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Does sound sounds better in a room full of furniture and stuff or without ? - Page 2

post #31 of 868
6/4/12 at 1:21pm
Quote:
Originally Posted by localhost127 View Post

can someone show me measurements past Dc for a given frequency in a small acoustical space (home residential room)??

You can measure RT60 in any room. The issue is whether what's measured reflects true reverb. The room we used in our Hearing is Believing video has true reverb at higher frequencies when totally empty. See my post #15 above with the Before / After graph.

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why do we need the large labs to do random-incidence absorption testing for porous absorbers?

Because the large reverb room in a real acoustics lab has true reverb down to at least 100 Hz if not lower. And the reverb is uniform versus frequency, without flutter echoes at specific frequencies. The temperature and humidity are also tightly controlled, which is needed for repeatable results. More related info in this article from Sound & Vibration magazine:

Test Methods for Acoustic Treatment Products

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i hope this isn't an attempt to discredit Schroeder's work?

OMG no! I'm just pointing out that the Schroeder frequency for a room is not a sudden transition at some frequency.

--Ethan
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post #32 of 868
6/4/12 at 1:29pm
Quote:
Originally Posted by Ethan Winer View Post

You can measure RT60 in any room.

i simply asked to see measurements "past Dc" - as is how RT60 should be measured (and with omni-source).

Quote:
Originally Posted by Ethan Winer View Post

Because the large reverb room in a real acoustics lab has true reverb down to at least 100 Hz if not lower. And the reverb is uniform versus frequency,

ah, so statistical reverberant sound-field does indeed require sufficient volume based on frequency -

Quote:
Originally Posted by Ethan Winer View Post

The room we used in our Hearing is Believing video has true reverb at higher frequencies when totally empty. See my post #15 above with the Before / After graph.

the rt60 graphs in post #15 doesn't tell me that the room has a statistically developed reverberant sound-field at higher frequencies.
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post #33 of 868
6/4/12 at 2:01pm
Quote:
Originally Posted by Ethan Winer View Post

The Schroeder frequency is not a sudden hard cutoff.

Yet another point in search of an argument.

The Schroeder large room frequency which specifies the volume necessary to support a complex statistically inhomogeneous (complex) reverberant specular environment  has nothing to do with the Schroeder (or Davis) 'frequency' that distinguishes the transition between modal and specular behavior! It is rather scary to think that one would make such a fundamental error!

 

And the mention of the Schroeder (or Davis) critical frequency or the dynamics of its nature in any form as a counter to the subject at hand, namely the existence of an effective reverberant sound field in a small acoustic space, is totally inappropriate and non-sequitar to the issue at hand, as they have nothing whatsoever to do with each other.

 

And rather than contribute to the issue at hand, the introduction of yet another behavior, simply in the basis that it is often associated with the name of Manfred Schroeder, of a subject that has nothing to do with the existence of reverberant sound fields, and rathewr than clarifying the issue, serves as nothing more than a red herring that further obfuscates an issue that is already confusing for many folks.

 

(Edit to elaborate further and to clarify a distinction that has now been tossed into the mix muddying the issue of the existence of an effective reverberant sound filed in a small acoustic space for those not intimate with the concepts that have been introduced:)

 

These two 'Schroeder' behaviors that have been mentioned, one of which has nothing to do with reverberant sound fields, are loosely analogous to the difference in thermo between the freezing point and the boiling point (and no, we are not dealing with an environment that supports sublimation!).

 

 

One behavior distinguishes the region whereby the incident acoustical energy wavelengths become equal to and shorter than the dimensions of the space, which determines whether the space supports their propagation in the form of modal standing waves (while the acoustic wavelengths are larger than the room dimensions) or whether the acoustic energy is reflected in the form of discrete specular rays when the energy wavelength is shorter than the room dimensions. Each dimension contributes to this environmentally conditioned behavior.

 

The longest space dimension determines the lowest frequency at which energy shifts from modal reinforcement to specular rays. The longest dimension generally defines the lowest fundamental modal frequency, the shortest dimension defines the highest fundamental frequency at which the acoustic energy ceases to be reinforced modally. Therefore this region of behavior behavior, while exhibiting discrete 'steps' within the region where various contributing dimensions reinforce either modal or specular behavior, exhibits a range where there is a mixture of both modal and specular reinforcement. In addition to the fundamental frequencies, there will also be exhibited a series of harmonic multiple frequencies.

 

Thus, what is often referred to colloquially as a single 'point' or frequency separating the behavior between where modal behavior stops and specular behavior begins (typically addressed in small acoustic spaces) is actually not a fixed point but a frequency region wherein the transitions occur at a series of frequencies corresponding to the various dimensions where the incident energy's wavelength changes from being larger than the incident surface and behaving modally to being smaller than the incident surface and thus reflecting in a specular manner.


Referring back to the "Large room Schroeder frequency" (FsubL) that defines the smallest volume at a given frequency that will support a naturally occurring reverberant sound field, a VOLUME does exhibit a minimum volume whereby this reverberant behavior can be supported. this is generally considered the 'break point' at which a volume space ceases to be a small acoustical space(SAS) and becomes a large acoustical space (LAS).

On the other end of the acoustical behavioral spectrum, the "Schroeder (or Davis) critical frequency" (fsubc) that describes the 'point' (actually a series of points in a range) at which the individual dimensions in a small acoustical space (SAS), which is defined in large measure specifically based upon a SAS' LACK of a significant reverberant soundfield, contribute to a variety of cutoff points that create a RANGE of low frequency 'end-points' whereby the behavior changes from modal to specular behavior, and in no cases does this issue even apply to the distinction between specular and statistically homogeneous reverberant behavior!

 

One should also note, that a reverberant sound field exists only beyond what is called the "critical distance" (Dsubc); the point at which, measured relative to the acoustical source, the direct sound is equal in gain to the ambient reflected sound in the volume.  Closer to the source and prior to Dc, the direct sound is higher in gain, and beyond Dc, the reverberant sound field is greater in gain than the direct source, This is a fundamental characteristic of a LAS. It is beyond Dc that a reverberant sound field can potentially become high enough in gain to obscure and mask low level dynamics of the direct signal, and thus becomes an impediment.

 

Conversely, in a SAS, what reverberant sound field may exist, is so high in frequency, and so low in gain as to reside above frequencies of interest and even more importantly, exists below the level of the ambient noise floor. Thus there is effectively no critical distance DC, and no reverberant sound field to address in a SAS.


Thus, if one wants to more accurately cite such distinctions in terms of a generalization relative to whichever facet of behavior, modal or specular, they are focused upon, they would refer either to the smallest dimension as corresponding to the lowest frequency that specular reflections would be supported, or to the longest dimension as corresponding to the highest frequency at which modal behavior would be supported.

 

In either case this is applicable to small acoustical spaces defined precisely by their LACK of a significant reverberant field at any frequencies of significance.

 

The Schroeder (or Davis) critical frequency, fc, while very  important in addressing the transition between modal and specular behavior in a SAS and as such is a term folks here should properly be both familiar and conversant, it  has nothing whatsoever to do with the existence of reverberant sound fields and is superfluous to the discussion of the topic at hand in this thread. Conversely, while the Large room frequency is an important concept in defining what constitutes the acoustics behavior defining a large acoustical space,LAS, as distinct from a small acoustical space, SAS, only the FsubL is pertinent to a reverberant sound field. and hence to this discussion.

 

The irony is that in the world of home theaters and listening rooms, all of which are SAS and none of which are LAS, the discussion of reverberant sound fields and the use of calculations that erroneously assume the existence of such behavior, especially in light of the fact that we alternatively have very precise easily obtained measurements (such as the Envelope Time Curve, ETC, and cumulative spectral decay(CSD)/waterfall plots) providing very detailed modal and specular information able to be precisely determined for all positions of interest in a space, which enable us to know precisely the nature of both the local summed behavior as well as to resolve the precise details of the discrete constituent specular energies that atomistically contribute to and define this locally variable behavior, renders the use of an erroneously derived quantity based upon math that both describes and assumes a predicate behavior that does not exist, a generalization without merit at best, and grossly inaccurate at worst.

 

The pertinent metric pertaining to the point (frequency) at which a volume (or a volume at the lowest frequency supported) that will support a reverberant sound field of a given degree is the Schroeder large room frequency, FsubL.

The fact that Manfred Schroeder's name is associated with both does not render them equivalent nor interchangeable.

Thus the point (fc) raised isn't even germane to the topic of the applicability of the concept of reverberant sound fields to small acoustical spaces and indicates a simple confusion of two distinctly different behaviors that hold only the name of their 'investigator' in commo. Real acousticians are well aware of both and employ them each properly.


Edited by dragonfyr - 6/6/12 at 7:50pm
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post #34 of 868
6/4/12 at 2:15pm
Quote:
Originally Posted by Ethan Winer View Post

You can measure RT60 in any room.

Reverberation is not a 'thing' that is directly measured.

It is a derivative calculation made based upon the identification of various variables derived from other direct measurements. This should be obvious to anyone who has spent any time making measurements of various small acoustical spaces where the spaces are dominated by not one, but multiple regions comprised of distinctly different slopes; including those commonly created by rooms exhibiting coupled spaces - easily providing significant sources of for the erroneous automatic determination of RTxx calculation based upon algorithms that by virtue of their limited programming are obliged to select data points regardless of the context in which they occur.

The first of two requirements for the determination of valid RTxx measurements are that "the RT60 is a measurement of the decay time of a well-mixed (statistically homogeneous) reverberant sound field well beyond Dc."

This requirement takes precedence over the second condition which states that "the RT60 is the time in seconds for the reverberant sound field to decay 60 dB after the sound source is shut off."

BOTH must be satisfied. You cannot simply and arbitrarily employ one and ignore the other!

Thus, if you take values and plug them into a formula that by definition assumes REQUIRED conditions not in evidence, the results are garbage!

The result is NOT subject to legitimate sources of error, but to that which constitutes a logical MISTAKE.


This is all well defined in acoustics. And likewise the "professional" and academic realm of acoustics addressed the topic in excess of 30+ years ago as well, only to have far too many 'apologists' simply pay lip service to the correct use of the term as they then casually persist in perpetuating the erroneous and misleading characterization of behavior in the form of misleading slang that serves only to further confuse those who would most benefit in understanding its proper use and implications!

And in keeping with the real meaning of a reverberant soundfield, I defy one to show me a small acoustical space where, in directly measuring the specular behavior at any spot, it can be said that the specular density is SO complexly developed that one CANNOT resolve a specular reflection into the constituent vector characteristics of gain and direction, thus leading us to conclude that the probability of the direction of arrival at that given point for the arriving energy is EQUALLY probable from EVERY direction simultaneously! As that is what a reverberant sound field literally implies!

...And meanwhile we are stuck in small acoustical spaces where we are literally hard pressed to maintain a later arriving sound field that is supported by even just a 3rd order reflection!

It serves no constructive purpose to perpetuate the ongoing perversion  (edit to add "of" ->) of a well understood definition of physical behavior via the use of jargonized colloquial slang similar to the  erroneous use of the term "reverb" as an FX associated with an amplifier knob.


Edited by dragonfyr - 6/6/12 at 6:07am
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post #35 of 868
6/4/12 at 5:22pm
Quote:
Originally Posted by dragonfyr View Post


Reverberation is not a 'thing' that is directly measured.

It is a derivative calculation made based upon the identification of various variables derived from other direct measurements. This should be obvious to anyone who has spent any time making measurements of various small acoustical spaces where the spaces are dominated by not one, but multiple regions comprised of distinctly different slopes; including those commonly created by rooms exhibiting coupled spaces - easily providing significant sources of for the erroneous automatic determination of RTxx calculation based upon algorithms that by virtue of their limited programming are obliged to select data points regardless of the context in which they occur.

The first of two requirements for the determination of valid RTxx measurements are that "the RT60 is a measurement of the decay time of a well-mixed (statistically homogeneous) reverberant sound field well beyond Dc."

This requirement takes precedence over the second condition which states that "the RT60 is the time in seconds for the reverberant sound field to decay 60 dB after the sound source is shut off."

BOTH must be satisfied. You cannot simply and arbitrarily employ one and ignore the other!

Thus, if you take values and plug them into a formula that by definition assumes REQUIRED conditions not in evidence, the results are garbage!

The result is NOT subject to legitimate sources of error, but to that which constitutes a logical MISTAKE.

This is all well defined in acoustics. And likewise the "professional" and academic realm of acoustics addressed the topic in excess of 30+ years ago as well, only to have far too many 'apologists' simply pay lip service to the correct use of the term as they then casually persist in perpetuating the erroneous and misleading characterization of behavior in the form of misleading slang that serves only to further confuse those who would most benefit in understanding its proper use and implications!

And in keeping with the real meaning of a reverberant soundfield, I defy one to show me a small acoustical space where, in directly measuring the specular behavior at any spot, it can be said that the specular density is SO complexly developed that one CANNOT resolve a specular reflection into the constituent vector characteristics of gain and direction, thus leading us to conclude that the probability of the direction of arrival at that given point for the arriving energy is EQUALLY probable from EVERY direction simultaneously! As that is what a reverberant sound field literally implies!

...And meanwhile we are stuck in small acoustical spaces where we are literally hard pressed to maintain a later arriving sound field that is supported by even just a 3rd order reflection!

It serves no constructive purpose to perpetuate the ongoing perversion a well understood definition of physical behavior via the use of jargonized colloquial slang similar to the similarly erroneous use of the term "reverb" as an FX associated with an amplifier knob.

Are you a pro or a hobbyist?
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post #36 of 868
6/6/12 at 2:56pm
Quote:
Originally Posted by dragonfyr View Post

It is rather scary to think that one would make such a fundamental error!

I honestly don't know what your point is, or your motive, but insults are inappropriate and unnecessary.

--Ethan
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post #37 of 868
6/8/12 at 11:45am
It never seemed like rocket science to me. If you know the level of the sound impulse and when it stops, and have accurate measuring gear, identifying the point in time when the SPL in the room is 60 dB below the initial sound is pretty straightforward. mORE Complex is understanding all the details of the reverberation patterns in specific rooms, but that's really a different matter, more relevant to folks who are trying to create real sounding digital reverbs . . . .
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post #38 of 868
6/9/12 at 11:23am
Quote:
Originally Posted by JHAz View Post

It never seemed like rocket science to me. If you know the level of the sound impulse and when it stops, and have accurate measuring gear, identifying the point in time when the SPL in the room is 60 dB below the initial sound is pretty straightforward. mORE Complex is understanding all the details of the reverberation patterns in specific rooms, but that's really a different matter, more relevant to folks who are trying to create real sounding digital reverbs . . . .

"If you know the level of the sound impulse and when it stops, and have accurate measuring gear, identifying the point in time when the SPL in the room is 60 dB below the initial sound is pretty straightforward."

The problem is that most would assume that this corresponds to an RT60 calculation, when in fact it does NOT.

What you describe can be easily measured by the use if an impulse response and elaborated upon by the convolution of the RIR (room impulse response) into any of its myriad frames of reference as defined in the Domain map that well illustrates and defines all of the relationships of the various measurable perspectives in both the time and frequency domains.

Unfortunately, the fact that a simple programmed calculation can spit out a number based on the selection of 2 data points does not insure that the prerequisite requirements for the existence of a reverberant sound field exist. And if they do not the calculation is spurious. And yet in the well established fact that significant statistically homogeneous reverberant sound fields do not exist at the frequencies of concern nor at significant gain levels above the ambient noise floor, many blindly attempt to make the number indicate something that is simply does not.

In lieu of a calculation that assumes a soundfield so complex that we cannot identify the vector orientation nor gain of any individual sound path as the definition assumes a complexity of the arriving sound energy such that it is equally probable that the energy arrives equally from ALL directions SIMULTANEOUSLY at ANY given point in the room, what we have in reality in a small acoustic space is a space where each point in the room exhibits a unique combination of finite energy arrivals of various gains and orientations. And that at any point this combination will be different than the point next to it. Thus we have a space defined, NOT by a uniform statistically uniform behavior, but by a locally variable set of contributing factors that must be properly addressed based upon the actual real variables.

This leads to the surgical placement of various appropriate treatments designed to modify the energy paths (e.g. reflection/redirection and diffusion) or to reduce the energy transmission (e.g. absorption).

If the room exhibited a homogenous reverberant sound field - and if such were a factor, it would assume that the listening position was beyond the critical distance (Dc) whereby the gain level of the direct and reverberant field were equal (a point that does NOT exist in a small acoustical space) and all we would have to do to control the room response would be to apply a broadband absorption to a certain percentage of the reflective boundary area. And such, while all too often done, is NOT an appropriate optimal treatment policy.

The fact remains, that while the RTxx calcs are a commonly tossed about metric that are VERY useful in large acoustical spaces, they have no practical application in small acoustical spaces where there exist much more accurate, descriptive and actionable metrics of real room behavior such as the waterfall/cumulative spectral decay(CSD) for modal behavior, and the envelope time curve (ETC) for specular analysis and the energy distribution time curve (EDT). And in a small acoustical space, the awareness of and the appropriate treatment of the locally variable behavior is of critical concern.

Unfortunately, the term 'reverb' as an electrical FX has been engrained in us for as long as I can remember, as jut about every guitar amplifier from the '60's on came with a "reverb' adjustment. (Most also came with a "tremolo" adjustment, and I am almost surprised that people, in the name of consistency, do not ask about tuning the "tremolo" of the room as well!)

But the fact is, that such FX adjustments about which all are familiar are simply delay, and they are NOT acoustical reverberation - a fundamental difference that seems lost on most. And simple persistence in decay as adjusted by a delayed decay is NOT acoustical reverberation.

Thus, the leap from the understanding of an FX colloquially used as slang to the strictly defined acoustical behavior known as reverberation is simply unfounded and a MISTAKE.

The fact is, we now have the tools and , if availed, the understanding to move beyond the misuse of slang terms and to properly understand the acoustical behavior of spaces and to use the proper tools to both ascertain and investigate the actual behaviors in spaces. Its long past time that we begin to do so, even if it means that some old habits must change.

To quote John Murray, a prominent engineer and experienced acoustician (I refrain from saying "professional" as was asked earlier, as there are plenty of folks who take money for their opinions but whom are neither formally trained nor very knowledgeable about the actual and current science of acoustics - a quality often dismissed that far exceeds and transcends the designation of "professional"...):


"Question: If I want to measure an acoustic parameter such as RT60 or frequency response in a small room like a home theatre or a recording studio, can I use a (SIA) SMAART Live acoustic-based (computer) measurement system? D...M...

Answer: A small room really doesn’t have an RT60 (reverberation time). Reverberation time requires an even slope of level decay, which is a smoothly sloping, dense field of reflections that has an even and measurable drop in level with respect to time. This smooth decay slope is what determines how many seconds it takes the sound to drop by 60 dB (RT60).

Without a dense field of decaying reflections, RT60 cannot be determined. A small room only has relatively few early reflections before the sound dies altogether. You may be able to get some measurement systems to produce a number for RT60, but this really is meaningless until you get to larger rooms with a mathematically statistical (sufficiently dense) decay field.

See figures Small Room 1, 2, & 3 (below). Note that a variation of only 0.24 seconds in RT60 indicates more than a 50 percent difference in room absorption, comparing the shortest calculation to the longest ( 0.47 and 0.71 seconds). All that was done differently in the three small room RT60 calculations was to change the data points that determine the calculations.

(Illustrations and the specifics of examples are omitted...)

Now, see figures Large Room 1, 2 & 3 (below). The data point selections still produced a 0.26 seconds variation, but this is only a four percent difference in room absorption rates. This is a much more reliable variation and will be much more useful as a predictive tool.

(Illustrations and the specifics of examples are omitted...)

I would advise against using RT60 calculations as a valuable measurement for rooms as small as home theaters and recording studio control rooms. It’s better to pay attention to room modes and flat or concave reflective surfaces within the room than to rely upon RT60 numbers.

In addition, no acoustic space has a single, overall frequency response. A room does impart an acoustic signature on a signal source, and it is called the impulse response.

This is the character that a room, a loudspeaker or even an electronic effects box applies to a neutral impulse source. If you have a perfectly neutral impulse, test loudspeaker and measurement microphone, and capture the reproduced impulse on an oscilloscope, this will “trace” the impulse response of the room relative to the position of the test loudspeaker and measurement microphone.

Unlike an effects box (or, to a lesser extent, a loudspeaker within its coverage pattern), a room imparts an infinite number of unique impulse responses for every point in the room. Every position has its own unique pattern of reflections in time and level, and therefore also has a unique impulse response. Some software packages can actually extrapolate a room’s impulse response for a given point in a room, and this can be applied to an anechoic recording. It can be heard binaurally (in stereo) on headphones as if located in the stereo recording microphone’s position with the source at the test loudspeaker’s position. This can sound very realistic. "



Likewise, a portion of Sound System Engineering the 2nd edition of which was published 25 years ago in 1987 regarding this topic is posted below that also makes reference to the work done by the esteemed Dr. Ted Schultz (whom some may also know by his definitive work on the design of perforated treatments and absorbers...) formerly of Bolt, Beranek and Newman. Again, this debate focuses on an OLD topic that was long ago properly put to bed in the professional and academic environments that included AES and ASA; yet the same misunderstanding that was the subject of a debate long since retired persists today in the form of misapplications of the term as slang along with footnotes that the RTxx do not properly apply to a non-existent reverberant field in a small acoustical space, while at the same time such sources ironically then actively proceed to violate the terms of their own pronouncement...as if calculations erroneously derived from behavior that do not meet the required criterion for said calculations can simply be used anyway... Unfortunately, that is NOT 'valid' acoustics, but rather nonsense.

It's long past time that we catch up to where the real and qualified acousticians were 25-35 years ago and both understand the nature of the acoustical behavior and apply the correct terms (and available tools) properly! ...Especially as the improper use of terms assuming behaviors not in evidence lead to mistakes in treatment.

SSE2ndEd..Davis,p.211,.png 76k .png file

edit: grammar
Edited by dragonfyr - 6/10/12 at 1:46pm
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post #39 of 868
6/17/12 at 4:52am
Quote:
Originally Posted by Ethan Winer View Post

I honestly don't know what your point is, or your motive, but insults are inappropriate and unnecessary.
--Ethan

I don't know what dragon's point is either. I think he's a professional hair-splitter.

All I know is, I've had to move several times in my life. An empty room echoes like crazy. A furnished room echoes less. And when I put up DIY mineral wool panels in my home theater, it barely echoes at all. According to RoomEQ Wizard, my room was measuring at .5 before I started. Now, my TopT, EDT, T20, and T30 (all listed under a tab labeled "RT60" in REQ) are all at about .2S down to 200Hz. TopT and T30 are about .4 from 100-200Hz, and my T20 and EDT is .2 down to 100Hz. Bass absorbers are planned.

If we were to listen to some people around here, those measurements are all meaningless. But strangely enough, they correlate to what I hear - much less reverb, or echo, or whatever in my room. I'll even use the cliche "My wife could tell the difference" because it's true. So this is not some esoteric "Monster Cable sounds better than 12ga zip cord" comparison, but a very real, definitely audible difference. That includes what I'm hearing from my speakers. Movies and music sound clearer. Also, I can have the volume turned up louder without it sounding "loud" since there is less echoes.

I guess it's just coincidence that what I'm hearing agrees with the measurements.
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post #40 of 868
6/17/12 at 6:55am
Quote:
Originally Posted by DanLW View Post

I don't know what dragon's point is either. I think he's a professional hair-splitter.
All I know is, I've had to move several times in my life. An empty room echoes like crazy. A furnished room echoes less. And when I put up DIY mineral wool panels in my home theater, it barely echoes at all. According to RoomEQ Wizard, my room was measuring at .5 before I started. Now, my TopT, EDT, T20, and T30 (all listed under a tab labeled "RT60" in REQ) are all at about .2S down to 200Hz. TopT and T30 are about .4 from 100-200Hz, and my T20 and EDT is .2 down to 100Hz. Bass absorbers are planned.
If we were to listen to some people around here, those measurements are all meaningless. But strangely enough, they correlate to what I hear - much less reverb, or echo, or whatever in my room. I'll even use the cliche "My wife could tell the difference" because it's true. So this is not some esoteric "Monster Cable sounds better than 12ga zip cord" comparison, but a very real, definitely audible difference. That includes what I'm hearing from my speakers. Movies and music sound clearer. Also, I can have the volume turned up louder without it sounding "loud" since there is less echoes.
I guess it's just coincidence that what I'm hearing agrees with the measurements.

It is readily apparent that you (and SO many others) do not understand the "point"...

But of course you proceed to observe that "an empty room echoes like crazy".

But the fact that you hear discrete echoes is PRECISELY why your understanding is flawed! As if there was a true reverberant field, what you would hear instead would be a smooth exponentially decaying soundfield INSTEAD of a discrete echo! The ecgho is precisely the result of a sparse NON-reverberant specular soundfield!

"I guess it's just coincidence that what I'm hearing agrees with the measurements." Really!?! So at every spot in the room, you achieve the same result which corresponds to the same measurement? And you do NOT gear an echo but a smoothly decaying soundfield? And your ETCs will be identical at every spot? And every spot sounds the same? No modal variation or variation in specular behavior? REALLY???? Nonsense.

You see, that localized variation is PRECISELY the aspect that invalidates the use of RTxx calculations in a small acoustical space!

What distinguishes such sites as this is the number of folks who, instead of noting distinctions about which they may not have been previously aware, how they take great pride in persisting in misusing concepts as slang and instead persist in using incorrect measurements to characterize behavior that which does not legitimately exist. As after all, when one pushes the button, the machine gives me a number!!!!

You see, as Ethan correctly pointed out earlier: "You can measure RT60 in any room. The issue is whether what's measured reflects true reverb."

And the fact is, it does not - and there are better, more appropriate measurements that provide more accurate actionable results, whereas the RTxx calculation made in the space is NOT accurate nor valid.....regardless of how much one's ignorance of the distinction allows them to willfully ignore reality and the actual science of acoustics as opposed to unsubstantiated belief.

No one debates the existence or persistence of excessively hot specular reflections! Nor of modal variations! In fact we assert this to be the case!
And the waterfall/CSD and the ETC easily enables one to both identify and to resolve each of these!

But in acoustics (as opposed to forums where few have any interest in actually studying or learning about actual acoustics and where marketing brochures substitute for reading actual acoustics texts - I know, I know, but they have math in them...), words have meaning. And what you and others describe is NOT a reverberant soundfield. And like it or not, the calculations that others are want to toss about as slang do NOT apply to a small acoustical space dominated by excessive localized specular reflections, regardless of how much you simply want to use terminology as slang and pretend that the real distinctions do not exist.

I am sorry that you and others who claim to know fail to recognize the point and as a result fail to use terminology and derivative calculations correctly - as RTxx are NOT direct measurements but calculations based upon measurements that assume the actual existence of a very specific behavior. And the fact that software packages now spit out a number regardless of the actual behavior simply means that it is the responsibility of the operator to correctly understand and to make determinations about the behavior in a space in order to apply various calculations correctly. But apparently, in an age when software spits out numbers without regard to actual behavior, and operators fail to have an actual grasp of the underlying acoustics, if a tool spits out numbers, they must mean something, right? Even if the meaning is that the operator is clueless as to what the numbers really mean - or do NOT mean! But hey, they are numbers! So it must be real!

I am sorry that the distinction between a statistically homogenous soundfield as compared to a space dominated by regionally variable specular reflections - regardless of how hot they are - is sooooo complicated to understand. The fact is, in a small acoustical space dominated by the later you do not have a one number calculation that describes the entire room.

So if "hairsplitting" means making a distinction between an actual understanding of acoustical concepts and correctly applying tools actually suited to real behavior, fine. At least it is not the willful ignorance whereby we use very specifically defined terms as slang and willfully choose to misapply calculations simply because a piece of software will blindly kick out a number when a button is pushed and the operator is not as smart as the tools they use.

But as you yourself have stated: "I don't know what dragon's point is either." Unfortunately, that pretty much sums up the problem. Even when that point is also presented by such folks as Dr. Ted Schultz, Don Davis and John Murray... And besides, one's amp and FX module also have knobs labeled as "reverb", so the resulting FX generated must be a real reverberant sound field where decay is mistaken for reverberation!!! I am amazed no one has suggested using them to adjust the RTxx calculation in the room!....
Edited by dragonfyr - 6/17/12 at 6:32pm
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post #41 of 868
6/17/12 at 11:32am
Quote:
Originally Posted by DanLW View Post

I don't know what dragon's point is either. I think he's a professional hair-splitter.

I see that often in forums - posts by people who read all the technical books, but have no practical experience. Another clue is when posts go on forever with endless minutiae that misses the big picture.
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If we were to listen to some people around here, those measurements are all meaningless. But strangely enough, they correlate to what I hear - much less reverb, or echo, or whatever in my room.

Exactly. This coincides with research done by the Harmon guys, Sean Olive and Floyd Toole. They found a strong correlation between good specs and people's preferences. So it's not at all a coincidence that your hearing agrees with the measurements!

--Ethan
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post #42 of 868
6/17/12 at 1:20pm
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Originally Posted by Ethan Winer View Post

I see that often in forums - posts by people who read all the technical books, but have no practical experience.

that's funny - i wouldn't consider experience utilizing measurement tools in spaces of which they are not valid very "practical".

Quote:
Originally Posted by Ethan Winer View Post

Another clue is when posts go on forever with endless minutiae that misses the big picture."

sorry, but the "big picture" that is missed here falls with your commentary that rt60 is in any way relevant to our residential spaces. it merely displays a lack of understanding of the measurement/calculations, how they are generated, and the requirements for such data to be considered valid. what good is practical experience if the tools being deployed produce invalid data. garbage in garbage out.

curious if you are you able to respond to my post?: http://www.avsforum.com/t/1413173/does-sound-sounds-better-in-a-room-full-of-furniture-and-stuff-or-without/30#post_22099490

did you take those rt60 measurements past Dc?
did you take those rt60 measurements with an omni-source?

*both* are requirements for rt60, fyi.

if you're interested in the topic further, i recommend Sound System Engineering by Davis/Patronis. it will explain in detail how rt60 is to be measured for the data to be considered valid.

your rt60 graphs in post #15 does not in any way indicate that you have "true reverb" at the higher frequencies as you have stated. im curious if you could define how one measures if they have 'true reverb' in their acoustical space at all?
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post #43 of 868
6/17/12 at 1:28pm
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Originally Posted by dragonfyr View Post

"I guess it's just coincidence that what I'm hearing agrees with the measurements." Really? So at every spot in the room, you achieve the same measurement? And your ETCs will be identical at every spot? And every spot sounds the same? No modal variation or variation in specular behavior? REALLY???? Nonsense.

it's been over 4 decades. when do you think this information regaridng basic acoustical behavior will start trickling down to the self-proclaimed "acoustical specialists"?
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Originally Posted by dragonfyr View Post

And the waterfall/CSD and the ETC easily enables one to both identify and to resolve each of these!.

remember also, we have acoustic specialists here that think the waterfall/CSD is "time-domain". tongue.gif:p
Edited by localhost127 - 6/17/12 at 2:04pm
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post #44 of 868
6/17/12 at 1:40pm
Quote:
Originally Posted by Ethan Winer 
I see that often in forums - posts by people who read all the technical books, but have no practical experience. Another clue is when posts go on forever with endless minutiae that misses the big picture.
I see that often in forums - posts by people who read all the technical books, but have no practical experience. Another clue is when posts go on forever with endless minutiae that misses the big picture.

Not bad for a guy who only discovered measurements in the form of ETF around 2005, while some of us were doing them in the mid 80's with a TEF. But you do come close to embodying exactly your description?

And your formal training in acoustics occurred when and where? And your introduction to MEANINGFUL measurements occurred when?

And your basis for selling absorption was based upon what??? I am curious, just what original (LOL!) research was it based upon?

You mean the research of those SynAudCon guys with TEFs in the 80's and the article Don published in Audio that was largely responsible for people discovering the the influence of those "bad reflections" that led so many (who failed to descern the qualifications therein) on a 15-20 year quest to eliminate all reflections with the proponents of this approach based upon their misguided and overly simplistic misinterpretation that all reflections were bad and which resulted in the laughable erroneous proclamation that one could not use too much absorption????

You should have read a bit more, as Don never said nor implied that, as you would have known had you actually participated in the research! But you were no where to be found!

And that was all because they read a small article out of context and misunderstood the larger total picture of what was proposed regarding the tuning of spaces and used this misunderstanding to build businesses.

Impressive.

The fact is, those you accuse of having no practical experience were farther ahead in not only the formal and theoretical , but in the practical applied arena before you ever read the article and began to make a panel. But now, like then, you're great at making unsubstantiated innuendos based on an incomplete understanding of not only acoustics and what others have done.

And ironically it is those who lack the formal education in acoustics and who lack real meaningful practical experience who fail to understand the meaning of the measurements and thus fail to use the actual measurements that DO accurately represent the actual behavior. But with such a philosophy, its no wonder so many wander about claiming that measurements have no correlation with actual behavior, based upon the mistakes and erroneous applied assumptions. But in that respect, quite a few have LOTS of experience. Take a bow. You've earned it.

But hey, what does one really need to know about acoustics, when one has played an instrument and is selling stuff to primarily to others who play instruments - while both groups eschew a knowledge of as well as any attempt to actually learn acoustics. Not to mention actively debating efforts to clarify and to correct the misapplication of concepts and tools when given the chance.

So isn't is interesting to watch those who misuse terminology and measurements make claims that it is not necessary to actually understand and apply acoustics properly. Now THERE'S a claim to fame you can properly hang on your website!

But hey, keeping that bar low and pandering to those who eschew the proper use of terminology and concepts sure makes it easier to sell stuff to that crowd, doesn't it!?

After all, properly understanding acoustical concepts such as reverberation just confuses that crowd and makes the "you can't have too much absorption" message even more absurd and difficult to sell.

So go ahead and complain about this post as you so often do - but it would be even more impressive if you chose to actually find one factually erroneous statement.

And its even funnier to watch you declare those Bolt Beranek and Newman boys and other esteemed literally world class acousticians to be wrong as well - especially if one bothers to take the time to learn who just a few of those associated with them are...!
Edited by dragonfyr - 6/17/12 at 2:24pm
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post #45 of 868
6/17/12 at 1:43pm
Quote:
Originally Posted by dragonfyr View Post

Not bad for a guy who only discovered measurements in the form of ETF around 2005, while some of us were doing them in the mid 80's with a TEF. But you do come close to embodying exactly your description?
And your formal training in acoustics occurred when and where? And your introduction to MEANINGFUL measurements occurred when?
And your basis for selling absorption was based upon what??? I am curious, just what original (LOL!) research was it based upon?
You mean the research of those SynAudCon guys with TEFs in the 80's and the article Don published in Audio that was largely responsible for people discovering the the influence of those "bad reflections" that led so many (who failed to descern the qualifications therein) on a 15-20 year quest to eliminate all reflections with the proponents of this approach based upon their misguided and overly simplistic misinterpretation that all reflections were bad and which resulted in the laughable erroneous proclamation that one could not use too much absorption????
You should have read a bit more, as Don never said nor implied that, as you would have known had you actually participated in the research! But you were no where to be found!
And that was all because they read a small article out of context and misunderstood the larger total picture of what was proposed regarding the tuning of spaces and used this misunderstanding to build businesses.
Impressive.
The fact is, those you accuse of having no practical experience were farther ahead in not only the formal and theoretical , but in the practical applied arena before you ever read the article and began to make a panel. But now, like then, you're great at making unsubstantiated innuendos based on an incomplete understanding of not only acoustics and what others have done.
And ironically it is those who lack the formal education in acoustics and who lack real meaningful practical experience who fail to understand the meaning of the measurements and thus fail to use the actual measurements that DO accurately represent the actual behavior. But with such a philosophy, its no wonder so many wander about claiming that measurements have no correlation with actual behavior, based upon the mistakes and erroneous applied assumptions. But in that respect, quite a few have LOTS of experience. Take a bow. You've earned it.
But hey, what does one really need to know about acoustics, when one has played an instrument and is selling stuff to primarily to others who play instruments - while both groups eschew a knowledge of as well as any attempt to actually learn acoustics. Not to mention actively debating efforts to clarify and to correct the misapplication of concepts and tools when given the chance.
So isn't is interesting to watch those who misuse terminology and measurements make claims that it is not necessary to actually understand and apply acoustics properly. Now THERE'S a claim to fame you can properly hang on your website!
But hey, keeping that bar low and pandering to those who eschew the proper use of terminology and concepts sure makes it easier to sell stuff to that crowd, doesn't it!?
After all, properly understanding acoustical concepts such as reverberation just confuses that crowd and makes the "you can't have too much absorption" message even more absurd and difficult to sell.
So go ahead and complain about this post as you so often do - but it would be even more impressive if you chose to actually find one factually erroneous statement.
And its even funnier to watch you declare those Bolt Beranek and Newman boys and other esteemed literally world class acousticians to be wrong as well - especially if one bothers to take the time to learn who just a few of those associated with them are...!

remember, dragon - it seems none of these vendors really want to show their customers how to utilize the ETC to identify the ACTUAL high-gain early arriving reflection points - because doing so would surgically limit the amount of required specular broadband absorption within the room (eg, only applying 'treatment' at specific, measured problem areas - not blindly applying absorption at any and all POSSIBLE reflection points)...which means less acoustical products sold.

maybe that's why the "mirror" is one of the more popular "measuring tools" on this forum :P
Edited by localhost127 - 6/17/12 at 2:28pm
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post #46 of 868
6/17/12 at 2:22pm
Quote:
Originally Posted by localhost127 View Post

maybe that's why the "mirror" is one of the more popular "measuring tools" on this forum :P

Yeah.... "the mirror"...

An exercise first used by Don Davis in the late 1970s and early 1980s to illustrate the concept of specular reflections (while introducing the ETC measurement) that in itself, unlike the ETC, was specifically fatally flawed in that it cannot distinguish between actual and possible indirect paths (as well as diffractive pathways) of specular energy, leading to the over treatment of a space (and to missing other important early paths in the case of diffraction). And hence the value and one of the practical applications for use of the ETC...

(Note: Ethan wasn't there either...)

But hey, why confuse folks with the facts?

Just another case of why learn from the example and become familiar with and then use the proper tool for the job, when we can be lazy and use a fundamentally flawed substitute that literally results in mistakes being made. But heaven forbid someone should challenge the improper use of a flawed tool (or concept - ironically in the "theory" section of a forum) that results in actual mistakes in treatment??? Such information simply further confuses those who prefer to continue willfully confused...

After all, a reflection is a reflection!

....And we have got to sell absorption!


But whatever, don't clarify concepts and help folks to learn the proper concepts and use of terminology (as it it has actual meaning!).
Let's just continue to obfuscate the situation and perpetuate misunderstanding and the improper use of tools that give misleading and erroneous readings rather that explain and suggest to folks the better and proper tools that will actually lead to a more precise understanding of complex behavior that can augment the precise analysis treatment of problems.

We certainly wouldn't want that! Especially as so many of the self-proclaimed authorities neither properly understand nor explain the concepts, nor the use and interpretation of the proper corresponding measurements.
Edited by dragonfyr - 6/17/12 at 6:03pm
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post #47 of 868
6/17/12 at 5:55pm
to the OP - if you're still around:

Here's a very informative primer (from a company that also sells acoustical engineering - and I *do* see Ethan's tutorials as educational.) be sure to click the links (modes, reflections, objects, putting it all together) on the left side of the page.

http://www.rivesaudio.com/resources/listening_room/frame.html

HTH.
Edited by citizen arcane - 6/17/12 at 6:01pm
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post #48 of 868
6/17/12 at 6:09pm
Quote:
Originally Posted by citizen arcane View Post

to the OP - if you're still around:

This site.........a question is rendered, then there is two weeks of posturing and dissimulation; the OP clicks off without a reasonable answer...........
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post #49 of 868
6/17/12 at 6:36pm
The original question was answered long ago.

What continues is proof that formal concepts, their application along with their accompanying measurements and calculations, are not properly understood.

And to the degree that you have missed that, can we assume that you are also not aware of the distinction?
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post #50 of 868
6/17/12 at 7:11pm
Quote:
Originally Posted by dragonfyr View Post

The original question was answered long ago.
What continues is proof that formal concepts, their application along with their accompanying measurements and calculations, are not properly understood.
And to the degree that you have missed that, can we assume that you are also not aware of the distinction?

...........dunno, mebbe it was lost in the crossfire, sheesh................
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post #51 of 868
6/18/12 at 9:18am
Quote:
Originally Posted by Ethan Winer View Post

I see that often in forums - posts by people who read all the technical books, but have no practical experience.

I should have added "And claim to be knowledgeable professionals yet they hide behind screen names and their forum profiles are empty." biggrin.gif

--Ethan
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post #52 of 868
6/18/12 at 2:32pm
Quote:
Originally Posted by localhost127 View Post

remember, dragon - it seems none of these vendors really want to show their customers how to utilize the ETC to identify the ACTUAL high-gain early arriving reflection points - because doing so would surgically limit the amount of required specular broadband absorption within the room (eg, only applying 'treatment' at specific, measured problem areas - not blindly applying absorption at any and all POSSIBLE reflection points)...which means less acoustical products sold.
maybe that's why the "mirror" is one of the more popular "measuring tools" on this forum :P

If one were to "surgically" treat their room, wouldn't they need to have their listening position in the same surgically accurate area? What does that do to all the other listening positions in a home theater room? Sure, you could surgically treat a room if you sat in the exact same spot every single time. But for those of us with families, we want every seat to be a good seat, and ideally no bad seats.

And the fact remains, my room definitely sounds much better with treatments. As for the measurements, no, it isn't measured from the same spot every time. Measurements I took were over the course of several months. But the trend was the same, and it matches up with what I hear - less echoes.

So what am I hearing? Are you saying the treatments are no good and have really made no difference? That I've fooled myself into thinking there is a huge positive difference in the way my room sounds? If Ethan's products are worthless, (and consequently my DIY knockoffs even more so), why are people's home theaters / listening rooms sounding so much better?
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post #53 of 868
6/18/12 at 3:32pm
Quote:
Originally Posted by DanLW View Post

If one were to "surgically" treat their room, wouldn't they need to have their listening position in the same surgically accurate area? What does that do to all the other listening positions in a home theater room? Sure, you could surgically treat a room if you sat in the exact same spot every single time. But for those of us with families, we want every seat to be a good seat, and ideally no bad seats.

and where was it stated such process is only valid or a single listening position?

Quote:
Originally Posted by DanLW View Post

And the fact remains, my room definitely sounds much better with treatments.
Quote:
Originally Posted by DanLW View Post

So what am I hearing? Are you saying the treatments are no good and have really made no difference? That I've fooled myself into thinking there is a huge positive difference in the way my room sounds? If Ethan's products are worthless, (and consequently my DIY knockoffs even more so), why are people's home theaters / listening rooms sounding so much better?

just what are you on about? my quote didn't make any reference to you, your treatments, or your perceived difference in response. are you sure you've meant to respond to me?

the discussion here is in response to those making an attempt to claim that RTxx calculations are in any way valid to small acoustical spaces of which lack a statistically random-incidence reverberant sound-field.
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post #54 of 868
6/18/12 at 4:09pm
Quote:
Originally Posted by dragonfyr View Post

Manfred Schroeder defined the large room frequency, and derivatively, the volume of a room necessary to support a reverberant field at the large room frequency and above.


There is NO reverberant sound field below that frequency.


Since we are concerned with volume, and using a generally accepted breakpoint value for RT of 1.6 seconds:



Volume = K^2 (RT60/(Lg Room freq^2))


K in SI (metric) is 2000 and 11,885 in imperial/US terms


Thus,

for 300 Hz and above, the room must be a MINIMUM of :


(11,885)^2 (1.6/(300^2)) = 2511.168 or

2511 ft^2


When someone has a room larger than 2511 ft^2 and is ONLY concerned with reverberant times ABOVE 300 Hz, determined properly - NOT with a directional home speaker but with a true omni-directional source stimulus - call me.


In a space less than that volume, you are necessarily dealing instead with non-homogenous locally variable combinations of modal and specular distributions. Any single generalized number value one tries to use to characterize the space is inaccurate at almost every single point in the room. And any point at which it might coincide is purely serendipitous.


Until then, believe whatever you like - seeing as how the root of the word "belief" is appropriately "to wish it so"...

As long as we are picking nits, there seems to be an error in your calculation. 2511 ft^2 would be a measure of surface area, not a measure of volume.
Rooms larger than 2511 ft^3 are not uncommon.

I think I agree with your point. Most homes deal with modal and specular distributions, so reverberant field nomenclature is probably not appropriate. But I would argue that decay time is still a useful concept in almost any room. But I'm not going to argue too hard - it is not worth my time
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post #55 of 868
6/18/12 at 5:48pm
Yes, in haste that was a typing error. Thanks. Unfortunately the larger concept is what continues to escape the majority.
(In fact, if you (like a few others are) were aware of how atrocious my typing skills are in chat sessions, you would instead be expressing amazement that I was able to state any of the rest of the post in a form other than code...rolleyes.gifwink.gifbiggrin.gif

NO ONE debates that the persistence of energy in a small space is not important! That continuing misnomer simply illustrates how misguided this entire debate is and just how much folks who do not understand this have to learn!

In fact we argue quite the opposite!

But the answer is not to blindly use inappropriate tools based on the erroneous assumption of the existence of effectively non-existent behavior!

So understand the PROPER concepts and the PROPER tools to evaluate the time domain behavior of specular energy with respect to gain and time!

And the RTxx calculations are NOT the correct tool, nor do they describe the correct corresponding behavior.
Edited by dragonfyr - 6/18/12 at 5:56pm
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post #56 of 868
6/18/12 at 5:53pm
Quote:
Originally Posted by DanLW View Post

If one were to "surgically" treat their room, wouldn't they need to have their listening position in the same surgically accurate area? What does that do to all the other listening positions in a home theater room? Sure, you could surgically treat a room if you sat in the exact same spot every single time. But for those of us with families, we want every seat to be a good seat, and ideally no bad seats.

And the fact remains, my room definitely sounds much better with treatments. As for the measurements, no, it isn't measured from the same spot every time. Measurements I took were over the course of several months. But the trend was the same, and it matches up with what I hear - less echoes.

So what am I hearing? Are you saying the treatments are no good and have really made no difference? That I've fooled myself into thinking there is a huge positive difference in the way my room sounds? If Ethan's products are worthless, (and consequently my DIY knockoffs even more so), why are people's home theaters / listening rooms sounding so much better?

And after this all you have gotten is that I am against treatment and such advanced concepts as the existence of reverberant sound fields in small rectangular rooms in acoustics. LOL!

While I appreciate your 'enthusiasm', you suffer from numerous misunderstandings of terms, acoustical response models, process and methodology, and goals. The fact is that your observations and conclusions could not be further from what is accurate in that analysis, just as are your conclusions about proposed acoustical methods - not to mention the specific misapplication of large acoustical model behavior with that of small acoustical space behavior.

You see, echoes are NOT diffuse behavior nor reverberation, despite how passionately you are want to equate the two. In fact, echoes are the 'opposite' of statistically diffuse reverberation in that they are focused specular behavior that exhibits a finite defined propagation path; which can be addressed in a number of ways including if that path is disrupted by absorption or diffusion, and where if the energy of said echo is dissipated by diffusion, the diffuse field is increased, not decreased!!

And such localized specular behavior is best examined via the ETC in terms of arrival time, gain, and propagation path. An echo is ANYTHING BUT reverberation! This irony of this confusion and the failure of your resources to explain this indicated a fundamental problem. ...Not to mention that discreet "echoes" are typically classified as reflections arriving after ~80 ms. ...And reflections are not correctly termed 'echoes'.

But as you may or not be aware, I was the one largely responsible for introducing the measurement called the ETC to several forums. Ironic at best as the measurement has literally been a fundamental fixture in real acoustical circles for more than 30 years. And even more ironic has been the EXTENSIVE backlash by in large the SAME folks who have not been aware, conversant, nor users of the tools.

The primary purpose of said measurement is that it allows us to 'see' with great detail exactly what is happening in the specular realm. From this, the surgical application of appropriate treatment (who effectiveness can be examined and verified to a high degree of precision with the same tools) is utilized to very specifically tailor the response to one that corresponds to an objective physical behavior that elicits the specific subjective/psychoacoustical response that is desired.

Now much of this assumes that one has a clue as to not only what is ACTUALLY happening in the room, but that one has an awareness of the response characteristics desired....more than the all too common "any response different from the original that results from the application of "treatment"." As, quite frankly, that is what serves as a solution for most who simply apply absorption because they have read that reflections are bad and that you need treatment.

The irony is that many of us were measuring with equipment that provides greater acuity and a greater range of measurements and utilizing treatments (along with those literally developing those forms now taken for granted) a decade before some read articles by such luminaries as Don Davis and discovered the concept that the superposition of early high gain sparse reflections (and other behaviors) could contribute to problems with localization, imaging and intelligibility.

But only someone totally unaware of this would posit something as fanciful as "Are you saying the treatments are no good and have really made no difference?"

Quite the contrary!

What we posit is that not only can treatments be very beneficial, but the corollary is that such treatments are of maximal use by having a complete understanding of hat is actually happening and that the SURGICAL application of specific treatments for specific purposes optimizes the achieved response. We do NOT simply advocate the random serendipitous application of treatment (in particular absorption) with the oft literally mentioned ludicrous admonition that "one cannot have too much porous absorption!

Unfortunately what you hold as the paradigm of acoustical insight is in fact a severely constrained incomplete synopsis of a much more complex behavioral realm, where there are many choices, preferences, and possible outcomes - of which almost any can be achieved provided one knows where they are starting from and where they wish to go.

And simply throwing too thin/inadequately broadband absorptive panels wherever mirror indicates a POSSIBLE path, regardless of actual behavior, is NOT an optimal pathway to an optimal response. You see, some of us actually expect, and know how to move beyond the 'if the response is different it must necessarily be better' mode of operation and would like to see others become aware of some of the techniques and tools involved with accomplishing this - without the crab mentality whereby an expanded view of acoustical behavior enabled in large measure by enhanced available tools (coupled with the apparently limiting factor of awareness of the concepts...) is discouraged in favor of erroneous application of concepts and measurements used as slang by those whose primary purpose in being here is their business model of trolling myriad forums in order to sell their wares. But they do not simply ignore such erroneous use of concepts, they go out of their way to actively debate the proper interpretation and use of the concepts as they actively decry and seek to dumb down such awareness. ..and judging from the impassioned responses and cheers from the audience, with obvious success!

But as to the larger subject of acoustical concepts, analysis and treatment. If you are impressed with the serendipitous application of concepts, thin panel treatments limited to porous absorption positioned on the basis of 'napkin analysis' (and I will leave it to you to investigate the limitations of such application), then you are in for an amazing experience should you decide to pursue the subject in more depth.

"That I've fooled myself into thinking there is a huge positive difference in the way my room sounds?" No, no one disagrees with the difference in how it sounds! But, unfortunately, such is really not a valid criterion for judging acoustical results. No, you have fooled yourself by imagining that you understand the concepts by which any improvement may have occurred, and as a result one only wonders how much more effective such treatment could be if one actually was enabled with a greater understanding and the ability to use the more capable and appropriate freely available tools now at our disposal; and as a result treated the real behavior based upon a more complete understanding of what was happening and how it can be optimally modified.

But at least you were most astute to catch the obvious important takeaway! I am obviously against valid acoustical analysis and room treatment based upon a greater understanding of valid acoustical rules that 'govern' behavior in small acoustical spaces.rolleyes.gifrolleyes.gifrolleyes.gif

So....maybe it is hopeless and I just persist in a fantasy world of thinking that some actually desire to understand this stuff and to learn to use the proper tools enabling one to actually and effectively treat and achieve the behavior desired..... But with continuing insights like this, maybe I too should simply adopt the convention of erroneously discussing reverberant sound fields and RTxx calcs in small spaces.
Edited by dragonfyr - 6/18/12 at 6:42pm
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post #57 of 868
6/18/12 at 8:52pm
Quote:
Originally Posted by DanLW View Post

I don't know what dragon's point is either. I think he's a professional hair-splitter.
All I know is, I've had to move several times in my life. An empty room echoes like crazy. A furnished room echoes less. And when I put up DIY mineral wool panels in my home theater, it barely echoes at all. According to RoomEQ Wizard, my room was measuring at .5 before I started. Now, my TopT, EDT, T20, and T30 (all listed under a tab labeled "RT60" in REQ) are all at about .2S down to 200Hz. TopT and T30 are about .4 from 100-200Hz, and my T20 and EDT is .2 down to 100Hz. Bass absorbers are planned.
If we were to listen to some people around here, those measurements are all meaningless. But strangely enough, they correlate to what I hear - much less reverb, or echo, or whatever in my room. I'll even use the cliche "My wife could tell the difference" because it's true. So this is not some esoteric "Monster Cable sounds better than 12ga zip cord" comparison, but a very real, definitely audible difference. That includes what I'm hearing from my speakers. Movies and music sound clearer. Also, I can have the volume turned up louder without it sounding "loud" since there is less echoes.
I guess it's just coincidence that what I'm hearing agrees with the measurements.
You mention a key thing in your post: what one is *hearing*. Much of these conversations is devoid of psychoacoustics or how our ears and brain work together to interpret what we hear. Before I get into that, what you did is right but is not supportive of Ethan's position that started the argument. In acoustics there is a lot of research around the concept of RT60. What I said, and Dragon then pounded into him smile.gif, is that such research is not applicable to small rooms (all of our rooms are thus). The research is around performance halls and their large dimensions significantly change the behavior of sound in them and hence, how we will look at them and design them. Dragon provided the explanation of all of this in his usual obscure way.

What you did however, is based on good science and answers a key question often asked: how much absorption should you have in a room? I think everyone agrees that an empty room with all bare and reflective surfaces is no place for good sound. At the other extreme, a completely "padded" room is not what you want either. A way to determine how live or dead the room is using the RT60 measurement and reading of 500 Hz frequency. The target for that is in the 0.3sec to 0.5 sec. Here is how simply Dr. Toole puts it: "The only reason to measure RT in a small room is to be certain that it is not excessively high (over about 0.5 s) to preserve high speech intelligibility or low (under about 0.2 s) to avoid oppressive “deadness.”

If this is your everyday living room, you would want to avoid the typical sin of human male: "if a little is good, a lot is better. smile.gif" In this case, too much absorption is not good per above. And to the context of this thread, he notes how ordinary furniture also serves this purpose well:

"Fortunately, the nuisance is easily overcome because if a room has normal domestic furnishings—carpet, drapes, upholstered chairs, bookcases, fi replace, lamps, side tables, and so on—it is probable that it falls within the broadly accepted midfrequency (around 500 Hz) reverberation time of 0.3–0.5 s. Rooms that are overly damped are not so much a problem for multichannel listening as they are for the inevitable pre- and postperformance conversation. Acoustically dead rooms are simply not very pleasant spaces to converse in. Vocal effort must be elevated, and face-to-face communication improves clarity. As has been explained in Chapter 10, room refl ections improve speech intelligibility. Unfortunately, in custom home theaters, overzealous consultants and installers sometimes sell too much fabric and fiberglass. Figure 16.1a shows the acoustical evolution of Figure 16.1a shows the acoustical evolution of a listening room; in this case, it was the prototype IEC listening room, and these measurements were made in 1975. It shows the very high RT of an empty room being signifi cantly tamed by the addition of wall-to-wall carpeting. The effect is dramatic."

Fig 16.1a is the one that I post on the first page. Here it is again:

i-jjWhnJp-X2.png

So that you don't think he is alone, here is Tony Grimani form his CEDIA course on home theater design: "Decay time should be .2 to .4 seconds; Research shows that most people like the same range of reverb time."

There is the notion of echo. Once again, Dragon is right. In small rooms we are not dealing with "echoes." The rooms are too small to create classic echoes so the terminology used by Ethan is wrong and surprisingly so coming from him. What we are dealing with here is reflection times. Again, Dr. Toole explains this well:

"The acoustical treatment of the room interior is an important matter and a small industry has developed to cater to it. Purveyors of acoustical materials and consulting services both actively promote the importance of a properly “designed” listening space. The design usually begins with traditional reverberation-time (RT) measurements. For small rooms, the name reverberation time is sometimes changed to refl ection-decay time to acknowledge the reality that there is no sustained reverberant sound fi eld in small, relatively dead listening rooms and that the sound fi elds are not very well diffused. It is an accurate description of what is measured, but whatever you choose to call it, the measurement process is the same (see Chapter 4). In this book, the traditional term reverberation time will be used out of respect for over 100 years of history and the fact that all instruments that measure it are so labeled."

Back to psychoacoustics, we have two ears which are separated by some distance. The sound from the speaker hits the reflector arrives a the ears at two different times. The head also blocks the sound for the other ear causing some filtering and hence, modification of frequency response. These two differing sounds is then presented to the brain which has to make sense out of it. Contrast this to a microphone which only picks up one sound and computer measurement and graph such as ETC that without interpretation shows said signals. What the brain interprets and what the graph shows are two different things. The former cares about the spectrum for example due to filtering just mentioned. The latter, only shows reflection energy and time. And again, represents only one signal, not two. Here, you absolutely want to listen to Dr. Toole because his background is psychoacoustics and his conclusions formed from countless listening tests:

""It seems obvious to look at reflections in the time domain, in a “reflectogram” or impulse response, a simple oscilloscope-like display of events as a function of time or, the currently popular alternative, the ETC (energy-time curve). In such displays, the strength of the reflection would be represented by the height of the spike. However, the height of a spike is affected by the frequency content of the reflection, and time-domain displays are “blind” to spectrum. The measurement has no information about the frequency content of the sound it represents. Only if the spectra of the sounds represented by two spikes are identical can they legitimately be compared.
[...]
All of this is especially relevant in room acoustics because acoustical materials, absorbers, and diffusers routinely modify the spectra of reflected sounds. Whenever the direct and reflected sounds have different spectra, simple broadband ETCs or impulse responses are not trustworthy indicators of audible effects."

Dragon talks about using the right tool and understanding acoustics yet he doggedly ignores said advice in constantly recommending using ETC, dealing with reflections based on how strong they are vs whether they are perceptually beneficial or not.

The best thing you can do for your room and your knowledge of audio is to buy Dr. Toole's book. And if you possibly can, spend a day with him at his training classes at CEDIA (next one in September). The man is an excellent teacher on the top of his 40 years of knowledge and wisdom in this space. For a free teaser and a sliver of what you will learn, here is a good audio interview: http://twit.tv/show/home-theater-geeks/14
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post #58 of 868
6/18/12 at 11:39pm
Quote:
Originally Posted by amirm View Post

.....
Back to psychoacoustics, we have two ears which are separated by some distance. The sound from the speaker hits the reflector arrives a the ears at two different times. The head also blocks the sound for the other ear causing some filtering and hence, modification of frequency response. These two differing sounds is then presented to the brain which has to make sense out of it. Contrast this to a microphone which only picks up one sound and computer measurement and graph such as ETC that without interpretation shows said signals. What the brain interprets and what the graph shows are two different things. The former cares about the spectrum for example due to filtering just mentioned. The latter, only shows reflection energy and time. And again, represents only one signal, not two. Here, you absolutely want to listen to Dr. Toole because his background is psychoacoustics and his conclusions formed from countless listening tests:

""It seems obvious to look at reflections in the time domain, in a “reflectogram” or impulse response, a simple oscilloscope-like display of events as a function of time or, the currently popular alternative, the ETC (energy-time curve). In such displays, the strength of the reflection would be represented by the height of the spike. However, the height of a spike is affected by the frequency content of the reflection, and time-domain displays are “blind” to spectrum. The measurement has no information about the frequency content of the sound it represents. Only if the spectra of the sounds represented by two spikes are identical can they legitimately be compared.
[...]
All of this is especially relevant in room acoustics because acoustical materials, absorbers, and diffusers routinely modify the spectra of reflected sounds. Whenever the direct and reflected sounds have different spectra, simple broadband ETCs or impulse responses are not trustworthy indicators of audible effects."
Dragon talks about using the right tool and understanding acoustics yet he doggedly ignores said advice in constantly recommending using ETC, dealing with reflections based on how strong they are vs whether they are perceptually beneficial or not.
The best thing you can do for your room and your knowledge of audio is to buy Dr. Toole's book. And if you possibly can, spend a day with him at his training classes at CEDIA (next one in September). The man is an excellent teacher on the top of his 40 years of knowledge and wisdom in this space. For a free teaser and a sliver of what you will learn, here is a good audio interview: http://twit.tv/show/home-theater-geeks/14

So we are again presented with the same cut and paste by another marketer who has absolutely no acoustics background and who has never himself actively taken measurements, let alone time domain measurements. But hey, he has read a book and now seeks to market solutions based upon his finally reading one book.

He likes to name drop and denigrate "my opinions" that apparently have no foundation in either physics or psychoacoustics as he is incredibly ignorant of just who was principally responsible for the development of such ideas. The irony is that every one of the, say 25, additional acousticians responsible for the development of such ideas are each responsible for more than what Toole and Olive have accomplished in their careers. But such is what one comes to expect when the person commenting is unaware of a first hand contextual history and who only knows what a book tells him.

You see, Toole asserted the same notion about the ETC back in the late 1980s, and it promptly went nowhere. The reason for this was apparent them with folks intimate with the process (just as was the inappropriateness of using statistical calculations for reverberant sound fields in small acoustical spaces were - along with an awareness of how such RTxx measurements must be taken with an omni source, which no one here has yet done...So, isn't it amazing that those who talk of using measurements and subsequent RTxx calculations don't even employ the proper procedure???)

So Microsoft Bob maintains that ETCs are not an appropriate tool as they are a time domain tool and do not focus primarily upon the frequency domain. Duh!

Why is this an issue or not?

Let's stop and look. As he continues this objection over and over without much awareness of how the tool is actually used, seeing as how he has never made measurements and how the book does not explain the process to the degree sufficient for him to understand...

So why is this important or not important?

Let's examine the environment in which such measurements are taken. One principal that was important for many years before Toole became involved in this is precisely the nature the nature of the boundaries (specifically, their acoustical impedance) that were of considerable concern. Likewise, this same concern extended to any treatments. (Now contrast this fundamental focus with those who are now just becoming aware that such characteristics can even be a variable deserving attention!)

You see, the great attention was spent by the acousticians to insure that the boundaries were broadband in their behavior, meaning that essentially from the specular frequencies upward that the boundaries treated all of the specular energy equally. What was incident on the boundaries all reacted uniformly, either being absorbed or reflected or diffused as evenly as possible. Thus the boundary did not have the effect of EQing the incident sound by unevenly interacting with it. As long as boundaries and boundary treatments are broadband, no uneven processing of incident energy occurs.

So, if the boundaries evenly process incident energy, we do not have a problem. And any problem we do have with reflected energy can be further modified with broadband treatment.

We only have a problem if said boundaries unevenly processed the incident signal and resulted in the effective EQing of the reflected signal, thus resulting in a resultant emission that was unlike both the direct and boundary incident signal.

Ironically, Toole is also in agreement with this concept and opposes the ALL TOO COMMON use of treatments that do not perform ion a broadband manner. Ironically, when we presented such a concept in the form of information concerning just how thick the common porous absorption needed to be everyone had a hissy fit complaining that it was just too thick and took up too much room, and subsequently insisted that it would be fine to use less as the effect was just as good as using the thicker stuff. thus the consensus on this forum is that they need not utilize broadband treatment and that using whatever is convenient and acceptable to the wife (as opposed to stuffy acousticians) works fine without problems - in fact, the benefits far outweighed any imagined' problems! But amazingly, MS Bob was silent on the issue, presumably as he had not finished reading his first 'acoustics' book.

So why does MS Bob have his panties in a wad over this issue?
Apparently the rooms in which he spends his time have all sorts of boundary materials and treatments that feature non-broadband behavior and thus effect indirect incident energy in a manner that effectively EQs it, rendering the reflections different in tonal composition than the direct incident energy. This IS a problem.

However, it is not a problem with the ETC. It is a problem with process and, quite frankly, ot os a problem as a result of lousy flawed planning and inappropriate treatments.

The irony is that the ETC CAN be used to analyze the time domain behavior if energy specifically by frequency band simply by using band limited ETC measurements. These are a useful investigative tool in order to determine if there is a problem with the boundary reflectivity. So all of the objections offered by one who has never used the measurements or actually performed an analysis are bogus.

The fact is that this capability was a fundamental capability introduced with the first ETC measurements introduced by Dick Heyser (another insignificant acoustician)in the 1960’s. And they are a great investigative tool IF one suspects that the boundary or treatment does not operate in a uniform broadband manner.

But seeing as a fundamental criterion for the design of boundaries and for the design and use of treatments is that they be broadband, once this consideration is met, there is no need to keep bringing up the use of band limited ETCs. But notice how MS Bob KEEPS incessantly harping on the need for this – apparently obviating the problem that the boundaries and treatments with which he is mistakenly concerned are NOT broadband!

The solution is not to jettison the tool, but rather to get one’s act in gear and to design and employ the proper boundary and treatments!

And then he brings up the OLD topic of binaural perception. It is nice to see he has read an article mentioning this behavior, as it too is a well understood behavior that is also easily measured and examined and which has been researched in depth. Ironically much of this research was made possible by those folks MS Bob likes to ignore in conjunction with the TEF analyzer! Carolyn (Puddie) Rodgers seminal research on the effects of the pinnae and similarly research such as that performed by Dr. Peter D’Antionio using dual TEF analyzers to analyze the interaural cross correlation (IACC) is apparently unknown as he simply chooses to selectively ignore it – as it was not mentioned in the single book he read. Fortunately the results are fundamental to those who actually have studied the phenomena.

And if one does want to investigate this themselves they can rather easily do it with a dual channel FFT such as ARTA. But it speaks volumes that he has neither pursued that which he claims is such an important topic himself or even become familiar with the actual research! But as a result of reading a reference to the subject in a limited text, he fancies himself now qualified to pass judgment on others who have been involved in such research and who are also well aware of it.

And if must confuse him to no end to realize that in a space featuring the recommended left-right symmetry, that such differentiation is minimal (well behaved) and quite natural. It only becomes a more complex and significant if the best practice of L-R symmetry is violated. So while its basic role in localization is important, unless someone makes a mistake in design and fails to follow best practices such as those mentioned regarding broadband responses, while it is great that he has now become aware of the issue, it is largely moot. But hey, some are continually amazed to find the world is larger than they had previously been aware. And his discoveries have just begun.

So, not only is his description of the power of the ETC extremely limited, greatly understating what it, and especially what it in conjunction with a few other measurements can depict in great detail, but his preoccupation is that its common use assumes a properly designed environment where both the boundaries and treatments are properly designed and implemented, and whereupon when then worry about their proper application and placement to achieve a desired result.

For you see, at that point, a properly designed room is far past the point of determining if boundaries are properly broadband and if the treatments to be utilized are properly broadband. It assumes that the operators are thoroughly versed in acoustics best practices and that they do not need to suddenly become preoccupied in the final stages with factors that should have properly been fundamentally addressed in the preliminary stages when the basic analysis of the characteristics and behavior of the space was properly conducted.

But seeing as simply reading a book pushing a particular approach does not adequately represent the larger world of what is best practice based upon what is actually known and done, it is of little surprise that MS Bob would be unaware of the basic tenets that, while he makes mention of them, he then fails to implement, which then results in a straw man concern later in the design and treatment process, As using broadband concepts are fundamental, and not a last minute Band-Aid requiring last minute band limited analysis as he falsely asserts – unless perhaps if you are adhering to one of his ill conceived projects where he aptly asserts that such issues are still concerns long after they should have been properly addressed. You see, the fact that he is still addressing mistakes in process is neither a fault nor limitation of the measurement but rather an indication of the lack of awareness and understanding on the part of the operator.

And this issue was already well understood when Toole himself originally became aware of it in the late 80’s. And it is no wonder that the response was an overwhelming “Duh, of course”, rather than some histrionic panic to adopt something that was already a fundamental concern addressed long before.

So, to paraphrase Don Davis: “The ancients keep stealing all of our inventions.” But I guess one should be encouraged to see a few more FINALLY become aware of factors that others have considered as fundamental for over 40 years.
Edited by dragonfyr - 6/18/12 at 11:58pm
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post #59 of 868
6/19/12 at 5:58am
Quote:
Originally Posted by dragonfyr View Post

So we are again presented with the same cut and paste by another marketer who has absolutely no acoustics background and who has never himself actively taken measurements, let alone time domain measurements. But hey, he has read a book and now seeks to market solutions based upon his finally reading one book.
He likes to name drop and denigrate "my opinions" that apparently have no foundation in either physics or psychoacoustics as he is incredibly ignorant of just who was principally responsible for the development of such ideas. The irony is that every one of the, say 25, additional acousticians responsible for the development of such ideas are each responsible for more than what Toole and Olive have accomplished in their careers. But such is what one comes to expect when the person commenting is unaware of a first hand contextual history and who only knows what a book tells him.
You see, Toole asserted the same notion about the ETC back in the late 1980s, and it promptly went nowhere. The reason for this was apparent them with folks intimate with the process (just as was the inappropriateness of using statistical calculations for reverberant sound fields in small acoustical spaces were - along with an awareness of how such RTxx measurements must be taken with an omni source, which no one here has yet done...So, isn't it amazing that those who talk of using measurements and subsequent RTxx calculations don't even employ the proper procedure???)
So Microsoft Bob maintains that ETCs are not an appropriate tool as they are a time domain tool and do not focus primarily upon the frequency domain. Duh!
Why is this an issue or not?
Let's stop and look. As he continues this objection over and over without much awareness of how the tool is actually used, seeing as how he has never made measurements and how the book does not explain the process to the degree sufficient for him to understand...
So why is this important or not important?
Let's examine the environment in which such measurements are taken. One principal that was important for many years before Toole became involved in this is precisely the nature the nature of the boundaries (specifically, their acoustical impedance) that were of considerable concern. Likewise, this same concern extended to any treatments. (Now contrast this fundamental focus with those who are now just becoming aware that such characteristics can even be a variable deserving attention!)
You see, the great attention was spent by the acousticians to insure that the boundaries were broadband in their behavior, meaning that essentially from the specular frequencies upward that the boundaries treated all of the specular energy equally. What was incident on the boundaries all reacted uniformly, either being absorbed or reflected or diffused as evenly as possible. Thus the boundary did not have the effect of EQing the incident sound by unevenly interacting with it. As long as boundaries and boundary treatments are broadband, no uneven processing of incident energy occurs.
So, if the boundaries evenly process incident energy, we do not have a problem. And any problem we do have with reflected energy can be further modified with broadband treatment.
We only have a problem if said boundaries unevenly processed the incident signal and resulted in the effective EQing of the reflected signal, thus resulting in a resultant emission that was unlike both the direct and boundary incident signal.
Ironically, Toole is also in agreement with this concept and opposes the ALL TOO COMMON use of treatments that do not perform ion a broadband manner. Ironically, when we presented such a concept in the form of information concerning just how thick the common porous absorption needed to be everyone had a hissy fit complaining that it was just too thick and took up too much room, and subsequently insisted that it would be fine to use less as the effect was just as good as using the thicker stuff. thus the consensus on this forum is that they need not utilize broadband treatment and that using whatever is convenient and acceptable to the wife (as opposed to stuffy acousticians) works fine without problems - in fact, the benefits far outweighed any imagined' problems! But amazingly, MS Bob was silent on the issue, presumably as he had not finished reading his first 'acoustics' book.
So why does MS Bob have his panties in a wad over this issue?
Apparently the rooms in which he spends his time have all sorts of boundary materials and treatments that feature non-broadband behavior and thus effect indirect incident energy in a manner that effectively EQs it, rendering the reflections different in tonal composition than the direct incident energy. This IS a problem.
However, it is not a problem with the ETC. It is a problem with process and, quite frankly, ot os a problem as a result of lousy flawed planning and inappropriate treatments.
The irony is that the ETC CAN be used to analyze the time domain behavior if energy specifically by frequency band simply by using band limited ETC measurements. These are a useful investigative tool in order to determine if there is a problem with the boundary reflectivity. So all of the objections offered by one who has never used the measurements or actually performed an analysis are bogus.
The fact is that this capability was a fundamental capability introduced with the first ETC measurements introduced by Dick Heyser (another insignificant acoustician)in the 1960’s. And they are a great investigative tool IF one suspects that the boundary or treatment does not operate in a uniform broadband manner.
But seeing as a fundamental criterion for the design of boundaries and for the design and use of treatments is that they be broadband, once this consideration is met, there is no need to keep bringing up the use of band limited ETCs. But notice how MS Bob KEEPS incessantly harping on the need for this – apparently obviating the problem that the boundaries and treatments with which he is mistakenly concerned are NOT broadband!
The solution is not to jettison the tool, but rather to get one’s act in gear and to design and employ the proper boundary and treatments!
And then he brings up the OLD topic of binaural perception. It is nice to see he has read an article mentioning this behavior, as it too is a well understood behavior that is also easily measured and examined and which has been researched in depth. Ironically much of this research was made possible by those folks MS Bob likes to ignore in conjunction with the TEF analyzer! Carolyn (Puddie) Rodgers seminal research on the effects of the pinnae and similarly research such as that performed by Dr. Peter D’Antionio using dual TEF analyzers to analyze the interaural cross correlation (IACC) is apparently unknown as he simply chooses to selectively ignore it – as it was not mentioned in the single book he read. Fortunately the results are fundamental to those who actually have studied the phenomena.
And if one does want to investigate this themselves they can rather easily do it with a dual channel FFT such as ARTA. But it speaks volumes that he has neither pursued that which he claims is such an important topic himself or even become familiar with the actual research! But as a result of reading a reference to the subject in a limited text, he fancies himself now qualified to pass judgment on others who have been involved in such research and who are also well aware of it.
And if must confuse him to no end to realize that in a space featuring the recommended left-right symmetry, that such differentiation is minimal (well behaved) and quite natural. It only becomes a more complex and significant if the best practice of L-R symmetry is violated. So while its basic role in localization is important, unless someone makes a mistake in design and fails to follow best practices such as those mentioned regarding broadband responses, while it is great that he has now become aware of the issue, it is largely moot. But hey, some are continually amazed to find the world is larger than they had previously been aware. And his discoveries have just begun.
So, not only is his description of the power of the ETC extremely limited, greatly understating what it, and especially what it in conjunction with a few other measurements can depict in great detail, but his preoccupation is that its common use assumes a properly designed environment where both the boundaries and treatments are properly designed and implemented, and whereupon when then worry about their proper application and placement to achieve a desired result.
For you see, at that point, a properly designed room is far past the point of determining if boundaries are properly broadband and if the treatments to be utilized are properly broadband. It assumes that the operators are thoroughly versed in acoustics best practices and that they do not need to suddenly become preoccupied in the final stages with factors that should have properly been fundamentally addressed in the preliminary stages when the basic analysis of the characteristics and behavior of the space was properly conducted.
But seeing as simply reading a book pushing a particular approach does not adequately represent the larger world of what is best practice based upon what is actually known and done, it is of little surprise that MS Bob would be unaware of the basic tenets that, while he makes mention of them, he then fails to implement, which then results in a straw man concern later in the design and treatment process, As using broadband concepts are fundamental, and not a last minute Band-Aid requiring last minute band limited analysis as he falsely asserts – unless perhaps if you are adhering to one of his ill conceived projects where he aptly asserts that such issues are still concerns long after they should have been properly addressed. You see, the fact that he is still addressing mistakes in process is neither a fault nor limitation of the measurement but rather an indication of the lack of awareness and understanding on the part of the operator.
And this issue was already well understood when Toole himself originally became aware of it in the late 80’s. And it is no wonder that the response was an overwhelming “Duh, of course”, rather than some histrionic panic to adopt something that was already a fundamental concern addressed long before.
So, to paraphrase Don Davis: “The ancients keep stealing all of our inventions.” But I guess one should be encouraged to see a few more FINALLY become aware of factors that others have considered as fundamental for over 40 years.

outstanding.

it's laughable that toole seems oblivious to the fact you can band-limit ETCs - he should know better. and to think the editors missed that mistake as well eek.gif
but just as toole's commentary states (as was well known before he even came on the scene) - we care about broadband treatments so the signal is not effectively EQ'd. i wouldn't expect much useful commentary from Microsoft Bob regarding the ETCs - as he directly told me once in another conversation on this forum that he sees "no reason" to utilize the ETC or time-domain measurements in small acoustical space. i even brought up the additional benefits it details you such as edge diffraction generators and it went right over his head.

but like you said, this is the frustration you get from someone who is not versed in acoustical measurements nor any fundamental understanding of basic acoustical models and why they exist. what is that old saying? something about knowing "just enough to be dangerous"?


and it's still utterly laughable that people are discussing RTxx without even knowing the basic requirements of measurements regarding utilization of an omni-source as well as being WELL past Dc. such fundamentals that are completely ignored! but hey, like you said, the computer spits out a number/graph so it MUST be valid, right?! lol -

and this quote from MS Bob is gem as well: "A way to determine how live or dead the room is using the RT60 measurement and reading of 500 Hz frequency. The target for that is in the 0.3sec to 0.5 sec.". unfortunately, people seem to think decay times are what determines "liveliness". the first significant reflection's gain is what determines liveliness. but this is what happens when you copy-paste parrot from a book and have no acoustical foundation of which to stand on. such Simple basics that are completely missed.
Quote:
Originally Posted by dragonfyr View Post

So, to paraphrase Don Davis: “The ancients keep stealing all of our inventions.” But I guess one should be encouraged to see a few more FINALLY become aware of factors that others have considered as fundamental for over 40 years.

cool.gifcool.gif
Edited by localhost127 - 6/19/12 at 6:36am
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post #60 of 868
6/19/12 at 7:24am
Question for Dragonfyr:

Are you of the mind set that a person should not add room treatments blindly, but rather, measure the room first, using something such as REW or the Dayton Omnimic system, and then using treatments to treat the various trouble spots? That is what I have gathered from your post, and, it seems to make sence to me.
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