Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 103 - AVS Forum
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Old 05-28-2013, 01:26 PM
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...and just because certain reflections have a positiv effect on speech intelligibility within certain environments, other sounds might not benefit the same, they might even suffer.

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Old 05-28-2013, 01:28 PM
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Well, now that I'm motivated, I'll see about putting together some ETC and maybe RT60 plots of our mains for public commentary/ridicule. For this purpose, I take it I should be running it w/o Audyssey, or since I'm going to be listening with Audyssey 100% of the time, leave it enabled? And if doing L/R vs. single speaker is OK, should I be including subs, or does that matter?

 

Stuart, I have compared ETC measurement graphs both with Audyssey off, and with it on.  I see little or no difference, so I am inclined to say it doesn't matter.  HST, I usually work with the Audyssey-off graphs.  The important thing to remember is to measure only one speaker at a time, and I would measure all three front speakers. 

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Old 05-28-2013, 01:45 PM
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+1 and to this end, is it outside the scope of this thread to start debating the pros and cons of the various models to try and systematically develop an approach one might take to achieve a nice compromise between movies and music (understanding that we're venturing into preference territory)?  More specifically, how the use of tools like REW and various room treatment options can be used to achieve this (e.g. decay times, reflections etc.)?  I realize the purists among us will want to adhere to the strictest of guidelines wrt each model but I'm gathering that if one model fit everyone's goal precisely then we wouldn't be debating things like speech intelligibility of movies vs. music.  It seems Stuart, Jerry and myself are at least a couple members of this thread that are looking for a means to achieve a good compromise that doesn't necessarily fall within the parameters of various other room models (e.g. LEDE, RFZ, ambiechoic, AE, NE etc.) and at least in my case, the abundance of information presented has me confused on next steps for my HT particularly wrt adding room treatments.

 

I don't think this would be out of bounds at all.  However, I also think that as a starting point, we should establish and agree upon some basic standards.  I have read Nyal's "Acoustics Measurement Standards", and while I think this is a wonderful and useful document, I think some of the standards are unrealistic for those of us who have a mixed-use listening room.  For example, I am currently working on reducing early reflections.  All of my reflections are -15dB or better in the 20ms time frame (except for that damn ceiling fan), and all are -20dB or better after 20ms.  However, I think I have heard that all reflections should be -20dB, regardless of the time frame.  An attainable standard for the purposes of this thread would be useful.

 

I believe we have already agreed upon a modal decay standard--all resonances below the 40dB noise floor by 450ms in the 40Hz-300Hz range.  This is somewhat less aggressive than Nyal's standard. 

 

So, I'm not sure I will ever adopt a "model" per se, but I am very interested in understanding the various theories.  I am especially interested in some topics we have not explored in detail, e.g. diffusion (when and where to use it), and how to re-direct reflections so they add spaciousness to the listening room, i.e. more good reflections, less bad reflections (and a clear understanding of what this means).

 

So much to learn, and so much fun on the journey!

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Old 05-28-2013, 01:59 PM
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I don't think this would be out of bounds at all.  However, I also think that as a starting point, we should establish and agree upon some basic standards.  I have read Nyal's "Acoustics Measurement Standards", and while I think this is a wonderful and useful document, I think some of the standards are unrealistic for those of us who have a mixed-use listening room.  For example, I am currently working on reducing early reflections.  All of my reflections are -15dB or better in the 20ms time frame (except for that damn ceiling fan), and all are -20dB or better after 20ms.  However, I think I have heard that all reflections should be -20dB, regardless of the time frame.  An attainable standard for the purposes of this thread would be useful.

I believe we have already agreed upon a modal decay standard--all resonances below the 40dB noise floor by 450ms in the 40Hz-300Hz range.  This is somewhat less aggressive than Nyal's standard. 

So, I'm not sure I will ever adopt a "model" per se, but I am very interested in understanding the various theories.  I am especially interested in some topics we have not explored in detail, e.g. diffusion (when and where to use it), and how to re-direct reflections so they add spaciousness to the listening room, i.e. more good reflections, less bad reflections (and a clear understanding of what this means).

So much to learn, and so much fun on the journey!

There are a lot of threads that discuss different room models, both here and at GS. Thats not to say we couldnt start a new one though.

I would advise a bit of hesitancy on working too hard in any direction on your room until you have a model in mind. How each deals with reflections differs considerably. Putting a lot of effort into minimizing early reflections (depending on how you define early) could lead to having to redo everything later. While most models work with the early (<10ms) being subdued, what you do with those >10ms, especially >20ms is all over the place.

What is a BAD reflection or a GOOD one depends in part on how the chosen model works. If you are not emulating any model, then its a crap shoot to whether reducing some given reflection will be beneficial or not.

But there is more to reflection analysis that just magnitude and timing. Bandwidth and directionality can be crucial as well.

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Old 05-28-2013, 02:04 PM
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Originally Posted by AustinJerry View Post

I don't think this would be out of bounds at all.  However, I also think that as a starting point, we should establish and agree upon some basic standards.  I have read Nyal's "Acoustics Measurement Standards", and while I think this is a wonderful and useful document, I think some of the standards are unrealistic for those of us who have a mixed-use listening room.  For example, I am currently working on reducing early reflections.  All of my reflections are -15dB or better in the 20ms time frame (except for that damn ceiling fan), and all are -20dB or better after 20ms.  However, I think I have heard that all reflections should be -20dB, regardless of the time frame.  An attainable standard for the purposes of this thread would be useful.

I believe we have already agreed upon a modal decay standard--all resonances below the 40dB noise floor by 450ms in the 40Hz-300Hz range.  This is somewhat less aggressive than Nyal's standard. 

So, I'm not sure I will ever adopt a "model" per se, but I am very interested in understanding the various theories.  I am especially interested in some topics we have not explored in detail, e.g. diffusion (when and where to use it), and how to re-direct reflections so they add spaciousness to the listening room, i.e. more good reflections, less bad reflections (and a clear understanding of what this means).

So much to learn, and so much fun on the journey!

Jerry,

You met Nyal's standard for reflected sound (-10dB reduction in energy by 40ms) by a large margin, so that metric was not unrealistic for your room! That said, I think it was raised earlier that there is some disagreement between the experts. In the absence of agreement, we may simply have to present all the theories and let the user decide amongst them, like the room models.

Mark
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Old 05-28-2013, 02:09 PM
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Jerry,

You met Nyal's standard for reflected sound (-10dB reduction in energy by 40ms) by a large margin, so that metric was not unrealistic for your room! That said, I think it was raised earlier that there is some disagreement between the experts. In the absence of agreement, we may simply have to present all the theories and let the user decide amongst them, like the room models.

Mark

 

Mark, maybe Jim is right--there are already a number of threads that discuss the various models.  Maybe the best thing here is to just provide links.  WRT to disagreement, you think so?  eek.gif

 

Edit:  BTW, I am seriously thinking about purchasing "Sound Reproduction", which I have yet to read.

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Old 05-28-2013, 02:37 PM
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Well, now that I'm motivated, I'll see about putting together some ETC and maybe RT60 plots of our mains for public commentary/ridicule. For this purpose, I take it I should be running it w/o Audyssey, or since I'm going to be listening with Audyssey 100% of the time, leave it enabled? And if doing L/R vs. single speaker is OK, should I be including subs, or does that matter?

 

Stuart, I have compared ETC measurement graphs both with Audyssey off, and with it on.  I see little or no difference, so I am inclined to say it doesn't matter.  HST, I usually work with the Audyssey-off graphs.  The important thing to remember is to measure only one speaker at a time, and I would measure all three front speakers. 

 

Same here - no real difference. So much for Audyssey working in the time domain huh?

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Old 05-28-2013, 02:47 PM
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Well, now that I'm motivated, I'll see about putting together some ETC and maybe RT60 plots of our mains for public commentary/ridicule. For this purpose, I take it I should be running it w/o Audyssey, or since I'm going to be listening with Audyssey 100% of the time, leave it enabled? And if doing L/R vs. single speaker is OK, should I be including subs, or does that matter?

 

Stuart, I have compared ETC measurement graphs both with Audyssey off, and with it on.  I see little or no difference, so I am inclined to say it doesn't matter.  HST, I usually work with the Audyssey-off graphs.  The important thing to remember is to measure only one speaker at a time, and I would measure all three front speakers. 

 

Same here - no real difference. So much for Audyssey working in the time domain huh?

 

Well, I'll need to double check my ETC's and RT 60 but I can say my waterfalls post XT32 calibration are improved wrt ringing in the bass frequencies.

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Old 05-28-2013, 02:52 PM
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Well, now that I'm motivated, I'll see about putting together some ETC and maybe RT60 plots of our mains for public commentary/ridicule. For this purpose, I take it I should be running it w/o Audyssey, or since I'm going to be listening with Audyssey 100% of the time, leave it enabled? And if doing L/R vs. single speaker is OK, should I be including subs, or does that matter?

 

Stuart, I have compared ETC measurement graphs both with Audyssey off, and with it on.  I see little or no difference, so I am inclined to say it doesn't matter.  HST, I usually work with the Audyssey-off graphs.  The important thing to remember is to measure only one speaker at a time, and I would measure all three front speakers. 

 

Same here - no real difference. So much for Audyssey working in the time domain huh?

 

Well, I'll need to double check my ETC's and RT 60 but I can say my waterfalls post XT32 calibration are improved wrt ringing in the bass frequencies.

 

My waterfalls are improved too. But the ETCs (R, L and C only) show little or no difference. I've never done RT60s as I have been led to believe they are fairly useless for small, domestic rooms. Nothing posted here recently has changed my mind on the latter.

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Old 05-28-2013, 02:57 PM
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BTW, I am seriously thinking about purchasing "Sound Reproduction", which I have yet to read.

That book is a must, seriously. While I don't agree with all of Toole's conclusions, there is no other book on this planet summing up decades of psychoacoustic literature in a such an accessible way.

Markus

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Old 05-28-2013, 04:02 PM
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OK, now we are definitely off-topic. Discussions of the merits of Audyssey belong in the Audyssey thread, IMO.
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Old 05-28-2013, 04:28 PM
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If your talking about a classroom and we are concerned with how well we hear a person speaking, then I agree. If your talking about room acoustics for audio reproduction, then I disagree strongly.
It is easy to disagree. Much harder to provide proof that you are right smile.gif. Are you saying that if I speak in a room the reflections help. But if you record my voice and then play it in your center speaker, the very same reflections all of a sudden don't do the same thing? How is that possible? How do the reflections know they are from a speaker and not a person? How does your ear?

And what do we do about the fact that much of the research into intelligibility of speech, including the ones I cited are often done with speakers??? Here is an example reference cited in what I provided earlier from Bradley et. al.:

"All simulated sound fields were produced using an 8-channel electroacoustic system with loudspeakers arranged around the listener in an anechoic room. The 8 loudspeakers were located at a distance of 1.7 m from the listener and their angular locations relative to the listener are described in Table I."

As you see, the reflections were simulated using speakers so that they could be precisely controlled -- something you can't do in your listening space. So if you are just relying on your own judgement and intuition, I am afraid is not a valid response. smile.gif

And no, you can''t change the volume control of your center channel to accomplish the same thing. Much of movie content is pumped into the center channel (because it is best associated with what is on screen) and if you mess with its levels, you screw up everything else. Why design the room poorly and then try to compensate by turning up he volume?

I realize these are non-intuitive concepts. But that is just how our brain is wired. And a good thing too since we live indoors with massive amount of reflections around us. We would go crazy if the brain had not learned to ignore their timing and summed them together!

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Old 05-28-2013, 04:41 PM
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Definitely. Looking at RT is like checking if your fridge is switched on when you actually wanted to know how cold it is inside. Not very meaningful.

it's like averaging the weather across the entire CONUS to determine if you need an umbrella in your local town at a particular time of day. meaningless. RT60 has assumptions regarding the behavior of the sound-field in order to be considered relevant. toole even goes on to specifically state how it is a "ball-park" (as useful as your eyes in viewing how reflective or dead the room is) - and lacking locational data that is required in such analysis.

RT60 doesn't tell you anything regarding the later arriving reflections as it doesn't tell you about how the energy impedes the listening position over time.

the worst is when the salesmen ("learning as he goes") in this thread first not only completely obliterate the conceptual understanding of what "critical-distance" is, but then go on to assume there is a single slope in an empty garage. neither of them could actually tell us what a "reverberant sound-field" really is. hint - it's two words and they failed to even mentioned it as it will quickly allow one to understand how the energy in a reverberant sound-field is different than the localized energy in a small acoustical space.

poor guy - no wonder everyone stopped replying that in that gearslutz thread. no sense continuing to do their homework for them. we already had embarrassed them of their erroneous understanding of just what "critical-distance" means and why their "2ft Dc" was an absolute laughable statement ... no sense wasting time any further; it's best to let them continue on their misguided ways and laugh from a distance ("well beyond Dc", that is! LOL).

although on the subject of beyond "well past Dc", it is comical that they erroneously used an equation to "calculate Dc", while completely ignoring the real world behavior of the acoustical space - as if whatever number a calculation spits out is somehow automatically the real and actual behavior of the energy in the garage. eek! and after that, they had to actually request from us how to measure Dc, as they themselves did not know.

oh, and you noticed they failed to produce the waterfall or measurement file for proof from the garage after numerous requests - it's pretty obvious why.
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Old 05-28-2013, 04:44 PM
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I think the multi-purpose room concept is the nub of the issue. We don't have music venues that look like (sound like) cinemas and we don't have cinemas that look/sound like concert halls. I believe they both have different requirements and it is trying to achieve the compromise of the multi-purpose space that makes things extra-difficult. It's one of the reasons I decided very early on in my journey that the HT would be for movies only.
I think cinemas and concert halls need to look quite different because their acoustic tasks are quite different: cinema--recreation of sound; concert hall--creation of, well, a concert hall effect. wink.gif

But at home, the tasks are much more similar between movies and music -- it is a sound reproduction task in either case. Yes, due to the nature (limitations?) of stereo, we use the room to act as a sort of mechanical spatial/surround enhancement system. We may even choose speakers like dipoles that go a step further down this path. I suppose it can be taken to such limits that it begins to impair the quality or intelligibility of movie soundtracks. Rather than such mechanical/acoustic solutions, I find PLIIx gives me the envelopment I like from music. But I was into that long before I had a dedicated home theater.

I also believe that between the extremes of great movie systems that sound mediocre on music and great music systems that do injustice to movies, there's a reasonable overlap where both genres can be very well served with one system. I happen to think I have struck that balance to such an extent that I pine not for improvements in either direction.

Dumb luck. Or maybe just dumb...

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Old 05-28-2013, 04:54 PM
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And no, you can''t change the volume control of your center channel to accomplish the same thing. Much of movie content is pumped into the center channel (because it is best associated with what is on screen) and if you mess with its levels, you screw up everything else.
We have to apply that same consideration to the room where the early reflections raise the loudness of the center speaker. When that happens, the drive signal to the speaker is reduced when the SPL calibrations are made.

Now, with both center channel cases (reflective and less so) calibrated to the same SPL relative to all the other speakers, which one sounds more intelligible?

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Old 05-28-2013, 05:02 PM
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That's just not true Roger smile.gif. \
I think you missed where I said "can possibly impair intelligibility". In particular, if the noise is high enough.

Please note I was answering Sanjay's hypothetical:
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So if early reflections raised the apparent loudness of the background the way they did with speech, then that wouldn't improve intelligibility?
I took that to mean the early reflections were indeed noise (unrelated with the desired speech), such as generated by the students, which I clarified in my very next reply in the same post.

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Old 05-28-2013, 05:14 PM
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OK, now we are definitely off-topic. Discussions of the merits of Audyssey belong in the Audyssey thread, IMO.

Fair enough--especially since I've beem known to talk about other threads going OT due to overfamiliarity of some posters with one another.

I'll look at generating those RT60 and ETC plots when I can access my L/C/R (pre-Audyssey) curve data.

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Old 05-28-2013, 09:35 PM
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OK - here's some RT60 plots for commentary. If I focus on the 500 to 1000 Hz range, according to the 0.2 to 0.5 'standard' Amir mentioned in his cookbook, am I "OK"? Or should I be focusing on absorbing some of these frequencies below 500 Hz, given that I really don't want an NE room (but haven't settled on exactly what my hypothetical model should be)?


RT60 plots are run with TOPT, and the full frequency range as per the plot Jerry ran.
Left speaker:


Right speaker:
[

Center speaker


FYI, I also ran an ETC (envelope) chart on my post-Audyssey measurement of mains (L/R) and subs. The raw plot is, well, reflection happy above -20 db in my untreated room:


Finally, if I understood what Jason suggested to Jerry, for comparison here's the same ETC plot filtered at 500 Hz:


Given the room that I described a couple of days ago, and my 60/40ish music vs. HT orientation, what do I do with this, besides break out the string? Remember, I'm running powered Mythos ST towers and CS-8080 HD powered center up front, and least to my taste, the sound's "spacious" enough. However, as we all know, you don't what's broken until you realize it, so to speak, by comparing to something else.

My 1/6th plot for frequency response, full-range on mains+subs Post-Audyssey, is included for completion:


Stuart

 

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Old 05-28-2013, 11:11 PM
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In my mind, the question is why start from the premise that a methodology that happens to aid intelligibility in a classroom should be applied to home theaters?
The classroom was an example that you brought up, not me, the previous time this topic came up. I didn't mind because it is one of many data points in the history of research into reflections indicating that early reflections tend to have a positive or, at worst, neutral impact on intelligibility. Keep in mind that I was originally replying to a post that suggested early reflections had a negative impact on intelligibility and that absorbers at early reflection pints could correct that problem. My experience and everything I had read suggested otherwise. So I posted an alternative.

Apparently that has morphed into me suggesting: tuning home theatres specifically for poorly mixed soundtracks, a universal need for improved intelligiblity, replacing volume controls with bare walls, designing home theatres using classroom methodology, intelligibility can't exist with headpones, etc. Your classroom example joins Ando's anechoic testing and Haas on the roof of his college building and a variety of dissimilar tests that all trend towards early reflections not being the detriment to intelligibility that many folks thought they were. The classroom was but one example of that. But that doesn't mean it's the only example or that home theatres should be designed around it.

Where examples of rooms with early reflections do have an impact on home theatres is when it comes to treatment. In the example I asked Keith, there are three basic ways to treat the early reflections of your centre speaker: absorb, diffuse or reflect. All three will sound different, and their use will come down to personal preference. But which of those three will yield greater intelligibility? Most people would reflexively say absorbtion. This is where I disagree. But that doesn't suddenly become a call for making home theatres sound like classrooms. It does mean that absorbing early reflections for the sake of intelligibility might not be needed or a good idea.
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I have not seen research that shows early reflections improve timbre. For imaging, it is a mixed bag as the nature of the reflections can vary quite a lot. Some may sound nice, others may not (e.g., glass).
Not sure what you mean by "improve" timbre. You said those reflections might alter timbre and I said research indicated the opposite (might not alter timbre). Michel Barron had done some research in the '70s on reflections from multiple directions actually reducing colourations. Toole & Olive found that early reflections made it harder to hear room resonances that colour the sound.

I agree about the imaging being dependent on the nature of the reflections, but preference tests point towards the effects (apparent source width, image size) being desirable more than not. The reason I mention Wolfgang Klippel's tests is because he pitted narrow dispersion speakers that had flat on-axis response against wide dispersion speakers that had flat on-axis response but terrible off-axis response. The listeners kept preferring the wide dispersion speakers.

Before anyone jumps to conclusions, that's not an endorsement to design speakers with crappy off-axis response. It just showed that listeners craved the bigger/wider soundstage so much, they were willing to take something (anything) from the side walls over nothing at all. Of course, speakers with good/consistent on and off axis response would have fared better.
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The same direction? How same? Haas did not stipulate same direction. All they have to do is arrive coincidentally.
Pops up from time to time in papers I've read. Couple of examples:

"An interesting aspect of the precedence effect is that the perception depends not just on the delay but also on the spatial separation between the two sources. For instance, if the two sources are located on a straight line extending from the listener so that the listening angle is the same to both sources, the sound will be perceived as colored. If the same delay settings are used but the speakers are separated horizontally, there is no perception of coloration. We simply hear the first source. If we put an omni-directional microphone in the place of the listener, the two experimental set-ups however yield two identical recordings (assuming the room is well-damped). Both sound awful. The second source interferes with the first one." - Mathias Johansson, Dirac Research

"Another difficult situation is one with only a single dominant reflection arriving from close to the same direction as the direct sound. In a control-room context, this could be a console reflection in an otherwise dead room. Fortunately such events are rare. Most reflections arrive from directions different from the direct sound, and perceptions vary considerably. Two ears and a brain have advantages over a microphone and an analyzer. The fact that the perceived spectrum is the result of a central (brain) summation of the slightly different spectra at the two ears attenuates the potential coloration from lateral reflections significantly.' -Toole, Loudspeakers & Rooms (under the section discussing effects on timbre)

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+1 and to this end, is it outside the scope of this thread to start debating the pros and cons of the various models to try and systematically develop an approach one might take to achieve a nice compromise between movies and music (understanding that we're venturing into preference territory)?  More specifically, how the use of tools like REW and various room treatment options can be used to achieve this (e.g. decay times, reflections etc.)?  I realize the purists among us will want to adhere to the strictest of guidelines wrt each model but I'm gathering that if one model fit everyone's goal precisely then we wouldn't be debating things like speech intelligibility of movies vs. music.  It seems Stuart, Jerry and myself are at least a couple members of this thread that are looking for a means to achieve a good compromise that doesn't necessarily fall within the parameters of various other room models (e.g. LEDE, RFZ, ambiechoic, AE, NE etc.) and at least in my case, the abundance of information presented has me confused on next steps for my HT particularly wrt adding room treatments.

I don't think this would be out of bounds at all.  However, I also think that as a starting point, we should establish and agree upon some basic standards.  I have read Nyal's "Acoustics Measurement Standards", and while I think this is a wonderful and useful document, I think some of the standards are unrealistic for those of us who have a mixed-use listening room.  For example, I am currently working on reducing early reflections.  All of my reflections are -15dB or better in the 20ms time frame (except for that damn ceiling fan), and all are -20dB or better after 20ms.  However, I think I have heard that all reflections should be -20dB, regardless of the time frame.  An attainable standard for the purposes of this thread would be useful.

I believe we have already agreed upon a modal decay standard--all resonances below the 40dB noise floor by 450ms in the 40Hz-300Hz range.  This is somewhat less aggressive than Nyal's standard. 

So, I'm not sure I will ever adopt a "model" per se, but I am very interested in understanding the various theories.  I am especially interested in some topics we have not explored in detail, e.g. diffusion (when and where to use it), and how to re-direct reflections so they add spaciousness to the listening room, i.e. more good reflections, less bad reflections (and a clear understanding of what this means).

So much to learn, and so much fun on the journey!

Jerry,

I agree that we need to set some standards and I realize not everyone is going to strictly adhere to a specific acoustic model. I do think one should choose a model and set that as the goal, then try to get as close as possible though.

I have ideas in mind, many of which are close to Nyal's BTW (but there are some key differences which push more towards LEDE/RFZ standards) but I have a big problem right now.

In the community as a whole, most all the experts agree with the long standing research on topics such as early reflections vs late reflections good/bad/what the targets should be but we have ONE poster who is coming in here, derailing us by telling folks they need to pay attention to an RT60 measurement which has no basis in reality for statistically small acoustical spaces, then also telling people to look at only a very specific range between 500hz and 1khz, not setting proper guidelines, getting ahead of the pack, and introducing all kinds of text/references that are irrelevant to the topic and none of his own information or proof of his concepts (peer reviewed and accepted info, for instance) which almost all are in absolute conflict with the proven standards which I aim to teach here.

This is disheartening to me because I personally don't feel like arguing with him, he already stated early on he would leave the thread, but we see that's not true, has personally questioned my credentials and attacked me in another thread, and if he continues I see this thread easily and quickly turning into all the other threads he's been involved in.

I don't want to see this thread go downhill and then fizzle out.

I hope people are learning who to listen to. Localhost, Markus, Roger, Nyal, Jeff Hedback, and a guy who has not graced us with his unlimited knowledge on these subjects by the name of Mark, who goes by "Dragonfyr" on AVS. These folks know what they are talking about (there are several others who I don't mention by name who are active in this thread and many others, and you know who you are talking about....THANK YOU ALL for your participation)

But this one guy is throwing us off, getting us to go down paths that are WAY ahead of where we stand now and aren't even relevant at all.

So.... At first, I suggested everyone pick a room model, list what they were interested in, then i planned to tally up the results and start teaching the most popular model first.

That hasn't happened and it seems as though a lot of folks have multi-purpose rooms and just want to get "close" in this thread.

That's fine. We simply need to decide what we need to focus on and what the majority would like to learn more about first.

I think we need to concentrate on and master one thing at a time.

Where do we begin?

Would you all like to talk more about the ETC, how to use it (and how/why it will give you accurate information that the TOPT feature on the RT60 tab in REW tries and only sometimes comes close to) and what those targets should be, plus of course how to get there?

Or should we concentrate on bass trapping, not overdoing broadband acoustics so we don't overdampen our rooms, etc?

Should we talk more about other methods besides just throwing up insulation to tame reflections, so we can preserve the finite amount of energy in our rooms and properly redirect it then reintroduce it laterally in an exponentially decaying form?

Should we talk about all the different types of room treatments and what they're used for first? Diffusers, 1D, 2D, Poly, QRD, PRD, Helmholtz, BAD panels, Membranes, etc?

Should we just look at one or two specific cases at a time, from helpful and popular posters, such as Jerry and Keith, who each want to accomplish a different model and go at their pace, filling in the information they need to know to accomplish their goals along the way?

This is YOUR thread, not mine. I'm just here to help and try to keep things straight.

What do you all want from me and expect from me? Tell me what you want to know and I'll try to work down the list from most popular to least popular.

BTW, I'm not saying that I know everything and I'm right and everyone else is wrong, but what I AM saying is since this isn't an advanced thread like you'd find over on Gearslutz and we don't have a lot of folks in the industry participating, we need to have a plan, go slow, and teach the methods that are TRIED AND TRUE - Not things from new papers released in the last few years - but methods that have been around for DECADES with proven results.

This isn't the forum/thread to try new methods and develop new room models.

This is a thread dedicated to new users of REW who wish to broaden their horizons and are just starting out. We need to give you the right information the first time so you don't find later that half the things you were told are WRONG or at least contested by most people in the industry.

I need some feedback and a vote. I'll take this wherever everyone wants to go and I'm willing to go wherever you all tell me. biggrin.gif

--Jason

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Old 05-28-2013, 11:54 PM - Thread Starter
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I don't think this would be out of bounds at all.  However, I also think that as a starting point, we should establish and agree upon some basic standards.  I have read Nyal's "Acoustics Measurement Standards", and while I think this is a wonderful and useful document, I think some of the standards are unrealistic for those of us who have a mixed-use listening room.  For example, I am currently working on reducing early reflections.  All of my reflections are -15dB or better in the 20ms time frame (except for that damn ceiling fan), and all are -20dB or better after 20ms.  However, I think I have heard that all reflections should be -20dB, regardless of the time frame.  An attainable standard for the purposes of this thread would be useful.

I believe we have already agreed upon a modal decay standard--all resonances below the 40dB noise floor by 450ms in the 40Hz-300Hz range.  This is somewhat less aggressive than Nyal's standard. 

So, I'm not sure I will ever adopt a "model" per se, but I am very interested in understanding the various theories.  I am especially interested in some topics we have not explored in detail, e.g. diffusion (when and where to use it), and how to re-direct reflections so they add spaciousness to the listening room, i.e. more good reflections, less bad reflections (and a clear understanding of what this means).

So much to learn, and so much fun on the journey!

There are a lot of threads that discuss different room models, both here and at GS. Thats not to say we couldnt start a new one though.

I would advise a bit of hesitancy on working too hard in any direction on your room until you have a model in mind. How each deals with reflections differs considerably. Putting a lot of effort into minimizing early reflections (depending on how you define early) could lead to having to redo everything later. While most models work with the early (<10ms) being subdued, what you do with those >10ms, especially >20ms is all over the place.

What is a BAD reflection or a GOOD one depends in part on how the chosen model works. If you are not emulating any model, then its a crap shoot to whether reducing some given reflection will be beneficial or not.

But there is more to reflection analysis that just magnitude and timing. Bandwidth and directionality can be crucial as well.

This is SO TRUE!

I'm finding most people on this thread are probably going to go one way or another.

So here's how I (and just about everyone else who is in this industry and knows what they're talking about) would recommend folks starting out, what goals to set, and what it should ultimately look like.

If you are more interested in 2-channel, meaning you more critically listen to it, whether or not you listen to it more than watch movies, then you want to work towards a LEDE/RFZ design.

If you are more interested in movies and mostly watch movies, plus aren't too critical of your 2-channel (don't sit with your head in a vice or buy special recliners with low backs, etc) then you are most likely going to work towards an NE model.

Here's the main difference regarding reflections.

First, reflections ARE NOT BAD!!! We have to quit saying that.

High Gain EARLY reflections (less than about 20ms) are bad. This goes for either room model and in fact ALL common acoustic models.

So, after the direct sound, you should have reflections no higher in gain than -15db and the real goal, especially if going for the specific NE or LEDE model should be -20db.

At around 20ms is where the models change. For NE, this simply continues. It should evenly decay more and more beyond about 20ms to infinity. Where this decays into the noise floor, looking at the ETC (NOT RT60 as that doesn't EXIST in small acoustical spaces) is your decay time and this is how you can figure out how live/dead your room is. (This is a real quick/dumbed down answer but we'll go into more detail later)

So if you mostly listen to movies and aren't too critical of or don't listen to a lot of 2-channel only music, you simply want to make sure you don't have any reflections higher than about -15db in the first 20ms (but really try to make that -20db) and that should simply continue at and after around 20ms to decay more and more, and EVENLY, into the noise floor.

Even AFTER 20ms, if you have a high gain reflection here and there, you need to take care of that too.

Plus, even with NE, you can have a "Too Dead" room so you needn't only use absorption and can still take advantage of redirection and diffusion. Nobody says an NE room has to sound dead. It's just that there aren't high gain reflections, whether early or late, so the response is "effectively anechoic" - but not dead. wink.gif

Now, for what I think most people will want to work towards as most of us use one room for both movies and music...

Same as above for up to around 20ms but at or around 20ms you need to have a high gain reflection. But not just one. That EARLY energy, if not absorbed and taken away forever, should be reintroduced laterally/behind at a level as close to around -12db or higher as possible and THEN - Naturally decay EVENLY into the noise floor. You NEED diffusers and simply cannot do this with just absorption/insulation/fluffy/fuzzy stuff.

You will most likely need redirection/reflection, too, because people use way too much fuzzy stuff/insulation and there is a finite amount of energy to work with.

The goal with this model is to hear only the direct sound followed by about 20ms of effectively anechoic (no high gain EARLY reflections) - then create a sense of a larger room and be able to hear all the sonic characteristics of the room the original recording was created and mixed. You need that ISD gap to achieve this, but if you don't then TERMINATE that ISD gap at around 20ms (depending on size of room) you are really just creating an NE room.

This is where those reflections become important and NECESSARY. All reflections are NOT bad and are needed to create a lively room that will let you hear ALL the information on the recording as is intended and you cannot really do this (2-channel rooms or 2-channel mode in a multi-channel room) without reflections.

If you just have one HIGH GAIN reflection at around 20ms but then the next several ms are back under -20db, then have another sparse high gain reflection here and there, you're just creating a mess and this is not what we are going for.

You have to be careful to not use too much absorption.

Jerry's room is looking great. But most other rooms are ALREADY under .2ms.

So, if you are going to look at the TOPT in the RT60 field, even though there are better ways, since it's been brought up and people are posting their graphs, even though this is also way ahead of where we really are (and if the previous information is adhered to this will take care of itself) here is what you should be looking for.

First, looking only at 500hz to 1khz is RIDICULOUS!!! That's taking 500hz of a sample even though the specular region is from about 350hz to 20000hz and makes no sense. I've NEVER heard of this recommendation anywhere else.

You should look at this in 1/3rd octaves. REW defaults to 1/1 so you need to change this in preferences.

You should be looking at THE FULL SPECTRUM. You do not need to zero in / zoom in on specific frequencies.

It SHOULDN'T matter whether you use one speaker, two, or all 7-11 for this.

If your room is properly treated (but see, we're not that far along yet and are jumping ahead, plus not really using the right tool for this - although if we are going to use the RT60 tab in REW, TOPT is the closest to accurate for our small acoustical spaces - so it's the best compromise, but make no mistake, it is a compromise and doesn't tell the whole or even necessarily accurate picture) this should be pretty even no matter which speaker(s) you use or what SPL you take the measurements at.

The goal should be no less than .2s across the range. If you have a VERY small room like Keith's then .2 is okay. If you have a lot of diffusion then .2 is okay. In fact, my own 20x26x8.8ft room, at 4500cu ft is right at .2. But it's even and there is proper diffusion. My ETC looks good and the room isn't dead.

If you are only using absorption and have a small room then that .2ms is going to sound a lot different.

You should NEVER be more than .5s.

It's okay for the Modal and Transition region to be a little higher than the specular region (let's say above 300hz for this thread) but not by a whole lot and even that should be even.

For instance, the modal/transition region graph showing .4 second (40hz to 300hz) then from around 300hz on the TOPT graph showing .25 second is fine. But if the whole frequency range from the graph limits of around 60hz up to 20khz ranges from .25s to .4s up and down up and down etc, that is NOT okay.

The BBC made some really good targets their studios had to adhere to, and while this is difficult to accomplish, we do need to at least set goals.

Their rule is no octave should be more than 10% below or above the previous/next octave. I think we can change that to 20% and be fine.

From the graphs that have been posted so far, although the rooms are on the dry/dead side for the most part, it's also true that most of them (pleasantly surprising to me, honestly) are pretty even. That's GREAT!

A good target for most rooms is about .3 seconds, but not less than .2 and few will get up past .35 to .4 and NONE should be more than .5. These need to be as even as possible from one octave to the next and it's okay for the modal/transition region (only due to compromise and not because acoustically it's okay - only because the lower frequencies are harder to threat, though) about 30% more than that.

Now, I know this post is jumbled and yet another novel as I don't seem to be able to make short posts, but Jerry, Keith, et al - If you would/could take this information and "pretty it up" so more people can read, understand/interpret, and be able to put this to use in a more clear/concise format I'd be forever grateful.

Thanks a bunch, and let's keep the conversation moving forward...

--J
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Old 05-29-2013, 12:01 AM - Thread Starter
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Jerry,


You met Nyal's standard for reflected sound (-10dB reduction in energy by 40ms) by a large margin, so that metric was not unrealistic for your room! That said, I think it was raised earlier that there is some disagreement between the experts. In the absence of agreement, we may simply have to present all the theories and let the user decide amongst them, like the room models.


Mark

Mark, maybe Jim is right--there are already a number of threads that discuss the various models.  Maybe the best thing here is to just provide links.  WRT to disagreement, you think so?  eek.gif

Edit:  BTW, I am seriously thinking about purchasing "Sound Reproduction", which I have yet to read.

I STRONGLY recommend starting with Master Handbook of Acoustics first, Jerry.

I highly respect Floyd Toole and his work, and actually do suggest you reading his book, but after MHOA because some of his topics regarding reflections go against, well.... Just about everyone else.

This is a recommendation I make for everyone.

Then, if you are still interested and your brain doesn't hurt too much, you can learn everything you'd ever want to know about acoustics by reading Sound System Engineering.

If you also want to learn how to build your own acoustic treatments and the why, along with when/how to deploy them, I recommend Acoustic Absorbers and Diffusers.

These are the best texts to read and you'll learn a ton!

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Old 05-29-2013, 12:11 AM - Thread Starter
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Well, now that I'm motivated, I'll see about putting together some ETC and maybe RT60 plots of our mains for public commentary/ridicule. For this purpose, I take it I should be running it w/o Audyssey, or since I'm going to be listening with Audyssey 100% of the time, leave it enabled? And if doing L/R vs. single speaker is OK, should I be including subs, or does that matter?

Stuart, I have compared ETC measurement graphs both with Audyssey off, and with it on.  I see little or no difference, so I am inclined to say it doesn't matter.  HST, I usually work with the Audyssey-off graphs.  The important thing to remember is to measure only one speaker at a time, and I would measure all three front speakers. 

Same here - no real difference. So much for Audyssey working in the time domain huh?

It's not that Audyssey doesn't work in the time domain per se (in other ways), but it DEFINITELY cannot/will not control reflections. I still don't see how that is possible although some higher end forms of RC that I haven't been able to try out do claim this. But I just don't see how it is possible as the reflection is a physical/analog thing AFTER the sound leaves the processor/speakers, so...

I've made many many tests though, some of which had only ONE reflection for Audyssey to deal with, as I purposely set it up that way, and Audyssey has NEVER made a difference in the ETC. wink.gif

--J

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BTW, I am seriously thinking about purchasing "Sound Reproduction", which I have yet to read.

That book is a must, seriously. While I don't agree with all of Toole's conclusions, there is no other book on this planet summing up decades of psychoacoustic literature in a such an accessible way.

A big +1!

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Old 05-29-2013, 12:24 AM - Thread Starter
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Definitely. Looking at RT is like checking if your fridge is switched on when you actually wanted to know how cold it is inside. Not very meaningful.

it's like averaging the weather across the entire CONUS to determine if you need an umbrella in your local town at a particular time of day. meaningless. RT60 has assumptions regarding the behavior of the sound-field in order to be considered relevant. toole even goes on to specifically state how it is a "ball-park" (as useful as your eyes in viewing how reflective or dead the room is) - and lacking locational data that is required in such analysis.

RT60 doesn't tell you anything regarding the later arriving reflections as it doesn't tell you about how the energy impedes the listening position over time.

the worst is when the salesmen ("learning as he goes acoustician") in this thread first not only completely obliterate the conceptual understanding of what "critical-distance" is, but then go on to assume there is a single slope in an empty garage. neither of them could actually tell us what a "reverberant sound-field" is. hint - it's two letters long and they failed to even mentioned it as it will quickly allow one to understand how the energy in a reverberant sound-field is different than the localized energy in a small acoustical space.

poor guy - no wonder everyone stopped replying that in that gearslutz thread. no sense doing their homework for them. we already had embarrassed them of their erroneous understanding of just what "critical-distance" means and why their "2ft Dc" was an absolute laughable statement ... no sense wasting time any further; it's best to let them continue on their misguided ways and laugh from a distance ("well beyond Dc", that is! LOL).

oh, and you noticed they failed to produce the waterfall or measurement file from the garage after numerous requests - too scared.

Local,

I've never found a post of yours I disagreed with. In fact, you are better at more eloquently stating your points that I am.

BTW, one of the sales"men" you are talking about was specifically asked to leave this thread early on for various reasons, not the least of which were because even then he was going against the popular and proven FACTS I'm trying to teach people and get folks to discuss in this thread but also because there is hardly ever much original thought or information in his posts, just quotes from others, none of which are the "heavy hitters" that have created acoustic models, written books, are highly acclaimed and admired in their fields, etc.

He said he would, BTW, but I guess he's not a man of his word.

It wouldn't be so bad if his thoughts had basis in reality or he had some proof or even if we understood exactly what his motives were.

I'd even accept posts wholly written by him and not just a few lines disagreeing for the sake of argument, on EVERY concept I try to introduce, followed by some quote from someone else that still doesn't even really make his point!

I can tolerate, and even admire, discussions and disagreements, but only when the motive is clear.

My only goal is to help people learn the right things the first time so they don't later have to try to forget the wrong info then start over, or worse, get discouraged and just give up.

I find the field of acoustics and psycho acoustics fascinating and applying what I have learned to my own dedicated HT build is more fun to me than even watching movies/listening to music. I'm very passionate about it and simply love to discuss it.

I have no ulterior motive and am honest about that.

I'm only replying to this post (besides to tell you thanks for your contributions, information, and correcting all the MISinformation) because you mention sales-"men" plural and I'm only aware of the one.

I hope you aren't talking about me or disagree with the information I'm sharing and what I'm trying to do here in this thread.

I've not mentioned several of the things you talk about in this post YET only because until recently most were still focused on getting set up right and trying to understand the basics of REW and what each of the graphs mean.

If you feel I'm leading folks down the wrong path or also giving misinformation or just plain wrong information or you feel I have an ulterior motive (I'm NOT in this business in any way shape or form, BTW) please feel free to directly call me out on it.

If I've misread you, then ignore this and just call me sensitive. wink.gif

Thanks again for all you do,

--J

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Old 05-29-2013, 12:41 AM - Thread Starter
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OK - here's some RT60 plots for commentary. If I focus on the 500 to 1000 Hz range, according to the 0.2 to 0.5 'standard' Amir mentioned in his cookbook, am I "OK"? Or should I be focusing on absorbing some of these frequencies below 500 Hz, given that I really don't want an NE room (but haven't settled on exactly what my hypothetical model should be)?


RT60 plots are run with TOPT, and the full frequency range as per the plot Jerry ran.
Left speaker:


Right speaker:
[

Center speaker


FYI, I also ran an ETC (envelope) chart on my post-Audyssey measurement of mains (L/R) and subs. The raw plot is, well, reflection happy above -20 db in my untreated room:


Finally, if I understood what Jason suggested to Jerry, for comparison here's the same ETC plot filtered at 500 Hz:


Given the room that I described a couple of days ago, and my 60/40ish music vs. HT orientation, what do I do with this, besides break out the string? Remember, I'm running powered Mythos ST towers and CS-8080 HD powered center up front, and least to my taste, the sound's "spacious" enough. However, as we all know, you don't what's broken until you realize it, so to speak, by comparing to something else.

My 1/6th plot for frequency response, full-range on mains+subs Post-Audyssey, is included for completion:


Hi Stuart,

It's about 2:30 A.M. here and I have to get to bed, but I promise I will try to go into more detail and comment on all your graphs/answer all your questions tomorrow.

For now, keeping in mind the RT60 is NOT what we need to be looking at and only considering it to be ballpark accurate, here's what I see.

First, you are in no danger of overdamping your room at this time.

You are WELL above the goals I just set in some ranges but what is most concerning is it appears you have EQ'd your FR by not using broadband treatments.

You have a common problem which is a falling response. Your bass needs tamed as some of it is well over .5s and should be more like .4 or preferably less, then as you move up in frequency, you can see your decay times get lower and lower.

You probably have thin treatments, even informal, such as carpet/curtains, furniture, etc, at this point that absorb the higher frequencies but not the lows.

The goal for this graph is for the line to be as even as possible all the way from the left (bottom/low frequencies) to the right (high frequencies) allowing for a shelf from about 300hz on down of maybe 30% (at the most) higher, and the closer to 20% (but of course ultimately/optimally the same as the specular region which is the frequencies above 300hz or so) the better.

Your graph simply shows that the higher the frequency the more absorption you have and the deader the room is. It's not balanced.

You need balance and you desperately need some absorption.

Your room is probably very lively and I can see it's full of reflections.

It wouldn't surprise me a bit to find that you have a hard time understanding song lyrics and even dialog in the movies you watch.

Turning up the CC isn't going to do any good and you need to use broadband absorbers plus specific absorbers made for the low frequencies to tame this a bit and try to get closer to .3seconds all across the board.

Don't overdo it though. It won't take much to get you at or below .3 seconds everywhere from about 150hz on up.

It will take more work to get the lower frequencies in line without then affecting the upper frequencies and that's the tricky part.

There are some good tips though on how to accomplish this without affecting the top end, but that will have to wait until tomorrow.

I'll try to give a lot more detail tomorrow evening.

Thanks,

--J

Thanks to EVERYONE that Helps Make These Threads so Awesome!

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Old 05-29-2013, 12:53 AM
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Where examples of rooms with early reflections do have an impact on home theatres is when it comes to treatment. In the example I asked Keith, there are three basic ways to treat the early reflections of your centre speaker: absorb, diffuse or reflect. All three will sound different, and their use will come down to personal preference. But which of those three will yield greater intelligibility?
That is similar to the question I asked Amir.
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Most people would reflexively say absorbtion. This is where I disagree. But that doesn't suddenly become a call for making home theatres sound like classrooms. It does mean that absorbing early reflections for the sake of intelligibility might not be needed or a good idea.
I agree absorption may not be required. Thus far I have not seen evidence that early reflections improve intelligibility in home theaters. If the untreated early reflections do not harm intelligibility in a home theater, but also do not improve it (taking into account proper level calibration in the comparison), it seems we can pretty much look to other criteria when deciding how to treat the room, like timbre, ASW, etc., as you well mentioned later.
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Not sure what you mean by "improve" timbre. You said those reflections might alter timbre and I said research indicated the opposite (might not alter timbre).
Maybe I misunderstood where you were going when you wrote:
>>Also, why start from the premise that those reflections might alter timbre or change the imaging in undesirable ways, when the research on both of those points the other way.<< I took it that "the other way" from changing timbre in an "undesirable way" would be to change it in a desirable way. Hence, improve timbre. If you are not saying the timbre improves, we are again in violent agreement. tongue.gif
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Michel Barron had done some research in the '70s on reflections from multiple directions actually reducing colourations. Toole & Olive found that early reflections made it harder to hear room resonances that colour the sound.

I agree about the imaging being dependent on the nature of the reflections, but preference tests point towards the effects (apparent source width, image size) being desirable more than not. The reason I mention Wolfgang Klippel's tests is because he pitted narrow dispersion speakers that had flat on-axis response against wide dispersion speakers that had flat on-axis response but terrible off-axis response. The listeners kept preferring the wide dispersion speakers.

Before anyone jumps to conclusions, that's not an endorsement to design speakers with crappy off-axis response. It just showed that listeners craved the bigger/wider soundstage so much, they were willing to take something (anything) from the side walls over nothing at all. Of course, speakers with good/consistent on and off axis response would have fared better.

Pops up from time to time in papers I've read. Couple of examples:
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"An interesting aspect of the precedence effect is that the perception depends not just on the delay but also on the spatial separation between the two sources. For instance, if the two sources are located on a straight line extending from the listener so that the listening angle is the same to both sources, the sound will be perceived as colored. If the same delay settings are used but the speakers are separated horizontally, there is no perception of coloration. We simply hear the first source. If we put an omni-directional microphone in the place of the listener, the two experimental set-ups however yield two identical recordings (assuming the room is well-damped). Both sound awful. The second source interferes with the first one." - Mathias Johansson, Dirac Research
Yes. Binaural hearing, also responsible for "cocktail party effect" is much better than a dumb mono mic. There are multiple interdependent variables at work in this precedence effect / timbre matter. Time offset, loudness offset, angular offset. I'm not sure we can totally absolve early reflections of close-proximity side walls of affecting timbre. We might want to address that, such as with diffusion, and see if there is a negative impact on ASW.

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Old 05-29-2013, 03:23 AM
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Old 05-29-2013, 03:33 AM
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I think the multi-purpose room concept is the nub of the issue. We don't have music venues that look like (sound like) cinemas and we don't have cinemas that look/sound like concert halls. I believe they both have different requirements and it is trying to achieve the compromise of the multi-purpose space that makes things extra-difficult. It's one of the reasons I decided very early on in my journey that the HT would be for movies only.
I think cinemas and concert halls need to look quite different because their acoustic tasks are quite different: cinema--recreation of sound; concert hall--creation of, well, a concert hall effect. wink.gif

But at home, the tasks are much more similar between movies and music -- it is a sound reproduction task in either case. Yes, due to the nature (limitations?) of stereo, we use the room to act as a sort of mechanical spatial/surround enhancement system. We may even choose speakers like dipoles that go a step further down this path. I suppose it can be taken to such limits that it begins to impair the quality or intelligibility of movie soundtracks. Rather than such mechanical/acoustic solutions, I find PLIIx gives me the envelopment I like from music. But I was into that long before I had a dedicated home theater.

I also believe that between the extremes of great movie systems that sound mediocre on music and great music systems that do injustice to movies, there's a reasonable overlap where both genres can be very well served with one system. I happen to think I have struck that balance to such an extent that I pine not for improvements in either direction.

Dumb luck. Or maybe just dumb...

 

I'm sure it is possible, Roger, and your experience bears that out. But you have massively more experience than everyone in this thread and your understanding of the issues is way deeper. For those of us with a lot less knowledge or experience, it is surely easier to just go with a HT room for movies and optimise for that, as I have done. I realise not everyone can do that for all sorts of domestic reasons, but if you can do it, it sure seems to make the job easier. As you have outlined above, the requirements for stereo music are different to those for movies.  Hopefully, the thread will develop into one where those with multi-purpose rooms can find help in designing them to give great results for both music and movies. Someone just suggested that a day or so ago and it seems to be a laudable intent.

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Old 05-29-2013, 03:33 AM
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The reflections help because they raise the SPL of the teacher's voice. That is not required in a HT because we have the volume control to raise the SPL if needed.
Can we stop pretending that a school teacher cannot raise her voice and stop acting like an A/V receiver's volume control raises the dialogue (signal) in relation to the rest of the soundtrack (background).
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I choose to kill the reflections. The reason is that all of the ambience I require (for movies only) is already recorded into the soundtrack and reproduced by the array of speakers around the room. I don't want any further influence of the room on the recorded sound.
So you absorb the early reflections of your centre speaker for reasons that have to do with ambience and not intelligibility? Do you think a room can be treated to improve intelligibility or do you think that the improvement can only happen with a volume control? The reason I ask is because if you believe the latter, then discussing treatment vs intelligibility is a moot conversation.
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Would you comment on the headphones issue I have mentioned before?  If these reflections are so important for dialogue intelligibility, why are there no problems with the latter when using headphones, where the possibility of reflections influencing anything is zero?
Where did anyone say there would be "problems" without early reflections? You're erecting a strawman. The discussion is whether early reflections aid or hamper intelligibility, not whether dialogue is in unintelligible without reflections.

BTW, do you believe that headphones provide an absolutely equal level of intelligibility as your room or do you think one might be better than the other?
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I absolutely agree with your general point there (and have been that man myself).
But you don't believe you are that man this time?

Sanjay
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