Please help me understand the basic principles and get me up to a good start in understanding this comment by Floyd Toole.

[Fastnet]

Please breakdown the concepts mentioned below and how they interact with each other to the very basics assuming the reader knows nothing about the subject.

Sorry for the seriously delayed response, I have been engaged in moving from California back to my "home' Ottawa, Canada - winter and all.

The following is a much simplified response. I will soon be working on a 4th edition of my book and this will be covered in great detail in it.

The basic flaw is that a steady-state room curve - which is what is measured at the listening position - is not a “target”, it is a “result”. We know that the shape of such curves is dominated by early reflected sound - off-axis radiation. The only reliable way to ensure neutral communication of sound is to start by understanding the loudspeaker - which is NOT what is revealed in a close-up moving mic measurement. Such a measurement can reveal an approximation to the direct sound/on-axis response, but the off-axis performance remains a mystery, and that is what is mainly responsible for the shape of the steady-state room curve at frequencies above the transition/Schroeder frequency. A room curve is well predicted by the "early-reflections" component of s spinorama ; BUT only above the transition frequency because low frequency performance is dominated by small-room resonances. These must be addressed and, fortunately, at low frequencies steady-state room curves have meaning. With bass accounting for about 1/3 of our overall impressions of sound quality it is clear that one must deal with the upper and lower frequencies differently. If a loudspeaker is well designed, i.e. free from audible resonances, spectrally flat on axis, and smooth off axis, the only adjustments that should be necessary at middle and high frequencies are broadband “tone control” spectral balance tweaking to address variations in program material. Low frequency room mode problems have to be addressed as a separate problem (see Todd Welti papers or my book), and once solved, again only “tone control” adjustments will be necessary for program variations. No fixed “calibration” can be perfect for all program material.

People keep looking for money-making ways to sell “calibrations” and most of them are lacking in some way. This is another one. It has a chance of making a truly bad loudspeaker sound better, but, in my opinion, it has an equal chance of degrading a truly good one. And so it goes . . . Pick the right demo material and the customer will be thrilled.

Concept list (for starters -not comprehensive- please expand):

1. Steady-state room curve
2. Room modes
3. Target
4. early reflected sound
5. audible resonances
6. small-room resonances
7. spectrally flat on axis
8. smooth off axis
9. direct sound/on-axis response
10. off-axis radiation
11. off-axis performance
12. low frequency performance
13. neutral communication of sound
14. broadband “tone control”
15. spectral balance
16. spectral balance tweaking
17. variations in program material
18. close-up moving mic measurement
19. Schroeder frequency
20. Spinorama
21. Fixed calibration

How the above concepts relate to each other and how they affect, effect or impact the gear used to create soundwaves and what we end up listening to?

1. Why the off-axis performance remains a mystery?
2. Why and how a room curve is well predicted by the "early-reflections" component of s spinorama?
3. Why low frequency performance is dominated by small-room resonances?
4. Why at low frequencies steady-state room curves have meaning?
5. How well established and/or acceped is this definition: if a loudspeaker is well designed, i.e. free from audible resonances, spectrally flat on axis, and smooth off axis...
6. What are the other accepted definitions of a well designed loudspeaker?
7. What are the ways to achieve "spectral balance tweaking" to address variations in program material? What are the cheapest ways available?
8. How to address low frequency room mode problems? Cheapest possible solution?
9. How to adjust “tone control” for program variations? Cheapest possible solution?
10. Why no fixed “calibration” can be perfect for all program material? (in depth please)
11. What are the alternatives to fixed calibration? Cheapest?

This, seems important, please breakdown taking in account the basic concepts explained above on list 1, please add missing items to both lists if included in your breakdown:

"With bass accounting for about 1/3 of our overall impressions of sound quality it is clear that one must deal with the upper and lower frequencies differently. If a loudspeaker is well designed, i.e. free from audible resonances, spectrally flat on axis, and smooth off axis, the only adjustments that should be necessary at middle and high frequencies are broadband “tone control” spectral balance tweaking to address variations in program material. Low frequency room mode problems have to be addressed as a separate problem (see Todd Welti papers or my book), and once solved, again only “tone control” adjustments will be necessary for program variations. No fixed “calibration” can be perfect for all program material."

 

[Purité Audio]

Toole has written a wonderful book with at least three editions, it is called ‘Sound Reproduction’ all the answers to your questions are within.
Keith

 

[SIY]

Please breakdown the concepts mentioned below and how they interact with each other to the very basics assuming the reader knows nothing about the subject.



Concept list (for starters -not comprehensive- please expand):

1. Steady-state room curve
2. Room modes
3. Target
4. early reflected sound
5. audible resonances
6. small-room resonances
7. spectrally flat on axis
8. smooth off axis
9. direct sound/on-axis response
10. off-axis radiation
11. off-axis performance
12. low frequency performance
13. neutral communication of sound
14. broadband “tone control”
15. spectral balance
16. spectral balance tweaking
17. variations in program material
18. close-up moving mic measurement
19. Schroeder frequency
20. Spinorama
21. Fixed calibration

How the above concepts relate to each other and how they affect, effect or impact the gear used to create soundwaves and what we end up listening to?

1. Why the off-axis performance remains a mystery?
2. Why and how a room curve is well predicted by the "early-reflections" component of s spinorama?
3. Why low frequency performance is dominated by small-room resonances?
4. Why at low frequencies steady-state room curves have meaning?
5. How well established and/or acceped is this definition: if a loudspeaker is well designed, i.e. free from audible resonances, spectrally flat on axis, and smooth off axis...
6. What are the other accepted definitions of a well designed loudspeaker?
7. What are the ways to achieve "spectral balance tweaking" to address variations in program material? What are the cheapest ways available?
8. How to address low frequency room mode problems? Cheapest possible solution?
9. How to adjust “tone control” for program variations? Cheapest possible solution?
10. Why no fixed “calibration” can be perfect for all program material? (in depth please)
11. What are the alternatives to fixed calibration? Cheapest?

This, seems important, please breakdown taking in account the basic concepts explained above on list 1, please add missing items to both lists if included in your breakdown:

"With bass accounting for about 1/3 of our overall impressions of sound quality it is clear that one must deal with the upper and lower frequencies differently. If a loudspeaker is well designed, i.e. free from audible resonances, spectrally flat on axis, and smooth off axis, the only adjustments that should be necessary at middle and high frequencies are broadband “tone control” spectral balance tweaking to address variations in program material. Low frequency room mode problems have to be addressed as a separate problem (see Todd Welti papers or my book), and once solved, again only “tone control” adjustments will be necessary for program variations. No fixed “calibration” can be perfect for all program material."

Had you considered buying his book and reading through it to help your understanding?

edit: @Purité Audio has faster fingers!

 

[Jim Taylor]

Floyd Toole Sound Reproduction - AbeBooks

Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms (Audio Engineering Society Presents) by Toole, Floyd and a great selection of related books, art and collectibles available now at AbeBooks.com.

www.abebooks.com

Jim

 

[LSPhil]

1. It is not a secret and you can measure it by changing the reading time of the received response.
2. see point 1.
3. there are and will be resonances in every room. Just as there is no matter without time.
4. I don't know why
5.
6. Linear characteristics and time consistency, e.g. all CANTON loudspeakers
7.Parametric Equalizer
8. see 7.
9. see 7.
10. can be and is
11. See 7.

 

[Floyd Toole]

Please breakdown the concepts mentioned below and how they interact with each other to the very basics assuming the reader knows nothing about the subject.



Concept list (for starters -not comprehensive- please expand):

1. Steady-state room curve
2. Room modes
3. Target
4. early reflected sound
5. audible resonances
6. small-room resonances
7. spectrally flat on axis
8. smooth off axis
9. direct sound/on-axis response
10. off-axis radiation
11. off-axis performance
12. low frequency performance
13. neutral communication of sound
14. broadband “tone control”
15. spectral balance
16. spectral balance tweaking
17. variations in program material
18. close-up moving mic measurement
19. Schroeder frequency
20. Spinorama
21. Fixed calibration

How the above concepts relate to each other and how they affect, effect or impact the gear used to create soundwaves and what we end up listening to?

1. Why the off-axis performance remains a mystery?
2. Why and how a room curve is well predicted by the "early-reflections" component of s spinorama?
3. Why low frequency performance is dominated by small-room resonances?
4. Why at low frequencies steady-state room curves have meaning?
5. How well established and/or acceped is this definition: if a loudspeaker is well designed, i.e. free from audible resonances, spectrally flat on axis, and smooth off axis...
6. What are the other accepted definitions of a well designed loudspeaker?
7. What are the ways to achieve "spectral balance tweaking" to address variations in program material? What are the cheapest ways available?
8. How to address low frequency room mode problems? Cheapest possible solution?
9. How to adjust “tone control” for program variations? Cheapest possible solution?
10. Why no fixed “calibration” can be perfect for all program material? (in depth please)
11. What are the alternatives to fixed calibration? Cheapest?

This, seems important, please breakdown taking in account the basic concepts explained above on list 1, please add missing items to both lists if included in your breakdown:

"With bass accounting for about 1/3 of our overall impressions of sound quality it is clear that one must deal with the upper and lower frequencies differently. If a loudspeaker is well designed, i.e. free from audible resonances, spectrally flat on axis, and smooth off axis, the only adjustments that should be necessary at middle and high frequencies are broadband “tone control” spectral balance tweaking to address variations in program material. Low frequency room mode problems have to be addressed as a separate problem (see Todd Welti papers or my book), and once solved, again only “tone control” adjustments will be necessary for program variations. No fixed “calibration” can be perfect for all program material."

These are all good questions. I have asked them myself, and they are all answered in the 3rd edition of my book- but it is not the "cheapest possible solution", sorry . If you search my contributions to this forum over the past few years you will find many answers at the right price.

 

[Keith_W]

Welcome to ASR! I can relate to your confusion. Struggling through his book with a long forgotten high school understanding of physics is an experience I will remember. None of what Dr. Toole said makes sense unless you have a fundamental grasp of what the terms mean. I am sure that many on ASR would love to help you, myself included. However, your questions cover at least 4-5 chapters of his book, and he does a far better job of explaining than any of us ever could.

This is an extreme summary of his quote: "Buy a good speaker, and leave the upper frequencies alone. Maybe apply some broad tone controls to adjust for different recordings if you must. Don't try to equalize the upper frequencies because you will likely degrade the speaker. Bass is different because it forms peaks and dips in every listening room, so these should be equalized".

The rest of what he said in that quote goes into far more detail to justify his opinion and can not be covered in a forum post.

 

[ahofer]

I can't improve on the book, but if you read about the Klippel measurement system here, you will pick up the concepts. The most important one to start with is that the sound at your listening position is the sum of direct and reflected sound. The waves coming directly at you from the speaker, and the reflected waves from the sides/back interact at your listening position, either adding to or subtracting from your perception. Their effect is determined by amplitude (volume) and phase (time delay of reflections). These are in turn influenced by the off-axis amplitude(volume) and frequency response of the drivers.

The room curve is the frequency response at the listening position.

The point of the "Spinorama" measurements is to estimate how a speaker might perform at the listening position in a 'standard' room, after taking into account the direct and off-axis behavior of the speaker.

Make sure you understand the above, then watch Amir or Erin's measurement video.

There are lots of good internet explanations of room modes and Schroeder frequency, with helpful graphics. Here's my first result

Divide and Conquer - The Schroeder Frequency | Prosoundtraining

Not all sound energy in a room is reverberation. The Schroeder frequency divides the spectrum based on sound wave behavior.

www.prosoundtraining.com

It's fascinating stuff, and the great thing about Toole is that it integrates what we know about sound perception with what we can measure in speakers to come to some solid conclusions about optimal design.

 

[akamatsu]

I have the book. I've read at the book, but haven't read the entire book. I'm a retired mechanical engineer and an audiophile/music listener since I was a child. I have to read Dr. Toole's book slowly, often re-reading sections in order to begin to understand. I believe Dr. Toole's book is used as a textbook in acoustical engineering curricula. In other words, this is advanced stuff. Start with the basics, and work your way up to Dr. Toole level.

 

[Jimbob54]

Disappointing..

 

[ahofer]

Gemini does pretty well with Room Modes

Room modes, also known as room resonances, are a major factor affecting how sound waves behave in a room, particularly at lower frequencies. They can significantly alter the audio you hear, sometimes drastically.

Here's how they work:

• Standing waves: Imagine sound waves bouncing back and forth between walls. When a sound wave matches a specific dimension of the room (length, width, or height), or a multiple of that dimension, a standing wave is created. These waves vibrate intensely at specific frequencies.
• Boosting and cancellation: At the resonant frequencies, sound gets accentuated in some areas of the room and suppressed in others. These areas of boosted and cancelled sound don't stay fixed – they change depending on your listening position.

Impact on Audio:

• Uneven bass response: The most noticeable impact is on bass frequencies. You might hear boomy bass in certain spots and almost no bass in others. This disrupts the overall balance of the sound.
• Coloration: Room modes can color the sound by emphasizing certain frequencies and weakening others. This can make the audio sound unnatural or muddy.

Why it matters:

• Mixing and mastering: For critical listening applications like mixing music or mastering recordings, room modes can be a nuisance. They make it difficult to get an accurate picture of how the audio will translate to other listening environments.
• Accurate sound reproduction: In any situation where accurate sound reproduction is desired, room modes can be a hindrance. They prevent you from hearing the audio exactly as it was intended.

How to deal with room modes:

• Room treatment: Bass traps and acoustic panels can absorb sound waves and reduce the effect of room modes, particularly at lower frequencies.
• Speaker placement: Experimenting with speaker positioning can sometimes help smooth out some room modes. Moving speakers away from walls and corners can make a difference.
• EQ (room correction): Some audio equipment has built-in EQ or room correction systems that can analyze the room acoustics and adjust the sound to compensate for room modes.

In conclusion, room modes are an important factor to consider when it comes to audio quality in a room. By understanding how they work and taking steps to minimize their impact, you can achieve a more balanced and accurate listening experience.

and CEA-2034

CEA-2034, also referred to as ANSI/CEA-2034-A-2015 (ANSI), is a standard developed by the Consumer Electronics Association (CEA) that outlines a specific method for measuring the performance of loudspeakers designed for in-home use. Here's a breakdown of what it is and its significance:

Purpose:

• This standard provides a standardized wayto measure a loudspeaker's:
  • Frequency response: How accurately the speaker reproduces different sound frequencies (bass, midrange, treble).
  • Directivity: How sound spreads out from the speaker at different angles.
  • Maximum output capability: How loud the speaker can play before distortion.

Benefits:

• Comparison across speakers: By using the same measurement techniques, CEA-2034 allows for a more objective comparison of the performance between different loudspeakers.
• Data for consumers: Manufacturers can use CEA-2034 to generate data (sometimes called Spinorama data) that reflects a speaker's performance characteristics. This data can be helpful for consumers when researching and choosing speakers.

Limitations:

• Not a guarantee of sound quality: While CEA-2034 provides valuable data, it doesn't directly translate to how a speaker will sound in your specific room. Room acoustics play a significant role in how sound is perceived.
• Focus on performance, not durability: The standard is designed to measure a speaker's audio capabilities, not its ability to withstand high power or extreme conditions.

Overall, CEA-2034 is a valuable tool for objectively measuring loudspeaker performance and can be a helpful resource for consumers when comparing speakers. However, it's important to consider other factors like room acoustics and personal listening preferences when making a final decision.

 

[kemmler3D]

If you are really starting from zero, this is a really dense kind of post to make sense of.

I would just start by getting a grip on what frequency response graphs mean.

A good way to do this is actually to play with REW and EQAPO if you are using windows. (Or any DAW or music player that includes a parametric equalizer. FL Studio is one that you can download and try for free.)

Play some pink noise and/or music, and put in some PEQ filters, and move them around in real time. Listen to how the sound changes. What does 50, 200, 1000, 12,000 hz actually sound like? What does a narrow peak vs. a wide one sound like? 2dB peak vs. 20dB? This will give you a wayyyyy better feeling of what you are looking at in most measurements.

One thing you can do to understand room modes: Play a steady tone over your speakers and walk around the room (low frequencies) or play a higher frequency and move your head around. Notice how the volume changes... those are modes / interferences.

I would then start to read up on the basics of acoustics. Sound reflects, refracts, and diffracts just like light does in optics. Once you get a grip on how that works in a general way, a lot of the stuff about resonances, rooms, modes, and such starts to make sense. However, it's much less intuitive than optics because the sound waves are large compared to the stuff we're talking about (speakers, rooms, people). So that makes acoustics pretty tricky, but there are some rules of thumb (Like shroeder) that help.

I think if you feel like you have some intuitive grasp of the above 3 things, all this stuff will start to make more sense.

 

[Purité Audio]

Alternatively I believe Jays Audio is offering just this sort of advice at a paltry $200 per hour!
Keith

 

[restorer-john]

Alternatively I believe Jays Audio is offering just this sort of advice at a paltry $200 per hour!

Good perspective Keith. Floyd Toole's book is a way better investment.

 

[Purité Audio]

Also who in their right mind would take advice from Jay.
Keith

 

[Killingbeans]

1. Why the off-axis performance remains a mystery?
2. Why and how a room curve is well predicted by the "early-reflections" component of s spinorama?
3. Why low frequency performance is dominated by small-room resonances?
4. Why at low frequencies steady-state room curves have meaning?
5. How well established and/or acceped is this definition: if a loudspeaker is well designed, i.e. free from audible resonances, spectrally flat on axis, and smooth off axis...
6. What are the other accepted definitions of a well designed loudspeaker?
7. What are the ways to achieve "spectral balance tweaking" to address variations in program material? What are the cheapest ways available?
8. How to address low frequency room mode problems? Cheapest possible solution?
9. How to adjust “tone control” for program variations? Cheapest possible solution?
10. Why no fixed “calibration” can be perfect for all program material? (in depth please)
11. What are the alternatives to fixed calibration? Cheapest?

1. A single measurement at a single point in a room shows you a mix of direct sound and reflections. You have no way of knowing what part of it comes from what.

2. Good question. I can only speculate. Read the book

3. Below the Schroeder frequency of the room, the resonances of said room dominates the response.

4. Because the wavelengths become large enough to move you from the realm of reflections to resonances.

5. Don't know how well established it is, but it seems to be these kinds of design choises that people largely prefer when tested unbiased.

6. Looks good. Fair price. Doesn't fall apart after a bit of use?

7. EQ. Software or hardware.

8. Knock down a wall to the outside? Besides that, it's a whole industry/science in itself. The good news is that dips are far less offensive than peaks. Bad news is that if you do a quick fix at one listening position, you are likely to f¤ck things up even more at other points in the room.

9. Same as '7'.

10. Because we have no way of knowing the performance of each and every studio monitoring setup, and they can have been messed up in all sorts of ways.

11. Same as '7'.