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post #151 of 218 Old 11-18-2011, 02:03 PM
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Quote:
Originally Posted by Dennis Erskine View Post

It is taught in every HAA class.

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Originally Posted by Dennis Erskine View Post

It is taught in every HAA class.

Its taught in every Home Audio Alliance class?

Given the professionals here, why then are most of us only hearing about it and beginning to understand the enormous benefit ETC provides from dragonfyr, Local and some others?

In the hundreds of threads of I've read about room treatments no one up until recently talked about ETC. (Unless you were at GS..and I'll let SAC discuss that))

Why is that?

Considering that with a $150 investment and a free REW download many could treat their rooms to a great degree themselves.

Even Ethan's site doesn't really get into ETC yet what he is selling is absolutely reliant on ETC measurements in a unique room.
(What type to buy, where to put it and why your putting it there)

I guess I'm a little astonished that this hasn't been a mainstream idea/topic when it comes to room treatment as a whole.

Maybe you guys think were too dumb or not ready for that leap. I dunno.
(I admit, not everyone who asks about room treatments wants to go there)
But those of us that do? Why not spill it?

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post #152 of 218 Old 11-18-2011, 02:27 PM
 
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Originally Posted by RUR View Post

How much value is there in the 3rd vs. the 2nd edition? The price difference is substantial.

Either version is FINE!!!!!!
If you can find the 2nd edition, unless you are seriously into DSP processing (and I am specifically referring to the math), the 2nd edition will work great.

In some respects with regards to what we are discussing, it actually has a few things that were left out of the 3rd edition (as the 3rd edition features a bit more electronic and DSP processing).
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post #153 of 218 Old 11-18-2011, 03:01 PM
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Quote:
Originally Posted by dragonfyr View Post

Either version is FINE!!!!!!

2nd Ed. ordered, thanks.
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post #154 of 218 Old 11-18-2011, 03:05 PM
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Quote:
Originally Posted by dragonfyr View Post

Either version is FINE!!!!!!
If you can find the 2nd edition, unless you are seriously into DSP processing (and I am specifically referring to the math), the 2nd edition will work great.

In some respects with regards to what we are discussing, it actually has a few things that were left out of the 3rd edition (as the 3rd edition features a bit more electronic and DSP processing).

I guess a good question at this point would be, once one has treated his /her room properly what need is there for Audyssey or the like?

Wouldn't a simple pre that has good switching abilities and a good Video processor with a few good Crown amps suffice?

I mean, why would someone spend a fortune on an AVR because it has all the bells and whistles when they have already fixed the issues said AVR's try to EQ away?

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post #155 of 218 Old 11-18-2011, 11:32 PM
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Quote:
Originally Posted by test4echo101 View Post

I guess a good question at this point would be, once one has treated his /her room properly what need is there for Audyssey or the like?

Wouldn't a simple pre that has good switching abilities and a good Video processor with a few good Crown amps suffice?

Acoustic treatments work on both minimum and non minimum phase problems encountered in small spaces. They are absolutely necessary to address the non minimum phase stuff, unless you use one of the more esoteric processors employing time domain corrections and have your head in a vice. I'm not fond of that route on general principles, and it seems like that 'movement' has somewhat fallen out of favor in any case.

That being said, even with good acoustic treatements you will still almost certainly end up with minimum phase errors, whether caused by aberrations in the speakers' native frequency response or especially from modal issues at low frequencies where it is increasingly difficult to place physical treatments of adequate size to correct problems. So for these cases, audyssey etc al have usefulness. Nothing that can't be addressed with a flexible multiband parametric eq (or several), measurement tools, and patience mind you. Really capable systems, like those from harman for example, can greatly expediate the process.

The general process should be to address as much of the time and frequency domain issues as possible with physical room construction and treatment, and nudge the remaining frequency domain issues with electronic means to get the best final result possible.

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post #156 of 218 Old 11-19-2011, 01:03 AM
 
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The caveat to the former suggestion is that Audyssey and similar are strictly limited to addressing MINIMUM phase errors.

The fact is, after treatment, few errors, IF ANY, in the specular realm are minimum phase. Thus there is a predominant likelihood that whatever errors remain due to the limitations of applied treatment will NOT be minimum phase in nature, and as such, Audyssey and any of the various EQ based systems are utterly inadequate to address such problems.

So it all depends on your perspective.

If someone is determined not to do anything but set the system up and search for a 'button' to optimize the system, well, EQ offers a very limited scope of benefits, primarily limited to anomalies below ~80 Hz and limited to only minimum phase specular issues, IF ANY.

A more comprehensive approach is to address the fundamental modal and specular issues with the variety of tools and treatment techniques that we have at our disposal and then, after all reasonable steps are taken, one can then analyze the spectrum for location specific minimum phase anomalies and very surgically apply EQ as a form of 'touchup' - being aware that they are location specific, and that averaged response based corrections do not result in an optimal tuning at any of the spots which they affect.

And if one does want to pursue EQ as a touchup after treatment, I would personally use one of the various tools that identifies minimum phase response regions and can either suggest filters, or provide sufficient information for one to determine the filters - depending upon one's comfort level = and then apply them via a decent parametric EQ rather than relying on a button to invoke 'automatic' correction systems that are rather infamous (in both the consumer and pro levels) for not being as smart as their manufacturers might like to believe. And as a part of the overall process, this alternative approach to Audyssey, et.al., to effect responsible equalization is also less expensive.

But in any case, there is no question that relying solely upon EQ, be it location specific or the still more compromised averaged response, is most definitely an inferior avenue to pursue compared to proper treatment. And in all cases EQ should be properly considered as a last step touchup in relation to speaker-room interaction; to the degree that minimum phase conditions actually exist that allow for its use.
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post #157 of 218 Old 11-19-2011, 07:47 AM
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Quote:
Originally Posted by dragonfyr View Post

The caveat to the former suggestion is that Audyssey and similar are strictly limited to addressing MINIMUM phase errors.

No caveat necessary as you are simply reatating what I previously said.

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The fact is, after treatment, few errors, IF ANY, in the specular realm are minimum phase.

Yet many non specular frequency domain errors will likely remain, and they will be minimum phase.

Quote:


Thus there is a predominant likelihood that whatever errors remain due to the limitations of applied treatment will NOT be minimum phase in nature, and as such, Audyssey and any of the various EQ based systems are utterly inadequate to address such problems.

I do not agree with your assumption as it contradicts my experiences with in room measurements.

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limited to only minimum phase specular issues, IF ANY.

Again, why do you incorrectly imply that errors can only be specular in nature?

Quote:


A more comprehensive approach is to address the fundamental modal and specular issues with the variety of tools and treatment techniques that we have at our disposal and then, after all reasonable steps are taken, one can then analyze the spectrum for location specific minimum phase anomalies and very surgically apply EQ as a form of 'touchup'

Thank you for restating and confirming my prior advice.

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And if one does want to pursue EQ as a touchup after treatment, I would personally use one of the various tools that identifies minimum phase response regions... and then apply them via a decent parametric EQ rather... to effect responsible equalization is also less expensive.

This I said as well.

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And in all cases EQ should be properly considered as a last step touchup in relation to speaker-room interaction...

Again, thank you for the confirmation of my advice.

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post #158 of 218 Old 11-19-2011, 10:23 AM
 
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Errors that are non-modal or non-specular in nature are direct signal errors.

Since when do we need validation for EQ to be used there, as EQ can only modify the direct signal?

The problem lies in that many think they are correcting room-speaker specular interaction issues with EQ and Audyssey (especially as they are specifically marketed making such claims without restriction), when they are not. EQ does not address that interactive behavior in the specular region, as they are by definition non-minimum phase as it makes no sense that a direct and an indirect path from the same source would be minimum phase if for no other reason than the path lengths are necessarily different, which necessarily translates to a different time of flight.

That is physics. I can't speak for what folks feel or believe.

I speak to the concept, not to the person - or at least I much prefer to do so! But he asked me for my opinion and I gave it. And the topic is more correctly 'what can EQ properly do, and what can it not do'. There is much more about the hows and whys of what EQ can and cannot do if one is interested. A subject about which many are not fully aware.

And this continued preoccupation with feelings and things personal is rather creepy.
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post #159 of 218 Old 11-19-2011, 11:51 AM
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Quote:
Originally Posted by Bigus View Post

Nothing that can't be addressed with a flexible multiband parametric eq (or several), measurement tools, and patience mind you.

Thats an interesting statement!

So you agree that Audyssey and the like CAN be left out of the equation when one uses the proper treatments using programs like (REW) in conjunction with a PEQ that REW can interface with and generate filters for said PEQ?


Test,

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post #160 of 218 Old 11-19-2011, 01:23 PM
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Quote:
Originally Posted by dragonfyr View Post

Since when do we need validation for EQ to be used there, as EQ can only modify the direct signal?

Well... never? Which is why I was a bit confused as to why you felt the need to add a 'caveat' to my response to only then restate nearly the same thing. If you agreed with me, seems it would have just been easier to say as much.

In any case, eq has a use beyond the direct response. It can also impact modal response, though the position dependent nature obviously makes it the last tool in the bag to reach for.

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post #161 of 218 Old 11-19-2011, 01:28 PM
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Quote:
Originally Posted by test4echo101 View Post

Thats an interesting statement!

So you agree that Audyssey and the like CAN be left out of the equation when one uses the proper treatments using programs like (REW) in conjunction with a PEQ that REW can interface with and generate filters for said PEQ?

Absolutely. I much prefer to see what is happening and have direct control over the result. However, to do this for a multichannel system might require a decent amount of gear. And the calculations performed by something like the synthesis system would take quite a bit of time to duplicate.

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post #162 of 218 Old 11-19-2011, 02:19 PM
 
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Quote:
Originally Posted by Bigus View Post

Quote:
Originally Posted by Dragonfyr View Post

The caveat to the former suggestion is that Audyssey and similar are strictly limited to addressing MINIMUM phase errors.


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Originally Posted by Bigus View Post

No caveat necessary as you are simply reatating what I previously said.

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Originally Posted by Bigus View Post

If you agreed with me, seems it would have just been easier to say as much.

If I had, I would have. But I do not.
And since you failed to understand my reference, I was taking exception to this statement:

Quote:
Originally Posted by Bigus View Post

...unless you use one of the more esoteric processors employing time domain corrections and have your head in a vice.

Despite the oft asserted claim so commonly found in the marketing brochures of various 'room correction'(sic) devices, the problem is that you cannot independently modify the phase of an indirect signal by modifying the direct source signal from which the indirect signal is derivative.

And I had hoped that as a result of the original topic being the control of specular reflections with absorption, and the use of the ETC which is useful for the examination of specular energy and an attempted focus on the measurement, analysis and treatment of specular anomalies, that we would at some point shift our focus beyond the already well addressed subject of modes - of which all of the exceptions you claim to have discovered through selective attention have in fact been asserted myriad times.

So, I guess we should pause in order for those so focused to make any more observations that one might feel are pertinent with regards to modes before the rest of us attempt to move on to focus on issues related to the ETC and specular behavior.
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post #163 of 218 Old 11-19-2011, 02:43 PM
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Originally Posted by dragonfyr View Post

the problem is that you cannot independently modify the phase of an indirect signal by modifying the direct source signal from which the indirect signal is derivative.

Not independently, but the system is solvable in the time domain and convolution filters can be found. Again, I don't agree with this on general principals, my head doesn't like vices, there are practical issues such as computation delay, and it seems this line of thinking has somewhat fallen out of favor.

But I don't know why you objected to my simple acknowledgement that such a thing exists, especially after applying the esoteric label and up front stating that I object to this in practical application.

As for the rest of your post, whatever. A question was asked about the usefulness of auto-eq systems and I provided an aswer as to the issues and applications for which it is indeed useful. Your thought process might be fixated on etc and specular effects, but the question was not nor was my (correct) response. And I can't help if I had to clarify something that has been common knowedge for a long time; I didn't make the overly broad misstatement.

Either I don't contribute, or don't contribute on topic (pot, kettle), or.... And to think that I extended an unconditional apology.

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post #164 of 218 Old 11-19-2011, 03:05 PM
 
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Not independently, but the system is solvable in the time domain and convolution filters can be found. ...

Yeah, and it is available where?

Quote:
Originally Posted by Bigus View Post

And I can't help if I had to clarify something that has been common knowedge for a long time; I didn't make the overly broad misstatement.

Look bigus toolus, the qualification regarding both minimum phase systems was mentioned how many times? And the relationship of modes to minimum phase as well as to modes specifically was mentioned how many times?

I'm tired of ms. congeniality constantly following me around like one other lost puppy dog some may know and trying to make points that simply do not exist had someone actually bothered to read the entire post for meaning.


I am tired of this. I hope he explains the remaining issues regarding the ETC and its use regarding issues involving specular reflections, for which Audyssey and similar 'room correction'(sic) devices simply cannot - despite spurious assertions of systems that can overcome fundamental limitations of physics...


If anyone has questions they might like to discuss regarding the theoretical or practical use of the ETC, or acoustic room response models, questions about concepts in SSE (etc.), or just about any subject for that matter, you can PM me and provide a phone# and/or YM or Skype username.

Have fun.
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post #165 of 218 Old 11-19-2011, 03:42 PM
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How unfortunate ...

The BAMA Theatre Build - feedback welcomed encouraged needed badly
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post #166 of 218 Old 11-19-2011, 05:16 PM
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So who's gonna read my frickin' measurements?
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post #167 of 218 Old 11-19-2011, 06:08 PM
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You're a real class act dragon. After being extended an unconditional apology, you devolve to schoolyard antics in response. Class.

Quote:
Originally Posted by dragonfyr View Post

Yeah, and it is available where?

Tact, ARC, audiolense, and yes even audyssey in a limited form. Look, if you don't understand or weren't aware of how deconvolution works, just say so.

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I'm tired of ms. congeniality constantly following me around

You followed my post with your 'caveats', not me of yours. But don't let facts get in the way of your tantrum.

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... trying to make points that simply do not exist had someone actually bothered to read the entire post for meaning.

For example, just as you did?

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post #168 of 218 Old 11-19-2011, 07:56 PM
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*******s. *******s evurywhere.

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post #169 of 218 Old 11-20-2011, 01:02 AM
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Quote:
Originally Posted by test4echo101 View Post

Given the professionals here, why then are most of us only hearing about it and beginning to understand the enormous benefit ETC provides from dragonfyr, Local and some others?

In the hundreds of threads of I've read about room treatments no one up until recently talked about ETC. (Unless you were at GS..and I'll let SAC discuss that))

Why is that?

Good question. Either the professionals here don't understand the enormous benefits OR they understand that the benefits aren't enormous. Considering how long various home theatre designers, professional calibrators, and acoustic treatment vendors have been posting here, do you think it is likely that they all somehow missed the usefulness of ETC? Or do you think it is more likely that they were focused on home theatres and consumer listening spaces, instead of recording/mixing rooms, that led to no one talking about ETC until recently (when posters from GS showed up)? Keep in mind that folks here at AVS often have different goals than folks posting at GS, so measurements that are spectrally (and directionally) blind, like ETC, might not be as useful to them as other items in a measuring toolkit.

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post #170 of 218 Old 11-20-2011, 05:41 AM
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As many threads go, a drift in the discussion leads to solid contributions and good information on a different topic. Unfortunately, only those curious about the thread as it is originally titled, are exposed to said sharing of information.

If I recall correctly, ETC has been discussed here prior to dragon and local pointing out it's virtues. Not significant discussion, but it's been mentioned. I don't think individuals are scared of the potential complexity, it's just enthusiasts have a finite amount of time they want to dedicate to any one issue of their HT. Obviously, if they'd just get it right once,..and be done,..they'd be golden. However, whatever the topic, many likely feel C+ is good enough,...and they move on to other areas of concern. Ultimately, they may go back and re-visit different system elements representing potential weak links, and hopefully sort them out with a much higher degree of certainty and performance results.

Imagine a logarithmic curve;





Hypothetically;
The y axis represents performance attained
The x axis represents effort put forth (investment, both in dollars, time, exertion)

At first, all the low hanging fruit is all cherry picked, you advance quickly up the performance axis in an efficient manner. Each Audio/HT endeavor, you pick what you feel is the the sweet spot, execute to that point, and move on. For each enthusiast it's different, but there's a point on that curve whereby it's still advancing upwardly in performance attained, yet one begins encountering the inevitable diminishing returns and excess effort/$,...thus they stop there.

Some are more inclined to pursue their specific area of interest. Those inclined to read technical info, ...acoustic threads/forums etc,. We view this differently,..this is our area of concern. I love a great image, but I don't read any of the video threads unless I need very particular information. For my modest, near-field space, an Oppo95, and a new Panny 65" plasma is fine. Now dragon and local, they may not be interested in resolving the infra-bass down to 5hz,...as I am. For them, C+ is good enough wrt infra-sonic resolution at realistic levels. Perhaps they picked an adequate point on the log scale, jumped in and executed at that level, ...and moved on to elements that interest them further.

Many savvy enthusiasts realize the big gains,..the huge jumps in real performance are not found in exotic cabling. They are not gleaned from chasing the latest power protection scheme, line cord, or any of the various feel good snake oil approaches. The big gains in performance are firmly entrenched in loudspeakers, and optimizing their acoustic interaction in room. I think it's clear to all here, that ETC plays a role in that effort.

Similar to sdurani, my question is, where does a properly fleshed out ETC effort fall in the log scale mentioned above?


Thanks
LL

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post #171 of 218 Old 11-20-2011, 06:56 AM
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An add on question, one that has been posed by myself and others in the past months, is if we identify ETC as the correct tool what is the correct goal?

This has been asked in abstract and literal forms. For example, and straight to the point, after much searching I come up empty with examples applying ETC to a ground up dedicated multichannel space.

One specific example. When discussing sidewall lateral splayed reflection or diffusion, a repeating theme is to preserve as much energy as possible and direct it to the rear of the room, where it reflects off the rear wall and provides a haas kicker. That is great when you have two speakers on the front wall. If we imagine a true multichannel system in the abstract with matched speakers at each location, does this behavior need to be preserved from rear to front, such that rear sounds get a haas kicker? Side to side? Or is there a single example of modern processing that will accomplish this electronically?

It isn't clear to me how to go from the discussions at gs to a multichannel dream system.

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post #172 of 218 Old 11-20-2011, 07:09 AM
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Nice post FOH. My guess is that it will be very hard to quantify where the benefits of ETC would fall on your curve without knowing where "you're at" to start.

For instance, take an "average" DIY build (not paying for a room plan/treatment plan) here. Reading posts and coming across general guidelines presented, hopefully most will recognize early on the concept of bass trapping and incorporate as much of that as they can. Most will also come come to the conclusion that first reflections are an important area to address, as that topic is very visible here. Degrees of treatment for that will vary based on advice, interpretation etc.

At the end of your build, either you've got it nailed or something less. How much less is it? Did he or she totally miss the mark? How does one who is not well versed in listening for desirable and undesirable traits (such as myself) know? Either it sounds "good enough" to you and you move on, or your personal desire to understand where you're at drives you to investigate further.

The concept of measuring for ETC makes sense to me. You can identify these early reflections, track them down, treat, and remeasure to see if they are resolved. Isn't the goal on treating first reflections the elimination of them? Is that concept only applicable to a 2 channel listening room, or mixing studio? I have to think not. I personally can't see a downside (outside of the learning curve), and don't understand why use of next to free measurement tools are not a hotter topic here. But, just as you pointed out, there's certainly effort to be exerted there in time and energy.

So if we take the ETC portion off the table, how about other features of measurement software such as RTA? To be able to move sub positions, speaker positions etc. while watching in real time that effect has on your room response seems very valuable. Lots of other stuff in there as well, but that's just one example.

Anyway, my feeling is that this topic of measurement could (and should) be proliferated more here, with some examples of measuring techniques that just about anyone could grasp and do, if indeed they are interested in pursuing.
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post #173 of 218 Old 11-20-2011, 07:43 AM
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Quote:
Originally Posted by fotto View Post

Isn't the goal on treating first reflections the elimination of them? Is that concept only applicable to a 2 channel listening room, or mixing studio? I have to think not.

You can reflect, diffuse, or absorb them based on your target room model/response and a multitude of constraints withinn which you are forced to work. And while I think the concepts are just as valid for a multichannel system, the devil is in the details. If you identified and properly absorbed high gain early arriving specular reflections from each speaker location in a 7 channel (or more!) system, you might easily end up with an overly damped room. Or if you tried to preserve energy, direct it to the room wall opposite the generating speakers, and diffuse it back to the listener to provide a haas kicker, you might find locations simultaneously requiring diffusion and reflection.

Dennis Erskine has on many occasions commented that the treatment goals for a two channel room are different from a multichannel space. Obviously he know what he is talking about. I and others have commented that given this unavoidable truth, the best option (and to myself and others, not a 'second best' at all but the preferred approach in any case) is to reproduce all music as multichannel, using processing such as ambiance extraction when discrete multichannel source isn't available.

But then we're back to my question above. Given a powerful tool, and research vetted over many years as to what is preferreable acoustically, how do we apply that to a multichannel environment? I don't know. Perhaps, in the end, the closest we can come in the vast majority of spaces reduces to the empirical advice offered by professionals here for years.

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post #174 of 218 Old 11-20-2011, 08:34 AM
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Originally Posted by sdurani View Post

Good question. Either the professionals here don't understand the enormous benefits OR they understand that the benefits aren't enormous.

I will retract my use of the words "enormous benefit" because ETC is a tool ONLY.
It is a tool that allows one to accurately treat ones room and removes guessing at where to put treatment and what type.
More importantly the process allows one to know WHY.
If one doesn't care why, that's fine. However i would think they wouldn't be reading this thread anyway.

Its DOES NOT MATTER whether its a studio or living room. ETC is equally valuable in either situation.

If anyone else here is like me and does not have a professionally designed HT space and you want to treat your room accurately while learning WHY treatment needs to go "there" or "there" and wants to know what type to use, the ETC is the tool we have to use. Besides the Mic/computer/pre its FREE.

If one treats a room (on there own) WITHOUT consulting the ETC I see two things that can happen:

1. They over treat the room. Placing absorbers everywhere. Creating a deader room than need be. (Without the ETC may not even be aware that they created a dead space) I'm sure if it was pointed out, they would want to fix it.

2. They under treat the room using wrong treatments/materials and/or put them in the wrong locations. Thereby creating a mess. (once again, without ETC many may not even be aware of it)

Its great that people can come here and ask for advice on treating ones room but the information needed to make accurate choices cannot be answered by generalizations and suggestions. No matter how well meaning the answers are. The ETC is the tool can answer those very specific questions.

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so measurements that are spectrally (and directionally) blind, like ETC, might not be as useful to them as other items in a measuring toolkit

Once again, if one ignores the ETC tool they are guessing.

One can use the "mirror" trick to find reflections from around 400-500Hz and up but its not as accurate and it does not tell one anything.

Localhost sums it up here:

Quote:


the ETC will detail you all of this specular energy, and will do the following things that the mirror-trick cannot:

1. MEASURE the incident energy at the listening position, versus just guessing with the mirror-trick
2. detail to you the gain of the reflection, and the attenuation once your absorber has been placed (details to you how effective your absorber is and whether you need to make it more effective)
3. identify other non-obvious sources of incident early reflection (desk, floor, edge diffraction off devices, etc)
4. allow you to take multiple measures within your 'working area' to verify that your absorbers are of sufficient sq. area to attenuate the reflection across the entire listening position in 3D space

Don't you think in the context of room treatment the ETC measurement should be ones First line of defense instead of some obscure measurement no one need to worry themselves about?

Of course if one has the money they can always have someone else do it via whatever means they use, but for those wanting to do it themselves, I just don't see a more valuable tool for creating a solid base to start from.

Test,

Mpray1983- "User error due to sneeze or fart occurred during measurement"
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post #175 of 218 Old 11-20-2011, 09:03 AM
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Originally Posted by Bigus View Post

You can reflect, diffuse, or absorb them based on your target room model/response and a multitude of constraints withinn which you are forced to work. And while I think the concepts are just as valid for a multichannel system, the devil is in the details. If you identified and properly absorbed high gain early arriving specular reflections from each speaker location in a 7 channel (or more!) system, you might easily end up with an overly damped room. Or if you tried to preserve energy, direct it to the room wall opposite the generating speakers, and diffuse it back to the listener to provide a haas kicker, you might find locations simultaneously requiring diffusion and reflection.

Dennis Erskine has on many occasions commented that the treatment goals for a two channel room are different from a multichannel space. Obviously he know what he is talking about. I and others have commented that given this unavoidable truth, the best option (and to myself and others, not a 'second best' at all but the preferred approach in any case) is to reproduce all music as multichannel, using processing such as ambiance extraction when discrete multichannel source isn't available.

But then we're back to my question above. Given a powerful tool, and research vetted over many years as to what is preferreable acoustically, how do we apply that to a multichannel environment? I don't know. Perhaps, in the end, the closest we can come in the vast majority of spaces reduces to the empirical advice offered by professionals here for years.

What does this have to do with ETC?
You are talking about acoustic models.

Whether or not one chooses one model or another, or a hybrid with compromises the ETC is still beneficial.

I just don't see how the shortcomings of any particular model invalidates the usefulness of using the ETC to apply even basic rooms treatments.

Test,

Mpray1983- "User error due to sneeze or fart occurred during measurement"
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post #176 of 218 Old 11-20-2011, 09:19 AM
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Bigus, whether one chooses to diffuse, absorb or whatever other method to fit a particular room modeling goal is in my opinion secondary as to what I am looking at ETC for.

I am looking at it as a tool to identify WHERE these reflections are occurring, nothing more. There's obviously much more to consider on what treatment method you use as you describe.

Perhaps I was mistaken in making a comment like they should be eliminated completely. I'm still learning
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post #177 of 218 Old 11-20-2011, 11:38 AM
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Originally Posted by fotto View Post

Isn't the goal on treating first reflections the elimination of them?

Wouldn't that depend on the direction and spectrum of the reflection?

If reflections are coming off the front wall, then they might be making it more difficult for my brain to create phantom images in the front soundstage, in which case I would likely eliminate them. Similar reflections coming off the side walls could give me a wider soundstage and greater spaciousness, in which case I wouldn't eliminate them.

Likewise, if a reflection is broadband, I might not find it objectionable (or even notice it), since it could be reinforcing the direct sound. But if most of that energy is focused around a headache-inducing 5kHz, then I would definitely want to eliminate it. Speakers typically have a different response off-axis than they do on-axis, which means their reflections will have different spectra than their direct sound.

A simple ETC measurement, which is broadband and omnidirectional, isn't going to give me the above information. And without that information, I can't tell you which first reflections I would eliminate.
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Originally Posted by fotto View Post

So if we take the ETC portion off the table, how about other features of measurement software such as RTA? To be able to move sub positions, speaker positions etc. while watching in real time that effect has on your room response seems very valuable. Lots of other stuff in there as well, but that's just one example.

I don't think there's any need to take ETC off the table, just be clear about its limitations and how to get around them. To that end, the Mellor/Hedback paper that RUR linked to earlier makes some useful recommendations on using bandpass filtered ETCs to do things like check consistency between your left & right speakers (should be done for L/R surrounds as well).

You also make an excellent point about the rest of the toolkit, like RTA, which can be just as valuable. Impressive how much better a system can sound, and how much detail can be unmasked, simply by fixing the bass response. Same with looking at slices of a waterfall, since you can see time, amplitude and spectrum simultaneously. So rather than treating ETC like some sort of superstar, I think it is better put it in perspective as part of a measuring ensemble. A little balance goes a long way.

Sanjay
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post #178 of 218 Old 11-20-2011, 11:43 AM
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No prob fotto, I probably just misread your post. ETC can certainly identify where specular reflections of sufficient gain are occurring.

That is without doubt valuable information to have. But despite many suggestions to the contrary, ETC doesn't tell you what to do with those locations. It can confirm that your treatment did what you wanted it to in that location, but the bigger problem remains that knowing what you want to do isn't well defined.

Test, yes, my comment goes beyond the usefullness of ETC as a tool. I don't question that (and there are many valuable tools one can use). I've raised this concern/question before and it never receives much attention. Likely, as I'm becoming more convinced, because there just isn't a really good answer.

The best answer that has been oft repeated is that you simply treat to match whatever target model you choose. Ok, but how does one choose? Build them all in your room with your equipment and determine your preference? Obviously impractical. Well, maybe just read up on the various models and try to make a best guess as to what would be most appropriate for your room. Well, I have problems there too, as I just don't find much information out there on research and model development in multichannel environments. And perhaps you could just take more fundamental principles, such as deflecting sound to the rear and diffusing it back to the listener, and try to just apply those to your room. Well, you can quickly run into more requirements for a location than can be simultaneously satisfied. So maybe you just want to find an example of someone using ETC to locate problem spots in a way optimized for multichannel surround, an emulate the approach taken. Well, I'm still looking. If you could point to an example of this on gs or hts, that might help clarify this for me. It isn't that I don't understand the principles of the various room models, or what ETC can reveal to the user, or even how to appropriately treat a single location based on the ETC data. But Everything I have found is people in studio environments working with two channels, or people in ht environments using rew in the frequency domain and/or treating their room as if it only had two channels.

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post #179 of 218 Old 11-20-2011, 01:01 PM
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Originally Posted by Bigus View Post

But despite many suggestions to the contrary, ETC doesn't tell you what to do with those locations.

no more than a hammer doesn't tell you what type of home to build.

get real.

circular arguing vs expanding knowledge base.
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post #180 of 218 Old 11-20-2011, 02:36 PM
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no more than a hammer doesn't tell you what type of home to build.

get real.

circular arguing vs expanding knowledge base.

I'm not 'circular arguing' local. I've asked some questions, and yes, of course some go beyond the basics. I would like to expand my knowledge. You have the opportunity to help do that.

But I really don't get the attitude around here sometimes. I say ETC is just a tool, and you have to come back by saying it's just a tool, that I'm circular arguing, and to get real?! I also offered an apology to you previously, even after rereading the entire thread and seeing clearly who was being abrasive. So what's the deal?

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