might be misleading. I think Toole 's ideas might be best discerned from the JBL EQ product that was developed at Harman on his watch.

As to the Onkyo AccuEQ, I do not know of anyone who holds it in high regard at all, so I do not see it as some exciting new direction. The basic idea of EQing all speakers to be the same as the measured in-room response of the main fronts in a Mch system has been around for awhile. There were even some implementations of Audyssey that had that option, not sure which from memory. And, a few other EQ tools have had this, Lyngdorf, possibly. Somewhere, there was also a tool that attempted separate quasi-anechoic measurement of the speakers and then of the room. Again, not sure, but I recall seeing it.

As you have agreed, the measured response of the main speakers is polluted by the room. Replicating that response to other channels merely enforces that on the other channels and does nothing about the room distortion. It is just a flawed idea from the get go. I could go on, but there are many other shortfalls in AccuEQ.

There appear to be two real reasons for Onkyo to have abandoned Audyssey in favor of their home grown product, which may have been derived from their acquisition of Pioneer and its Mccac. That Pioneer system was also not highly regarded anywhere. AccuEQ first eliminated licensing fees to Audyssey. Second, it requires less DSP computing resources during playback than Audyssey did, allowing resources to be allocated instead to more channels for Atmos, Auro, etc. without much more expensive DSP processors. I think if you look carefully at what it does and does not do, it is not in any way a paradigm of where we should be headed.

Like Amir, I also do not see that the speaker's actual response, anechoicaly or whatever, or even the designer's intent is necessarily the standard we should be shooting for. Rooms, even treated ones, are not alike, so there is no way the designer could have anticipated your own room. And, speaker designers disagree on what is right. Also, real world, in room power response is not necessarily smooth even for pro speakers and even above the bass modal issues, based on measurements I have seen. They are all variable.

But, in forums, I have seen others who do try to replicate the actual measured response of their main fronts by custom manual edits of the target curves for all channels to follow the measured response. I do not see the sense in that myself. And, you need a good EQ tool to be able to do the target curve manipulation.

Before criticizing the considerable psychoacoustic research on target carves done by many independently, I think it would behoove you to get a better EQ tool so that you can yourself experience the sonic impact of different targets in your own room. Yes, research gives some different answers to what is right, sometimes strangely different. Look at what Audyssey did, for example. But, aside from that, there is some degree of general agreement on the ballpark of what the target curve should be. Note also, that the B&K curve you provided is quite similar to the default Dirac curve, and that is generally consistent with Harman, Lyngdorf, etc.

So, I understand your budget constraints. Treating your room is not necessarily a bad idea, but you will find it a complex, daunting task, I believe. In acoustics, like a lot of things, a little bit of knowledge is a dangerous thing. Even then, correcting bass modal issues via treatments is really difficult and generally requires really big structures for absorption or custom resonators, etc. Even then, I believe suitable EQ can do an even far better job in the deep bass also even with attempts at treatment in place.

In the bass, where the biggest room deviations are invariably located, there are essentially no off the shelf passive treatments that are particularly effective much below 100Hz, unless you use a lot of them, which can get quite expensive and ugly. But, that may also have other negative consequences at higher frequencies. Citing Toole out of context, he once remarked that he did not like absorbing treatments because he felt they were a broad frequency band solution to a narrow band problem.
 
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audioguy

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Apr 21, 2010
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#91
Interesting thread. Anyone know the X and relative Y data points on this (black) target curve?
image.jpeg

If push comes to shove, I am sure I can approximate it but if I can get the exact data, it might be helpful.

If I recall correctly, when Harmon did this study, they used music. Anyone know what this might look like if Harmon had used movies instead. With current subwoofer abilities and more movies providing sub 25HZ content, this particular target looks like it might (relatively) hide those frequencies.
 
Apr 3, 2010
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#92
I don't think I have ever seen the actual numbers for the target curve JBL Synthesis uses. But here is the latest version/measurement of our theater at work when we first built it:



The dashed line is the target curve for main channels with an 80 Hz crossover. Faint red is pre-correction and bright red is post correction measurement.

I don't think there is much research as to what needs to be there below 80 Hz especially for movies where it is all artificial anyway. So best is to adjust that by ear as we do (in general, the target curve should also be adjusted by ear after the initial optimization).
 

dallasjustice

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Apr 12, 2011
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#93
There is no universal target. But I've found that a hinge at 1khz out to 20khz at -4db is very desirable and consistently good. I believe there are psychoacoustic reasons for HF to be attenuated a bit in so called "small rooms."

Below 1khz, I prefer pretty flat response down to 15hz. IME, this preference varies depending on bass accuracy of the recording. There are many bass shy recordings. In those cases, a little LF tilt can help. The newest version of Acourate Convlolver has a real time tilt the user can play with and various presets. I'll prolly set up a few different bass settings.

IMO, I believe there is so much inconsistency with bass in recordings partly because many professionals think they are EQing the recording. Instead, they are really EQing their own room-boom bass problems. There are prolly some other factors too. (None of which is my system/room.) :p


I don't think I have ever seen the actual numbers for the target curve JBL Synthesis uses. But here is the latest version/measurement of our theater at work when we first built it:



The dashed line is the target curve for main channels with an 80 Hz crossover. Faint red is pre-correction and bright red is post correction measurement.

I don't think there is much research as to what needs to be there below 80 Hz especially for movies where it is all artificial anyway. So best is to adjust that by ear as we do (in general, the target curve should also be adjusted by ear after the initial optimization).
 
Last edited:
Mar 23, 2015
1,442
16
38
UK
#94
There is no universal target. But I've found that a hinge at 1khz out to 20khz at -4db is very desirable and consistently good. I believe there are psychoacoustic reason for HF to be attenuated a bit in so called "small rooms."

Below 1khz, I prefer pretty flat response down to 15hz. IME, this preference varies depending on bass accuracy of the recording. There are many bass shy recordings. In those cases, a little LF tilt can help. The newest version of Acourate Convlolver has a real time tilt the user can play with and various presets. I'll prolly set up a few different bass settings.

IMO, I believe there is so much inconsistency with bass in recordings partly because many professionals think they are EQing the recording. Instead, they are really EQing their own room-boom bass problems. There are prolly some other factors too. (None of which is my system/room.) :p
Dallas - your target sounds like the one that Bob Katz uses I think? I like the bog standard B&K.
 

dallasjustice

Member Sponsor
Apr 12, 2011
2,090
0
0
Dallas, Texas
#96
It is funny how much consensus there is among those who use target curves. Almost everyone agrees on a downward tilt into the very high frequencies.

IMO, this normal human preference might explain a lot about the attraction to certain pieces like tubes, true NOS ladder DACs (eg. TotalDAC) and certain speaker cables.

The new JBL 4367 allows the user to reduce the HF as well. I think this is very smart. Some other speaker manufacturers design their speakers like this as well.

One of the best side effects to using high performance DSP like this is that it greatly reduces gear swapping, as long as the user starts off with relatively neutral gear.
 
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Mitchco

New Member
Dec 5, 2011
28
0
0
#97
Interesting topic. Just passing along some info and impressions as I spent over 30 years with room curves starting with RTA's, 31 band eq's then TEF, 10 years of which working professionally in a variety of recording studios/control rooms and the last 5 years with digital loudspeaker and room correction software systems. In addition to the Harman and B&K target responses, there is also the European Broadcast Union produced a Tech note (EBU-Tech 3276) called, “Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic”. https://tech.ebu.ch/docs/tech/tech3276.pdf Check out Figure 2 on Page 6.

However, these "targets" are all very similar where the spectral response is flat to some frequency hinge point and then some slope of a roll off, typically between -4 dB and -10 dB ending at 20 kHz depending on the amount of HF absorption in your room and of course personal taste :) The Bob Katz curve which I documented in an article in Acourate on CA is flat to 1 kHz and then a straight line to -6 or -7 dB at 20 kHz. Again, some tolerance variability for personal taste, HF absorption, program material being listened to (pop rock mixes with heavy dynamic range compression tend to have a brighter spectral balance than minimal mic'd orchestra music).

Toole's latest free paper at AES: http://www.aes.org/journal/online/JAES_V63/7_8/#paper1 also supports this approach. See Figure 14 on preferred room curves and the comments about trained listeners.

I have a lot of respect for JJ Johnston and feel his presentation on the Acoustic and Psychoacoustic Issues in Room Correction that can be downloaded from here: http://www.aes-media.org/sections/pnw/pnwrecaps/2008/jj_jan08/ represents the state of the art understanding of room correction. Since then, most of the DRC products use frequency dependent windowing (FDW) based on jj's research which is a major leap forward from 1/3 or 1/6 octave analysis and correction systems.

What I find interesting is that if one is looking for the most neutral or natural response, something close to Bob Katz's spec seems to be closest. What do I base this on? Well, doing some correlation with a number of diyAudio members, we shared our measured responses at the listening position. Here is one example, where throughput the passband, myself and another diyAudio member are basically listening to the exact same response, yet our systems and rooms and have nothing in common. His speakers are 25 full range 5" driver line arrays and mine are 3-way old school active horn system. Aside from different gear, we are also using different DRC systems:

mitch_zpsiocwyxfe.jpg

Several other members share virtually the same measured response at the listening position. Coincidence? I just find it interesting. Given the power of computers and sophisticated DSP software like Acourate, one can modify a target curve, regenerate the filters, and be listening to a new response in less than a minute. If using playback software like JRiver, one can AB correction FIR filters with different targets in real-time and determines one's own preference.

Personally, I am waiting for the industry to catch up and start looking at target step responses (i.e. time coherent speakers), in addition to target frequency responses, like the step response described in the latter half of this post: http://www.diyaudio.com/forums/mult...at-vs-accurate-hi-fidelity-4.html#post4258668 But that's another can of worms :) Hope some of that is helpful and Happy Listening in 2016!

Cheers, Mitch

PS. Very kind of you Michael. Happy New Year to you!
 
Mar 23, 2015
1,442
16
38
UK
#99
Interesting topic. Just passing along some info and impressions as I spent over 30 years with room curves starting with RTA's, 31 band eq's then TEF, 10 years of which working professionally in a variety of recording studios/control rooms and the last 5 years with digital loudspeaker and room correction software systems. In addition to the Harman and B&K target responses, there is also the European Broadcast Union produced a Tech note (EBU-Tech 3276) called, “Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic”. https://tech.ebu.ch/docs/tech/tech3276.pdf Check out Figure 2 on Page 6.

However, these "targets" are all very similar where the spectral response is flat to some frequency hinge point and then some slope of a roll off, typically between -4 dB and -10 dB ending at 20 kHz depending on the amount of HF absorption in your room and of course personal taste :) The Bob Katz curve which I documented in an article in Acourate on CA is flat to 1 kHz and then a straight line to -6 or -7 dB at 20 kHz. Again, some tolerance variability for personal taste, HF absorption, program material being listened to (pop rock mixes with heavy dynamic range compression tend to have a brighter spectral balance than minimal mic'd orchestra music).

Toole's latest free paper at AES: http://www.aes.org/journal/online/JAES_V63/7_8/#paper1 also supports this approach. See Figure 14 on preferred room curves and the comments about trained listeners.

I have a lot of respect for JJ Johnston and feel his presentation on the Acoustic and Psychoacoustic Issues in Room Correction that can be downloaded from here: http://www.aes-media.org/sections/pnw/pnwrecaps/2008/jj_jan08/ represents the state of the art understanding of room correction. Since then, most of the DRC products use frequency dependent windowing (FDW) based on jj's research which is a major leap forward from 1/3 or 1/6 octave analysis and correction systems.

What I find interesting is that if one is looking for the most neutral or natural response, something close to Bob Katz's spec seems to be closest. What do I base this on? Well, doing some correlation with a number of diyAudio members, we shared our measured responses at the listening position. Here is one example, where throughput the passband, myself and another diyAudio member are basically listening to the exact same response, yet our systems and rooms and have nothing in common. His speakers are 25 full range 5" driver line arrays and mine are 3-way old school active horn system. Aside from different gear, we are also using different DRC systems:

View attachment 24679

Several other members share virtually the same measured response at the listening position. Coincidence? I just find it interesting. Given the power of computers and sophisticated DSP software like Acourate, one can modify a target curve, regenerate the filters, and be listening to a new response in less than a minute. If using playback software like JRiver, one can AB correction FIR filters with different targets in real-time and determines one's own preference.

Personally, I am waiting for the industry to catch up and start looking at target step responses (i.e. time coherent speakers), in addition to target frequency responses, like the step response described in the latter half of this post: http://www.diyaudio.com/forums/mult...at-vs-accurate-hi-fidelity-4.html#post4258668 But that's another can of worms :) Hope some of that is helpful and Happy Listening in 2016!

Cheers, Mitch

PS. Very kind of you Michael. Happy New Year to you!
Mitch - what are your thoughts on the future of dsp and what do you think about the future of dsd and potentially the two?
 

dallasjustice

Member Sponsor
Apr 12, 2011
2,090
0
0
Dallas, Texas
I like Toole's reference to rental car stereos with boosted bass and HF. Untrained listeners surely like their boom and sizzle. :D

Happy New Year Mitch!

Interesting topic. Just passing along some info and impressions as I spent over 30 years with room curves starting with RTA's, 31 band eq's then TEF, 10 years of which working professionally in a variety of recording studios/control rooms and the last 5 years with digital loudspeaker and room correction software systems. In addition to the Harman and B&K target responses, there is also the European Broadcast Union produced a Tech note (EBU-Tech 3276) called, “Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic”. https://tech.ebu.ch/docs/tech/tech3276.pdf Check out Figure 2 on Page 6.

However, these "targets" are all very similar where the spectral response is flat to some frequency hinge point and then some slope of a roll off, typically between -4 dB and -10 dB ending at 20 kHz depending on the amount of HF absorption in your room and of course personal taste :) The Bob Katz curve which I documented in an article in Acourate on CA is flat to 1 kHz and then a straight line to -6 or -7 dB at 20 kHz. Again, some tolerance variability for personal taste, HF absorption, program material being listened to (pop rock mixes with heavy dynamic range compression tend to have a brighter spectral balance than minimal mic'd orchestra music).

Toole's latest free paper at AES: http://www.aes.org/journal/online/JAES_V63/7_8/#paper1 also supports this approach. See Figure 14 on preferred room curves and the comments about trained listeners.

I have a lot of respect for JJ Johnston and feel his presentation on the Acoustic and Psychoacoustic Issues in Room Correction that can be downloaded from here: http://www.aes-media.org/sections/pnw/pnwrecaps/2008/jj_jan08/ represents the state of the art understanding of room correction. Since then, most of the DRC products use frequency dependent windowing (FDW) based on jj's research which is a major leap forward from 1/3 or 1/6 octave analysis and correction systems.

What I find interesting is that if one is looking for the most neutral or natural response, something close to Bob Katz's spec seems to be closest. What do I base this on? Well, doing some correlation with a number of diyAudio members, we shared our measured responses at the listening position. Here is one example, where throughput the passband, myself and another diyAudio member are basically listening to the exact same response, yet our systems and rooms and have nothing in common. His speakers are 25 full range 5" driver line arrays and mine are 3-way old school active horn system. Aside from different gear, we are also using different DRC systems:

View attachment 24679

Several other members share virtually the same measured response at the listening position. Coincidence? I just find it interesting. Given the power of computers and sophisticated DSP software like Acourate, one can modify a target curve, regenerate the filters, and be listening to a new response in less than a minute. If using playback software like JRiver, one can AB correction FIR filters with different targets in real-time and determines one's own preference.

Personally, I am waiting for the industry to catch up and start looking at target step responses (i.e. time coherent speakers), in addition to target frequency responses, like the step response described in the latter half of this post: http://www.diyaudio.com/forums/mult...at-vs-accurate-hi-fidelity-4.html#post4258668 But that's another can of worms :) Hope some of that is helpful and Happy Listening in 2016!

Cheers, Mitch

PS. Very kind of you Michael. Happy New Year to you!
 

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