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So what is "Group Delay" anyway?


Raider

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Some short comments on Kramskois commentsas they touch on many interrelated topics (many of which have their underpinnings n the chapters on Room Acoustics - as the concepts are presented there - at least in basic form - hint, hint! [:P]). You will see that the time domain is not a fragmented pespective! And it is SO easy to run off chasing rabbits with so many interrelated concepts!<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Good layman's term description, Im of the same opinion as Doc on the time delay issue...these are time-domain issues, and to say that they arent interrelated would be a bit premature IMO...They are ABSOLUTELY related! a constant delay through the signal envelope "is" desirable Rather, it is acceptable, but it is not ideal. We are dealing with the tolerances of the ear, the gross limits of perception and the broad area of psycho-acoustics. If we had better (read ideal) transducers the entire signal component of an infinitely short impulse would be reproduced in an infinitely short period identical to the input. In other words, the transform would be unity. would be produced but here we are talking about delay in the 2-4 msec range in the higher frequencies and anywhere from 10 to 100msec in the lower bass range down to 10 Hz... I will defer on this, as we are also entering into the realm described by the Haas, or more accurately, the Henry Precedence Effect.

For more on this area, may I suggest folks start reading more of the Room acoustics chapters!!! As this becomes fundamental there and is dealt with in much more detail as this is a very important topic!!!

it is my thinking that the "room" is the great equalizer in all this. If we agree that the basic loudspeaker is a high pass circuit, passing the highs and rolling off the lows, would this "temporal shift" be more noticeable in an anechoic chamber? How much is the "room" masking the issue? The critical range is the early first order reflections of the Lre field. This becomes important in establishing what is referred to as the initial time delay (or more correctly, the initial signal delay) gap. This is a period where the signal arrival processing is anechoic. in what is referred to a especially larger rooms, with their reverberant sound fields. The reverberant field only adds to the noise floor and thus the S/N of the room. It is sufficiently late that it has not impact on the earlier time field. And this will be prevalent and fundamental in both small and large listening rooms. But here we get into the use be it at one end of the spectrum where precise intelligibility is key, or on the other end where we are listening to music

Again, this area is dealt with in greater depth in the room acoustics discussion!

Or perhaps our ear/brain learning has compensated for this phase shift between high and low frequencies...over many years of less than perfect acoustic reproduction. Evolved? Or never had to begin withOf course, one can never be too sure regarding the destructive effects of Rap music on hearing [:P]

Keeping the phase shift as minimal as possible seems to contradict the practice (by some) of crossing over mains to the subwoofer at frequencies appreciably lower than 80-100 Hz...for example, 40 Hz, which would add twice the group delay of an 80 Hz crossover...cross lower and it becomes even worse...

Aaaaa. Here I will disagree in the sense that you can align the gross signals between transducers in time to a degree and this limitation is due primarily to what is referred to as cosine error and this is also the primary force' behind the concept of co-axial driver development. Additionally, with most transducers, the rate change of phase is not necessarily a constant throughout the frequency range. And as this varies with transducer type, I am hesitant to make any over-reaching pronouncements here.

Of course, the biggest question is always "when does it become audible"? That is the $64,000 question. Another perhaps even more important aspect is when does it become grossly apparent, and when does it become subtly apparent!

Also, there is no need to go running in search of speculation on these topics when you can go to the source of those who are directly addressing these topics.

What this should do, is to stimulate folks to become more interested in looking at the physics of acoustical phenomena to a greater degree from the time domain. Not because you see things that do not exist in the other domains, but because the time domain enables you to see things that are not readily apparent from the more traditional frequency domainas what from one point of view may seem as a point in space, from another perspective is actually a complex line. And that is exactly what the time domain provides. And that is but the beginning of the trip through the looking glass as I promise it gets even more intriguing!

After all, if ANY of this piques your interest, there is yet another structure (the Nyquist and, in particular, the Heyser spirals) that will radically change your paradigm! You will see that ALL of the various aspects of acoustics and electronics come together in a grand unified image that transcends them both, and it will lead to both insights and even more questions! And we now have a tool that can accurately ascertain this aspect. And I would LOVE for folks to get a bit more of the fundamentals of the time domain down before we can jump into that topic! As that topic is what really fascinates me. Group delay is simply one of the 'micro' aspects...but one that can have a major impact in some systems. But then most are not familiar with the intricacies of coupling Bessel arrays to chase that rabbit! ...So many intriquing tangents!!!![:D]

How is That for being intentionally obtuse!? [:P]

But we should be aware that we are in danger of becoming overwhelmed by how everything is inter-related to everything else - and only our limited perceptions and habits of the past are preventing many from seeing this. So it will require a bit of discipline to reign this tendency in in order to pursue aspects in an orderly manner! [;)]

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Good layman's term description, Im of the same opinion as Doc on the time delay issue...these are time-domain issues, and to say that they arent interrelated would be a bit premature IMO...They are ABSOLUTELY related! a constant delay through the signal envelope "is" desirable Rather, it is acceptable, but it is not ideal. We are dealing with the tolerances of the ear, the gross limits of perception and the broad area of psycho-acoustics. If we had better (read ideal) transducers the entire signal component of an infinitely short impulse would be reproduced in an infinitely short period identical to the input. In other words, the transform would be unity. would be produced but here we are talking about delay in the 2-4 msec range in the higher frequencies and anywhere from 10 to 100msec in the lower bass range down to 10 Hz... I will defer on this, as we are also entering into the realm described by the Haas, or more accurately, the Henry Precedence Effect.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

it is my thinking that the "room" is the great equalizer in all this. If we agree that the basic loudspeaker is a high pass circuit, passing the highs and rolling off the lows, would this "temporal shift" be more noticeable in an anechoic chamber? How much is the "room" masking the issue? The critical range is the early first order reflections of the Lre field. This becomes important in establishing what is referred to as the initial time delay (or more correctly, the initial signal delay) gap. This is a period where the signal arrival processing is anechoic.

Keeping the phase shift as minimal as possible seems to contradict the practice (by some) of crossing over mains to the subwoofer at frequencies appreciably lower than 80-100 Hz...for example, 40 Hz, which would add twice the group delay of an 80 Hz crossover...cross lower and it becomes even worse...

Aaaaa. Here I will disagree in the sense that you can align the gross signals between transducers in time to a degree and this limitation is due primarily to what is referred to as cosine error and this is also the primary force' behind the concept of co-axial driver development. Additionally, with most transducers, the rate change of phase is not necessarily a constant throughout the frequency range. And as this varies with transducer type, I am hesitant to make any over-reaching pronouncements here.

Of course, the biggest question is always "when does it become audible"? That is the $64,000 question. Another perhaps even more important aspect is when does it become grossly apparent, and when does it become subtly apparent!

okay MAS..."uncle"...i have'nt much to add here...

I'm still in the infant phase with most of these advanced sound concepts...the driving force behind most of my curiosity is subwoofers...the what, when, why and wherefore of any and everything pertaining to them...there's a slow focus with all the hazy generalizations/myths that persist in the audio community...i guess the learning curve depends on your desire to uncover the ultimate truths.

These concepts become important from a design and integration standpoint, with the room weighing in as a "major factor" in total system synthesis...as such, one needs to be wary of all mitigating factors which inhibit said integration.

I guess that "gross signal alignment between transducers" would be a DSP issue? Or could we manage it manually with the appropriate software and a laptop? How many HT enthusiasts actually undertake what "seems" a painstaking process of precise time alignment between all channels? This delay compensation would give us something close to the unity you stated, no?

In any event, i look forward to an increasing knowledge of the "deviled" details of sound reproduction...Thanks for the great posts...

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"I guess that "gross signal alignment between transducers" would be a DSP issue? Or could we manage it manually with the appropriate software and a laptop? How many HT enthusiasts actually undertake what "seems" a painstaking process of precise time alignment between all channels? This delay compensation would give us something close to the unity you stated, no?"

Actually, this can be done with a simple active crossover with 'time delay' (as if you can delay time! [:P] ). Ideally you would use the delay to align the acoustic centers with impulse response sweeps, as you can see with great clarity the individual transducer's arrival time. A gross but useful poor man's technique is to use a highly defined pink noise click track. Even a mechanical metronome can be used.

Just be aware that this alignment in time for transducers that do not share the same 'spot' in space (at minimum co-axial) will be accurate for one listening location, as when you move relative to the source(s), the relative distance between you and each driver will change, causing that alignment in time to 'shift' with the changing relative spacing. (Avoiding this error is the fundamental idea behind coaxial drivers and coaxial systems like the Frazier coaxial horns.) (Gee this is SO easy to show by illustration but so awkward to state coherantly in words - I will see what I can do on this incredibly awkward windows box to find an effective draw tool!!)

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You're opening a can of worms with that question!

As I understand it, for a fixed diameter piston the lower it plays, the further it needs to travel in order to "create" the frequency. You could almost think of group delay as the time it takes for the driver to produce that note. I hesitate saying that because I know it's wrong, but I don't know how else to describe it (which probably means I don't understand it correctly).

I do know that a google search brings up crap loads of debates on the issue. The "audibility of group delay - round 5, start!"

I too would be intersted in a good explanation.

This is a very good,simple description. When a cone/piston has to travel say 4" to produce a given note a say X dB the group delay will be much higher than say the same note produced with a 4mm travel and Y dB. In a perfect world there would be no group delay and full range,point source would be the summum of perfection.In the real world the engineers have to work to minimize group delay or at least keep it in check,if I may say.

Also more travel means recuperation time,the woofer's cone/piston does not reach its central position as fast when under full excursion as it does at moderate levels where the cone has little travel.

Going back to Ear's description above about cone/piston travel, it would make sense then that horns, displaying minimal driver travel, would have lower group delay.

In reading Tom Danley's description of his DTS-20 (horn-loaded) tapped design, he writes:

The DTS-20 a.k.a. The Tower of Power is simply the most powerful, lowest frequency reproducing subwoofer on the planet. Solid output down to 15Hz, single digit distortion and incomparably low group delay put this amazing subwoofer in a class by itself.

The low group delay on this sub is probably related to the fact that few subs out there are horn-driven these days.

Did I deduce this correctly?

Chris

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Richard C. Heyser, "Loudspeaker Phase Characteristics and Time Delay Distortion: Part 1," J. Audio <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Eng. Soc., vol. 17, p. 31 (Jan., 1969). Also available in the Heyser Anthology Time Delay Spectroscopy published by AES<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

H. Suzuki, S. Morita, and T. Shindo, "On the Perception of Phase Distortion," J. Audio Eng. Soc., vol. 28, pp. 570-574 (1980 Sep.). Also available in the Anthology Loudspeakers, Volume 2 published by AES

I think this is where I am going to remove myself from this discussion. And I hope that no one misunderstands my reasons.

It is a wonderful area for exploration, and it is an area where we do not yet have all of the answers at least not in a coherent form that will simply answer everyones questions in a simple manner!

But my reason for withdrawing is this. Pursuing this topic is akin to delving into chapter 356 of the Advanced Time Domain Chronicles when we are having a heck of a time getting through chapter 1 in the Basic Large and Small Room Acoustics thread.

And just as it is difficult to get a handle of the latest string and TOE theories without a basic grasp of quantum electrodynamics, we are necessarily going to run into a problem here without a good grasp of the basic time domain concepts as well.

I wish it were possible to just skip over the more mundane aspects in order to arrive at a simple three sentence answer that can be understood with just a simple non-technical understanding. Maybe it can be done. But I know that I cant!

In response to the idea that horns necessarily exhibit lower group delay My gut is that the answer is both yes and no. The fact that a horn diaphragm undergoes less movement in space due to its efficiency in its generation of an acoustic signal would suggest that its group delay will be less than a dynamic transducer such as a LF woofer. But then we also get to deal with the apparent acoustic origin such as that in a constant directivity horn which appears to be located (and measures thusly) further out in the throat of the horn. And to make issues even more complex, this acoustic origin varies with frequency. Thus we have a degree of complexity over correlating the two concepts in at least some variants of a horn.

My other concern is that this topic (like many others) is difficult to discuss in words. Words arent the native tongue for such phenomena, and I am loath to jump into the math that does more accurately describe such behavior and it is guaranteed to drive everyone away! And I suspect that includes even those of us who are proficient with the tools. And I say this as I know I certainly want to avoid going there! Topics such as negative time, and pre-causal stimuli describing acoustic behavior that happen before we apply a stimuli will be confusing enough as the basic concepts of measurement are presented without introducing the confusement of math!

My recommendation is to maintain an open mind regarding this topic, and to refrain from jumping to any quick conclusion based upon ANY marketing claim you may read!

And again, my agenda is to encourage folks to begin to pursue an understanding of the basics of acoustics as they are rendered via the perspective of the time domain, as that is both the rabbits hole and the entrance to the looking glass through which a simultaneously confusing and utterly fascinating and enlightening journey enhancing your current level of understanding will really begin! But please be realistic! For while this journey will resolve many questions that have been heretofore shrouded by limitations in the traditional approaches, there will also be new challenges and new questions that will be raised with new quests to be solved. But from my perspective, that is precisely what currently makes acoustics such a fascinating areafor unlike many other areas of study where most of the really tough issues were addressed a hundred years ago and most modern challenges simply consist of plugging a few values into well behaved models and equations, acoustics is still a relatively unknown frontier with yet still many regions to be explored and better understood. And if one only avails themselves of the current tools, you will realize that we are in the modern renaissance of acoustic study.

OK, well my soapbox is getting pretty rickety, so I had best be quiet.

I have also attached a discussion from the ProSoundWeb Smaart posting regarding phase. There is a mixture of both confusion and clarity within, and I will leave you to wade through it. After all, what else would you be doing on a beautiful fall weekend? ;-)) My unsolicited suggestion is to forget this stuff and to get out and enjoy!!!

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<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

I think this is where I am going to remove myself from this discussion. And I hope that no one misunderstands my reasons.

After all, what else would you be doing on a beautiful fall weekend? ;-)) My unsolicited suggestion is to forget this stuff and to get out and enjoy!!!

MAS, I thank you for your honesty on this point. Clearly, when derivatives and calculus are involved, abstraction will keep us from passing first base. I know that trying to distill this to a simple concept will be just about impossible.

I totally agree with your second statement. Time to get outside and smell the cool fall breezes and the crunch of leaves underfoot. I DO miss the early Octobers in New England.

And the first snowfall ...

Then fast forward to mid-May and the smell of mud and emerging flowers and greenage. Goin' green.

Chris.

PS: Bottom line, if PWK didn't sweat it, probably better that we just accept the fact that it's an obtuse subject and not a biggie ... and just enjoy the music.

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Richard C. Heyser, "Loudspeaker Phase Characteristics and Time Delay Distortion: Part 1," J. Audio <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Eng. Soc., vol. 17, p. 31 (Jan., 1969). Also available in the Heyser Anthology Time Delay Spectroscopy published by AES<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

H. Suzuki, S. Morita, and T. Shindo, "On the Perception of Phase Distortion," J. Audio Eng. Soc., vol. 28, pp. 570-574 (1980 Sep.). Also available in the Anthology Loudspeakers, Volume 2 published by AES

I think this is where I am going to remove myself from this discussion. And I hope that no one misunderstands my reasons.

It is a wonderful area for exploration, and it is an area where we do not yet have all of the answers at least not in a coherent form that will simply answer everyones questions in a simple manner!

But my reason for withdrawing is this. Pursuing this topic is akin to delving into chapter 356 of the Advanced Time Domain Chronicles when we are having a heck of a time getting through chapter 1 in the Basic Large and Small Room Acoustics thread.

And just as it is difficult to get a handle of the latest string and TOE theories without a basic grasp of quantum electrodynamics, we are necessarily going to run into a problem here without a good grasp of the basic time domain concepts as well.

I wish it were possible to just skip over the more mundane aspects in order to arrive at a simple three sentence answer that can be understood with just a simple non-technical understanding. Maybe it can be done. But I know that I cant!

In response to the idea that horns necessarily exhibit lower group delay My gut is that the answer is both yes and no. The fact that a horn diaphragm undergoes less movement in space due to its efficiency in its generation of an acoustic signal would suggest that its group delay will be less than a dynamic transducer such as a LF woofer. But then we also get to deal with the apparent acoustic origin such as that in a constant directivity horn which appears to be located (and measures thusly) further out in the throat of the horn. And to make issues even more complex, this acoustic origin varies with frequency. Thus we have a degree of complexity over correlating the two concepts in at least some variants of a horn.

My other concern is that this topic (like many others) is difficult to discuss in words. Words arent the native tongue for such phenomena, and I am loath to jump into the math that does more accurately describe such behavior and it is guaranteed to drive everyone away! And I suspect that includes even those of us who are proficient with the tools. And I say this as I know I certainly want to avoid going there! Topics such as negative time, and pre-causal stimuli describing acoustic behavior that happen before we apply a stimuli will be confusing enough as the basic concepts of measurement are presented without introducing the confusement of math!

My recommendation is to maintain an open mind regarding this topic, and to refrain from jumping to any quick conclusion based upon ANY marketing claim you may read!

And again, my agenda is to encourage folks to begin to pursue an understanding of the basics of acoustics as they are rendered via the perspective of the time domain, as that is both the rabbits hole and the entrance to the looking glass through which a simultaneously confusing and utterly fascinating and enlightening journey enhancing your current level of understanding will really begin! But please be realistic! For while this journey will resolve many questions that have been heretofore shrouded by limitations in the traditional approaches, there will also be new challenges and new questions that will be raised with new quests to be solved. But from my perspective, that is precisely what currently makes acoustics such a fascinating areafor unlike many other areas of study where most of the really tough issues were addressed a hundred years ago and most modern challenges simply consist of plugging a few values into well behaved models and equations, acoustics is still a relatively unknown frontier with yet still many regions to be explored and better understood. And if one only avails themselves of the current tools, you will realize that we are in the modern renaissance of acoustic study.

OK, well my soapbox is getting pretty rickety, so I had best be quiet.

I have also attached a discussion from the ProSoundWeb Smaart posting regarding phase. There is a mixture of both confusion and clarity within, and I will leave you to wade through it. After all, what else would you be doing on a beautiful fall weekend? ;-)) My unsolicited suggestion is to forget this stuff and to get out and enjoy!!!

thanks MAS...enjoyed the posts...and point taken!...*wink

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Hey guys...

It may be more involved then what some have hoped, and less than what others desire, but may I invite you guys to take a look and jump on the Large & Small Room Acoustics Thread in the Architectural Forum.

It is my desire (and still my intention - hey a fellow can dream can't he!?) to try to get this herd of cats to sit down and take baby steps until we have a group that has a good foundation in the basics of room behavior and the basics of time domain behavior and measurements.

From there we can take those same foundational ideas and concepts and go in a variety of ways - from the micro approach of applying the concepts to small signals, to transducers and speakers, to the macro of clusters and arrays of speakers and their interactions both with each other and with the room/environment...as well as as what the implications of the new measurements tell us...and I think that some of them will truely surprise you! (Hint: Take a look at the domain chart at the end of the SACGroupDelay article/attachment!)

You think you have questions now? You will have still more! But hopefully with allot of answers too!

Besides, here's a claim that I will guarantee:

If you have EVER wondered what in the %@!* "imaginary" numbers are and what they really mean (and Who hasn't?!?!), you need to follow this thead as well when we get to some of the advanced measurement tools. Not only will they cease to be imaginary, but you will wonder WHY they were never presented as clearly and as meaningfully as they will be presented! EVEN if you don't know or like math! And that is just the beginning! Think about it - even if you have a graduate degree in mathematics, engineering or physics - this subject can be made to even make you go "Wow! I get it now!" And it will open allot of locked doors in a very useful and practical manner!

Does this boast sound too big to be true? Take me up on it! Just think...If it can do that, think of the other things that can happen![:D]<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

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Wow. This thread sure took a different tack than I expected.

I thought I was asking what time it was, and found out how the watch works instead.

After carefully reading the posts I have concluded that:

1) No one really knows, or

2) If they know they may not be able to explain it, or

3) If they can explain it, it will be with terms that I probably won't understand either.

:)

Having said that . Let me take a stab at what I think I know (or maybe not) so far:

In an ideal world, all frequencies from a speaker would arrive at the listener at the same time, with the same phase relationships as when they left the speaker. Group delay is when some portion of the frequency spectrum arrives later, or is percieved to arrive later due to a change in phase relationship from the original signal. This may be due to:

1) Spacing and location of drivers in multi-way systems.

2) Reflected signal that interferes with the primary signal.

3) Selective absorption of part of the signal spectrum.

4) Phase relationship changed by electrical crossover selection.

5) Phase relationship changed by mechanical influences, especially by the enclosure, or mechanical characteristics of the drivers themselves.

6) Phase relationship changed by other components in the signal path.

Any group delay issues introduced by the above are minimal, in terms of actual perception, as compared to acoustic issues in the room which are many, many times more influential. This is evidenced by the study that showed headphones were needed often to perceive the phenomenon, which would remove room acoustics from consideration. The brilliance in the design of the ear and brain, and its ability to interpret and interpolate acoustic information cannot be overstated.

I started the thread after seeing the term "group delay" mentioned several times. I thought it would be more easily concisely defined, as some acoustic terms are. Given the complexity which has since evolved, it is apparent to me that there are too many interdependent variables for this to be the case.

Thanks for your contributions here, nevertheless, as each added another layer of understanding.

I agree with MAS that energies are better applied in a more systematic study, such as what is already in progress in the "Large Room/Small Room" thread in the Architectural section of the forum.

See you there.

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And a bit out of the track...

In the real world you cannot have have a speaker system with no(absolute zero) group delay.

As long as you have what Thiel is preaching as time aligned speakers,properly designed crossovers and near perfect driver to driver in cabinet integration and low distortion.It is all godd,very good. In the real world sounds from a band or orchestra do not arrive from a point source.

Alot of big talk for not much,it is important for engineers to study all aspects of acoustics but I think to concentrate on the most important aspects that really matter improving audibly the sound.In a realistic natural way.

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Let me take a stab at what I think I know (or maybe not) so far:

In an ideal world, all frequencies from a speaker would arrive at the

listener at the same time, with the same phase relationships as when

they left the speaker. Group delay is when some portion of the

frequency spectrum arrives later, or is percieved to arrive later due

to a change in phase relationship from the original signal. This may be

due to:

1) Spacing and location of drivers in multi-way systems.

2) Reflected signal that interferes with the primary signal.

3) Selective absorption of part of the signal spectrum.

4) Phase relationship changed by electrical crossover selection.

5) Phase relationship changed by mechanical influences, especially by

the enclosure, or mechanical characteristics of the drivers themselves.

6) Phase relationship changed by other components in the signal path.

Yet you have group delay with single drivers in an anechoic chamber.

I wouldn't worry too much about the factors outside the speaker when trying to figure out what "group delay" is in terms of the speaker or amplifier or whatever.

And apparently group delay is going to be a topic of discussion in one

of my classes over the following week, so maybe I'll come away with

something practical. I am led to believe it has more to do with how the

input waveform doesn't come out looking anywhere close to the input,

which is the result of time-arrival differences between different

frequencies. I almost want to claim that the difference in packet width

between the output and input is what the group delay is actually

measuring, but that's just speculation. All the lectures will be

available in pdf format so I'll be sure to take a few snippets of the

diagrams if I come across any.

Talk about crazy timing!

(maybe I'll finally get an answer too).

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In the time domain, like most other domains, we can focus on the large picture, or we can begin to focus more cloesly on a particular aspect of the environemtn, or we can continue to focus on ever smaller orders of magnitudes...

Examples of this in acoustics would be to focus say on the characterisitics of the complex signals in large or small acoustic spaces. We could then focus more closely on how a particular speaker array or a cluster interacts with the room. We could focus more closely on how a particular speaker (several drivers- ie a LaScala) interacts in the room. We could then focus more closely on a particular speaker and examine how the various individual drivers and the cabinet interact. We could then focus more closely on the individual speaker components, be they the crossover or individual drivers. And so on...

In other words, there are many orders of magnitude, from large to small, that we can choose to focus upon.

So we have issues of polarity, phase and group delay. And while they are related, they are absolutely not interchangeable.

Group delay tends to be a characterisitic that is most commonly addressed at the 'smaller end' of the list. It is not a significant factor in items 1-3 of your list. But those items are much more significant. So, while I am not trying to say that group delay is unimportant, I would say that the effect of group delay is MUCH less than other more important aspects. In other words, if I had to pick a characterisitic that would generate the biggest return, it would be in other areas, beginning at the 'larger' end of the spectrum focusing on room acoustics and then followed by the interaction of various drivers in a speaker.

Edit:

As Doc and I were evidently replying at the same time...Doc is right. And I think we were trying to same roughly the same thing.

I think a problem here is that the term 'group delay' is being used to describe much more than it is. It is not a general time domain measurement that describes the different arrival times of various distinct signals. It is much more focused than that. It deals with the distortion of a 'single signal'. It applies to the rate of change in phase which may occur in contiguous or a discontiguous manner.

My suggestion would be to 'lose' the term for awhile. It is Not used in room acoustics or large scale systems. You might even think of group delay as occurring at the 'micro' level relative to room acoustics. Note: I f you read the 2 chapters posted so far in the Large and small acoustics thread, "group delay" is not even referred to.

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