Why evaluating the sound of a single speaker is essential

[RickS]

That this thread be renamed to:

"Why evaluating the sound of a single speaker plus multiple speakers is essential"

Single < Single + Multiple

You are welcome to start your own thread. This one is not changing after over 1000 posts.

 

[krabapple]

Paul Newman obviously

Not Sir Paul?

 

[Satanica]

I still sense a confusion of purpose in this discussion, at least when my name and the Harman tests come up.

Back in post 1043 I said:
"Yes, mostly because of a confusion of purpose. The double-blind, equal loudness multiple-loudspeaker evaluations were designed to maximize the detection of resonances, not to determine if the overall spectral balance flattered specific recordings - recordings do not have consistent spectral balance. Resonances are more easily heard in mono - discussed in Chapters 4 and 5. The elimination of resonances, results in smooth, flattish direct sound, and if directivity is also smoothly changing, high sound quality ratings. If such a spectral balance is not found to be enjoyable in a particular situation, it is then a challenge to decide what is responsible. Often a bass issue (30% of our overall sound quality rating) which is a small room acoustics problem that is often inadequately corrected. Excessive bass is easily confused with insufficient HF, and vice versa. As I have said, only trustworthy anechoic data will describe what the speaker is doing, and in-room measurements are needed to evaluate what the room is contributing. Spinoramas enable the variables to be sorted out and addressed."

All mono tests were comparisons of 3 or 4 loudspeakers designed to maximize the detection of resonances, the most audible problem in loudspeakers. Listeners rated the sound quality as if they were judging absolute "fidelity" to some conscious or subconscious criteria of what sounded best. However, because of the rapid randomized comparison method of the test, the unspoken question being asked of listeners was "what is the loudspeaker doing to the sound?". Positional substitution rendered the room a constant factor, and 30 s musical loops ensured that all loudspeakers were evaluated with the same monotonous test sounds. The dominant variable was the loudspeaker. Problems were quickly revealed, and as could be seen in measurements resonances were clearly the dominant problem. They were easily heard, and the highest rated loudspeakers exhibited the least evidence of resonances, which by definition corresponds to smooth flat frequency response in the sound which is perceptually dominant, the direct sound. It was quickly observed that the highest rated loudspeakers also had smooth off axis frequency responses. This has been true since the first tests I did in 1966.

The music was a variable, but only in the sense that not all music revealed all resonances, and certainly not all at the same time. Some music was much more revealing than others. Pink noise was the most revealing of all sounds. Solo voices and instruments were generally the least revealing - use these to demo flawed loudspeakers. Measurements reliably reveal all resonances, audible or not.

But, then comes the question that reviewers and consumers ask: how does the loudspeaker sound with recordings?. This is where the "reference axis" might matter. But, at this point we confront the "circle of confusion", because recordings are not standardized test signals. They were mixed and. mastered using loudspeakers in rooms that are not the same as yours or mine, not even considering how they might have been equalized or acoustically treated. There are no standards.

Differences in spectral balance inevitably occur and over the years playback electronics have included tone controls, occasional "tilt" controls and now user-accessible parametric equalization to compensate for these variations. Fussy listeners use them - they are not "fix and forget" controls. Fortunately, things today are far better than in years past - just listen to some of the old "classics" through modern, neutral, loudspeakers. Remixes have helped in some cases, but we learned to like them with flaws.

The discussion about which listening axis is most flattering to most recordings is academically interesting, perhaps, but in the real world a tweak of a tone control or simple EQ fixes many concerns - a different loudspeaker is not a requirement, so long as it is not burdened by resonances or gross frequency-dependent directivity problems.

Finally, humans adapt. We normalize, learn to ignore, some kinds of flaws in sounds we spend time with. Problems may be there, but we are not aware of them. This explains why so many flawed loudspeakers have been satisfying so many listeners for so long. The adaptation can be instantly broken if there is a comparison to a superior sound, which is what drove the scientific investigations, and the multiple-loudspeaker comparison method.

Overlayed on all of this are the soundstage and imaging illusions of stereo. Inevitably the room is involved and no two are alike, so debates arise. Again there are no standards and the principle determinant of these perceptual factors is the mix itself, not the playback apparatus.

Does this make sense? All these topics are elaborated on in the 4th edition of my book for those who might be interested. Learning to interpret spinorama curves is a huge asset in choosing a loudspeaker, and using it to its best advantage. In-room bass measurements and EQ complete the exercise. Relying on subjective opinions formed in the commonly available circumstances leads nowhere reliable - but it feeds forum discussions.

"Does this make sense?"

Yes, thank you, thumbs up.

"The discussion about which listening axis is most flattering to most recordings is academically interesting, perhaps, but in the real world a tweak of a tone control or simple EQ fixes many concerns - a different loudspeaker is not a requirement, so long as it is not burdened by resonances or gross frequency-dependent directivity problems."

Yep sure, and I effectively use tone controls on bass frequencies with multiple target curves and LOUNDESS compensation.
But, the "normal" audiophile isn't going for it (tone controls), it's just not part of "the hobby".
So unfortunately some of the best, most easy, affordable, and practical advice falls on the deafest ears; their only valid tone controls are their speaker and seating position (of course that's worthwhile too).

 

[Satanica]

OK, I think it's gotten to the point where the discussion has become circular. I could respond to the responses again but I would have nothing else to add than what I've written in previous posts. So...

I can see this easily becoming my most liked post.

 

[Floyd Toole]

But, the "normal" audiophile isn't going for it (tone controls), it's just not part of "the hobby".
So unfortunately some of the best, most easy, affordable, and practical advice falls on the deafest ears;

Absolutely true. But it is good for commerce as for decades it has generated a never ending parade of differently flawed loudspeakers, each with a catalog of real or imagined virtues and deficiencies. The aversion to tone controls and EQ is simply evidence of ignorance. An aversion to measurements is another. "If I hear it, it is real, and true". Ignorance can be bliss - but a science-based approach offers a much higher probability of genuine satisfaction.

 

[Satanica]

I said that very thing in the next sentence in the post you quoted.

OK, thank you for the measurements you posted by the way.

 

[item]

Learning to interpret spinorama curves is a huge asset in choosing a loudspeaker, and using it to its best advantage. In-room bass measurements and EQ complete the exercise. Relying on subjective opinions formed in the commonly available circumstances leads nowhere reliable - but it feeds forum discussions.

This is a fundamental. A local playback environment (including 'the room') is rarely the subject of the rigorous analysis it deserves, and yet it informs the majority of a listening impression. If we could subject the subjective to the same analysis too, we might all agree more often, and forums would be far quieter. As it stands, there's too much noise in the signal, creating randomised public opinion, biased by marketing.

 

[Buckchester]

This is a fundamental. A local playback environment (including 'the room') is rarely the subject of the rigorous analysis it deserves, and yet it informs the majority of a listening impression. If we could subject the subjective to the same analysis too, we might all agree more often, and forums would be far quieter. As it stands, there's too much noise in the signal, creating randomised public opinion, biased by marketing.

The room is only critical below the room transition frequency and is best treated through EQ and multiple subs. Above this point, it is the speaker that dominates our perception of the sound.

 

[Mike123]

The room is only critical below the room transition frequency and is best treated through EQ and multiple subs. Above this point, it is the speaker that dominates our perception of the sound.

Past experience with equalizing the room in low frequencies had taught me that removing bass resonances not only improves bass, but has a remarkable (good) effect on notes above that range. Resonances boost certain bass frequencies. In time domain that lengthens the amount of time it takes for those high energy notes to go away. And that steps on much lower level notes in higher frequencies.

 

[jeffaegrim]

Excellent illustration of why and how a speaker might be optimized for off-axis listening; the "why" being a huge increase in sweet-spot-width, and the "how" being what I would call "time-intensity trading", in this case built into the loudspeaker design itself.

Unfortunately the "ruling dogmas on this forum" (to use your words) would indeed label this a "worse measuring speaker", and unfortunately many here would probably reject it without taking the time to understand why the measurements actually indicate good performance for the intended use case. So that would be just one more uphill battle to be fought (and probably lost) by a designer who optimizes for an unorthodox use case.

Apologies for excavating your response so late - I missed it at the time. The "time/intensity trading" you oftentimes spoke about on the forum and also partially utilized in your own designs always made me think about the variable directivity horns mentioned above - so yes, I think it is a very similar concept.

The resulting sound in off axis listening positions is sort of "out-of-phase-y", which is nonetheless greatly preferable to a total lack of stereo. Additionally, if I understand Dr. Toole correctly, off axis positions don't suffer from the "HRTF dip" at ~2khz, only the MLP does. In that sense the tonality off axis might even be slightly more correct. Unsure about this though. What I also wonder is - if one were to measure a speaker like that in anechoic or semi-anechoic conditions - what would one pick as the reference on-axis position?

Chapter 4.3.3. of the 4th edition of Sound Reproduction (Page 111) briefly talks about time/intensity trading, but concludes that it is not a solution (mostly due to the limitations of stereo itself)

 

[Sal1950]

The room is only critical below the room transition frequency and is best treated through EQ and multiple subs. Above this point, it is the speaker that dominates our perception of the sound.

A bit too simplistic. The room, it's RT60, and the speakers radiation pattern can have a huge influence on the systems general sound, it's imaging and focus at the MLP.

 

[krabapple]

The room is only critical below the room transition frequency and is best treated through EQ and multiple subs. Above this point, it is the speaker that dominates our perception of the sound.

Hah, try reconciling that with flutter echo.

 

[livinon2wheels]

Absolutely true. But it is good for commerce as for decades it has generated a never ending parade of differently flawed loudspeakers, each with a catalog of real or imagined virtues and deficiencies. The aversion to tone controls and EQ is simply evidence of ignorance. An aversion to measurements is another. "If I hear it, it is real, and true". Ignorance can be bliss - but a science-based approach offers a much higher probability of genuine satisfaction.

It is awfully hard to argue with the most qualified person in the room (not that i am inclined to at all in this case). It must be wonderful to have the credibility you command Dr. Poole, especially after so many years in audio. My own experience (in terms of satisfaction) bears this out for sure. The caveat remains that measurements have to be measured honestly and with standardized methods for them to have any meaning and context. If manufacturers could be held to a measurement standard for all marketing materials then making apples to apples comparisons of speaker a to speaker b would be much simpler. For example, frequency response measurements among manufacturers are done in such widely different ways the numbers are impossible to compare unless the conditions under which the measurements are made are the same.

I am relatively certain that the obfuscation of the numbers by using different measurement parameters is completely intentional and not all by accident. Hence the need for rigid measurement standards. How the heck can you be expected to objectively choose what measures better when you cannot even be sure that the published specs were measured the same way? This is one of the biggest problems in the industry in my estimation. And your point about this being good for commerce I enthusiastically agree with your assessment.

In a perfect world I would like to see frequency response curves published using the same scale and sensitivity, distortion curves for the entire audio spectrum, as well as guidelines for room placement as well as the size room recommended for a given design. There are other measurements worth comparing beyond distortion and frequency response too but getting all of the possible measurements done the same way by everyone selling speakers is a hard sell to an industry that profits so heavily on NOT doing so. Still it would be helpful to have some standards so legitimate comparisons could be made.

In some ways it would be good for dealers and manufacturers alike to help reduce the incidence of people buying the wrong speaker, or any other component for that matter. By steering people towards what will work well in their actual living space they increase the odds of having happy customers and avoiding the possible tarnishing of a brand because of a misinformed choice. As enthusiasts who have been in this audio marketplace for many years, all of us here, I think, see thru most of the marketing babble and can make informed choices, in spite of the deck being stacked against us. People new to this will be challenged I think.

 

[Buckchester]

A bit too simplistic. The room, it's RT60, and the speakers radiation pattern can have a huge influence on the systems general sound, it's imaging and focus at the MLP.

Didn’t Floyd Toole say rt60 doesn’t play much of a factor, if any, in small rooms?

 

[Floyd Toole]

Didn’t Floyd Toole say rt60 doesn’t play much of a factor, if any, in small rooms?

Yes, typically furnished listening rooms have insufficient "traditional" diffusive reverb to be consequential. The delayed energy reaching listeners is dominated by first reflections.

 

[Floyd Toole]

In a perfect world I would like to see frequency response curves published using the same scale and sensitivity,

The standardized spinorama is making this possible. Its use is increasing.

 

[landco1]

Absolutely true. But it is good for commerce as for decades it has generated a never ending parade of differently flawed loudspeakers, each with a catalog of real or imagined virtues and deficiencies.

Hello, Mr. Toole!
I am not sure how appropriate it is to ask about loudspeaker design in this thread, but I will ask anyway.

Could you please tell me, do you consider speakers with multi-way amplification and an active crossover to be justified in terms of an AUDIBLE result?

Or do you prefer traditional designs with a passive filter?

 

[Floyd Toole]

Hello, Mr. Toole!
I am not sure how appropriate it is to ask about loudspeaker design in this thread, but I will ask anyway.

Could you please tell me, do you consider speakers with multi-way amplification and an active crossover to be justified in terms of an AUDIBLE result?

Or do you prefer traditional designs with a passive filter?

If you read my books or review my comments in ASR over the years you will see that active loudspeakers have several advantages over passive equivalents in that resonant imperfections in transducers can be corrected in amplitude and phase using parametric filters. These are the most audible defects in loudspeakers. That said, there are a few well-designed passive designs that closely approach that of active systems, but identifying them requires understanding comprehensive anechoic measurements, like spinoramas. They may not be inexpensive.

The following link should give you access to a PowerPoint slide show explaining how to do this.

Dr. Toole's 4th Edition Book is Coming! (Discount)

Your wife's suggestion would cause you to miss a bunch of useful stuff:(. Sorry about the problem. Only the publisher can help. Go to Routledge.com, scroll down to the very bottom - the dark blue area - and click on customer service. Good luck. Good news, I followed the same steps on my PC...

www.audiosciencereview.com

 

[john61ct]

Dr Toole to you & us

 

[landco1]

If you read my books or review my comments in ASR over the years you will see that active loudspeakers have several advantages over passive equivalents in that resonant imperfections in transducers can be corrected in amplitude and phase using parametric filters. These are the most audible defects in loudspeakers. That said, there are a few well-designed passive designs that closely approach that of active systems, but identifying them requires understanding comprehensive anechoic measurements, like spinoramas. They may not be inexpensive.

The following link should give you access to a PowerPoint slide show explaining how to do this.

Thank you for the link to your book, Mr. Toole.
Since my English is not good, it is unlikely that reading it will be enjoyable for me.

It is easier to ask here.

In your opinion, can application of external DSP correction bring classic passive filter speakers very close to active multi-amped systems in terms of quality?
It is not about laboratory tests, but from the perspective of psychoacoustics.