Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 214 - AVS Forum
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post #6391 of 10741 Old 11-05-2013, 02:00 PM
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Originally Posted by jkasanic View Post

Jim, thanks for detailing the process.  Since I usually respond from a computer without REW and seem to forget details I could lock away in a vault and regurgitate ad nauseam years later, I recall back when we first started discussing ETC's and slicing that I had actually done this procedure before in REW! rolleyes.gif   Apparently, the only bit I retained from that exercise was the importing of a measurement multiple times...sorry to make you go through the process when I had already completed it several months back.

Anyway, with all of these "pristine" ETC's being posted in what I would consider to be heavily treated rooms (since I have bare walls!), I thought it might be a good idea for us "regular Joe's" to see what a completely untreated room looks like in comparison (especially one that has used Audyssey XT32 and achieved a relatively flat FR from 20-20k Hz):

All plots are created as described above including 0.2ms smoothing applied.  Also, each speaker is set to full band (sub off) and I kept the color scheme consistent (e.g. Red is 500Hz, Green is 1000Hz, Gold is 2000Hz and Blue is 4000Hz):

Left Speaker Only Full Band:



Right Speaker Only Full Band:



Center Speaker Only Full Band, 0.2ms Smoothing:



Now I've already stated that for my listening space (99.9% movies), I'm starting out with an approach that will not emphasize taming high gain early ipsilateral reflections but rather focusing more on the left and right speaker contralateral reflections as well as front wall absorption (to tame reflections from surrounds) and back wall absorption (for the mains).  I will also mention that during these measurements I discovered an audible echo eek.gif  in my listening space that I plan to address with my latest treatment plan.

Anyway, I didn't post these graphs with the intent of soliciting ideas on how to identify and treat these reflections but more as a reality of what a typical room with no treatments might look like for those taking measurements and wondering why their ETC's aren't as pretty as what Jim, Keith and Jerry are posting! wink.gif   HST, I welcome any and all feedback.

So your trying to preserve same side reflections but tame opposite side ones without regard to their gain or timing (just trying to understand) ?

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post #6392 of 10741 Old 11-05-2013, 02:12 PM
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Originally Posted by sdurani View Post
 
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Originally Posted by jkasanic View Post

All plots are created as described above including 0.2ms smoothing applied.  Also, each speaker is set to full band (sub off) and I kept the color scheme consistent (e.g. Red is 500Hz, Green is 1000Hz, Gold is 2000Hz and Blue is 4000Hz):
Would you be willing to post a different set of overlays? A graph with just L/R speakers at 500Hz, another graph with the same two speakers at 1000Hz, and a third graph of those same speakers at 2000Hz.

I'm more curious about left vs right consistency than the individual reflections themselves. The former has to do with something objective (achieving a symmetrical soundstage) while the latter is more subjective (your preference with regards to early reflections).

 

And here I thought you didn't use the ETC "at all"...of course I would be willing to endulge your curiosity!:D

 

So here is the overlay of the L+R (no sub and also from the same set of measurements I took before so mic location is consistent) at the 500, 1000 and 2000Hz slices with 0.2ms smoothing applied and same color scheme as before (Red is Left and Blue is Right):

 

500Hz

 

1000Hz

 

2000Hz

 

Interested to see your thoughts on this since we know my soundstage is currently not symmetrical due to the 2, door size openings on the right side of the room.

 

EDIT:  Updated plots

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post #6393 of 10741 Old 11-05-2013, 02:16 PM
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Originally Posted by jkasanic View Post

And here I thought you didn't use the ETC "at all"...of course I would be willing to endulge your curiosity!biggrin.gif

So here is the overlay of the L+R (no sub and also from the same set of measurements I took before so mic location is consistent) at the 500, 1000 and 2000Hz slices with 0.2ms smoothing applied and same color scheme as before (Red=500Hz, Green=1000Hz and Gold=2000Hz):




Interested to see your thoughts on this since we know my soundstage is currently not symmetrical due to the 2 door size openings on the right side of the room.

I think he meant Left AND Right, not Left PLUS Right (for each slice).

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post #6394 of 10741 Old 11-05-2013, 02:27 PM
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Originally Posted by jkasanic View Post

And here I thought you didn't use the ETC "at all"
I don't. But I also don't impose my view onto others. IF I were to use it, about the only thing I would be curious to measure would be left vs right consistency/symmetry, as recommended in Nyal's white paper.
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"...of course I would be willing to endulge your curiosity!
Thanx, but it's kinda hard to see with all the slices overlayed on a single graph. So let me repeat my request: a graph with just L/R speakers at 500Hz, another graph with the same two speakers at 1000Hz, and a third graph of those same speakers at 2000Hz. So each of the three graphs would have only two traces (left speaker and right speaker) at one frequency slice.

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post #6395 of 10741 Old 11-05-2013, 02:41 PM
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Originally Posted by jim19611961 View Post

So you want to see channel to channel sliced ETC's ?
Yes, because soundstage symmetry is often overlooked, especially in multi-channel set-ups where inconsistencies can be more difficult to detect when there are 5 or 7 speakers firing simultaneously. With a 2 speaker layout, it is much easier to hear an imbalance between the left and right sides of the soundstage.

So, without telling people how they should address early reflections (absorb, diffuse, reflect, deflect), I think it is worth suggesting they get both sides as similar as possible.
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I think he meant Left AND Right, not Left PLUS Right (for each slice).
Exactly.

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post #6396 of 10741 Old 11-05-2013, 02:46 PM
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Originally Posted by AustinJerry View Post
 

It will be interesting to hear how you determine which reflections are good, and which are bad.  There will be differences of opinion here, I suspect.

 

Edit:  Doesn't this lead back to the "Pick a model" question?

 

You had to say it didn't you... :eek:

 

One of the reasons I haven't done ANYTHING with respect to treating my room (besides the fact that I'm a habitual procrastinator) is I kept going back and forth wrt which model I wanted to pursue and when J mandated this was not optional in our pursuit of audio nirvana, I was frozen and afraid to do anything wrt treatments for fear I might change my mind and want to pursue a different model (just see this thread with over 400 posts and as far as I can tell the OP's original question of which model to choose for multi-channel movies never gets answered!).  As a result, I've spent an inordinate amount of time researching the various schools of thought on reflections as this seems to be where most models diverge.  I've decided it's worth exploring treating my room in this fashion:

 

  1. Add absorption and lots of it for all the reasons previously mentioned (e.g. horrific decay times, unwanted reflections, echoes :eek: etc.)
  2. Create a symmetrical soundstage - adding treatments to anything but a symmetrical stage means I'll always be at risk of some sort of an imbalance.  My room is fairly symmetrical but the right side has two large openings - or as the Placemeister likes to call them, perfect absorbers.  Since I can't add doors or block the openings, the next best thing is to add broadband absorption to the left wall directly opposite these openings.
  3. Treat unwanted reflections - in my case, I'm focusing on reflections that originate from locations they shouldn't be coming from (i.e. contralateral L/R reflections, front wall for surrounds and rear wall for mains etc.)

 

My goal is to get the room to this level and then take my usual inordinate amount of time to evaluate the differences wrt preference.  This could take a while since I don't have a refined ear and I've been conditioned over many years to boomy bass and a relatively "bright" soundstage.  Once I get passed this stage, I will evaluate the pros and cons of taming the high gain early reflections.  Since I'm sitting squarely in the Toole camp at the moment (don't cringe Jim!), I'm going to develop some trust in my own ears and let me preference decide how I proceed from there.

 

I realize this approach is somewhat debatable (especially for the "pros" among us) but it's hard to deny the logic of creating a symmetrical soundstage and then systematically applying treatments or EQ to the room to deal with any and all remaining issues.  The difficult part will be in deciding what truly is an issue - because if there's one thing I've learned down in this particular rabbit hole, there's a whole lot of opinions out there (and egos to boot) so most of the battle is wading through all of that and ultimately (imho) settling in on some form of preference since there truly is no reference for multi-ch movies to go by (just other peoples preference as far as I can tell).

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post #6397 of 10741 Old 11-05-2013, 03:05 PM
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Originally Posted by sdurani View Post

Yes, because soundstage symmetry is often overlooked, especially in multi-channel set-ups where inconsistencies can be more difficult to detect when there are 5 or 7 speakers firing simultaneously. With a 2 speaker layout, it is much easier to hear an imbalance between the left and right sides of the soundstage.

So, without telling people how they should address early reflections (absorb, diffuse, reflect, deflect), I think it is worth suggesting they get both sides as similar as possible.
Exactly.



500hz



1K



2K

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post #6398 of 10741 Old 11-05-2013, 03:08 PM
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I think he meant Left AND Right, not Left PLUS Right (for each slice).
Exactly.

 

Sorry, blond moment...original post updated.

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post #6399 of 10741 Old 11-05-2013, 03:18 PM
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Originally Posted by jkasanic View Post

You had to say it didn't you... eek.gif

One of the reasons I haven't done ANYTHING with respect to treating my room (besides the fact that I'm a habitual procrastinator) is I kept going back and forth wrt which model I wanted to pursue and when J mandated this was not optional in our pursuit of audio nirvana, I was frozen and afraid to do anything wrt treatments for fear I might change my mind and want to pursue a different model (just see this thread with over 400 posts and as far as I can tell the OP's original question of which model to choose for multi-channel movies never gets answered!).  As a result, I've spent an inordinate amount of time researching the various schools of thought on reflections as this seems to be where most models diverge.  I've decided it's worth exploring treating my room in this fashion:
  1. Add absorption and lots of it for all the reasons previously mentioned (e.g. horrific decay times, unwanted reflections, echoes eek.gif  etc.)
  2. Create a symmetrical soundstage - adding treatments to anything but a symmetrical stage means I'll always be at risk of some sort of an imbalance.  My room is fairly symmetrical but the right side has two large openings - or as the Placemeister likes to call them, perfect absorbers.  Since I can't add doors or block the openings, the next best thing is to add broadband absorption to the left wall directly opposite these openings.
  3. Treat unwanted reflections - in my case, I'm focusing on reflections that originate from locations they shouldn't be coming from (i.e. contralateral L/R reflections, front wall for surrounds and rear wall for mains etc.)

My goal is to get the room to this level and then take my usual inordinate amount of time to evaluate the differences wrt preference.  This could take a while since I don't have a refined ear and I've been conditioned over many years to boomy bass and a relatively "bright" soundstage.  Once I get passed this stage, I will evaluate the pros and cons of taming the high gain early reflections.  Since I'm sitting squarely in the Toole camp at the moment (don't cringe Jim!), I'm going to develop some trust in my own ears and let me preference decide how I proceed from there.

I realize this approach is somewhat debatable (especially for the "pros" among us) but it's hard to deny the logic of creating a symmetrical soundstage and then systematically applying treatments or EQ to the room to deal with any and all remaining issues.  The difficult part will be in deciding what truly is an issue - because if there's one thing I've learned down in this particular rabbit hole, there's a whole lot of opinions out there (and egos to boot) so most of the battle is wading through all of that and ultimately (imho) settling in on some form of preference since there truly is no reference for multi-ch movies to go by (just other peoples preference as far as I can tell).

There is a lot here. But research is a HUGE part of it. Guys like Dragonfyr and Localhost (wrt thead link) are guys to pay attention to. But you do reach a point where your ready to implement something. Congratulations! A big piece of the puzzle done!

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post #6400 of 10741 Old 11-05-2013, 04:10 PM
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What do you mean "again"? Why did they stop?

Cross-Spectrum had suspended taking new orders for the MiniDSP UMIK-1 for a while. I assume they were overwhelmed with initial ordered and the product went on back-order (meaning they were unable to manufacture enough product to meet demand). A message on their website stated they would start taking orders sometime this week, and they have.
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post #6401 of 10741 Old 11-05-2013, 04:16 PM
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Joe: considering the open doorway in the front right side of your room, the L/R traces don't look anywhere near as different as I would have guessed. Sure, the details vary, but the general traces for both sides are surprisingly similar for the first 20-30 ms, going up and down at roughly the same times. If you were to draw a line through the middle of the traces, both sides would have similar slopes. Will be interesting to see the improvement once you have the room more symmetrical.

Jim: can always count on you for measurements that make my jaw drop. Now that you see the left vs right traces, are the visual differences around 6-7 ms in the 500Hz and 1kHz graphs audible to you?

All: since Nyal chimed in, I'm going to suggest those interested review pps 5-9 of his paper:

http://www.acousticfrontiers.com/static/513e1e34e4b00efcff5b05fd/51523db2e4b05218a1268532/51523db3e4b05218a126876f/1340681100537/acoustic_measurement_standards.pdf

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post #6402 of 10741 Old 11-05-2013, 04:39 PM
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Jim: can always count on you for measurements that make my jaw drop. Now that you see the left vs right traces, are the visual differences around 6-7 ms in the 500Hz and 1kHz graphs audible to you?

All: since Nyal chimed in, I'm going to suggest those interested review pps 5-9 of his paper:

http://www.acousticfrontiers.com/static/513e1e34e4b00efcff5b05fd/51523db2e4b05218a1268532/51523db3e4b05218a126876f/1340681100537/acoustic_measurement_standards.pdf

No. I believe matching ETC slice levels at -20db or -25db (channel to channel) are not very significant given their gain. However, someone working in the -5db or even -10db area must pay much more attention to it.

Nyal's paper is what perked my initial interest in sliced ETC's to begin with. But I am curious about something. Nyal's example is dealing with fairly audible levels of reflection (-10 db to -15db). When you got them down below -20db or -25db, do the same goals hold true wrt trying to get them to run at the same levels?



Here is my 2k (green) and 500hz (black) for the left channel. They are within 5db - 10db most of the way (discounting the kicker at 24ms). Is this variance acceptable? Preferable? Problematic?

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Originally Posted by jim19611961 View Post

Nyal's paper is what perked my initial interest in sliced ETC's to begin with. But I am curious about something. Nyal's example is dealing with fairly audible levels of reflection (-10 db to -15db). When you got them down below -20db or -25db, do the same goals hold true wrt trying to get them to run at the same levels?
?

That's a very good question.

Based on my understanding of how the ear/brain works in that what you hear is a superposition of direct sound plus all reflected sounds within ~40ms then I would say the lower the level of the reflection the less important to your overall perception of the sound it is going to be. Especially when you remember that the decibel scale is logarithmic.

Having said that I have found that the ear can pick up things (particularly resonances, which are I admit different) at -50dB, and some (Newell) have reported -70dB.

Jim you should also take a look at your 1/3rd octave smoothed waterfall. It's pretty interesting. Use a 40ms window, 1ms rise time.


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post #6404 of 10741 Old 11-05-2013, 05:42 PM
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Omnimic has limitations in this regard, but this was the closest I could come up with. Yours is much prettier and easy to interpret. My Haas kicker at 24ms must be taken into account. I don't have a rise time feature.

I really dont think this is giving an accurate picture of things frown.gif

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There is a lot here. But research is a HUGE part of it. Guys like Dragonfyr and Localhost (wrt thead link) are guys to pay attention to. But you do reach a point where your ready to implement something. Congratulations! A big piece of the puzzle done!

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That's a very good question.

Based on my understanding of how the ear/brain works in that what you hear is a superposition of direct sound plus all reflected sounds within ~40ms then I would say the lower the level of the reflection the less important to your overall perception of the sound it is going to be. Especially when you remember that the decibel scale is logarithmic.

Having said that I have found that the ear can pick up things (particularly resonances, which are I admit different) at -50dB, and some (Newell) have reported -70dB.

Jim you should also take a look at your 1/3rd octave smoothed waterfall. It's pretty interesting. Use a 40ms window, 1ms rise time.

I questioned Dragonfyr about a year ago in mtbdudex thread on how to look at band sliced ETC (I thought it would be a good idea to see what frequencies were contributing to the ETC) and he shot me down (with no lube rolleyes.gif) saying it doesn't matter.....find the ETC and use broadband treatment to kill it....you don't need to know about spectrum. So, as I read through this, the spectrum does appear to matter as different frequencies have bigger impact at different ETC delays, corresponding to different paths/incidence of reflection. So, was he out to lunch with that advice?
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post #6406 of 10741 Old 11-05-2013, 07:02 PM
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I questioned Dragonfyr about a year ago in mtbdudex thread on how to look at band sliced ETC (I thought it would be a good idea to see what frequencies were contributing to the ETC) and he shot me down (with no lube rolleyes.gif) saying it doesn't matter.....find the ETC and use broadband treatment to kill it....you don't need to know about spectrum. So, as I read through this, the spectrum does appear to matter as different frequencies have bigger impact at different ETC delays, corresponding to different paths/incidence of reflection. So, was he out to lunch with that advice?

For me, I am exploring the issue. If someone came along and had very good arguments to why its unimportant, then id give it up. I spoke with Dragonfyr by phone once. But we didn't discuss this issue. As far as what he said to you, id like to see his words in their full context (got a link?).

find the ETC and use broadband treatment to kill it... That does sound like something he would say, or at least the way he would say it. I would speculate though that quote doesn't necessarily contradict it having meaning. If you use broadband absorption (broadband meaning equal absorption down to 200hz or so), and you use a lot of it, then your reflections will generally be in order on their own. Many though try to get by with thin and sparse treatments, and that will cause a tilt in your reflection control in broadband terms. And ETC slicing will uncover this fact. But one could say that if you do your treatment right, you need not worry about it.

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There is a lot here. But research is a HUGE part of it. Guys like Dragonfyr and Localhost (wrt thead link) are guys to pay attention to.

There goes your credibility. But that shouldn't surprise anyone who follows the literature. You've been advocating approaches that have zero support in the literature, and those who you call upon as your gurus do the same.

It's time for you to admit that these approaches you advocate have no support in the literature whatsoever.

Let me be more specific. Dragonfyr and localhost are cranks and their misguided information should in no way influence anyone seeking a rational solution to their acoustical problems.
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Wow, where did that come from? And who are you?

Who am I anyway? Jerry, I live in Pflugerville to be exact. But more to the point, I'm disgusted by bogus arguments presented as fact. My home page is here.
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Originally Posted by jim19611961 View Post

Quote:
Originally Posted by fotto View Post

I questioned Dragonfyr about a year ago in mtbdudex thread on how to look at band sliced ETC (I thought it would be a good idea to see what frequencies were contributing to the ETC) and he shot me down (with no lube rolleyes.gif) saying it doesn't matter.....find the ETC and use broadband treatment to kill it....you don't need to know about spectrum.
As far as what he said to you, id like to see his words in their full context (got a link?).
Nearly impossible to oblige from the thread fotto referenced, since dragonfyr deletes as many of his posts as he can.

....Unless someone quoted one of his posts. Click on links below quotes for full context.
Quote:
Originally Posted by dragonfyr View Post

Don't band limit. Just run a full out broadband sweep.
http://www.avsforum.com/t/1351247/using-energy-time-curve-for-acoustic-analysis-developing-a-home-theatre-primer/90#post_21037843
Quote:
Originally Posted by dragonfyr View Post

Unfortunately, with the mention of the non-uniform power response of speakers has been an increase in many thinking they must perform band limited ETCs as they now mistakenly feel the ETC is insufficient as they instead again chase the frequency response albeit in another form!

But it is not too surprising that many seem to find solace in this approach as it seems to comfortable to cling to remnants of the frequency domain as if it were Linus' blanket rather than refocusing their attention onto the time domain behavior of ALL of the specular energy.
http://www.avsforum.com/t/1351247/using-energy-time-curve-for-acoustic-analysis-developing-a-home-theatre-primer/210#post_21467880

That thread also has references to the same sentiment:
Quote:
Originally Posted by localhost127 View Post

i still see zero reason for band-limiting the ETC.
http://www.avsforum.com/t/1351247/using-energy-time-curve-for-acoustic-analysis-developing-a-home-theatre-primer/210#post_21483936
Quote:
Originally Posted by omholt View Post

I don't think there's much more to say after dragonfyr explained why we don't need to use bandlimited ETC. That made perfectly sense to me.

But can someone point me to dragonfyr's explanation of this? I want to read it again, but I can't find it.
http://www.avsforum.com/t/1351247/using-energy-time-curve-for-acoustic-analysis-developing-a-home-theatre-primer/240#post_21837645

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post #6411 of 10741 Old 11-05-2013, 09:41 PM
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I finally found his full response. I am still digesting it.

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post #6412 of 10741 Old 11-05-2013, 10:15 PM
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Originally Posted by jim19611961 View Post

I finally found his full response.
I linked to that post above but I think there must have been a full-er response, at least based on omholt's respose near the end of the thread (see above).

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post #6413 of 10741 Old 11-05-2013, 10:18 PM
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I guess Mr. Local was saying that if you know the off axis response of your speakers then why band limit the ETC. You should have enough knowledge from the off axis response to just use the full bandwidth ETC.

It kind of makes sense. However, imagine looking at the full bandwidth ETC and seeing a spike at say 6ms. One would then have to track down that spike to it's reflecting surface (say a ceiling) and then consider the spectral balance of the speaker's radiation at that off axis angle to determine if it was a spike that needed absorbing because it had an uneven spectral balance.

Seems easier just to look at a band filtered ETC and find areas where the lines diverge?

Of course my school of thought is in the maximum amount of spectrally similar reflections camp so maybe that's just the way I think about things...I'm only looking for areas of spectral dissimilarity.

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post #6414 of 10741 Old 11-05-2013, 10:20 PM
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Originally Posted by jim19611961 View Post



Omnimic has limitations in this regard, but this was the closest I could come up with. Yours is much prettier and easy to interpret. My Haas kicker at 24ms must be taken into account. I don't have a rise time feature.

I really dont think this is giving an accurate picture of things frown.gif

Looks like the rise time is too long. I think Omnimic must have a better mode...what are the recommended settings for examining cabinet / driver resonances...that might help?

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post #6415 of 10741 Old 11-05-2013, 10:55 PM
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Originally Posted by Nyal Mellor View Post

I guess Mr. Local was saying that if you know the off axis response of your speakers then why band limit the ETC. You should have enough knowledge from the off axis response to just use the full bandwidth ETC.

It kind of makes sense. However, imagine looking at the full bandwidth ETC and seeing a spike at say 6ms. One would then have to track down that spike to it's reflecting surface (say a ceiling) and then consider the spectral balance of the speaker's radiation at that off axis angle to determine if it was a spike that needed absorbing because it had an uneven spectral balance.

Seems easier just to look at a band filtered ETC and find areas where the lines diverge?

Of course my school of thought is in the maximum amount of spectrally similar reflections camp so maybe that's just the way I think about things...I'm only looking for areas of spectral dissimilarity.

I think this (bolded) is part of what was meant. I think the other part is that you can trust the full bandwidth ETC to show the power response in the time domain. And thus, if you treat the high gain energy that is shown there, it doesnt matter what the frequency constituents are (just my take).
Quote:
Originally Posted by dragonfyr View Post

So when is someone going to jump out and tell we have all been punked by someone simply pretending to know what he is talking about?


Welcome to the lastest installment of: :
Operator Mistakes Can Lead to erroneous data which can be further compounded by the clueless interpretation of said wacked data! DUH!!!!!



Bigus, when you stop and recognize the absolutely amazing mistake this guy has made you will laugh your posterior off!

"Measuring Reflections

The message is that we need to know the spectrum level of reflections to be able to gauge their relative audible effects. This can be done using time-domain representations, like ETC or impulse responses, but it must be done using a method that equates the spectra in all of the spikes in the display, such as bandpass filtering. Examining the “slices” of a waterfall would also be to the point, as would performing FFTs on individual reflections isolated by time windowing of an impulse response. Such processes need to be done with care because of the trade-off between time and frequency resolution, as explained in Section 13.5. It is quite possible to generate meaningless data. All of this is especially relevant in room acoustics because acoustical materials, absorbers, and diffusers routinely modify the spectra of reflected sounds. Whenever the direct and reflected sounds have different spectra, simple broadband ETCs or impulse responses are not trustworthy indicators of audible effects". p. 93


DUH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!rolleyes.gifrolleyes.gifrolleyes.gif

If you need a text to explain this to you, the book won't help! It's too late! And what is scarier is the asinine conclusion that is drawn from this!

So, if we have a stimulus such as a tone at 500 Hz, the total modulation envelope of the signal may not be the same as a tome at say 5kHz.

Absolutely someone without a clue can generate wacked data! And only someone similarly clueless as to why would blame the tool!.

Combine that with the fact that existing treatments may indeed effectively EQ the incident energy and act as equalization, effecting some frequencies more than others.

Thus if one uses live material as a stimulus that may feature varying spectral content at differing times of the program, and you have boundaries or boundary treatments that do not behave in a broadband manner and may indeed effectively EQ the incident and reflected energy, you may indeed end up with whacked data.

And anyone who conducts a test in such a manner is an idiot.

Best practices require that we evaluate the behavior of the boundaries and /or treatments specifically to ascertain their behavior over the full specular spectrum.

Such boundaries that do not exhibit such a broadband response should be corrected.

And since when has it ever been best practice to play stimuli consisting of different spectra and attempting to equate them? Again, this is not a source of error, it is a MISTAKE. A MAJOR MISTAKE. And the sign of an incompetent operator.

And apparently we need a book to tell us that measurements made via a MISTAKE are not valid!

And this is further compounded by some interpreting this as a fundamental flaw of the measurement process and not of an operator who hasn't a clue as to what they are doing?!?!?!?!?!?!?!

To quote Bill Engvall: "Here's your sign!!!"

Of course boundaries that are not broadband and which do not function in a linear fashion will effectively EQ the incident energy!

And attempting to compare unlike stimuli which by definition consist of non-equivalent energy content, is so whacked as to render the label of a “mistake” an understatement!!!

Best practices mean that we first evaluate boundaries for their behavior, and effect correction if such is the case.

And then testing ALWAYS dictates that we compare apples with apples!

And the fact that someone can construct a test focusing on the arrival time and gain of energy with respect to time and not be aware that the energy being compared must be equivalent is a fool.

But apparently a few amazed that conducting measurements improperly can result in whacked data feel the need to repeat their shocked amazement to readers who are also apparently assumed to be fools, as they all sit amazed at the OBVIOUS ramifications of such an asinine practice.

Thus, for those, unlike the intended crowd above, who have a few functioning brain cells, you have several CORRECT choices in properly using the tool!

As the tool can be used for a near limitless array of applications, (including a plethora of well designed variations) with regards to boundary investigations a simple rule of thumb implies that one:

1.)Ascertain the spectral nature of the boundaries followed by the behavior of any existing treatments. This will most probably require that one remove any treatments and first establish a baseline of performance for the boundaries.

2.)Once this is established and any lack of uniform broadband behavior rectified, insure that any treatments employed (assuming they are necessary and perform the desired function) are also broadband.

And except for the purposes of selectively ascertaining degrees of deficiency, identical broadband sweeps should generally be used for testing, with any tests intended to be directly compared conducted with equivalent stimuli under equivalent conditions. And if broadband sweeps are not employed, care MUST be exercised in comparing any results generated by dissimilar stimuli! Depending upon the nature of the behavior to be examined, sweeps maybe be bandwidth limited in a narrow fashion, realizing the reduction in resolution, or 'bandwidth limited' in the broadband, increasing the resulting resolution and generally employed..

"The message is that we need to know the spectrum level of reflections to be able to gauge their relative audible effects. This can be done using time-domain representations, like ETC or impulse responses, but it must be done using a method that equates the spectra in all of the spikes in the display, such as bandpass filtering.".Toole

OF COURSE IT CAN! And if you know how to use the tool properly, you would be doing this anyway!

Yup, The ETC which 'can be used properly' is declared "obsolete" by someone both unable to read and who hasn't a clue as to how to use it!
The next time we have someone present a book report, is it possible to ask that they be able to properly read for meaning?

And it become obvious from Chicken Little's rant that he hasn't a clue as to how to properly use the ETC or any such similar measurements!

And before he becomes even more upset, using identical broadband sweep stimuli is satisfies the same requirement as the perceived mistaken need to use limited band=ass measurements. The effective bandpass is simply wider!.

Failure to use best practices in testing does not indicate a flaw in the measurement technique; it instead indicates that the person conducting the tests is an idiot who is not qualified to conduct such tests.

Bandwidth limited tests can indeed be used for diagnostic purposes, provided one is familiar with how to do them.

Provided that such tests are properly conducted and that the results are interpreted properly.

NEWSLASH!!!! Cars are defective!!! Congress demands recall of all vehicles after man blames car for decreased gas mileage after filling the gas tank with sand!

This has been stated on multiple times ever since a few amazed souls imagined that some would be so stupid as to conduct such flawed tests and to improperly attempt to compare apples with oranges and to think such a comparison is valid!

But it is not the limitation of the tool that there are idiots who are not qualified to use them.

And it is likewise a foolish endeavor of some who are unable to recognize such mistakes of process who then attempts to fault the tool and not the operator. And in doing they would not be much smarter than those who conduct such flawed tests. And the need to point out such an OBVIOUS MISTAKE in understanding and process where MISTAKEN PROCEDURES LEAD TO WACKED RESULTS seems like the result of someone having in fact made that very mistake and now subsequently redirecting the attention to not only others but in some braindead manner to the tool, as if the tool prevented them from thinking! As if someone stops and thinks about this, going to such trouble to illustrate that a flawed measurement practice can result in whacked data that one cannot directly compare begs the question of proper measurement technique.

And it seriously appears to be a case where someone feels the need to deflect the attention from their own mistaken use of the tool and to make it look as if only ‘others’ would fall victim to their own foolish mistake!

So, fundamentally there is NOTHING here except an example of flawed measurement process, and it is NOT the fault of the tool – except insofar as the tool does not absolutely prevent one from making a mistake! And I guess in that respect, yes, the tool is flawed in that it does NOT prevent you from being an idiot and doing things incorrectly.

Yup, doing that is a MISTAKE! And thank goodness that we have a book that you can buy that identifies one of a myriad ways that an ignorant operator cam make mistakes.

But where I come from, that is the fault of the ignorant operator, NOT of the tool.

But seeing as we live in a culture literally dominated by the “victim mentality where no one is responsible, such a warning may indeed be applicable for the intended audience off the book which are apparently assumed to not be smart enough to conduct such a test properly. Well, at least Toole has found one reader for whom the message was aptly intended! And he is still running about blaming the tool!


And when you thought things could not become more ridiculous!!!!

But stay tuned, as will be treated to a book report blaming the manufacturers of medical equipment after some fool at home operates on themselves in order "to let the heat escape" as a result of their setting a thermometer on a radiator and misinterpreting the reading to imply that their body temperature was 180 F.


.

There is a lot of ranting going on here. But also several points are made concerning proper interpretation of results and how to obtain them.

I think it may take me a week to wrap my head around this ^^^^^

And if you really like your head to spin, give this thread a try:

http://www.avsforum.com/t/1413173/does-sound-sounds-better-in-a-room-full-of-furniture-and-stuff-or-without/0_50

eek.gif

I feel like pure novice all over again frown.gif

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post #6416 of 10741 Old 11-06-2013, 12:01 AM
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Yep it's official, I now have a brain hernia!
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post #6417 of 10741 Old 11-06-2013, 12:21 AM
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Originally Posted by Nyal Mellor View Post

That's a very good question.

Based on my understanding of how the ear/brain works in that what you hear is a superposition of direct sound plus all reflected sounds within ~40ms then I would say the lower the level of the reflection the less important to your overall perception of the sound it is going to be. Especially when you remember that the decibel scale is logarithmic.

What contributes to perceived timbre is still an ongoing discussion. It probably shifts from steady state at low frequencies to direct sound at high frequencies. See AES papers by Salmi/Kates.

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post #6418 of 10741 Old 11-06-2013, 03:10 AM
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Originally Posted by Nyal Mellor View Post

Jim you should also take a look at your 1/3rd octave smoothed waterfall. It's pretty interesting. Use a 40ms window, 1ms rise time.

 

Nyal - could you elaborate on what we can learn from looking at a 1/3 smoothed waterfall please?

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post #6419 of 10741 Old 11-06-2013, 03:35 AM
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Quote:
Originally Posted by Nyal Mellor View Post

Jim you should also take a look at your 1/3rd octave smoothed waterfall. It's pretty interesting. Use a 40ms window, 1ms rise time.
 
Nyal - could you elaborate on what we can learn from looking at a 1/3 smoothed waterfall please?

+1 Especially since you mentioned a waterfall and posted a decay plot (at least per REW nomenclature?!). confused.gif
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post #6420 of 10741 Old 11-06-2013, 09:13 AM
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What MacBook do you have? What model year?

I have an old 17incher, still with discrete mouse button. Assuming you have a mac, have you tried doing the right-click to find the distance thing?
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