How to Choose a Loudspeaker -- What the Science Shows - Page 161 - AVS Forum | Home Theater Discussions And Reviews
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post #4801 of 5320 Old 09-08-2019, 02:28 PM
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Originally Posted by craig john View Post
If the speaker designer "pads down" the frequencies above and below the mid-bass by manipulations in the crossover in an effort to accentuated the mid-bass, that has nothing to do with the natural frequencies or the resonances of the "conceptual black box." It's a design choice by the designer.
Every resonance (of anything) is the result of a design decision. Just because somebody decides to add a resonance to something doesn't make it not a resonance.
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post #4802 of 5320 Old 09-08-2019, 02:28 PM
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To Resonate or not to Resonate, That is the Question?

Apologies to Shakespeare . . .

This discussion has drifted into an area of literal interpretations of classical definitions with some semantics thrown in. If there is a shallow hump in a frequency response, in literal terms it is a very low-Q resonance, implying a mechanical, electrical or acoustical system with a "favored" frequency range. In a physical system as complex as a loudspeaker it may sometimes be difficult to decide what is happening. Crossovers are equalizers, by any other name, that interact with transducers having inherently non-flat tendencies - the result is a combination of both electrical and mechanical elements. Equalizers can be resonators just as surely as acoustical cavities, enclosure panels and cone breakup. So a frequency response feature may be partly mechanical and partly electrical , but the end result can be that of a resonance having Q. Achieving a desirable flat on-axis sound using passive or active networks can result in non-flat off-axis behavior because transducers have frequency-dependent directivity. In a room the result is that even with flat direct sound, the early reflected and later reflected sounds may exhibit emphasis over a range of frequencies that could forgivably be interpreted as a low-Q resonance.

As discussed many times in this thread, transducers are inherently minimum-phase devices, so electrical EQ can modify the performance of mechanical resonances - a huge advantage for active loudspeakers or those for which accurate anechoic data are available.

In the crossover between a 6- to 8-inch woofer and a 1-inch tweeter, a directivity mismatch at crossover is unavoidable. Above crossover, the tweeter has much wider dispersion than the woofer, so there is an energy rise over a wide frequency range. Is this a resonance? Technically not, in the dictionary definition sense. However, there is a broad hump in radiated energy, so perceptually it may appear to be so. Figure 4.13 shows such an example where even crude room curves were adequate to recognize the energy excess in an above-crossover energy excess and attenuate it. Because wide bandwidth (low-Q) phenomena are detected at very small deviations there was a clear improvement in perceived sound quality even though medium and higher-Q "real" resonances were essentially unchanged. Addressing all of the "resonances" was not surprisingly the best.

So, don't get hung up on semantics. Deviations from a linear frequency response are all describable as "resonances" if one chooses to. Broadband trends are very low-Q, narrower trends, medium Q, and so on. Even a bass tone control is an opportunity to manipulate a "resonance" - in this case the hump that develops above the low cutoff frequency which, depending on the system design will have a Q.

Narrow dips are usually the result of destructive acoustical interference and are usually audibly innocuous because they change with direction/position. Broader dips can be interpreted as anti-resonances if one chooses to, whether there is an associated frequency selective absorption process or not. Mostly not.

All fodder for more discussion
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post #4803 of 5320 Old 09-08-2019, 02:32 PM
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Originally Posted by SouthernCA View Post
The key is not how Wikipedia describes "resonance". I would like to understand what Dr. Floyd calls "neutral" as it is necessary to understand his book and his posts correctly. That was the question that Craig asked.
Well sure, but as long as Dr. Toole isn't posting replies at the moment, what's the harm in me chiming in with my two cents?

The hangup seems to be when Dr. Toole equates neutrality with lack of resonances.

All I'm saying is that this makes 100% perfect sense if you consider a deviation from flat frequency response to be a resonance, which is a possible interpretation of the Wikipedia article for "resonance."

EDIT: Ninja'ed by Dr. Toole.

EDIT 2: reworded to make my point more clear.

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post #4804 of 5320 Old 09-08-2019, 02:42 PM
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Originally Posted by Floyd Toole View Post
...
In the crossover between a 6- to 8-inch woofer and a 1-inch tweeter, a directivity mismatch at crossover is unavoidable. Above crossover, the tweeter has much wider dispersion than the woofer, so there is an energy rise over a wide frequency range. Is this a resonance? Technically not, in the dictionary definition sense. ...
If we're being pedantic, how is this not a resonance? An increase of output over a frequency range (wide or not) seems like it would be the dictionary definition of a resonance?
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post #4805 of 5320 Old 09-08-2019, 03:22 PM
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If we're being pedantic, how is this not a resonance? An increase of output over a frequency range (wide or not) seems like it would be the dictionary definition of a resonance?
I guess it depends on the dictionary. In my engineering schooling resonances were associated with mechanical, acoustical or electrical systems that by virtue of mass, compliance and damping - in the case of mechanical resonances or their analogs for the others - combined to favor specific frequencies by differing amounts.

The effect of these in loudspeakers is an emphasized output over a range of frequencies, so feel free to call anything that has that effect a resonance. The perceptual system will never know nor care

EDIT: The reason it really doesn't matter is that humans do not hear the ringing, we hear the spectral hump. At low Q there really is no significant ringing in any event.
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post #4806 of 5320 Old 09-08-2019, 03:43 PM
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Originally Posted by Floyd Toole View Post
I guess it depends on the dictionary. In my engineering schooling resonances were associated with mechanical, acoustical or electrical systems that by virtue of mass, compliance and damping - in the case of mechanical resonances or their analogs for the others - combined to favor specific frequencies by differing amounts.

The effect of these in loudspeakers is an emphasized output over a range of frequencies, so feel free to call anything that has that effect a resonance. The perceptual system will never know nor care
Does this mean if I boost frequencies via my AVR’s equalizer DSP feature, I’m adding acoustic resonances?

That’s only a half serious question, because I do understand what’s being said here: From a mathematical perspective, you can deem any increase or decrease of a particular frequency a “resonance”. Beyond that it’s all semantics. From an engineering perspective, it depends on your definition, i.e. depending on what particular source of this distortion you’re looking to diagnose. When most people speak of resonances in the context of speakers though, I think it’s fair to say they’re not usually talking about DSP or filters — I could be wrong, but that’s certainly the impression I get.

BTW I’d be curious to hear your interpretation of the Ascend Sierra 2EX’s spinorama, since there seems to be quite a bit of confusion and debate circulating around it — including some people even saying it’s a “bad design”, despite what seems to be excellent measurements. Independent of the design itself, I think many of us would be quite curious for your thoughts purely on interpretation of its measurements.

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post #4807 of 5320 Old 09-08-2019, 03:56 PM
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Originally Posted by echopraxia View Post
Does this mean if I boost frequencies via my AVR’s equalizer DSP feature, I’m adding acoustic resonances?
Yes. As I said, because loudspeaker transducers are minimum-phase devices one can use electrical parametric EQ to attenuate the mechanical resonances in transducers - using anechoic data of course. So, if you add a hump to an otherwise neutral/resonance free speaker you have added a resonance. This is why it is crucial to pay attention to what "room equalizers" are doing. If they "see" a ripple in a measured curve caused by acoustical interference of direct and reflected sound, and try to flatten it, they may be adding a resonance and degrading a good loudspeaker.
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post #4808 of 5320 Old 09-08-2019, 03:58 PM
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Originally Posted by Floyd Toole View Post
Apologies to Shakespeare . . .

This discussion has drifted into an area of literal interpretations of classical definitions with some semantics thrown in. If there is a shallow hump in a frequency response, in literal terms it is a very low-Q resonance, implying a mechanical, electrical or acoustical system with a "favored" frequency range. In a physical system as complex as a loudspeaker it may sometimes be difficult to decide what is happening. Crossovers are equalizers, by any other name, that interact with transducers having inherently non-flat tendencies - the result is a combination of both electrical and mechanical elements. Equalizers can be resonators just as surely as acoustical cavities, enclosure panels and cone breakup. So a frequency response feature may be partly mechanical and partly electrical , but the end result can be that of a resonance having Q. Achieving a desirable flat on-axis sound using passive or active networks can result in non-flat off-axis behavior because transducers have frequency-dependent directivity. In a room the result is that even with flat direct sound, the early reflected and later reflected sounds may exhibit emphasis over a range of frequencies that could forgivably be interpreted as a low-Q resonance.

As discussed many times in this thread, transducers are inherently minimum-phase devices, so electrical EQ can modify the performance of mechanical resonances - a huge advantage for active loudspeakers or those for which accurate anechoic data are available.

In the crossover between a 6- to 8-inch woofer and a 1-inch tweeter, a directivity mismatch at crossover is unavoidable. Above crossover, the tweeter has much wider dispersion than the woofer, so there is an energy rise over a wide frequency range. Is this a resonance? Technically not, in the dictionary definition sense. However, there is a broad hump in radiated energy, so perceptually it may appear to be so. Figure 4.13 shows such an example where even crude room curves were adequate to recognize the energy excess in an above-crossover energy excess and attenuate it. Because wide bandwidth (low-Q) phenomena are detected at very small deviations there was a clear improvement in perceived sound quality even though medium and higher-Q "real" resonances were essentially unchanged. Addressing all of the "resonances" was not surprisingly the best.

So, don't get hung up on semantics. Deviations from a linear frequency response are all describable as "resonances" if one chooses to. Broadband trends are very low-Q, narrower trends, medium Q, and so on. Even a bass tone control is an opportunity to manipulate a "resonance" - in this case the hump that develops above the low cutoff frequency which, depending on the system design will have a Q.

Narrow dips are usually the result of destructive acoustical interference and are usually audibly innocuous because they change with direction/position. Broader dips can be interpreted as anti-resonances if one chooses to, whether there is an associated frequency selective absorption process or not. Mostly not.

All fodder for more discussion
Sooo.... given the above, can you *please* answer my original question: What is the definition of a neutral speaker?

Am I to understand that *if one chooses* to call all FR anomalies "resonances" then a neutral speaker is one that has no FR anomalies, i.e., no "resonances"?

I guess that kinda jives with my definition of neutral, but it's certainly a different way to look at it.

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post #4809 of 5320 Old 09-08-2019, 04:15 PM
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Originally Posted by craig john View Post
Am I to understand that *if one chooses* to call all FR anomalies "resonances" then a neutral speaker is one that has no FR anomalies, i.e., no "resonances"?
As has been stated countless times: the goal is flat and smooth on axis, and smooth off axis, but not necessarily flat (exception: a constant directivity, e.g. omni speaker). If this is achieved, it is unlikely that there will be audible resonances - i.e. neutral sound.
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Originally Posted by craig john View Post
Sooo.... given the above, can you *please* answer my original question: What is the definition of a neutral speaker?

Am I to understand that *if one chooses* to call all FR anomalies "resonances" then a neutral speaker is one that has no FR anomalies, i.e., no "resonances"?

I guess that kinda jives with my definition of neutral, but it's certainly a different way to look at it.
...
It's not really a different way of looking at anything. A neutral speaker has the same amplitude of output regardless of the frequency of the input. In other words, it has a flat frequency response plot. In other words, the frequency response plot has no anomalies, as you put it.

You're both saying the same thing. Dr. Toole is calling frequency response anomalies resonances but you don't have to if you don't want to. There should really be no struggle or confusion here since you guys are saying the same thing ultimately, and looking at things the same way, just using different terminology.
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I am very curious about good organ music with good low end. Could you recommend some recordings that you like?

I heard a statements as harsh as "Bach is the only great organ music" (that was a conversation between two organ players), but what good recordings are there? While with my tastes, recently only Hans Zimmer's Interstellar soundtrack got me to really enjoy organ sounds (especially Live in Prague 2016)
I found the Interstellar soundtrack boring...try his Batman series

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Originally Posted by Floyd Toole View Post

In the crossover between a 6- to 8-inch woofer and a 1-inch tweeter, a directivity mismatch at crossover is unavoidable. Above crossover, the tweeter has much wider dispersion than the woofer, so there is an energy rise over a wide frequency range.
Is this directivity mismatch unavoidable even with a very low crossover point? What if you have a 1" tweeter capable of very high excursion, and you can cross the tweeter over at say, somewhere between 1200 - 1400 hz with a 6 inch woofer?

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Originally Posted by Floyd Toole View Post
Yes. As I said, because loudspeaker transducers are minimum-phase devices one can use electrical parametric EQ to attenuate the mechanical resonances in transducers - using anechoic data of course. So, if you add a hump to an otherwise neutral/resonance free speaker you have added a resonance. This is why it is crucial to pay attention to what "room equalizers" are doing. If they "see" a ripple in a measured curve caused by acoustical interference of direct and reflected sound, and try to flatten it, they may be adding a resonance and degrading a good loudspeaker.
Likely not, at least with the better ones - as they create their filters based on a spatial average of anywhere from 5-10 measurements, each spaced several inches apart. Tighter groupings of measurements give a better, but smaller, sweet spot. Shouldn't this help the software learn enough to make informed decisions and mitigate at least some of your concern?

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Originally Posted by motrek View Post
Well sure, but as long as Dr. Toole isn't posting replies at the moment, what's the harm in me chiming in with my two cents?



The hangup seems to be when Dr. Toole equates neutrality with lack of resonances.



All I'm saying is that this makes 100% perfect sense if you consider a deviation from flat frequency response to be a resonance, which is a possible interpretation of the Wikipedia article for "resonance."



EDIT: Ninja'ed by Dr. Toole.



EDIT 2: reworded to make my point more clear.
I apologize. I did not mean to imply that others should not chime in. My bad.
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Originally Posted by Floyd Toole View Post
Apologies to Shakespeare . . .

This discussion has drifted into an area of literal interpretations of classical definitions with some semantics thrown in. If there is a shallow hump in a frequency response, in literal terms it is a very low-Q resonance, implying a mechanical, electrical or acoustical system with a "favored" frequency range. In a physical system as complex as a loudspeaker it may sometimes be difficult to decide what is happening. Crossovers are equalizers, by any other name, that interact with transducers having inherently non-flat tendencies - the result is a combination of both electrical and mechanical elements. Equalizers can be resonators just as surely as acoustical cavities, enclosure panels and cone breakup. So a frequency response feature may be partly mechanical and partly electrical , but the end result can be that of a resonance having Q. Achieving a desirable flat on-axis sound using passive or active networks can result in non-flat off-axis behavior because transducers have frequency-dependent directivity. In a room the result is that even with flat direct sound, the early reflected and later reflected sounds may exhibit emphasis over a range of frequencies that could forgivably be interpreted as a low-Q resonance.

As discussed many times in this thread, transducers are inherently minimum-phase devices, so electrical EQ can modify the performance of mechanical resonances - a huge advantage for active loudspeakers or those for which accurate anechoic data are available.

In the crossover between a 6- to 8-inch woofer and a 1-inch tweeter, a directivity mismatch at crossover is unavoidable. Above crossover, the tweeter has much wider dispersion than the woofer, so there is an energy rise over a wide frequency range. Is this a resonance? Technically not, in the dictionary definition sense. However, there is a broad hump in radiated energy, so perceptually it may appear to be so. Figure 4.13 shows such an example where even crude room curves were adequate to recognize the energy excess in an above-crossover energy excess and attenuate it. Because wide bandwidth (low-Q) phenomena are detected at very small deviations there was a clear improvement in perceived sound quality even though medium and higher-Q "real" resonances were essentially unchanged. Addressing all of the "resonances" was not surprisingly the best.

So, don't get hung up on semantics. Deviations from a linear frequency response are all describable as "resonances" if one chooses to. Broadband trends are very low-Q, narrower trends, medium Q, and so on. Even a bass tone control is an opportunity to manipulate a "resonance" - in this case the hump that develops above the low cutoff frequency which, depending on the system design will have a Q.

Narrow dips are usually the result of destructive acoustical interference and are usually audibly innocuous because they change with direction/position. Broader dips can be interpreted as anti-resonances if one chooses to, whether there is an associated frequency selective absorption process or not. Mostly not.

All fodder for more discussion
Doctor Toole,

I much prefer we be precise in our language other wise we have difficulty communicating. This thread is a perfect example. When someone says resonance to me I immediately think of the classical definition. Like you, in one of my engineering classes for electronics I was introduced to mechanical resonances with springs, masses and dampers with the associated equations before I was introduced to RLC circuits. Like you said, if someone tells me that a speaker as a resonance at 2Khz with a magnitude of 3 Db and a Q of 1 I know I can EQ it out and improve the sound without even seeing a response plot. To be a little facetious here, Galloping Gertie's resonance was visible no matter which angle you were looking at it from.

Cheers,
OldMoveNut
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Originally Posted by Soulburner View Post
Likely not, at least with the better ones - as they create their filters based on a spatial average of anywhere from 5-10 measurements, each spaced several inches apart. Tighter groupings of measurements give a better, but smaller, sweet spot. Shouldn't this help the software learn enough to make informed decisions and mitigate at least some of your concern?
That's not enough. You need to combine that with frequency dependent windowing to get as much of the room out of the response above Schroeder as you can. My problem with the commercial EQ systems is they are black boxes and you don't know exactly what they are doing. That's why I like DRC-FIR so much as I can see and control exactly what it does.

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Das Orgelwerks! My favourite topic. I'll only recommend a few that should still be available if the Archive site is up to date.

To test the lungs of any stereo system (low D that will give a sub a work out at 19 Hz): Mendelssohn played by Peter Hurford on Decca. Good tunes too.

Also played by Hurford, a Decca 2-fer of Bach giving a range of his output.

Another Romantic piece played by Simon Preston of Reubke's Sonata on the 94th Psalm on DGG.

And modern music by Oliver Messiaen played by Louis Thiry, and inexpensive 3-fer on Caliope.

These would be my musical picks of some 150 organ CDs and another 150 LPs. I would love to add others, but for availability and not knowing others' musical tastes.

Message me if you'd like other suggestions.
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Likely not, at least with the better ones - as they create their filters based on a spatial average of anywhere from 5-10 measurements, each spaced several inches apart. Tighter groupings of measurements give a better, but smaller, sweet spot. Shouldn't this help the software learn enough to make informed decisions and mitigate at least some of your concern?
No.

Have you compared good speakers equalized from bottom to top with good speakers only corrected (EQ stopping at transition region)? If not, try it. It does not matter if you use Audyssey XT (assuming you have the app, which adds functionality sufficient to turn Audyssey into a functional product), Dirac, or ARC. Presumably not RoomPerfect or Trinnov either. I have yet to hear an improvement from full-band equalization. Sometimes broadband tone controls ostensibly part of RC systems - such as the "tilt" built into ARC Genesis - are useful to store as presets to compensate for recording variation.

The trick is to start with good speakers, though. Crappy speakers (defined by performance not price - the B&W N802 used in the Harman RC studies a dozen or so years ago counts as crappy speaker) may sound better with extra electronic manipulation.

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I'm still not understanding concept of resonance being applied to every frequency response aberration in a speaker:
Quote:

Resonance

In sound applications, a resonant frequency is a natural frequency of vibration determined by the physical parameters of the vibrating object. This same basic idea of physically determined natural frequencies applies throughout physics in mechanics, electricity and magnetism, and even throughout the realm of modern physics. Some of the implications of resonant frequencies are:

1. It is easy to get an object to vibrate at its resonant frequencies, hard to get it to vibrate at other frequencies.Example
2. A vibrating object will pick out its resonant frequencies from a complex excitation and vibrate at those frequencies, essentially "filtering out" other frequencies present in the excitation.Example
3. Most vibrating objects have multiple resonant frequencies.
http://hyperphysics.phy-astr.gsu.edu...und/reson.html

As I understand that definition, a "natural resonant frequency" is tied to the physical parameters of the speaker, (size, mass, volume, internal bracing, etc.) It doesn't say that external influences that cause the speaker to oscillate at frequencies other than its natural frequencies are considered resonances.
@sdurani likes to use the example of blowing across the top of a bottle as example of resonance. When you blow across the top of the bottle, the air inside the bottle will resonate at its natural frequency. If you add some water to the bottle, you change the volume of the chamber and therefore the natural resonant frequency:




Adding water to the bottle is a change to a physical property of the system, and that changes the natural oscillating frequency or the resonant frequency.

I guess what I'm still having trouble understanding is, if the natural resonant frequency is tied to mass or volume, how does externally/electronically adding a rise in the response in a certain bandwidth change the natural oscillating frequency? How does an external electrical adjustment, (i.e., something done in a crossover), change any physical parameter of the speaker, or change it's *natural* frequency of oscillation? It can certainly change the levels at which the driver oscillates in a certain frequency band, but it doesn't change any of the inherent physical attributes of the speaker. Moreover, the frequency band of the external adjustment does not even consider any natural oscillating frequency of anything in the system. It's simply a choice made by a design engineer. Since frequencies other than the natural oscillating frequency are harder to make oscillate, it seems counter-intuitive to call an externally induced oscillation a resonance.

The definition of resonance being used here excludes the concept of the "natural resonant frequency" and replaces it with any oscillating frequency. If this is the way the term resonance is used, and that usage is what is used to define neutrality of a speaker, I will readjust my thinking, even if it doesn't match the definitions I've always used.

Having said that, I think it would be more clear to use the definitions as they've generally been used, because I think many/most forum members were and are using those terms in that way. The only time I've ever encountered someone calling a designer induced mid-bass hump, (or any other external FR change), a "resonance" has been in this thread.

Craig
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post #4820 of 5320 Old 09-09-2019, 08:37 AM
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Originally Posted by craig john View Post
I'm still not understanding concept of resonance being applied to every frequency response aberration in a speaker:
http://hyperphysics.phy-astr.gsu.edu...und/reson.html

As I understand that definition, a "natural resonant frequency" is tied to the physical parameters of the speaker, (size, mass, volume, internal bracing, etc.) It doesn't say that external influences that cause the speaker to oscillate at frequencies other than its natural frequencies are considered resonances.
@sdurani likes to use the example of blowing across the top of a bottle as example of resonance. When you blow across the top of the bottle, the air inside the bottle will resonate at its natural frequency. If you add some water to the bottle, you change the volume of the chamber and therefore the natural resonant frequency:


https://youtu.be/PZVeJ2rh6ts


Adding water to the bottle is a change to a physical property of the system, and that changes the natural oscillating frequency or the resonant frequency.

I guess what I'm still having trouble understanding is, if the natural resonant frequency is tied to mass or volume, how does externally/electronically adding a rise in the response in a certain bandwidth change the natural oscillating frequency? How does an external electrical adjustment, (i.e., something done in a crossover), change any physical parameter of the speaker, or change it's *natural* frequency of oscillation? It can certainly change the levels at which the driver oscillates in a certain frequency band, but it doesn't change any of the inherent physical attributes of the speaker. Moreover, the frequency band of the external adjustment does not even consider any natural oscillating frequency of anything in the system. It's simply a choice made by a design engineer. Since frequencies other than the natural oscillating frequency are harder to make oscillate, it seems counter-intuitive to call an externally induced oscillation a resonance.

The definition of resonance being used here excludes the concept of the "natural resonant frequency" and replaces it with any oscillating frequency. If this is the way the term resonance is used, and that usage is what is used to define neutrality of a speaker, I will readjust my thinking, even if it doesn't match the definitions I've always used.

Having said that, I think it would be more clear to use the definitions as they've generally been used, because I think many/most forum members were and are using those terms in that way. The only time I've ever encountered someone calling a designer induced mid-bass hump, (or any other external FR change), a "resonance" has been in this thread.

Craig
Look at it this way:

Once connected to the other equipment "speaker", by itself, stops existing - it is now a single system where "natural resonant frequencies" of both electrical and mechanical parts (and parametric EQs are creating resonances or notches) become somewhat equal.
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post #4821 of 5320 Old 09-09-2019, 11:12 AM
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Originally Posted by craig john View Post
...
Adding water to the bottle is a change to a physical property of the system, and that changes the natural oscillating frequency or the resonant frequency.

I guess what I'm still having trouble understanding is, if the natural resonant frequency is tied to mass or volume, how does externally/electronically adding a rise in the response in a certain bandwidth change the natural oscillating frequency? How does an external electrical adjustment, (i.e., something done in a crossover),
A crossover isn't external, though, is it. It's inside the speaker. Like I said in an earlier post, consider the speaker to be an entire system. If you change the crossover, you've changed a physical property of the system, just like changing the amount of water in a bottle.

I will agree that it's counterintuitive to somebody who learned about resonances with simpler systems like springs, as we both did. That's why I had to look up the definition on Wikipedia a few days ago. But it does make sense if you consider the speaker to be a system.

Imagine using an oscilloscope to do a blind analysis of a violin string vs. a loudspeaker with a mid-bass hump. You can't hear the output of either, and you have no idea what you're analyzing, the only thing you can see is the amplitude of the waveform on the oscilloscope. I think you'd say the loudspeaker has a resonance.
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post #4822 of 5320 Old 09-09-2019, 11:34 AM
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Likely not, at least with the better ones - as they create their filters based on a spatial average of anywhere from 5-10 measurements, each spaced several inches apart. Tighter groupings of measurements give a better, but smaller, sweet spot. Shouldn't this help the software learn enough to make informed decisions and mitigate at least some of your concern?
Yes spatial averaging smooths curves; they look better - that is one reason why it is favored. However, because these curves are typically steady-state curves little of value is learned about the speaker, and nothing is specific to the prime listening location. Spectral smoothing is another "feature" that smooths curves. Tradeoffs are not always advantages.

Spatial averages reduce the ability to be analytical about room modes/standing waves.

So, it comes down to "how much do you know about the loudspeaker - in anechoic data?" If none, the usual case, such room curve data cannot be trusted. If one knows a lot, e.g. a spinorma, one can predict the room curve with reasonable precision. The room curve, by itself, is not reliably associated with sound quality.
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post #4823 of 5320 Old 09-09-2019, 01:16 PM
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My interpretation of speaker neutrality from the previously mentioned quotes from Dr. Toole's book:

Neutral = smoothest and flattest frequency response to include absence of audible resonances.
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post #4824 of 5320 Old 09-09-2019, 01:18 PM
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Originally Posted by OldMovieNut View Post
Doctor Toole,

I much prefer we be precise in our language other wise we have difficulty communicating. This thread is a perfect example. When someone says resonance to me I immediately think of the classical definition. Like you, in one of my engineering classes for electronics I was introduced to mechanical resonances with springs, masses and dampers with the associated equations before I was introduced to RLC circuits. Like you said, if someone tells me that a speaker as a resonance at 2Khz with a magnitude of 3 Db and a Q of 1 I know I can EQ it out and improve the sound without even seeing a response plot. To be a little facetious here, Galloping Gertie's resonance was visible no matter which angle you were looking at it from.

Cheers,
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I think one way to understand the seeming contradictions in this discussion is to think in terms of equivalent circuits. A resonant system can be modeled using RLC elements. If more RLC elements are included into the system the resonance is modified. In a minimum-phase loudspeaker transducer these added elements can be acoustical - the cavity behind the diaphragm - or purely electronic - as in an equalizer internal to the loudspeaker or externally added. The final result is the combination of all of these "equivalent" elements. So, it is possible to modify or even eliminate a mechanical loudspeaker transducer resonance using an electronic equalizer. It is not magic - it is old fashioned engineering.

EDIT: As stated earlier, although one associates ringing with resonances it is an interesting and highly advantageous property of human hearing that we largely ignore it. What we hear is best described by the frequency response, not the time-domain response. Hence it is entirely logical to focus on the amplitude response of loudspeakers, and not get hung up on semantics or interrogations of cause.

EDIT 2: The clearest example of combined mechanical and acoustical elements in a resonant system is that of a woofer and enclosure. The system performance is defined by a combination of mechanical transducer parameters (often called the Thiele/Small parameters), the compliance of the air in the enclosure, and the mass of the air in a port if there is one. Electronic equalization can then be applied to modify all of the above to achieve a desired final result. These are minimum-phase systems and are eminently predictable in their linear performance.
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post #4825 of 5320 Old 09-09-2019, 04:29 PM
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Just to be sure I'm following things here. It seems then that although any FR aberration is a resonance, the important thing about the spinorama is it can identify "resonances" with varying degrees of directivity. For example, a cabinet wall "resonance" would radiate in an omnipolar fashion - and visible throughout the curves, whereas a "resonance" caused by a surface defect on the face of the speaker might radiate within a narrower directivity pattern - perhaps only visible in one or two curves. They're both resonances, but not equal for the end user since after the design is complete the end user's only fix is electronic EQ, and the former seems far less amenable to correction than the latter with that particular tool.

I wouldn't have called both of them a resonance prior to this discussion, but ultimately it's just semantics. Hopefully I'm not entirely confused.
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post #4826 of 5320 Old 09-09-2019, 04:46 PM
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I wouldn't have called both of them a resonance prior to this discussion, but ultimately it's just semantics. Hopefully I'm not entirely confused.
That's exactly how I feel.
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post #4827 of 5320 Old 09-09-2019, 06:21 PM
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Just to be sure I'm following things here. It seems then that although any FR aberration is a resonance, the important thing about the spinorama is it can identify "resonances" with varying degrees of directivity. For example, a cabinet wall "resonance" would radiate in an omnipolar fashion - and visible throughout the curves, whereas a "resonance" caused by a surface defect on the face of the speaker might radiate within a narrower directivity pattern - perhaps only visible in one or two curves. They're both resonances, but not equal for the end user since after the design is complete the end user's only fix is electronic EQ, and the former seems far less amenable to correction than the latter with that particular tool.

I wouldn't have called both of them a resonance prior to this discussion, but ultimately it's just semantics. Hopefully I'm not entirely confused.
I have not been adequately thorough in my explanations, obviously, because there can be fluctuations in frequency response on a single measurement axis caused by acoustical interference. These are audibly innocuous because they change with mic location and spatially average out. This is the reason why we focus most of our attention on the listening window data because it is sufficiently spatially averaged to attenuate evidence of interference, so that one has a chance of identifying those bumps attributable to resonances, which are the dominant sources of coloration in loudspeakers. Those bumps that persist through the increasing spatial averages of "early reflections" and ultimately "sound power" are unquestionably resonances having perceptual consequences. Whether they are solely attributable to the "classic" mass/spring kind of resonance does not matter. As I have said all loudspeakers have some amount of built in equalization - the crossover network, which often incorporates narrow band filters to shape the frequency response. Active digital networks are much more capable than the passive ones. Then there is frequency-dependent transducer directivity that modifies the off-axis radiated energy vs frequency compared to direct sound. The audible consequences of this depends significantly on the listening setup.

All of this and more is in the 3rd edition. It really is not complicated.
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post #4828 of 5320 Old 09-09-2019, 08:08 PM
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Originally Posted by Floyd Toole View Post
Yes spatial averaging smooths curves; they look better - that is one reason why it is favored. However, because these curves are typically steady-state curves little of value is learned about the speaker, and nothing is specific to the prime listening location. Spectral smoothing is another "feature" that smooths curves. Tradeoffs are not always advantages.

Spatial averages reduce the ability to be analytical about room modes/standing waves.

So, it comes down to "how much do you know about the loudspeaker - in anechoic data?" If none, the usual case, such room curve data cannot be trusted. If one knows a lot, e.g. a spinorma, one can predict the room curve with reasonable precision. The room curve, by itself, is not reliably associated with sound quality.
Of course, I wasn't touching on equalization of anechoic vs in-room response. I agree that your logic is sound there. I was speaking to your comment about equalizing small ripples that are mostly interference - I think the process accounts for that by taking multiple measurements. I'm going to make a guess here, but based on my experience in another hobby (astrophotography), the processing should know better what is real and what isn't by comparing what is common between measurements taken a few inches apart, and much more. I think these room correction processes are learning much more about the speakers and the room than meets the eye.

I do agree that it makes sense to get the best-measuring speakers you can afford, perform the best placement you can muster, add multiple subs, then use room correction up to 300-500 Hz, before experimenting with correcting full-range. Some setups benefit from that extra mile, some do not. It depends on the system.

HT: Samsung PN64H5000 (recommended settings) | NAD T758 V3 | Buchardt S400 (2) | Emotiva E2 (2) | Rythmik Audio F12 (2)

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post #4829 of 5320 Old 09-09-2019, 11:21 PM
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Originally Posted by Soulburner View Post
Of course, I wasn't touching on equalization of anechoic vs in-room response. I agree that your logic is sound there. I was speaking to your comment about equalizing small ripples that are mostly interference - I think the process accounts for that by taking multiple measurements. I'm going to make a guess here, but based on my experience in another hobby (astrophotography), the processing should know better what is real and what isn't by comparing what is common between measurements taken a few inches apart, and much more. I think these room correction processes are learning much more about the speakers and the room than meets the eye.

I do agree that it makes sense to get the best-measuring speakers you can afford, perform the best placement you can muster, add multiple subs, then use room correction up to 300-500 Hz, before experimenting with correcting full-range. Some setups benefit from that extra mile, some do not. It depends on the system.
What if that ripple is caused by a reflection between the microphone capsule and the stand? Or the microphone and the seat of a chair? Or between the seat and the back of the chair? Even the supposedly 'advanced' systems such as Dirac require the user to intervene in several ways as it 'corrects' matters that absolutely do not need correcting. Can we still call this a calibration? I'm not against using these systems in a restricted capacity, but if EQ above the transition of the room is implemented, it should be done so based on anechoic or as-close-to-as-possible data.
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post #4830 of 5320 Old 09-10-2019, 05:01 AM
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Those bumps that persist through the increasing spatial averages of "early reflections" and ultimately "sound power" are unquestionably resonances having perceptual consequences. Whether they are solely attributable to the "classic" mass/spring kind of resonance does not matter.
So there it is. Finally a response that directly addresses my question. You're calling things resonances that don't fit the "classical" definition of resonances. This is exactly why I was confused and why it is so important for communication that the definition of terms be precise. All this time I was thinking that if one merely removes all "resonances" in the classical sense, (i.e., any vibrations that are related to the physical structure of the speaker and the associated natural frequencies of oscillation), one would have a "neutral" speaker. Now I realize that it is far more than that, and that all deviations from a flat and smooth frequency response are being called resonances, no matter what causes them, or what frequency they are related to.

That was a fundamental disconnect in my understanding.

I realize that terms or phrases within a scientific field of endeavor can get "colloqialzed" within that field to mean things that are slightly different than the way the same term or phrase is used by people outside that field of endeavor. For example, in heart surgery, the chambers that lead to the ventricles are called "atriums", the Right Atrium and the Left Atrium. However, if you look in all the classic textbooks of anatomy and physiology, they're called "auricles." I was once in a conversation with a professor of A&P. I was describing a mitral valve repair procedure to her, (the mitral valve sits between the Left Atrium/Auricle and the Left Ventricle), and I used the term "atrium" several times. Finally, she stopped me and asked what an atrium was.

Going forward, I will assimilate this new (to me) definition of resonance, and the ensuing definition of neutral as it relates to speakers.

Are there any other terms used by sound engineers that have different meanings than their "classical" definitions?

Craig
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