[pinnahertz]

   
1. Maybe the all rooms I've measured are just freaks of nature but I've never seen or even heard of room which does not have very significant variation in FR response throughout the audible spectrum, with high res, non-smoothed RTA measurements from about 1kHz upwards typically resembling a seismograph during an earthquake!  Freqs at/below the Shroeder commonly consume much/most of the treatment budget in a studio build but we certainly never just ignore treatment well above the schroeder.
 
2. Your statement ("room modes affect lower freqs only") appears to contradict 2a? 2a. Agreed to an extent and even then, certainly not a flat/random reverb!
 
3. I did not say a 40dB dip in response, I said "peaks and troughs". Looking at the worst peak and worst trough, a 30-40dB variation between these two points is not only entirely common in my experience but something I've witnessed pretty much without exception in every untreated room I've ever measured. At the standard RTA resolution of 1/3 octave, I can't remember off the top of my head ever seeing anything quite so drastic but using a 1/6 or 1/12 8ve non-smoothed, to see more precisely what's going on, it's entirely common.
 
3a. Again, total variation between worst peaks and worst troughs at higher than 1/3 8ve resolution. Generally, there is at least 10dB between those points, even in world class studios! Pro studios are, as you mentioned, quite a different kettle of fish though. One obvious difference is a large reflective surface right in front of the LP (the mixing desk) and of course we can't solve this by just covering the desk with a trap or two (or with the use of additional subs)! Also, absorption panels (traps) are ineffective below about 80-100Hz, to treat the almost inevitable LF problems in any relatively small room requires treatment other than simple absorption traps; tuned panels, Helmholtz resonators, etc., treatments which are generally well beyond all but a tiny minority of the most extreme consumers.
 
4. Thanks, I'll try to look out for that paper but I've not been a member of the AES for quite a few years. That Shroeder freq tallies well with my experience but I'd be very surprised if the paper really concludes what you appear to be implying. Maybe I'm mis-reading but the implication I've understood from you post  is that room response above approximately 200Hz is largely inconsequential. This would fly in the face of standard pro studio design, where we always treat well beyond the Shroeder freq, typically not just (and sometimes not at all) with broad band absorption (traps) but also with various forms of diffusers, to randomise the interactions of higher room mode harmonics/reflections. Additionally, commercial studios are specifically constructed to avoid certain quite severe acoustic problems, problems which are often inherent (without treatment) to consumer listening environments. Flutter-echo being an obvious example.
 
5. I agree. I wasn't talking about what is the most audibly objectionable form of distortion though, just very significant measurable variations from flat, as opposed to the difficult to measure, let alone audible, distortion of say ADC jitter. Most consumers, even many/most audiophiles are blissfully unaware of their acoustic problems, even less so above their Shroeder freq but that doesn't mean the problems don't exist or aren't audible. Trained listeners, such as experienced pro audio engineers, would be aware of these problems (including those an octave or 3 above Shroeder!), and the consequences (when surgically EQ'ing for example).  I also wasn't speaking about extreme circumstances, pushing a system/speakers beyond their capabilities (towards Xmax for example), although I make no judgement about how common those extreme circumstances may be amongst consumers.
 
6. Unlike you, I have no experience of measuring turntables. I've never owned one myself and have only experienced other peoples'. In those cases, they were expensive well maintained units and while even the best turntables are obviously still susceptible to the deficiencies of vinyl (HF inaccuracies, etc.), I didn't realise the FR variation was generally as bad as you indicate.
 
If we consider that by the time we're 1m or so away from our speakers, what's hitting our ears is roughly a 50:50 balance of reflections vs direct sound, then acoustics is obviously a very major player and by two meters or more, easily the dominant player, at least as far as FR is concerned, if not conscious awareness. Certainly I've measured and heard $1k speakers in a well treated room which perform significantly better than speakers at pretty much any price in an average consumer's untreated room. I'm not really disagreeing with the principles you've mentioned, mainly just with degree and from my personal experience I would switch the positions between your #1 and #3. It's entirely possible/likely I was incorrect with my "degree"as far as turntables are concerned and of course we can come up with extreme examples which don't conform to my assertion that acoustics is the dominate factor of FR but I do stick to that assertion as generally true and that acoustics, speaker and turntable distortion is likely to add up to well over 1000x the distortion of a competent ADC.
 
 

1. No, the rooms you measured are likely not freaks of nature.  However, your measurement technique is at fault. High res non-smoothed RTA (I'll bet also measured at a single point) is not representative of real room response.  I'm not even sure how you'd respond to your measurements.  Yeah, it'll look like a seismograph.  If you must use an RTA (and I still do a lot of the time), you need at least use a little smoothing, limit resolution to 1/24th octave or 1/12th octave, then most importantly, average many measurements over an area that includes more measurements clustered in critical listening positions, but includes several at the edges of each of the LPs too.  The technique is not new, it's the old "spacial/temporal average" thing.  The point is you're seeing a lot of inaudible detail that is specular, confined to a single mic location. People don't hear that way, it's an anomaly of measurement only. 
 
2. What I meant was that room modes affect measured frequency response at lower frequencies only.  I think you did get it, and there's no contradiction. 
 
3. My first comment would be the use of the RTA technique again.  Using high res unsmoothed...you aren't actually seeing precisely what's going on, you're seeing excessive inaudible detail that nobody hears, because nobody's ears are the equivalent of a single omnidirectional mic on a stand.  We have two ears, we move around.  We always hear an approximation of a spacial average.  
 
3a.  Yeah, the console reflection.  I know the problem well.  Can't solve it with treatment at all, has to be a positional fix.  But the effects of the reflection coming off a console surface wouldn't be into the sub range much at all, both because of wavelength and dimensions of the reflecting surface, and wavelenght vs time delay.  Those properties place the effects of the console reflection in the mid-band and up to frequencies where the console becomes a diffuser, so it has nothing to do with subs anyway.  You also wouldn't address the issue with traps of any sort, it's just not in that frequency range.  The only means of addressing it is physical positioning of the console and speakers.  Ideally the console goes away and becomes virtual, which is now possible, though still a bit impractical.  Fortunately (or not, depending on your perspective) the issue doesn't exist in the home.  It is possible in a fresh design to put the console reflection at a point where it lands away from the ears, it's just not often completely practical. 
 
4. PM me if you can't find the paper somehow.  It's based on over 500 rooms, multi-point time-domain based analysis.  
 
5. I think we agree on this.  I'd be very cautious about applying surgical-precision EQ above Schroeder without doing the multi-point average, though.  Chasing tails, problems that aren't really there in more than one specular measurement.  Consider a wavelength above 1kHz, and how little positional delta is required to move out of a deep null.  
 
"If we consider that by the time we're 1m or so away from our speakers, what's hitting our ears is roughly a 50:50 balance of reflections vs direct sound, then acoustics is obviously a very major player and by two meters or more, easily the dominant player, at least as far as FR is concerned, if not conscious awareness. "
 
It would take a live, tiny room and speakers with very wide dispersion to get that 50/50 ratio at 1m.  Above the transition reflections don't have the same effect on audible response as they would below transition because there are so many, and wavelengths are so small.  Again, to see what's really audibly going on you have to get away from high res single position measurements, do a bit of smoothing and average multiple positions with a position delta of inches to feet.  See "Sound Reproduction....", F. Toole, ch 4.3.1, "One Room, Two Sound Fields—The Transition Frequency", particularly Fig. 4.10 and discussion. 
 
We may tend to EQ a live room by reducing HF energy, because a live room tends to sound bright.  But that's not real frequency response, thats integration of multiple arrivals over time.  The EQ solution doesn't really work.  
 
In small rooms at home or in control rooms, the reverberant field is pretty easy to control.  In fact, the cited paper in my previous post shows analysis of RT in hundreds of "untreated" rooms with a surprisingly short RT.  When we consider what the "typical" room actually is, we can see that the dominant quality determining factor is always the speaker first above the transition frequency, room first below it.  

 

[watchnerd]

 
3a.  Yeah, the console reflection.  I know the problem well.  Can't solve it with treatment at all, has to be a positional fix.  But the effects of the reflection coming off a console surface wouldn't be into the sub range much at all, both because of wavelength and dimensions of the reflecting surface, and wavelenght vs time delay.  Those properties place the effects of the console reflection in the mid-band and up to frequencies where the console becomes a diffuser, so it has nothing to do with subs anyway.  You also wouldn't address the issue with traps of any sort, it's just not in that frequency range.  The only means of addressing it is physical positioning of the console and speakers.  Ideally the console goes away and becomes virtual, which is now possible, though still a bit impractical.  Fortunately (or not, depending on your perspective) the issue doesn't exist in the home.  It is possible in a fresh design to put the console reflection at a point where it lands away from the ears, it's just not often completely practical. 
 

 
There are actually a couple of monitors with DSP crossovers that try to address this via a settings switch (no, it's not the same as the near wall / not near wall setting some have).  If I recall, Eve Audio is one of those.  I have no idea how well such an approach actually works.

 

[pinnahertz]

   
There are actually a couple of monitors with DSP crossovers that try to address this via a settings switch (no, it's not the same as the near wall / not near wall setting some have).  If I recall, Eve Audio is one of those.  I have no idea how well such an approach actually works.

They address a relatively minor mid bass issue (sort of), but do nothing for the 1kHz and up reflection. Eve Audio applies a very generalized filter that is adjustable as a boost/cut at two different frequencies.  This would already have been done when calibrating the room anyway.  The mid-band and up reflection effects are kind of impossible to correct with a simple filter. 

 

[gregorio]

  1. High res non-smoothed RTA (I'll bet also measured at a single point) is not representative of real room response. [1a]  I'm not even sure how you'd respond to your measurements.  Yeah, it'll look like a seismograph.
 
3. My first comment would be the use of the RTA technique again.  Using high res unsmoothed...you aren't actually seeing precisely what's going on, you're seeing excessive inaudible detail that nobody hears, because nobody's ears are the equivalent of a single omnidirectional mic on a stand.  We have two ears, we move around.  [3a] We always hear an approximation of a spacial average. 
 
4. PM me if you can't find the paper somehow.  It's based on over 500 rooms, multi-point time-domain based analysis.  
 
5. I'd be very cautious about applying surgical-precision EQ above Schroeder without doing the multi-point average, though.  Chasing tails, problems that aren't really there in more than one specular measurement.  Consider a wavelength above 1kHz, and how little positional delta is required to move out of a deep null.  
 
[6] It would take a live, tiny room and speakers with very wide dispersion to get that 50/50 ratio at 1m.

 
1 & 3. I think we're talking at cross purposes. Referring again to my point #5 previously, I am not talking about what we hear or what we perceive, I am talking purely in terms of the distortion (changes in the input waveform) caused by acoustics. That non-smoothed hi-res RTA is an accurate representation/measurement of the distortion created by room acoustics, it's not however representative of how we would actually hear/perceive room response. If we move the measurement mic even by a relatively small distance then the measurement from about an 8ve or so above shroeder normally changes and from about 2 8ves above schroeder changes quite dramatically, we've still got a seismograph type response though.
 
3a. True as a generality. Although some of the specifics of this perception are sometimes quite strange/problematic and also an engaging challenge!
 
1a. Generally I would use the industry standard (1/3 8ve RTA un-smoothed response) in a number of different positions around the LP.  If there's something untoward I will often dial in a higher res to identify more precisely the range and depth of the problem freq and if they're the same problem freqs in other mic positions. If so, it might be worth identifying what's causing it and if anything can be done about it. My response to your statement would therefore be; usually nothing at all but not always.
 
5. No choice I'm afraid, my work constantly requires identifying and applying surgical EQ, although as already mentioned I'm obviously not relying on a setup/calibration derived from a single hi-res measurement from a single position. A similarly experienced audio engineer would also be well aware of the issues. In my case, if I'm surgically EQ'ing a freq which also happens to be an issue in my own mix room's response, I'll check what I'm doing with cans or briefly pan the track to a different monitor.
 
6. Depends. Speakers close to a wall or corner at the back of a fairly large reflective surface, say a work/computer desk is not by any means an uncommon scenario.
 

  There are actually a couple of monitors with DSP crossovers that try to address this via a settings switch (no, it's not the same as the near wall / not near wall setting some have).  If I recall, Eve Audio is one of those.  I have no idea how well such an approach actually works.

 
Even going back before DSP adjustment, it was not uncommon for near-field monitors to have an EQ switch/setting specifically aimed specifically at the problem caused by placing the near-fields on the meter bridge and the resultant reflections from the mixing desk, typically 300-400Hz. Results are typically variable, often only a slight improvement, no improvement or slight deterioration, virtually never an actual cure. I've not tried the more recent DSP incarnations though, so can't say how much more effective they may or may not be.
 
This is an age old problem with no real practical solution. No studio has ideal acoustic performance, some are better than others of course but all are flawed to some degree and the desk certainly contributes one of those flaws.
 
G

 

[pinnahertz]

   
1 & 3. I think we're talking at cross purposes. Referring again to my point #5 previously, I am not talking about what we hear or what we perceive, I am talking purely in terms of the distortion (changes in the input waveform) caused by acoustics. That non-smoothed hi-res RTA is an accurate representation/measurement of the distortion created by room acoustics, it's not however representative of how we would actually hear/perceive room response. If we move the measurement mic even by a relatively small distance then the measurement from about an 8ve or so above shroeder normally changes and from about 2 8ves above schroeder changes quite dramatically, we've still got a seismograph type response though.
 
3a. True as a generality. Although some of the specifics of this perception are sometimes quite strange/problematic and also an engaging challenge!
 
1a. Generally I would use the industry standard (1/3 8ve RTA un-smoothed response) in a number of different positions around the LP.  If there's something untoward I will often dial in a higher res to identify more precisely the range and depth of the problem freq and if they're the same problem freqs in other mic positions. If so, it might be worth identifying what's causing it and if anything can be done about it. My response to your statement would therefore be; usually nothing at all but not always.
 
5. No choice I'm afraid, my work constantly requires identifying and applying surgical EQ, although as already mentioned I'm obviously not relying on a setup/calibration derived from a single hi-res measurement from a single position. A similarly experienced audio engineer would also be well aware of the issues. In my case, if I'm surgically EQ'ing a freq which also happens to be an issue in my own mix room's response, I'll check what I'm doing with cans or briefly pan the track to a different monitor.
 
6. Depends. Speakers close to a wall or corner at the back of a fairly large reflective surface, say a work/computer desk is not by any means an uncommon scenario.
 
 
Even going back before DSP adjustment, it was not uncommon for near-field monitors to have an EQ switch/setting specifically aimed specifically at the problem caused by placing the near-fields on the meter bridge and the resultant reflections from the mixing desk, typically 300-400Hz. Results are typically variable, often only a slight improvement, no improvement or slight deterioration, virtually never an actual cure. I've not tried the more recent DSP incarnations though, so can't say how much more effective they may or may not be.
 
This is an age old problem with no real practical solution. No studio has ideal acoustic performance, some are better than others of course but all are flawed to some degree and the desk certainly contributes one of those flaws.
 
G

 "3. I think we're talking at cross purposes. Referring again to my point #5 previously, I am not talking about what we hear or what we perceive, I am talking purely in terms of the distortion (changes in the input waveform) caused by acoustics. That non-smoothed hi-res RTA is an accurate representation/measurement of the distortion created by room acoustics, it's not however representative of how we would actually hear/perceive room response."
 
Perhaps, but only at a single point.  And if it's not representative of what we actually hear, why bother?  And what would you use the curve for anyway?  You can't respond to it with correction because there's far too much detail.  What you have may technically be specifically accurate, but it's useless data.  
 
"If we move the measurement mic even by a relatively small distance then the measurement from about an 8ve or so above shroeder normally changes and from about 2 8ves above schroeder changes quite dramatically, we've still got a seismograph type response though."
 
But so what?  I'm sure you're more than familiar with the audibility of a response excursion based on gain and Q, right?  The reason broad response changes of only a dB or so are audible where a 40dB notch with a Q of more than 1000 is inaudible?  So, you see these dramatic changes when you move your mic an inch.  What do you do now? What does it mean?  If the answers are "nothing" and "nothing", they why measure that way? 
 
"1a. Generally I would use the industry standard (1/3 8ve RTA un-smoothed response) in a number of different positions around the LP."
Hmm... interesting statement.  In most FFT spectrum analyzers (I say most, it's probably all) you choose between a fixed RTA bandwidth like 1/3 octave, or 1/12th octave, OR a full spectrum with defined smoothing.   If you're really using a 1/3 octave RTA you won't be using an additional smoothing function, and you won't see the "seismograph", now will you?  So, which is it?  1/3rd or smoothed spectrum?    
 
1/3 industry standard?  Well, perhaps somewhere, but not a "standard" for many years.  Trying to calibrate a room using a 1/3 octave analyzer is hardly "surgical", unless you're performing surgery with boxing gloves on.  THX has recommended 1/12th or greater for nearly two decades, for analysis.  I gave up on 1/3 octave analysis the very second I had something better, never looked back.
 
 
"If there's something untoward I will often dial in a higher res to identify more precisely the range and depth of the problem freq and if they're the same problem freqs in other mic positions. If so, it might be worth identifying what's causing it and if anything can be done about it. My response to your statement would therefore be; usually nothing at all but not always."
 
Just a suggestion, but you might try a spacial average from the beginning using 6 or 8 positions, 1/12 octave.  You'll find your answer much faster and with less frustration. 
 
"5. No choice I'm afraid, my work constantly requires identifying and applying surgical EQ,"
Just curious: what does "surgical EQ" mean to you?  Perhaps I've been using the term wrong.  I've used it to mean high precision EQ.  Do you mean corrective EQ?  Something else?
 
"although as already mentioned I'm obviously not relying on a setup/calibration derived from a single hi-res measurement from a single position."
Sorry, that was not obvious from what you wrote.  I still have not read anything about how many positions you measure, how they are correlated to each other, or their spacing. But so long as you're doing more than one or two positions, I think we are fine.
 
"A similarly experienced audio engineer would also be well aware of the issues."
What?
 
"In my case, if I'm surgically EQ'ing a freq which also happens to be an issue in my own mix room's response, I'll check what I'm doing with cans or briefly pan the track to a different monitor."
Given all the analysis and, I presume, corrective action, why is there a frequency that is such an issue as to cast doubt?  Just something impossible to correct?
 
 
"6. Depends. Speakers close to a wall or corner at the back of a fairly large reflective surface, say a work/computer desk is not by any means an uncommon scenario."
Wouldn't that create response issues below transition?  
 
"Even going back before DSP adjustment, it was not uncommon for near-field monitors to have an EQ switch/setting specifically aimed specifically at the problem caused by placing the near-fields on the meter bridge and the resultant reflections from the mixing desk, typically 300-400Hz. Results are typically variable, often only a slight improvement, no improvement or slight deterioration, virtually never an actual cure. I've not tried the more recent DSP incarnations though, so can't say how much more effective they may or may not be.
 
This is an age old problem with no real practical solution. No studio has ideal acoustic performance, some are better than others of course but all are flawed to some degree and the desk certainly contributes one of those flaws."
 
Agreed.  However the best DSP solution would involve a good multi-position measurement set in-situ, and a precisely complimentary filter(s).  I don't see that built into a monitor.

 

[gregorio]

   "3. I think we're talking at cross purposes. Referring again to my point #5 previously, I am not talking about what we hear or what we perceive, I am talking purely in terms of the distortion (changes in the input waveform) caused by acoustics. That non-smoothed hi-res RTA is an accurate representation/measurement of the distortion created by room acoustics, it's not however representative of how we would actually hear/perceive room response."
 
[1] And if it's not representative of what we actually hear, why bother?
 
"If we move the measurement mic even by a relatively small distance then the measurement from about an 8ve or so above shroeder normally changes and from about 2 8ves above schroeder changes quite dramatically, we've still got a seismograph type response though."
 
[2] So, you see these dramatic changes when you move your mic an inch.  What do you do now? What does it mean?  If the answers are "nothing" and "nothing", they why measure that way? 
 
"1a. Generally I would use the industry standard (1/3 8ve RTA un-smoothed response) in a number of different positions around the LP."
 
[3] If you're really using a 1/3 octave RTA you won't be using an additional smoothing function, and you won't see the "seismograph", now will you?  So, which is it?  1/3rd or smoothed spectrum?    
 
[3a] 1/3 industry standard?  Well, perhaps somewhere, but not a "standard" for many years.
 
"5. No choice I'm afraid, my work constantly requires identifying and applying surgical EQ," [4] Just curious: what does "surgical EQ" mean to you?
 
"although as already mentioned I'm obviously not relying on a setup/calibration derived from a single hi-res measurement from a single position."
[5] Sorry, that was not obvious from what you wrote.  I still have not read anything about how many positions you measure, how they are correlated to each other, or their spacing. But so long as you're doing more than one or two positions, I think we are fine.
 
"A similarly experienced audio engineer would also be well aware of the issues."
[6] What?
 
"In my case, if I'm surgically EQ'ing a freq which also happens to be an issue in my own mix room's response, I'll check what I'm doing with cans or briefly pan the track to a different monitor."
[7] Given all the analysis and, I presume, corrective action, why is there a frequency that is such an issue as to cast doubt?  Just something impossible to correct?
 
"6. Depends. Speakers close to a wall or corner at the back of a fairly large reflective surface, say a work/computer desk is not by any means an uncommon scenario."
[8] Wouldn't that create response issues below transition? 

 
1. With few exceptions, none of the OP's points/questions were "representative of what we hear", most of the points were either around the limit of audibility or considerably beyond it. For this reason, I have been responding to the actual distortion which occurs, NOT to what we would normally hear/perceive. However, my personal situation is different to the average consumer and due to the nature of my work, some of what "we would not normally hear/perceive" I not only have to hear but have to work on (see #4 below).
 
2. That depends. I am not interested in all those dramatic changes, I'm interested in those peaks and dips which do not change, those which are in common between different measuring positions. Occasionally, some of those peaks and dips can be addressed/corrected but the vast majority can't be, some of these I make note of, depending on the location in the spectrum and the severity.
 
3a. Well that "somewhere" is pretty much the whole planet! It's the standard basic setup/installation for cinemas, built into the cinema processor. Some cinemas go beyond that basic standard (those seeking THX certification for example) but the vast majority do not. In my own studio I do go beyond the basic cinema standard but nevertheless, that standard always has to be my reference. There is no industry standard for music studios, it's pretty much down to what you want and what you can afford.
 
3. No, with a 1/3 8ve you won't see the "seismograph", you'll just effectively see the effect of that "seismograph" averaged over each 1/3 8ve band. The seismograph is still there of course, just effectively hidden from view. A high Q dip (or peak) of sufficient magnitude will likely have a small affect on the 1/3 8ve band average but just seeing a slight dip in one of the 1/3 8ve bands doesn't tell us whether that dip has been caused by numerous small insignificant dips or a big (and potentially significant) one, for example. Yes, it would be easier just to use say a smoothed 1/12 8ve and forget 1/3 8ve measurements altogether but in my case I can't because that is the basic reference to which I must adhere. In other rooms and situations, which don't have to adhere to those standards then yes, I would ditch the 1/3 8ve measurements.
 
4. Relatively high Q and gain (usually negative gain, cut) values. Most of my work is in the film/TV industry. I frequently have to deal with location sound recordings which are very poor quality (relative to music recordings made in acoustically controlled environments) and typically require considerable work/processing. One of the many common faults I have to rectify is various electrical type hums from the filming equipment itself as well as from the filming environment (fridges and other appliances, etc.). This typically means an unwanted fundamental frequency + various (most commonly odd) harmonics, for which surgical (a series of high Q and cut value, "notch" type) EQ is the most common treatment. Before applying that treatment though, I obviously have to identify the problem frequencies and make various quantitative judgements, such as how many (if any) of the harmonics are worth treating and then how that surgical EQ is affecting/interacting with the rest of the recording. If that fundamental (or harmonics) happen to fall on one of those severe peaks or dips (common between multiple mic measurement positions) in my studio, then I could find myself applying treatment where it isn't necessary or conversely, not treating freq/s which require treatment. Which is why a big peak or dip in the seismograph type measurements, although of no relevance to normal hearing, is potentially significant to me (if they occur with multiple mic measurement positions) as mentioned in point #3 and why it could be useful to know some of those problem freqs, as mentioned in point #2.
 
5. Your quote is from point #5, prior to that (#1a) I stated "Generally I would use the industry standard (1/3 8ve RTA un-smoothed response) in a number of different positions around the LP.", which is about as obvious as it gets and also more generally, a hi-res measurement from a single position is not representative of how we normally hear and this fact should be obvious to anyone with experience of room analysis beyond the newbie level, which includes both of us. How many mic measurement positions I take depends on the room, the system I'm measuring, the time I've got available to make the measurements and why I'm making them in the first place. It would never be just 1, would almost never be less than 3 and could be as high as 12.
 
6. An audio engineer with a similar amount of experience in my segment of the audio industry would be equally aware of the issue I detailed in point #4 and alluded to in previous points/posts.
 
7. See #4 above as to "why". And yes, some can't be corrected.
 
8. Yes, and above but my point was; there are common consumer listening scenarios where the ratio of reflections to direct sound are close to or even above equal, even at relatively short distances from the speakers, even though human perception tends to deliberately alter that ratio (and therefore we are not consciously aware of it).
 
G

 

[pinnahertz]

   
1. With few exceptions, none of the OP's points/questions were "representative of what we hear", most of the points were either around the limit of audibility or considerably beyond it. For this reason, I have been responding to the actual distortion which occurs, NOT to what we would normally hear/perceive. However, my personal situation is different to the average consumer and due to the nature of my work, some of what "we would not normally hear/perceive" I not only have to hear but have to work on (see #4 below).
 
2. That depends. I am not interested in all those dramatic changes, I'm interested in those peaks and dips which do not change, those which are in common between different measuring positions. Occasionally, some of those peaks and dips can be addressed/corrected but the vast majority can't be, some of these I make note of, depending on the location in the spectrum and the severity.
 
3a. Well that "somewhere" is pretty much the whole planet! It's the standard basic setup/installation for cinemas, built into the cinema processor. Some cinemas go beyond that basic standard (those seeking THX certification for example) but the vast majority do not. In my own studio I do go beyond the basic cinema standard but nevertheless, that standard always has to be my reference. There is no industry standard for music studios, it's pretty much down to what you want and what you can afford.
 
3. No, with a 1/3 8ve you won't see the "seismograph", you'll just effectively see the effect of that "seismograph" averaged over each 1/3 8ve band. The seismograph is still there of course, just effectively hidden from view. A high Q dip (or peak) of sufficient magnitude will likely have a small affect on the 1/3 8ve band average but just seeing a slight dip in one of the 1/3 8ve bands doesn't tell us whether that dip has been caused by numerous small insignificant dips or a big (and potentially significant) one, for example. Yes, it would be easier just to use say a smoothed 1/12 8ve and forget 1/3 8ve measurements altogether but in my case I can't because that is the basic reference to which I must adhere. In other rooms and situations, which don't have to adhere to those standards then yes, I would ditch the 1/3 8ve measurements.
 
4. Relatively high Q and gain (usually negative gain, cut) values. Most of my work is in the film/TV industry. I frequently have to deal with location sound recordings which are very poor quality (relative to music recordings made in acoustically controlled environments) and typically require considerable work/processing. One of the many common faults I have to rectify is various electrical type hums from the filming equipment itself as well as from the filming environment (fridges and other appliances, etc.). This typically means an unwanted fundamental frequency + various (most commonly odd) harmonics, for which surgical (a series of high Q and cut value, "notch" type) EQ is the most common treatment. Before applying that treatment though, I obviously have to identify the problem frequencies and make various quantitative judgements, such as how many (if any) of the harmonics are worth treating and then how that surgical EQ is affecting/interacting with the rest of the recording. If that fundamental (or harmonics) happen to fall on one of those severe peaks or dips (common between multiple mic measurement positions) in my studio, then I could find myself applying treatment where it isn't necessary or conversely, not treating freq/s which require treatment. Which is why a big peak or dip in the seismograph type measurements, although of no relevance to normal hearing, is potentially significant to me (if they occur with multiple mic measurement positions) as mentioned in point #3 and why it could be useful to know some of those problem freqs, as mentioned in point #2.
 
5. Your quote is from point #5, prior to that (#1a) I stated "Generally I would use the industry standard (1/3 8ve RTA un-smoothed response) in a number of different positions around the LP.", which is about as obvious as it gets and also more generally, a hi-res measurement from a single position is not representative of how we normally hear and this fact should be obvious to anyone with experience of room analysis beyond the newbie level, which includes both of us. How many mic measurement positions I take depends on the room, the system I'm measuring, the time I've got available to make the measurements and why I'm making them in the first place. It would never be just 1, would almost never be less than 3 and could be as high as 12.
 
6. An audio engineer with a similar amount of experience in my segment of the audio industry would be equally aware of the issue I detailed in point #4 and alluded to in previous points/posts.
 
7. See #4 above as to "why". And yes, some can't be corrected.
 
8. Yes, and above but my point was; there are common consumer listening scenarios where the ratio of reflections to direct sound are close to or even above equal, even at relatively short distances from the speakers, even though human perception tends to deliberately alter that ratio (and therefore we are not consciously aware of it).
 
G

1. I've chosen to respond to the OP by attempting to delineate between audible issues worth worrying about and those that are not.  The word "neurosis" was my indicator that the approach was probably necessary.  
 
2. You owe it to yourself to try some of the software that lets you average multiple points in higher resolution.  It's saved my bacon on many of my pro and consumer calibrations.
 
3a.  You've confused "standard" with "common tool".  The 1/3 octave RTA isn't a standard, it's a common tool.  A "standard" is a usually a minimum performance target.  A standard may be written based on the best tools at the time, but there is wisdom to using better tools to hit an older standard.  A 1/3 octave RTA would be a tool that could be used in making sure a system meets the standard.  That doesn't mean there aren't better tools, or that the minimum tool must be used or the standard cannot be met.  I will concede that in larger rooms and theaters, 1/3 octave may be adequate and expedient..  But as we collect more data we also have to know what to do with it.   High res RTA up to 1/24th octave, and averaging over time and space have been around now for almost 20 years.  I have several, and use them all as needed.  The one thing I almost never use, apart from my quick/dirty hand-held analyzer, is 1/3 octave. Not in any room of any size.  And with time-domain data available, we can now see why we couldn't fix that pesky 1/3 octave EQ issue before.   And those have been around for 30 years, commonly and cheaply for 15 or more.  
 
Most standards, like the X-curve(s) for example, are continuous curves, not a series of points 1/3 octave apart.  The effort to make sure a room hits the published standard may well be better achieved by using higher resolution tools.  In fact, using a 1/3 octave analyzer likely insures you will miss the target curve at some point, and never know it.   I know of no target curves that are defined by 1/3 octave spaced data points alone, all are continuous curves.  
 
3. Ever do any time-domain measurements?  Many of those un-correctable peak and dips have a time-domain component that will shed some light.  RTAs are time-blind, hearing is not.  I can appreciate the problem of a small peak landing on a power frequency harmonic, but after the third, they're above the transition, and would be easily correctible.  Heck, even the fundamental shouldn't be all that hard to deal with. And second harmonic should be easy.  Puzzled by this,  but then, I'm not there to see it.  
 
4. That explains what you mean by "surgical EQ", corrective.  I find it strange, however, that a working studio would have such a significant peak or dip at a power line frequency fundamental or harmonic that couldn't be corrected, and would throw off the judgement of how much to notch it out.  After the second harmonic, we're above transition, and EQ works, pretty much all the time.  Below the second harmonic, we are into modal issues, but if they're that big, I wonder why they cannot be corrected.  Again, perhaps a bit of time-domain info would help. 
 
5. Great, we agree on multiple measurement positions, even if how we correlate them is still out there somewhere.  I like averaging measurements, or fuzzy clustering.  My brain won't absorb the visual impression of lots of different spectrum data to average several positions.  I need other tools, reserve the brain for analysis and interaction. 
 
6.  Thanks.  It was every bit the dig I though it was intended to be.  
 
7.  Yeah, and see my #4.  It's probably happening in the time domain.  What determines if it's correctable or not is money, not dB.  

 

[gregorio]

  2. You owe it to yourself to try some of the software that lets you average multiple points in higher resolution.  It's saved my bacon on many of my pro and consumer calibrations.
 
3a.  You've confused "standard" with "common tool".  The 1/3 octave RTA isn't a standard, it's a common tool.
 
3. Ever do any time-domain measurements?
 
4. That explains what you mean by "surgical EQ", corrective.  I find it strange, however, that a working studio would have such a significant peak or dip at a power line frequency fundamental or harmonic that couldn't be corrected, and would throw off the judgement of how much to notch it out.
 
6.  Thanks.  It was every bit the dig I though it was intended to be. 

 
2. No I don't.
3a. No, I'm not confused, you are! The standard and the common tools are effectively one and the same thing in cinema sound. All cinemas require a cinema processor and that means either a Dolby or DTS cinema processing unit, these units have the room analysis software built-in, which has to be employed during set-up/installation (by Dolby or DTS employees only) and therefore effectively defines the standard. THX is a specification which attempts to go beyond the basic cinema setup and is independent of the (higher resolution) measurement tools employed but the THX specification is only implemented in a tiny minority of the world's cinema screens, the vast majority just to the basic Dolby/DTS installation procedure and leave it at that. I agree that some of how it's typically done is an anachronism but anachronism or not, what I do has to adhere to those standards/tools.
3. On occasion.
4. I would find that strange too and my studio does not have any particular problems with mains freq (50Hz or 60Hz) or their harmonics! I said "electrical type hums" not earth loop/mains power hums. The hums I have to deal with can have a fundamental anywhere from about 70Hz to around 600Hz or so and have harmonics requiring treatment sometimes into the 1-2kHz range. And it's not uncommon to have to deal with two completely unrelated simultaneous hums.
6. Film sound is very significantly different to the music industry. Having expertise in the music industry, doesn't equate to expertise in the film industry. And the broadcast industry is something different again. This is something I'm intimately acquainted with, having started in the music industry and moved into the (TV) broadcast and film industries, a transition which was more complicated and required more time than I could ever have imagined when I started. My comment was not intended as a dig, it was intended to highlight the fact that there are many kinds/fields of audio engineers. It's entirely possible to be a very competent, even expert engineer in one or more audio fields and yet still be relatively ignorant of my field and of course vice versa.
 
G

 

[Joe Bloggs]

I'll walk past the room acoustics discussion and just put down my two cents, that I don't think the speaker designers would have designed them that way (ADC with no digital inputs) if they thought the ADC step would matter to the final sound in the slightest, and who am I to argue with them?

 

[hekeli]

I'll walk past the room acoustics discussion and just put down my two cents, that I don't think the speaker designers would have designed them that way (ADC with no digital inputs) if they thought the ADC step would matter to the final sound in the slightest, and who am I to argue with them?

 
Most stuff is designed for a certain price point, not for ultimate sound. I think EVE Audio commented that pretty much nobody would actually use digital inputs even if they had them. I think there is some truth to that so why waste (their) money.
 
As EVE user, I have little bit of the first posters neurosis too. But that's something I'll figure out myself, why ask here when it's the usual DACs are the same and acoustics matter more (I've got both sorted by my own ear and measurements, but thanks).

 

[pinnahertz]

   
2. No I don't.
3a. No, I'm not confused, you are! The standard and the common tools are effectively one and the same thing in cinema sound. All cinemas require a cinema processor and that means either a Dolby or DTS cinema processing unit, these units have the room analysis software built-in, which has to be employed during set-up/installation (by Dolby or DTS employees only) and therefore effectively defines the standard. THX is a specification which attempts to go beyond the basic cinema setup and is independent of the (higher resolution) measurement tools employed but the THX specification is only implemented in a tiny minority of the world's cinema screens, the vast majority just to the basic Dolby/DTS installation procedure and leave it at that. I agree that some of how it's typically done is an anachronism but anachronism or not, what I do has to adhere to those standards/tools.
3. On occasion.
4. I would find that strange too and my studio does not have any particular problems with mains freq (50Hz or 60Hz) or their harmonics! I said "electrical type hums" not earth loop/mains power hums. The hums I have to deal with can have a fundamental anywhere from about 70Hz to around 600Hz or so and have harmonics requiring treatment sometimes into the 1-2kHz range. And it's not uncommon to have to deal with two completely unrelated simultaneous hums.
6. Film sound is very significantly different to the music industry. Having expertise in the music industry, doesn't equate to expertise in the film industry. And the broadcast industry is something different again. This is something I'm intimately acquainted with, having started in the music industry and moved into the (TV) broadcast and film industries, a transition which was more complicated and required more time than I could ever have imagined when I started. My comment was not intended as a dig, it was intended to highlight the fact that there are many kinds/fields of audio engineers. It's entirely possible to be a very competent, even expert engineer in one or more audio fields and yet still be relatively ignorant of my field and of course vice versa.
 
G

2. Ok, that's fine.  I'll use my tools, you use yours.  
 
3a.  Cinema, as I mentioned, may get away with 1/3.   That doesn't mean you have to use it, nor that it's the best tool for the job.  The job is: match the Cinema system to the X-curve appropriate for its size. SMPTE 202M-1998 defines the target curve, but not the specific tools required to achieve it.  Yes, I know there's a 1/3 octave analyzer built into the Dolby processors, as well as EQ. However, even the Dolby hardware itself is not required to hit the curve in SMPTE 202M-1998, though in most cinemas, it is used.  I've used 1/3 octave analyzers since it was done with analog filters and it was the best we had.  The original Dolby Stereo processors had 1/3 octave EQ on a card you needed to extend outside the box to adjust, and we had things like the Ivie IE-30 to lug around. For acoustic analysis, I've even used the original TEF (and have one longer arm to prove it).  Regardless, no tool defines a standard.  The standard is the target curve.  And again, there is no requirement to use less capable or lower resolution tools to comply with the standard, and in fact, often the reverse is more desireable. I'm well aware of the THX specs having had that certification now for many years.  And yet, when it comes to EQ in the cinema, the standard for THX is also SMPTE 202M-1998!  Yes, THX recommends different tools...because the result is better and more accurate.  Using what you seem to consider standard tools that result in less accurate conformity to the standard is NOT following some standard.  I'm also well aware, having done it, that most cinemas have used the built-in tools in the Dolby processors, not because they are the standard, or are required to meet the standard.  We use them because they are there (and have likely invested in the compatible mics and multiplexer kit), and in some respects, easy to use.  Easy = fast = cheaper. Not better.  But apart from the convenience, even those tools are somewhat incomplete.  
 
4. The hums I have to deal with can have a fundamental anywhere from about 70Hz to around 600Hz or so and have harmonics requiring treatment sometimes into the 1-2kHz range. And it's not uncommon to have to deal with two completely unrelated simultaneous hums.
 
So, not power line related.  No matter. I've shared your pain many times. Remember trying to get rid of linear SMPTE timecode bleed?  Ha! Today we probably could, and of course, we don't use LTC anymore.   But as those problems relate to the performance of the room, the third harmonic is still above transition, and not in a range where you should have an uncorrectable response error.  I still question why a professional working room would have uncorrectable response anomalies that hamper notch filtering any of those frequencies.  I guess it's good you know where they are and can work around them.
 
6. Your comment was clearly revealing an assumption that someone else may not share your experience, and therefore be relatively ignorant.  While none of us could possibly share an identical total career experience, I would open the possibility that some of us have indeed crossed similar ground.  And it's also possible for someone to work in a field and yet also remain relatively ignorant of certain deeper technical aspects of engineering.  There is often a gap between operations, theory, and design. 

 

[gregorio]

  2. Ok, that's fine.  I'll use my tools, you use yours.  
 
3a.  ... [1] most cinemas have used the built-in tools in the Dolby processors, not because they are the standard, or are required to meet the standard.  We use them because they are there ... [2]. even those tools are somewhat incomplete.  
 
4. [a] I still question why a professional working room would have uncorrectable response anomalies that hamper notch filtering any of those frequencies.  I guess it's good you know where they are and can work around them.

 
2. They are not necessarily "my" tools but tools which have to be used.
 
3a. 1. In practise, they are required to meet the standard! You agree that a cinema requires the use of a (DTS or Dolby) cinema processor? Dolby and DTS require that the cinema processor is installed/setup by one of their own trained technicians and those technicians are trained in a specific setup procedure, which includes using the built-in tools. In practice then, it's not possible to meet the standard or even get a functional system without employing those tools. There are some exceptions, some cinemas which go well beyond this basic setup but probably 99% of the world's cinema screens don't, because it's not financially viable. 2. I'm not arguing that they are complete, in fact in my last post I specifically said that in some ways they are an anachronism (both the tools and standards!).
 
4a. That appears to contradict what you stated earlier. You appeared to agree previously that there's relatively little which can be done about the acoustic flaws introduced by the mixing desk. So, let's say the mixing desk caused (amongst others) a steep dip at/around say 398Hz and let's say we have a PSU or electric motor of some sort on set causing a hum on our location sound recording whose fundamental (or say 1st harmonic) just happens to also be 398Hz. That uncorrectable response anomaly of our room is obviously going to hamper our treatment; we're likely to miss the fact we even have a problem requiring treatment in the first place and secondly, even of we do somehow notice, how do we accurately judge how much treatment to apply?
4b. Which is why I sometimes want to know exactly what is going on, rather than have a smoothed measurement. I reiterate though, I'm not noting dips in response from just one measurement position.
 
We seem to be off-topic. I don't think discussing my studio or MO is of any benefit to others here, it's a very specific circumstance which I doubt applies to even one other head-fi member. For the benefit of those still reading who are bored rigid by this tech talk, here's a pic of my studio.
 

 
 
G

 

[pinnahertz]

   
2. They are not necessarily "my" tools but tools which have to be used.
 
3a. 1. In practise, they are required to meet the standard! You agree that a cinema requires the use of a (DTS or Dolby) cinema processor? Dolby and DTS require that the cinema processor is installed/setup by one of their own trained technicians and those technicians are trained in a specific setup procedure, which includes using the built-in tools. In practice then, it's not possible to meet the standard or even get a functional system without employing those tools. There are some exceptions, some cinemas which go well beyond this basic setup but probably 99% of the world's cinema screens don't, because it's not financially viable. 2. I'm not arguing that they are complete, in fact in my last post I specifically said that in some ways they are an anachronism (both the tools and standards!).
 
4a. That appears to contradict what you stated earlier. You appeared to agree previously that there's relatively little which can be done about the acoustic flaws introduced by the mixing desk. So, let's say the mixing desk caused (amongst others) a steep dip at/around say 398Hz and let's say we have a PSU or electric motor of some sort on set causing a hum on our location sound recording whose fundamental (or say 1st harmonic) just happens to also be 398Hz. That uncorrectable response anomaly of our room is obviously going to hamper our treatment; we're likely to miss the fact we even have a problem requiring treatment in the first place and secondly, even of we do somehow notice, how do we accurately judge how much treatment to apply?
4b. Which is why I sometimes want to know exactly what is going on, rather than have a smoothed measurement. I reiterate though, I'm not noting dips in response from just one measurement position.
 
We seem to be off-topic. I don't think discussing my studio or MO is of any benefit to others here, it's a very specific circumstance which I doubt applies to even one other head-fi member. For the benefit of those still reading who are bored rigid by this tech talk, here's a pic of my studio.
 

 
 
G

2. They are not necessarily "my" tools but tools which have to be used.
There is nothing stated in the standard that dictates what tools must be used. 
 
3a. 1. In practise, they are required to meet the standard! You agree that a cinema requires the use of a (DTS or Dolby) cinema processor? Dolby and DTS require that the cinema processor is installed/setup by one of their own trained technicians and those technicians are trained in a specific setup procedure, which includes using the built-in tools. 
 
There is nothing stated in the standard that dictates what tools must be used.   There is nothing in the Dolby publications and manuals that implies any specific tools must be used to meet the standards.  They provide tools and procedures only.  
In practice then, it's not possible to meet the standard or even get a functional system without employing those tools. 
Absolutely incorrect.  Using the provided tools is convenient, and well defined, but not required.  You can meet the standard without using a Dolby or DTS processor!  They aren't part of the standard, they just happen to be required to reproduce a soundtrack and happen to have calibration tools built in.  
 
4a. That appears to contradict what you stated earlier. You appeared to agree previously that there's relatively little which can be done about the acoustic flaws introduced by the mixing desk.
Incorrect.  I do not agree the medium LF acoustic flaws caused by the desk cannot be corrected.  I don't believe the mid-HF location-specific flaws caused by reflection can be corrected electronically, but they can be corrected positionally. 
 
So, let's say the mixing desk caused (amongst others) a steep dip at/around say 398Hz and let's say we have a PSU or electric motor of some sort on set causing a hum on our location sound recording whose fundamental (or say 1st harmonic) just happens to also be 398Hz. That uncorrectable response anomaly of our room is obviously going to hamper our treatment; we're likely to miss the fact we even have a problem requiring treatment in the first place and secondly, even of we do somehow notice, how do we accurately judge how much treatment to apply?
LF desk issues are much lower in frequency.  See the correction built into the EVE product, for example.  There should be no dip at nearly 400Hz that is uncorrectable.  Notching a specific frequency, as I'm sure you know, isn't all that subjective.  The issues are mostly what the notch does to surrounding audio.  If you can accurately judge a mix at all in that frequency band, you can accurately judge if the notch is working without damaging the desired audio.  
 
4b. Which is why I sometimes want to know exactly what is going on, rather than have a smoothed measurement. I reiterate though, I'm not noting dips in response from just one measurement position.
An unsmoothed single point measurement doesn't tell you "exactly what's going on" at all.  You must average or combine multiple points.  Lots of them.  More than 2 or 3.  Smoothing will let you see the audible differences.  An unsmoothed measurement only hides what you need to see. 
 
Yeah, we are off topic.  

 

[pinnahertz]

...Just to add one thing...
1/3 oct. might be the minimum res usable for a large cinema, but it's completely inadequate for a small room.