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post #181 of 303 Old 02-17-2014, 12:39 PM
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Originally Posted by jim19611961 View Post

Please elaborate on what data you feel is meaningless and why.
One example of data would be full band ETCs that to tell you you are at -20db for a given reflection, only to find out that specific bands of the same reflection (particularly lower ones) are considerably higher. Why, because you go through the trouble of attenuating the reflection by the wrong amount and then wonder why you can still hear some of it.

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post #182 of 303 Old 02-17-2014, 12:40 PM
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Originally Posted by mtbdudex View Post



What I'm trying to nail down is basic design goal, and the basis for that.

I wanted to speak to this as well.

The basic design goal is going to depend on what you want it to sound like. That is to say, what are your personal subjective biases describing what you like. Pin point or broad sound stage images for instance.

But probably more to the point is what the characteristics of the room you have to work with are and what are you willing/able/allowed to do with it.


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post #183 of 303 Old 02-17-2014, 12:44 PM
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Quote:
Originally Posted by sdurani View Post

One example of data would be full band ETCs that to tell you you are at -20db for a given reflection, only to find out that specific bands of the same reflection (particularly lower ones) are considerably higher. Why, because you go through the trouble of attenuating the reflection by the wrong amount and then wonder why you can still hear some of it.

I am still not understanding your point.

edit: In your example, are you saying the data is bad. Or are you saying that the data is good, but the treatment was insufficient?


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post #184 of 303 Old 02-17-2014, 01:18 PM
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Quote:
Originally Posted by jim19611961 View Post

I am still not understanding your point.
You posted a Toole quote describing why full band ETCs could generate meaningless data, which is the reason he recommends looking at band-limited slices.

You confirmed with your own expericence of a full-band ETC showing a reflection at -30dB only to find that at lower frequencies (500Hz) it was actually 10dB louder.

I post agreement with both comments that full-band ETCs can be meaningless when they give incorrect data about the level of a reflections (incorrect when compared to the spectral slices).

When you then asked me what data is meaningless, I pointed to your example of the full-band ETC giving incorrect reflection levels.

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post #185 of 303 Old 02-17-2014, 01:20 PM
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Quote:
Originally Posted by sdurani View Post

You posted a Toole quote describing why full band ETCs could generate meaningless data, which is the reason he recommends looking at band-limited slices.

You confirmed with your own expericence of a full-band ETC showing a reflection at -30dB only to find that at lower frequencies (500Hz) it was actually 10dB louder.

I post agreement with both comments that full-band ETCs can be meaningless when they give incorrect data about the level of a reflections (incorrect when compared to the spectral slices).

When you then asked me what data is meaningless, I pointed to your example of the incorrect reflection level.

Clear now. Thanks.


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post #186 of 303 Old 02-17-2014, 01:47 PM
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Quote:
Originally Posted by sdurani View Post

You posted a Toole quote describing why full band ETCs could generate meaningless data, which is the reason he recommends looking at band-limited slices.

Even if we do look at band-limited ETC's, is it really more than cargo cult science?

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
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post #187 of 303 Old 02-17-2014, 01:49 PM
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Originally Posted by mtbdudex View Post

then the "goal" of a small listening room is to be between the green and yellow curves for a "high quality" listening experience
"The" goal or your goal? Personally, depending on the direction of the early reflections, I like them above the green curve in order to get a bigger/wider soundstage. But my tastes are more common (consumer) than refined (studio).

Is your goal based on your personal preference or general guidelines? If the latter, then getting reflections between the green and yellow curves is a good start. I would definitely "season to taste" afterwards.

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post #188 of 303 Old 02-17-2014, 01:59 PM
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Originally Posted by markus767 View Post

Even if we do look at band-limited ETC's, is it really more than cargo cult science?
Have you read the Mellor/Hedback white paper?

http://www.hedbackdesignedacoustics.com/files/QuickSiteImages/AMS_for_Stereo_List._Rms.pdf

If so, do you think their use of band-limited and smoothed ETCs is cargo cult science?

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post #189 of 303 Old 02-17-2014, 02:03 PM
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Originally Posted by sdurani View Post

"The" goal or your goal? Personally, depending on the direction of the early reflections, I like them above the green curve in order to get a bigger/wider soundstage. But my tastes are more common (consumer) than refined (studio).

Is your goal based on your personal preference or general guidelines? If the latter, then getting reflections between the green and yellow curves is a good start. I would definitely "season to taste" afterwards.

What constitutes a general guideline depends on what model or approach your emulating.

IMO, trying to get ALL/MOST of your reflections into the "spacious" region out to 30-40ms (or further) in a smooth fashion is one of the most demanding approaches I know of. No easy task.


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post #190 of 303 Old 02-17-2014, 02:18 PM
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Jim - I've seen your threads on Gearslutz, very detailed and informative, for simplicity I feedback in RED
I appreciate the dialogue.
Quote:
Originally Posted by jim19611961 View Post



Here are the detection thresholds for different room environments (for speech).

Quote:
Originally Posted by jim19611961 View Post

Quote:
Originally Posted by mtbdudex View Post

I'm para-phrasing here, helps me remember instead of just reading:
  • So using band pass ETC (and smoothed),
  • based on psycho-acoustic studies done by Toole and Sean Olive with test subjects in a statistically validated environment,
  • then the "goal" of a small listening room is to be between the green and yellow curves for a "high quality" listening experience
.

How we get there, (below in priority order)
  1. room size/layout,
  2. by speaker selection/placement,
  3. seat(s) placement
  4. acoustic treatment type/placement
  5. Eq

Is part of the acoustic design strategy.

That applies for all sound freq above the Fs, approx 250hz in small rooms.

Below Fs, say 200hz below, is out of this discussion

What I'm trying to nail down is basic design goal, and the basis for that.

Jim - your 3 ETC charts are end results, not design goals correct?

Bold 1) Even if we agree (not all do), that reflection(s) in this range add to the pleasure of the listening experience, there are tons of mitigating factors and Toole, as many others, insist the research is incomplete. But a few points come to mind.

1) How many reflections need bring about the desired effect?
I don't know, as I'm not a acoustic research specialist, is there ongoing research to review/learn from?
2) Some aim for the entire reflection response to be in the spacial zone
3) Some feel two is enough (Haas Kicker) with a near anechoic response up to the terminator (LEDE/RFZ models).
4) The timing, direction, and spectra of given reflections.

5) Smoothness of the overall energy curve.
6) Cross correlation and ipsilateral vs contralateral predominate reflection patterns.
belonging to or occurring on the same side of the body vs relating to or denoting the side of the body opposite to that on which a particular structure or condition occurs

Is there research that show this matters?
And this list is far from complete.

Bold 2) You would have to point me to what 3 ETC's you mean (I have posted too many to keep track of).
I post your 3 charts above

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post #191 of 303 Old 02-17-2014, 02:22 PM
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Sanjy - for simplicity I feedback in RED

Quote:
Originally Posted by sdurani View Post

Quote:
Originally Posted by mtbdudex View Post

then the "goal" of a small listening room is to be between the green and yellow curves for a "high quality" listening experience
"The" goal or your goal? Personally, depending on the direction of the early reflections, I like them above the green curve in order to get a bigger/wider soundstage. But my tastes are more common (consumer) than refined (studio).

Is your goal based on your personal preference or general guidelines? If the latter, then getting reflections between the green and yellow curves is a good start. I would definitely "season to taste" afterwards.
Good point, can we possibly genarize ETC goal with target line into a few buckets/categories:
[*] Dedicated Home Theater room (fully enclosed with door)
[*] General open floor plan home Theater, such as living room
[*] Dedicated 2 channel listening room (fully enclosed with door)
[*] General open 2 channel listening room, such as living room
[*] etc (please add)



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post #192 of 303 Old 02-17-2014, 02:31 PM
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Originally Posted by mtbdudex View Post

can we possibly genarize ETC goal with target line into a few buckets/categories
You'd be better off asking folks that use ETC (I don't).

Sanjay
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post #193 of 303 Old 02-17-2014, 03:25 PM
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Quote:
Originally Posted by mtbdudex View Post

Jim - I've seen your threads on Gearslutz, very detailed and informative, for simplicity I feedback in RED
I appreciate the dialogue.

I know of no research that is a slam dunk on what to do or specific answers or research that answers them. I am merely asking questions that I asked myself when I decided to plunge in and upgrade my room.

The (3) ETC's merely show how the detection threshold changes when the reflective nature of the room changes. My own room has specific ETC goals, yes. Some models do as well.

My general advice is to read as much about established room models as possible. Then see which are doable in your space. Then try to emulate the most essential criteria that the one you have decided on calls for.


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post #194 of 303 Old 02-17-2014, 07:04 PM
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Quote:
Originally Posted by jim19611961 View Post

Quote:
Originally Posted by mtbdudex View Post

Jim - I've seen your threads on Gearslutz, very detailed and informative, for simplicity I feedback in RED
I appreciate the dialogue.

I know of no research that is a slam dunk on what to do or specific answers or research that answers them. I am merely asking questions that I asked myself when I decided to plunge in and upgrade my room.

The (3) ETC's merely show how the detection threshold changes when the reflective nature of the room changes. My own room has specific ETC goals, yes. Some models do as well.

My general advice is to read as much about established room models as possible. Then see which are doable in your space. Then try to emulate the most essential criteria that the one you have decided on calls for.

Jim - I'm "done" with my room - mostly, look at my signature sticky threads.....I went thru my acoustics pilgramage in 2010/2011, now doing look back and re-visiting.

I'm trying to help others here (AVS, not necessary this thread, as most here are accomplished ) by de-mistify acoustic theory into practical usage, sorta the applied stuff viewpoint. Hence by posting in this thread I hope to get the collective wisdom distilled.
Way too often, IMO, people jump into "what treatments do I need" instead of defining the basic goal to be achieved first.
Hence I'm trying to re-state acoustics into simple, readable layman's terms.
I've got some test subjects, co-workers at work, my non-engineer brother, that I've engaged into listening/reading what I'll post.

Took my 8 year old to his basketball practice tonight, I've brought out Tooles book and jumped into chapter 6 again, re-reading that portion.....after 2+ years I see things from different viewpoint.

fwiw, I captured my lessons learned in this post, it's evolving also.
I've re-posted this more than a few times in other threads when people start asking about acoustics......
http://www.avsforum.com/t/1312693/diy-construction-methods-of-hang-able-acoustic-panels-moveable-corner-traps-not-fixed-frames#post_19947420
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Discussion related to corner bass traps; gas flow resistivity, why cover them to reflect mid-high's, etc
[*] http://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/177600-could-someone-help-out-interpreting-materials-gas-flow-properties.html
[*] http://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/583307-nasa-lf-absorption-gas-flow-resistivity.html
[*] http://www.gearslutz.com/board/9610921-post12.html
[*] http://www.avsforum.com/t/1378864/does-gik-acoustic-panel-auralex-foam-suiting-my-room#post_21327290
[*] http://www.avsforum.com/t/1460653/on-covering-bass-traps
[*] http://www.avsforum.com/t/255432/acoustical-treatments-master-thread/8490#post_21513507
[*] http://www.avsforum.com/t/1354504/corner-bass-traps


Side note:
I have this general suggestion for those wanting to learn about acoustics:
A) read this Acoustics/Treatment Reference Guide , via gearslutz, its a easy read in layman terms, starts you off with basics and good foundation with practical discussion. Studio acoustics and Home Theater acoustics.
From that, simple/straight forward advice via Jens Eklund:
Quote:
1. Learn how to make measurements: REW - Room EQ Wizard Home Page
Don’t do anything without measurements.
2. Define your MLP (Master listening position). Confirm with measurements.
3. Identify and treat your modal and SBIR - Speaker Boundary Interference Response related issues and educate yourself about different bass-absorbing techniques.
Other info: SBIR by Bryan Pape
4. Treat areas that otherwise creates early reflections.
5. If the room is big enough, add diffusers
Always base your decisions regarding different treatment, on measurements. Avoid thin porous only absorbers (including wall to wall –carpet, drapes etc.) unless a measurement indicates the need for it.
B) Knowing that for “best” audio/sound in a listening room, these parameters are tackled in prioritized order:
1. Speaker location, 2. Listener position, 3. Acoustic treatments, 4. Electronic correction.
Understand the small room acoustic model you will follow.
Looking at this link, everyone can see visually the various small room models, it's 7 pages from the book "Acoustics and Psychoacoustics Applied"

http://eetimes.com/design/audio-desi...n?pageNumber=0
C) If you have desire for more knowledge:
-read one of many books out there, a great 1st book is "Master Handbook of Acoustics" by F. Alton Everest, a perfect follow-up book is "Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms" by Floyd Toole.
-shameless plug for Ethan Winers book also, "The Audio Expert".

.. ..

-study Ethan Winers site, http://www.ethanwiner.com/acoustics.html
-Become familiar with the different small room acoustic models for home listening spaces
-This is also a 101 read on Room Acoustics, http://www.crutchfield.com/learn/learningcenter/home/speakers_roomacoustics.html
-SAE Home Acoustics info site has many definitions and explanations http://www.sae.edu/reference_material/audio/pages/fullindex.htm
-There are many other sites on the web, like
........One of the first ones, StudioTips small room acoustics forum http://forum.studiotips.com/index.php,
........Acoustical measurements defined Rives audio http://www.positive-feedback.com/Issue12/rives2.htm,
........RPG Acoustics Library papers http://www.rpginc.com/news/library.htm, etc.
-Be careful of info overload all at once

D) Measurement info/threads:
-online downloadable file with the Sound System Engineering chapter 6 on measurements http://www.focalpress.com/uploadedFiles/Books/Book_Media/Audio/9780240808307.pdf
-Get the hardware side of REW down quickly, this thread by member omegaslast dummy's guide on setting up REW and his blog http://polaraudio.blogspot.com/2012/01/calibration.html easy 101 read with pictures to walk you thru the mechanical of set-up and taking measurements
-Highly recommend Nyal Mellor's site, http://www.acousticfrontiers.com/Aco...surements.html , and a very detailed/helpful white paper http://blog.acousticfrontiers.com/st...ist.%20Rms.pdf
-Room Measurement & Treatment by "fotto" (Floyd)


- Envelope Time Curve - ETC - Impulse gearslutz thread
-Using energy time curve for acoustic analysis: by "mtbdudex" (Mike R)
-http://www.avsforum.com/t/1421599/etc-isd-gap-question ETC - ISD gap by
-Basic acoustic measurement primer v2.1 (via gearslutz "DanDan")
-http://www.realtraps.com/art_measuring.htm


-http://www.avsforum.com/t/1316623/diy-custom-printed-movie-poster-acoustic-panels-cheap/60#post_20147783 DIY Custom-Printed Movie Poster Acoustic Panels
-first reflection software: http://www.avsforum.com/t/822273/free-software-to-help-determine-your-first-reflection-points/240#post_22619555
-a while back I downloaded this Measurement/calibration sequence from Dennis Erskine.

RoomMeasurementSet-up.zip 5k .zip file

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post #195 of 303 Old 02-17-2014, 07:28 PM
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"The" goal or your goal? Personally, depending on the direction of the early reflections, I like them above the green curve in order to get a bigger/wider soundstage.
Quote:
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You'd be better off asking folks that use ETC (I don't).

if you "don't" use the ETC, how do you know the actual indirect arrivals (and their subsequent time/gain/spectral content) in order to make the distinction that you "like them above the green curve"?
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post #196 of 303 Old 02-17-2014, 08:53 PM
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Notice that attenuating them up to 10dB during those same 25ms aids in spaciousness (area between green and yellow curves).

in small, untreated residential rooms, the indirect arrivals within this zone are sparse reflections. it is not a dense, exponentially decaying sound-field (approaching "reverberation" of which takes place naturally in larger, more "spacious" rooms). it is localized behavior that changes based on your 3space position with respect to the source(s).

a sparse reflection from a large surface (boundary) arriving within this zone is not going to imply anywhere near the perceived "spaciousness" or "envelopment" of a dense, reflection-rich burst of spatially and temporally dispersed energy flows. the density and decay rate, IACC, etc are key - not some "single", "sparse" reflection arriving within this "zone" which is going to magically impart large room "spaciousness". the physical behavior of the energy flows are wildly different; thus why we have strict acoustical definitions between Small and Large rooms.

the development of the schroeder diffusers [http://www.rpginc.com/docs%5CTechnology%5CPresentations%5CMRS%20Online.pdf] ... eg, reflection phase grating of QRD or PRD variety, were of such paramount importance with regards to small room acoustics. it allows one to mimic the energy flows ("randomness", "well-mixing") of a reverberant (diffuse) sound-field. one can then continue to "drive" the diffusers over time with delayed, redirected (longer flight path) specular reflections (eg, RFZ geometric approach to achieve LEDE response) to contribute to the exponentially decaying (later-arriving) sound-field.

the time-arrival of these first significant reflections within the room dictates the perceived acoustical size of the space. if you attenuate (delay) the room's naturally induced high-gain (early) reflections, you increase the perceived size of the space (otherwise, the room will impart a "small room" mask on top of the source material). the goal of RFZ (LEDE) in this case, is the allow the ear-brain adequate time to process the direct signal (free from any "small room" destructive masking), and then to provide a non-destructive sense of the room via that of a later arriving, lateral-arriving, exponentially decaying diffuse sound-field - which specifically mimics the energy flows of "reverberation" (read: spaciousness) in large acoustical spaces. you get a larger perceived size of reproduction space (than what the room's dimensions naturally allow), attenuation of the indirect signals that are destructive to intelligibility, localization, and imaging, and a later-arriving sound-field that emulates the physical energy flows of "spacious" reverberation. this "well-mixing" of the later-arriving sound-field (room contributions) provide a more even response across the room - providing more closely spaced and dense comb-filtering within the frequency-domain at a given location.
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post #197 of 303 Old 02-17-2014, 09:53 PM
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Originally Posted by localhost127 View Post

in small, untreated residential rooms, the indirect arrivals within this zone are sparse reflections. it is not a dense, exponentially decaying sound-field (approaching "reverberation" of which takes place naturally in larger, more "spacious" rooms). it is localized behavior that changes based on your 3space position with respect to the source(s).

a sparse reflection from a large surface (boundary) arriving within this zone is not going to imply anywhere near the perceived "spaciousness" or "envelopment" of a dense, reflection-rich burst of spatially and temporally dispersed energy flows. the density and decay rate, IACC, etc are key - not some "single", "sparse" reflection arriving within this "zone" which is going to magically impart large room "spaciousness". the physical behavior of the energy flows are wildly different; thus why we have strict acoustical definitions between Small and Large rooms.

the development of the schroeder diffusers [http://www.rpginc.com/docs%5CTechnology%5CPresentations%5CMRS%20Online.pdf] ... eg, reflection phase grating of QRD or PRD variety, were of such paramount importance with regards to small room acoustics. it allows one to mimic the energy flows ("randomness", "well-mixing") of a reverberant (diffuse) sound-field. one can then continue to "drive" the diffusers over time with delayed, redirected (longer flight path) specular reflections (eg, RFZ geometric approach to achieve LEDE response) to contribute to the exponentially decaying (later-arriving) sound-field.

the time-arrival of these first significant reflections within the room dictates the perceived acoustical size of the space. if you attenuate (delay) the room's naturally induced high-gain (early) reflections, you increase the perceived size of the space (otherwise, the room will impart a "small room" mask on top of the source material). the goal of RFZ (LEDE) in this case, is the allow the ear-brain adequate time to process the direct signal (free from any "small room" destructive masking), and then to provide a non-destructive sense of the room via that of a later arriving, lateral-arriving, exponentially decaying diffuse sound-field - which specifically mimics the energy flows of "reverberation" (read: spaciousness) in large acoustical spaces. you get a larger perceived size of reproduction space (than what the room's dimensions naturally allow), attenuation of the indirect signals that are destructive to intelligibility, localization, and imaging, and a later-arriving sound-field that emulates the physical energy flows of "spacious" reverberation. this "well-mixing" of the later-arriving sound-field (room contributions) provide a more even response across the room - providing more closely spaced and dense comb-filtering within the frequency-domain at a given location.
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post #198 of 303 Old 02-18-2014, 01:25 AM
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Have you read the Mellor/Hedback white paper?

http://www.hedbackdesignedacoustics.com/files/QuickSiteImages/AMS_for_Stereo_List._Rms.pdf

If so, do you think their use of band-limited and smoothed ETCs is cargo cult science?

I'm a strong supporter of strict reproduction standards. It's the only way to break free from http://seanolive.blogspot.ch/2009/10/audios-circle-of-confusion.html
Nevertheless yes, I do believe that common room measuring/treatment practices by and large are just cargo cult science. We don't know enough about our hearing.

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post #199 of 303 Old 02-18-2014, 08:33 AM
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Originally Posted by localhost127 View Post

in small, untreated residential rooms, the indirect arrivals within this zone are sparse reflections. it is not a dense, exponentially decaying sound-field (approaching "reverberation" of which takes place naturally in larger, more "spacious" rooms). it is localized behavior that changes based on your 3space position with respect to the source(s).

Is there a tipping point where the density is considered reverberant as opposed to specular? I.E. number of reflections per millisecond for instance?
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Originally Posted by localhost127 View Post

a sparse reflection from a large surface (boundary) arriving within this zone is not going to imply anywhere near the perceived "spaciousness" or "envelopment" of a dense, reflection-rich burst of spatially and temporally dispersed energy flows. the density and decay rate, IACC, etc are key - not some "single", "sparse" reflection arriving within this "zone" which is going to magically impart large room "spaciousness". the physical behavior of the energy flows are wildly different; thus why we have strict acoustical definitions between Small and Large rooms.

A single sparse reflection between 20-30ms is sometimes used as a Haas trigger. It would seem your saying that looking at this reflection alone would provide or establish a sense of greater room size, but less so in terms of spaciousness. The "tail" following a Haas Kicker type termination is the part of the equation that provides the spaciousness aspect. Yes?
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Originally Posted by localhost127 View Post

the development of the schroeder diffusers [http://www.rpginc.com/docs%5CTechnology%5CPresentations%5CMRS%20Online.pdf] ... eg, reflection phase grating of QRD or PRD variety, were of such paramount importance with regards to small room acoustics. it allows one to mimic the energy flows ("randomness", "well-mixing") of a reverberant (diffuse) sound-field. one can then continue to "drive" the diffusers over time with delayed, redirected (longer flight path) specular reflections (eg, RFZ geometric approach to achieve LEDE response) to contribute to the exponentially decaying (later-arriving) sound-field.

One thing that has always confused me about standard LEDE/RFZ models whereby the diffusion is primarily in the rear of the room is how such a layout provides for lateral arrival of said diffuse reflections. Can you explain?


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Looking at these typical layouts, it would seem the diffuse energy would arrive more from the rear than from a lateral direction. What I am I missing?

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Originally Posted by localhost127 View Post

the time-arrival of these first significant reflections within the room dictates the perceived acoustical size of the space. if you attenuate (delay) the room's naturally induced high-gain (early) reflections, you increase the perceived size of the space (otherwise, the room will impart a "small room" mask on top of the source material). the goal of RFZ (LEDE) in this case, is the allow the ear-brain adequate time to process the direct signal (free from any "small room" destructive masking), and then to provide a non-destructive sense of the room via that of a later arriving, lateral-arriving, exponentially decaying diffuse sound-field - which specifically mimics the energy flows of "reverberation" (read: spaciousness) in large acoustical spaces. you get a larger perceived size of reproduction space (than what the room's dimensions naturally allow), attenuation of the indirect signals that are destructive to intelligibility, localization, and imaging, and a later-arriving sound-field that emulates the physical energy flows of "spacious" reverberation. this "well-mixing" of the later-arriving sound-field (room contributions) provide a more even response across the room - providing more closely spaced and dense comb-filtering within the frequency-domain at a given location.

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post #200 of 303 Old 02-18-2014, 08:43 AM
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Originally Posted by localhost127 View Post

in small, untreated residential rooms, the indirect arrivals within this zone are sparse reflections. it is not a dense, exponentially decaying sound-field (approaching "reverberation" of which takes place naturally in larger, more "spacious" rooms). it is localized behavior that changes based on your 3space position with respect to the source(s).
That is only true below transition frequency of a few hundred hertz which is not the topic here. I demonstrated all of this in gory details in the Gearslutz thread to you: http://www.gearslutz.com/board/8887203-post397.html. As I show there the modal density rises up to 12 at just 500 Hz. Keep going and it absolutely becomes a dense sound field. And I showed how above the transition frequency there is exponentially decaying response. You had no response to my detailed post there covering both theory and measurements. Everyone agreed in that thread including some authors of acoustic books that it was the definitive answer. So please lets not rehash battles already lost.

Here is the full thread if anyone wants to read it: http://www.gearslutz.com/board/studio-building-acoustics/821073-can-small-rooms-have-real-reverb.html

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post #201 of 303 Old 02-18-2014, 09:40 AM
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One other often overlooked limitation/quirk of ARC I only became aware of after Roger Dressler & I were tinkering with Kris Deering's system is that once you run/engage ARC, the subwoofer low pass is fixed for all channels. In other words, regardless of if you set the crossover for your mains at 40 Hz and your surrounds at 100 Hz, if you left the LFE/sub channel correction and low pass at 120Hz in the software, the low bass info from every channel will get routed through a 120Hz low pass. This can create a lot of overlap with the speakers and muddied sound if you don't know how it is behaving.

If you turn off ARC, bass management behaves as we would expect, where the low pass from each channel is routed through a low pass corresponding to the crossover setting.

The result is that you mostly need to choose a global subwoofer low pass for all bass content in the system. With this understood the results can sound very good. Hopefully Anthem will decide to make the software fix to this bizarre, unexpected, and undocumented behavior, but be sure to understand this before trying to make a comparison to Audyssey.

Bass management is a function of the DSP, not of ARC aside from its selection of the xover frequencies, and the "bizarre and unexpected" configuration, where all channels not set to full range are summed with LFE before being run through LPF, is indeed documented, though in the confidential Dolby Consumer Decoder Licensee Information Manual. The Freescale DSPs, formerly known as Motorola, work like this. The Anthem AVM/D models use them. As of AVM 20 v2.1, an additional control is provided such that LFE can bypass the crossover if the user chooses to do so, which means only the redirected bass is routed through LPF. For the models that use ARC (AVM 40/ARC and later, and all Statement models), the LFE bypass is in effect when ARC is on, regardless of the LFE Xover Bypass menu setting. (Behind the scenes in either case, there's compensation to prevent the wild frequency response that would result if summing a signal with its filtered, i.e. phase-delayed, counterpart should the main channels and LFE channel contain the same info.) It's possible that while you were toggling ARC on/off, you were also toggling the LFE crossover control.

MRX x00 (Gen 1) models use a completely different DSP, and this one sends bass to the subwoofer according to the xover frequencies set in the other channels, in other words according to your expectation which also means that the comments about the bass management are irrelevant to all MRX, a model of which was the subject of kbarnes701's comments.

MRX x10 (Gen 2) models use yet another completely different DSP, which in this regard works like that of MRX Gen 1 except that there is an additional control for dialing in LFE xover frequency, and not to be confused with sub channel xover frequencies. Like the bypass control in AVM/D, its purpose is to prevent LFE from being rolled off prematurely as would be the case if xover frequency was determined by a combined sub+LFE control set to, for example, 40 Hz.

Note that sub correction range, also called cutoff range, shown in the targets window of ARC software, both versions, is not the sub xover frequency. It's in essence the range that's worth eq'ing. ARC avoids wasting resources in trying to make speakers play something they can't play, for example, if the sub has little in-room response above 80 Hz, ARC may set the LFE xover in the MRX Gen 2 menu to 120 Hz, more or less a bypass, while the eq cutoff is set to 80 Hz in the ARC software and rolled off accordingly. These two parameters work in concert such that two 80 Hz xovers wouldn't cascade one another.

Some of this is of course is not immediately apparent, even counter-intuitive, although using ARC-2 software, which applies to MRX Gen 2 and has more visuals than ARC-1 software while changing targets, makes it easier to understand.

For any additional questions or concerns, please contact Anthem directly as I am not a regular follower of forum discussions. This one came to my attention from a reader of the MRX 710/510/310 thread on AVForums (UK) after Mark Seaton's comments were copied there.
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post #202 of 303 Old 02-18-2014, 09:54 AM
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Originally Posted by localhost127 View Post

in small, untreated residential rooms, the indirect arrivals within this zone are sparse reflections. it is not a dense, exponentially decaying sound-field (approaching "reverberation" of which takes place naturally in larger, more "spacious" rooms). it is localized behavior that changes based on your 3space position with respect to the source(s).
That is only true below transition frequency of a few hundred hertz which is not the topic here. I demonstrated all of this in gory details in the Gearslutz thread to you: http://www.gearslutz.com/board/8887203-post397.html. As I show there the modal density rises up to 12 at just 500 Hz. Keep going and it absolutely becomes a dense sound field. And I showed how above the transition frequency there is exponentially decaying response. You had no response to my detailed post there covering both theory and measurements. Everyone agreed in that thread including some authors of acoustic books that it was the definitive answer. So please lets not rehash battles already lost.

Here is the full thread if anyone wants to read it: http://www.gearslutz.com/board/studio-building-acoustics/821073-can-small-rooms-have-real-reverb.html

Thx Amir for posting the gearslutz thread, I need to read that now.

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post #203 of 303 Old 02-18-2014, 12:07 PM
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Originally Posted by Nick @ Anthem View Post

Quote:
Originally Posted by Mark Seaton View Post

One other often overlooked limitation/quirk of ARC I only became aware of after Roger Dressler & I were tinkering with Kris Deering's system is that once you run/engage ARC, the subwoofer low pass is fixed for all channels. In other words, regardless of if you set the crossover for your mains at 40 Hz and your surrounds at 100 Hz, if you left the LFE/sub channel correction and low pass at 120Hz in the software, the low bass info from every channel will get routed through a 120Hz low pass. This can create a lot of overlap with the speakers and muddied sound if you don't know how it is behaving.

If you turn off ARC, bass management behaves as we would expect, where the low pass from each channel is routed through a low pass corresponding to the crossover setting.

The result is that you mostly need to choose a global subwoofer low pass for all bass content in the system. With this understood the results can sound very good. Hopefully Anthem will decide to make the software fix to this bizarre, unexpected, and undocumented behavior, but be sure to understand this before trying to make a comparison to Audyssey.

Bass management is a function of the DSP, not of ARC aside from its selection of the xover frequencies, and the "bizarre and unexpected" configuration, where all channels not set to full range are summed with LFE before being run through LPF, is indeed documented, though in the confidential Dolby Consumer Decoder Licensee Information Manual. The Freescale DSPs, formerly known as Motorola, work like this. The Anthem AVM/D models use them. As of AVM 20 v2.1, an additional control is provided such that LFE can bypass the crossover if the user chooses to do so, which means only the redirected bass is routed through LPF. For the models that use ARC (AVM 40/ARC and later, and all Statement models), the LFE bypass is in effect when ARC is on, regardless of the LFE Xover Bypass menu setting. (Behind the scenes in either case, there's compensation to prevent the wild frequency response that would result if summing a signal with its filtered, i.e. phase-delayed, counterpart should the main channels and LFE channel contain the same info.) It's possible that while you were toggling ARC on/off, you were also toggling the LFE crossover control.

MRX x00 (Gen 1) models use a completely different DSP, and this one sends bass to the subwoofer according to the xover frequencies set in the other channels, in other words according to your expectation which also means that the comments about the bass management are irrelevant to all MRX, a model of which was the subject of kbarnes701's comments.

MRX x10 (Gen 2) models use yet another completely different DSP, which in this regard works like that of MRX Gen 1 except that there is an additional control for dialing in LFE xover frequency, and not to be confused with sub channel xover frequencies. Like the bypass control in AVM/D, its purpose is to prevent LFE from being rolled off prematurely as would be the case if xover frequency was determined by a combined sub+LFE control set to, for example, 40 Hz.

Note that sub correction range, also called cutoff range, shown in the targets window of ARC software, both versions, is not the sub xover frequency. It's in essence the range that's worth eq'ing. ARC avoids wasting resources in trying to make speakers play something they can't play, for example, if the sub has little in-room response above 80 Hz, ARC may set the LFE xover in the MRX Gen 2 menu to 120 Hz, more or less a bypass, while the eq cutoff is set to 80 Hz in the ARC software and rolled off accordingly. These two parameters work in concert such that two 80 Hz xovers wouldn't cascade one another.

Some of this is of course is not immediately apparent, even counter-intuitive, although using ARC-2 software, which applies to MRX Gen 2 and has more visuals than ARC-1 software while changing targets, makes it easier to understand.

For any additional questions or concerns, please contact Anthem directly as I am not a regular follower of forum discussions. This one came to my attention from a reader of the MRX 710/510/310 thread on AVForums (UK) after Mark Seaton's comments were copied there.

Hi Nick,

Thanks for the response and explanations of the differences in the models. That partly clarifies the issues observed. Although @Kris Deering had the current updates for his D2 as of mid July, I don't recall which numeric version it was. The issue we observed was that while behavior was as expected with ARC turned off, once ARC was turned on, crossover settings for the L/C/R speakers had no impact on the redirected bass signal sent to the subwoofer. It did affect the speaker's high pass response. The only thing which had any impact was the frequency range selected in the software for the subwoofer. IOW, a full range test signal to the center channel would show the correct high pass to the center, but no matter the crossover setting, the subwoofer portion of this signal had a 120Hz low pass or whatever the subwoofer was set to. I have a number of customers using our speakers with Anthem surround processors and am interested to confirm how to avoid this confusing behavior. From your description, this shouldn't be an issue with the MRX products.

It could be that somehow loading ARC had forced the sub XO to bypass, but note that doing nothing more than turning ARC off in the menu restored expected operation. @Roger Dressler & I were both scratching our heads on the behavior. It would be interesting if anyone could confirm expected behavior with the current firmware and ARC software. I'll have Kris double check if the sub XO is set correctly in the menu with ARC both on and off.

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post #204 of 303 Old 02-18-2014, 03:31 PM
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Is there a tipping point where the density is considered reverberant as opposed to specular? I.E. number of reflections per millisecond for instance?

reverberation is a noise floor. in a true (sic) reverberant sound-field, one cannot resolve a single indirect reflection's gain, time-arrival, vector, etc. an echo (large room characteristic) for example, is not reverberation as the reflection's properties (ingress boundary/time arrival) can be easily identified. dense reflections, long decay times (decay rates) do not automatically imply random incidence sound-field. it's possible (in garages, especially tongue.gif ) to have multiple slopes, but those who don't know any better would never "see" that. Chapter 7 (Large Room Acoustics) of Sound System Engineering (Davis/Patronis) may be of interest to you. standing on the shoulders of giants: don davis, richard heyser, chip davis, russ berger, peter d'antonio, leo beranek, peter d'antonio, manfred schroeder (!!). but hey, on this forum toole is on the be-all-end-all and no one has heard of schroeder!

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A single sparse reflection between 20-30ms is sometimes used as a Haas trigger. It would seem your saying that looking at this reflection alone would provide or establish a sense of greater room size, but less so in terms of spaciousness. The "tail" following a Haas Kicker type termination is the part of the equation that provides the spaciousness aspect. Yes?

right - the decay rate and well-mixing of the later-arriving sound-field emulate the natural sound-field in larger spaces. the gain of the termination (or first significant reflection) dictates the liveliness of the room, as i'm sure you've "heard" (even though technically you don't "hear" the termination - you know what i mean).

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Originally Posted by jim19611961 View Post

One thing that has always confused me about standard LEDE/RFZ models whereby the diffusion is primarily in the rear of the room is how such a layout provides for lateral arrival of said diffuse reflections. Can you explain?

there are multiple ways to achieve a LEDE psycho-acoustic response - and RFZ was just a geometric way to achieve that goal. one can induce specular reflections from the rear side-walls (laterally), and this is also why 1-dimensional phase gratings are utilized with the wells oriented vertically to disperse energy in the horizontal plane (which will then impede listening position from horizontal angles to achieve passive envelopment). there are multiple preferences in this area of design as well - no concrete answer. bear in mind you are not dealing with a "client couch" in the rear of your room to also account for in your requirements smile.gif

hey, did those guys who didn't even know how to measure critical-distance ("3.1ft Dc" - tongue.gif lol!) in their publication ever get around to posting the waterfall or .mdat file of that garage yet? it was asked repeatedly. apparently showing a single measurement from a single mic in a single location is sufficient to "prove" reverberation ... let alone how many concert halls can be proven otherwise. quite a special garage that is. where is the waterfall? wink.gif


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post #205 of 303 Old 02-18-2014, 04:20 PM
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OP - djbluemax1;

I brought up basics/fundamentals in post 162 and now see 2 distinct conversations happening.

How do you feel, as this is "your" thread.

Shall they both stay in your thread, or would you like me to create a specific thread to discuss the topic I introduced, copy/past the posts there so not to clutter your thread and it's discussion?
Now is the time to split them if we will, before too much more dialogue happens.

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post #206 of 303 Old 02-18-2014, 09:04 PM
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I do believe that common room measuring/treatment practices by and large are just cargo cult science. We don't know enough about our hearing.
I think its the other way 'round: we know enough about hearing to make measurements useful.

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post #207 of 303 Old 02-18-2014, 11:39 PM
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I think its the other way 'round: we know enough about hearing to make measurements useful.

No, there is no research looking at how number, spectrum, angle, level, delay of reflections, reverberation times, modal decay and adaption affect perception of different recording techniques presented over 2 or more speakers. There's also not much knowledge how our hearing really works. Even very low level hearing mechanisms like those happening in the cochlea aren't fully understood. Good read: http://auditoryneuroscience.com

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post #208 of 303 Old 02-19-2014, 04:41 AM
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No, there is no research looking at how number, spectrum, angle, level, delay of reflections, reverberation times, modal decay and adaption affect perception of different recording techniques presented over 2 or more speakers. There's also not much knowledge how our hearing really works. Even very low level hearing mechanisms like those happening in the cochlea aren't fully understood. Good read: http://auditoryneuroscience.com

???

these tests and "research" were precisely what was focused on in workshops with regards to development of LEDE - especially once the TEF was introduced and the Polar ETCs could be taken from in-ear Knowles microphones (introduced by Doug Jones), performing interaural cross correleation measurements ... and the accompanying research of Carolyn (Puddie) Rodgers (www.aes.org/aeshc/docs/jaes.obit/JAES_V30_7_8_PG567.pdf).

to see claims of "no research" being presented is astounding!
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post #209 of 303 Old 02-19-2014, 05:24 AM
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to see claims of "no research" being presented is astounding!

It is. After more than 80 years nobody ever looked at the stuff that matters. The only studies in that direction that I know of were done by Naqvi.

http://www.aes.org/e-lib/browse.cfm?elib=10024
http://www.aes.org/e-lib/browse.cfm?elib=9897
http://www.aes.org/e-lib/browse.cfm?elib=11315

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
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post #210 of 303 Old 02-19-2014, 07:04 AM
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Originally Posted by markus767 View Post

It is. After more than 80 years nobody ever looked at the stuff that matters.

keep telling yourself there is "no research" and that "nobody every looks at the stuff that matters". the ignorance is entertaining; a good litmus test regarding the subject.

I'm casually looking at workshops starting from mid 80s performing tasks of which you claim don't exist - yet here are some of the most renowned acoustical giants diving deep and investigating (now that the proper tools were available thanks to the late/great Richard Heyser).
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