Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 112 - AVS Forum
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post #3331 of 12230 Old 06-07-2013, 11:48 AM
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That sounds like a thread title that Jason would pick....   wink.gif

However, I do have a page on the string method in the Guide.

But appropriate smile.gif. And it keeps the REW guide more focused, and IMHO less overwhelming to newbies.

 

TBH, as someone who bought an OM kit solely on the "plug and play" premise and was completely new to REW, USB mics et al, I really like how Jerry's guide has evolved from just setting up the equipment and running REW to actually interpreting the information and emploring different methods to resolve issues in the space.  There is a very methodical approach to reading the guide and the additional info like using the string method makes it somewhat of a "one-stop" guide for improving SQ in your listening space.  Afterall, if someone is intimidated to read the guide at 77 pages with huge pictures and larger font, what business do they really have diving down this rabbit hole?!  I know I'm not speaking for the masses but the more info available in one place the better at least for me! YMMV

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post #3332 of 12230 Old 06-07-2013, 11:50 AM
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Originally Posted by jkasanic View Post

TBH, as someone who bought an OM kit solely on the "plug and play" premise and was completely new to REW, USB mics et al, I really like how Jerry's guide has evolved from just setting up the equipment and running REW to actually interpreting the information and emploring different methods to resolve issues in the space.  There is a very methodical approach to reading the guide and the additional info like using the string method makes it somewhat of a "one-stop" guide for improving SQ in your listening space.  Afterall, if someone is intimidated to read the guide at 77 pages with huge pictures and larger font, what business do they really have diving down this rabbit hole?!  I know I'm not speaking for the masses but the more info available in one place the better at least for me! YMMV

I don't think we're 'the masses'cool.gif. The masses are doing "set and forget" Audysssey or other RC, and thinking they're replacements for treatments, or that RC solves their problems as the ultimate tool in the toolbox (I can but won't mention one member of that club that's a frequent Audyssey poster LOL). This is for denizens of the rabbit hole biggrin.gif

Stuart

 

Denon 4311 with XT32 and Audyssey Pro

Oppo 93 and 103

Panasonic VT50

Sherwood R-972 with its version of the Trinnov Optimizer

MiniDSP 10x10 HD

PSB Imagine T2, Center, and Surrounds (as of 5/2014); HSU ULS-15 subs (2)

 

The Audyssey FAQ Guide can be found here:

http://www.avsforum.com/...

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post #3333 of 12230 Old 06-07-2013, 11:56 AM
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Thanks for the info on the GIK 242 vs 244.  I was just wondering if the string method directed you to your first reflection points immediately or if you "automatically" treated those areas independent of any testing?  Also, I don't think I'm familiar with the "blocking" method?  Could you share some links as a quick search of the site as well as Google revealed several mentions of it but nothing about the technique (that I could find anyway)?  Thanks.

Here's a test I did using the string method back in 2011 that is probably lost in the archives at this point. I cut/pasted a portion of that below as well.
http://www.avsforum.com/t/1374014/room-measurement-treatment


Hopefully this has demonstrated how ETC can be used to locate reflections, and verify effectiveness of treatment. It's really not that complicated.

 

Thanks Floyd for the informative post.  I've actually seen your broom stick referenced in other threads so it was nice to understand how you used it in your room.

 

p.s.

Go Spurs! wink.gif

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post #3334 of 12230 Old 06-07-2013, 11:59 AM
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I don't think we're 'the masses'cool.gif. The masses are doing "set and forget" Audysssey or other RC, and thinking they're replacements for treatments, or that RC solves their problems as the ultimate tool in the toolbox (I can but won't mention one member of that club that's a frequent Audyssey poster LOL). This is for denizens of the rabbit hole biggrin.gif

 

Haha...yeah, I guess I should've said "other AVS forum members" or even "followers of this thread" instead of 'the masses'!

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post #3335 of 12230 Old 06-07-2013, 12:10 PM
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p.s.
Go Spurs! wink.gif

Oh yeah...could it be any other way? biggrin.gif
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post #3336 of 12230 Old 06-07-2013, 12:11 PM
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Visual of overall string path with my "treatment stick" holding it up:



 

 

I acknowledge your "treatment stick", and counter with my ceiling fan treatment:

 

 

Who is the Rube Goldberg now? 

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post #3337 of 12230 Old 06-07-2013, 12:17 PM
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Well after my initial introduction into room interaction with sound and the EE Times article my Definitive bipolar towers "seem" like the may prove to be problematic.


I would like to hear a few opinions on these speakers. I can certainly sell them and use some of these Studio Monitor 65's instead. That would certainly be the easiest change to rid of the rear firing drivers. I know I am still waiting on my UMM-6 and haven't even had the chance to get going. But I'm thinking long term. Perhaps one day I will change speakers but that isn't in my radar as subwoofer upgrades and other things are. And like I said that would be the easiest fix. On a side note Brian at GIK said diffusion needs to be used behind them and the can be problematic.

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post #3338 of 12230 Old 06-07-2013, 12:25 PM
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Who is the Rube Goldberg now? 

LOL...Mr. Goldberg I presume, or perhaps the "Blade Damper". I cringe imagining my 7 year old turning on the switch eek.gif
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post #3339 of 12230 Old 06-08-2013, 02:58 AM
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It's all very interesting but the purpose of this thread, as stated by the Thread Starter in the first post or two, is to help newcomers to REW to get it up and running and then provide them with basic advice on interpretation of their graphs, with more advice on how to improve their room, using REW as their guide.
The purpose of this thread, as stated by the Thread Starter, has always been two parts:
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The first step was introducing folks to a new and easier way to take measurements and getting everyone on the same page with how to display and interpret the measurements themselves.

I believe we've accomplished that.

The second part has always been Choosing an acoustical model. Folks need to start doing this.
With that goal in mind, discussions about room reflections are on topic (even necessary) in a thread where folks need to choose an acoustical model. So cut 'em a little slack maybe?

 

Agreed about the objectives. But endless back-and-forth bickering between various 'experts' isn’t very helpful, IMO, to the people who really need this thread (like me for example) in order to get a grip on the basics. AFAICS there has been almost zero information posted on how to choose the acoustic model, but a lot of discussion about which expert is 'right' and which is 'wrong'. This is, of course, seen through the prism of my own level of expertise. Your expertise is far greater than mine and so, looking at the posts through your prism, the discussions probably make all sort of sense. But the stated aim of the thread is to help people who are just starting - the various experts in the thread provide most value, IMO, if they try to help newcomers rather than engaging in esoteric discussions among themselves. There are plenty of threads for expert discussion and disagreement already. Just how I see it. 

 

EDIT: cases in point from the last page or two:

 

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I'm pretty sure I have a lot of work to do wrt these reflections but I'm stuck on this "pick a room model" or bust mentality.  How should I know which model will fit my preference if I've never experienced either one?!  Clearly, I've done enough research now to be considered dangerous and I comprehend the basic philosophical differences between the various models but this doesn't mean I understand how picking one model over another will sound in my room.  Given the cost involved, picking the wrong model could potentially have a significant impact financially. I'd prefer to take some of the guesswork out of it so I'll start by treating my room for the high gain early reflections which by most accounts everyone agrees are bad but once that's complete, where do I go?!

 

 

 

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Regarding picking a model, and after hearing the discussions on this thread, I have come to the conclusion that the LEDE/RFZ model is the one to work towards. I think we should have two objectives: taming the modal response as measured by the waterfall, and reducing early reflections (<20ms) to -15db or better, depending on the level of effort you want to expend. For those of us with non-dedicated rooms, we may never get to the more advanced objectives of the model, I.e. re-introducing diffuse reflections past 20ms.

The LEDE/RFZ model sounds like a better fit for me because listening to music is a very high priority.

 

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Jerry, are these models and their philosophies in full descriptive theory in this thread prior or elsewhere? I would love to learn about them.
 
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post #3340 of 12230 Old 06-08-2013, 03:16 AM
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Stuart, thanks for asking the question as I've been wondering the same thing myself.  As you might recall from my earlier posts, my post Audyssey FR, Waterfall and Decay charts are a significant improvement in my room but as it has been stated numerous times, the improvement from Audyssey in the time domain appears to be limited to bass ringing and have almost no impact on high gain early reflections (which I believe my ETC's will show).  I'm pretty sure I have a lot of work to do wrt these reflections but I'm stuck on this "pick a room model" or bust mentality.  How should I know which model will fit my preference if I've never experienced either one?!  Clearly, I've done enough research now to be considered dangerous and I comprehend the basic philosophical differences between the various models but this doesn't mean I understand how picking one model over another will sound in my room.  Given the cost involved, picking the wrong model could potentially have a significant impact financially. I'd prefer to take some of the guesswork out of it so I'll start by treating my room for the high gain early reflections which by most accounts everyone agrees are bad but once that's complete, where do I go?!

Regarding picking a model, and after hearing the discussions on this thread, I have come to the conclusion that the LEDE/RFZ model is the one to work towards. I think we should have two objectives: taming the modal response as measured by the waterfall, and reducing early reflections (<20ms) to -15db or better, depending on the level of effort you want to expend. For those of us with non-dedicated rooms, we may never get to the more advanced objectives of the model, I.e. re-introducing diffuse reflections past 20ms.

The LEDE/RFZ model sounds like a better fit for me because listening to music is a very high priority.

 

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Originally Posted by AustinJerry View Post

That sounds like a thread title that Jason would pick....   wink.gif

However, I do have a page on the string method in the Guide.

But appropriate smile.gif. And it keeps the REW guide more focused, and IMHO less overwhelming to newbies.

 

TBH, as someone who bought an OM kit solely on the "plug and play" premise and was completely new to REW, USB mics et al, I really like how Jerry's guide has evolved from just setting up the equipment and running REW to actually interpreting the information and emploring different methods to resolve issues in the space.  There is a very methodical approach to reading the guide and the additional info like using the string method makes it somewhat of a "one-stop" guide for improving SQ in your listening space.  Afterall, if someone is intimidated to read the guide at 77 pages with huge pictures and larger font, what business do they really have diving down this rabbit hole?!  I know I'm not speaking for the masses but the more info available in one place the better at least for me! YMMV

 

Agreed +1.

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post #3341 of 12230 Old 06-08-2013, 03:19 AM
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post #3342 of 12230 Old 06-08-2013, 07:32 AM
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Is anyone else not getting email notifications of new posts from AVS or is it just me?

Don't know, Keith, I don't use email notifications.
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post #3343 of 12230 Old 06-08-2013, 07:34 AM
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Is anyone else not getting email notifications of new posts from AVS or is it just me?

Same issue here, last email notifications were received yesterday at 3:48 PM ET.
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post #3344 of 12230 Old 06-08-2013, 09:36 AM
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Agreed about the objectives. But endless back-and-forth bickering between various 'experts' isn’t very helpful, IMO, to the people who really need this thread (like me for example) in order to get a grip on the basics. AFAICS there has been almost zero information posted on how to choose the acoustic model, but a lot of discussion about which expert is 'right' and which is 'wrong'. This is, of course, seen through the prism of my own level of expertise. Your expertise is far greater than mine and so, looking at the posts through your prism, the discussions probably make all sort of sense. But the stated aim of the thread is to help people who are just starting - the various experts in the thread provide most value, IMO, if they try to help newcomers rather than engaging in esoteric discussions among themselves. There are plenty of threads for expert discussion and disagreement already. Just how I see it. 

EDIT: cases in point from the last page or two:

At the heart of the matter is no amount of information really will tell you what a model sounds like in a direct sense. The basic information regarding models has already been said redundantly throughout the web. I think there should be an assumed meeting point somewhere between those seeking it and those possessing it. For those seeking it, I think you owe it to the discussion to do the educational part yourself to the point where the basics are grasped. You cant expect those possessing it to have to repeat the long and arduous chore of repeating the basics in every thread.

The bickering you speak of is a natural consequence of personal subjectivity in regards to what one likes as a personal preference and different interpretations of the available facts. The more generalized the inquiry, the more this will be the case. Questions like "what model should I choose" is a bit like asking "what color should be my favorite". It just invites unnecessary controversy.

What I think is the most constructive scenario for discussion of room models is clarification of the specifics of a given model and how that may play out in a certain situation (or particular room).

edit: The most important and revealing knowledge is obtained from actual listening. Those of you serious about this might consider that half an hour of listening to a room treated a particular way will provide more info than 100 hours (perhaps smile.gif ) of blogging. If I were starting out and unsure which direction to go, I would find people who have done actual models, find out where they are, find those closest, and strike up a conversation with them. In my experience, most people are more than happy to share what they have built, and extend invitation fairly readily once the ice is broken. This may take some time and effort, but considering what you do to your room may very well be what constitutes what your room sounds like for a decade or more to come, I view the effort as one with enormous returns and little investment.

My Room
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Rega - Apollo, Rega - DAC, Goldpoint Passive, (2) Classe CA-100 bridged power amps (350w)
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post #3345 of 12230 Old 06-08-2013, 09:59 AM
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Agreed about the objectives. But endless back-and-forth bickering between various 'experts' isn’t very helpful, IMO, to the people who really need this thread (like me for example) in order to get a grip on the basics.
I provided a one-stop-shop, complete end to end tutorial on how to go about analyzing the information and what to do about it in your room. Didn't see any feedback and so no bickering either. Here it is again:
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Thanks for asking. If I may, I like to give a complete answer to what we need to do to get good sound in our home listening spaces so that the context is understood. And that there is a comprehensive story as there should be.

1. Optimize low frequencies. Due to simply physics of sound, the room dominates the response we get here. The speaker plays a smaller role here than the room (sans how low it goes and how powerful it might be). The tool of choice to know what is wrong is a simple frequency response measurement going to a few hundred hertz. The response here should be smooth (not to be confused with flat) with as little variation as possible. And it should be tilting down if you took a wider view all the way up to 20 Khz. The tools at your disposal to remedy issues here is placement of speaker/listener, acoustic solution, more than one subwoofer, and electronic processing (EQ and multi-sub optimization). Sanjay has provided some of the best posts in this thread on this. If you want a complete end to end story, get Dr. Toole's book as his team's work on use of multiple subs has revolutionized the science of better low frequency response. Beyond that, you can try to read their AES papers although they are not as easy to understand.

Keep in mind that perception of bass accounts for 25 to 30% of what we think fidelity is all about. If one were to walk away with one take away from this thread and your guide, it would be to optimize the bass. Cool thing is that optimizing the bass almost entirely is intuitive in that it does not pull in the science of psychoacoustics that the other items below do. The wavelengths are so large that both ears hear the same thing so a single microphone measurement we use is representative of what we hear.

Note that I said nothing about using waterfalls. You don't need to look at waterfall displays. If you optimize your frequency response measurements per above, and do it correctly, then the time axis that waterfall attempts to show comes along for a free ride. Dr. Toole provides a proof of this and I do a much more extensive one using REW for measurements. Click on the first link in this search to read about it. For now, here is a representative graph of how by applying EQ to fix one peak in frequency response, the time domain response improved just the same:

i-z7Cg55m-L.png
Notice how the peak at 53 Hz in brown is brought down with the single band eq and with it, the "ringing," i.e. it dragging on in time from back to front was also sharply reduced. The mathematics of this are quite powerful in how they govern this and no amount of stomping one's feet will get around time and frequency being interconnected in low frequencies this way. Alas, waterfall displays are pretty and people fall in love with them and hate to let go. As with ETC, there is a psychological barrier to giving it up, lest one feels less of an expert without it. But there really is no additional information to be had there and if anything, as I describe in the article, you can easily get false data by setting the obscure parameters in waterfall wrong.

Note also that you can use your ears just the same to know if the time domain in waterfall has fixed itself. Apply your eq and do a before and after with something that has low frequency and has "sharp" transients. I use guitar in the Chris Jones "no sanctuary" track and listen with just the subs playing. You can easily hear when without correction they notes run into each other and how they "tighten" and become shorter in time when you simply apply an EQ to one or more peaks. BTW, in all cases here you want to use your ears wherever you can instead of blindly trusting what you measure.

So in summary, you need to get a smooth response. And the judge of that is a frequency response measurement. The measurement if performed in at least 1/10 octave resolution will match what we hear.

2. Get well designed speaker. Here is a quick hint: the way you know if you have a good room designer next to you is if they pay as much attention if not more about what speaker you have than your room. Try to get someone like Keith Yates to design a room around some random speaker you bought is hard, hard, hard. He will pull on your ear for hours trying to convince you to go with a better choice. Likewise, Dr. Toole's book, in-session training, and AES paper always, always have considerable amount of space dedicated to what makes a good speaker. The speaker is the thing that makes sound in your room. Above the transition frequencies of a few hundred hertz, it dominates the sound you hear, not the room. Don't believe me? Listen to two different speakers in an audio speaker. Don't they sound radically different to you above low frequencies even though the room stays constant? Of course they do. That is because the speaker dominates the sound we hear, not the room. The room has some impact to be sure but the speaker players a huge role.

Now everyone will violently accept that one should get "well-designed speakers.'" But ask them what that is, or look at the speaker they bought and either find that they can't tell you what makes a good speaker. Or the speaker they bought clearly is not well designed. What is a well-designed speaker? Well, there are as many stories on that as there are speaker manufacturers. Everyone will have their angle of what they have done to make a good speaker and all the rest is bad. In my book however, there is only one scheme that is validated with double blind test across hundreds of speakers: whether a speaker puts out off-axis (side-ways or up and below) signal that is similar to what it puts out on-axis (directly in front). Having such good response highly correlates with preference scores in double blind listening tests. Again, this is true of testing myriads of speakers from cheap in-wall speakers to high-end audiophile ones. I have sat in these double blind tests and had to agree with this notion kicking and screaming. Speakers that I thought were great due to fancy drivers, etc. fell apart when curtains were closed and all you could do is compare sounds and the ones with good off-axis response won.

The discussions around Dennis Erskine's thoughts on this front exactly mirror what I just said. As he properly said, you need to run away from any manufacturer who doesn't follow the above scheme (or the opposite of it which is to control what sound goes off-axis such as Geddes). Do not attempt to create a room optimization strategy that assumes you have a bad speaker. Why throw good money after bad? Sell your speaker to someone who hasn't taken the time to educate themselves and buy the proper speaker. The proper speaker will give you a lot more options. It can be equalized better. It can be used to get maximum effect out of what I am about to explain about room reflections, and can be the last speaker you buy.

Here is an ultimate litmus test: a well-designed speaker sounds excellent even in an "untreated" room. If your speaker sounds bad, then it is not well-designed. I bought a set of speakers for my empty theater that only had carpet on the floor. It had nothing else and clearly was live. I turned on the speakers and I could not believe the fidelity of what I was hearing. I sat there for hours listening. Sure, we can improve the sound further as I will explain but the foundation needs to be good. Please don't waste time with the rest of what I am about to say if you have not found good speakers. Read Dr. Toole's book and he will go in huge amount of detail on what matters there and again, you can then follow by reading the AES papers. But the story is as simple as what Dennis has said and I repeated here. Get that right, and the rest will take care of itself. Once there, you can read speaker manufacturer marketing material and if they follow that, even if they don't give you the data, you will be able to see it there.

3. Now to the question you asked. We have two ears, not one. Those ears are separated by some distance. As you go above the low frequencies, the wavelength of sound waves becomes small enough that your head will cast an acoustic shadow on sounds coming from the other direction. That causes that ear to hear something different than the other ear. Further, the distance between the source of sound and the two ears may be different. If they are, certain characteristics of sound such as "comb filtering" (two waves combining) will be different in each ear. We don't however hear these sounds as I just described. Sitting in your room as you are now, you will not hear countless versions of someone talking to you even though there are many reflection sources. You hear one sound. The reason for that is that the brain combines what the two ears hear and determines one result out of it. This is the science of "psychoacoustics" at work. Just as we don't measure fidelity of two MP3 encoders with a simple audio measurement, we can't trust the readings we get from a single microphone using REW. That measurement does not tell you what one ear hears let alone two. Our ears do not have flat frequency response or remotely so as our mics do for example. And clearly no mic will tell us how the brain is combining the complex signals it is detecting in both ears.

The investigations into what we hear then almost completely rely on listening tests. You can read Dr. Toole's book for all the gory details but here is the sum total of it:

3a) Side walls should be left reflective. These accentuate the difference that each ear hears resulting in "image widening" meaning the sound does not appear to just come out of the cone of the speaker. That is a good thing! We like to be lost in our music or movies. We don't want to hear the sound coming out of one point. Think of the center speaker. Its sound needs to span the full width of your screen, not just the one spot it occupies. Each side reflection will appear to pull the sound toward its direction. Mind you, you will have no trouble telling the sound is still coming from the front. But it will appear to have wider origination than if you had no reflection. These reflections will also help reduce the effects of comb filtering. And help fill in the response for phantom images (i.e. sounds between speakers).

There is a small group of people who mix or record music for a living. They know precisely how to add the sound of the room to a recording. And hence their ears are trained to hear reflections. For them, and specific to the work they do to tune the amount ambiance they add to their recordings, they opt to absorb such reflections. Please don't follow them blindly just because they are "pros." As I just explained, and Dr. Toole goes through far more detail in his book, they are not the same as us. Are there others who are recreational listeners with similar preferences? Sure. But based on collective knowledge we have, as a population they are in the minorities. Your baseline assumption therefore should be that you are NOT in this bucket. Start with no absorption on the sides and see how you like the sound. It costs less to try this alternative since you won't have to buy something and then have to remove or return it.

If you have already put absorption there because you read here that you should have, remove them and try to set aside your bias that they were good for you. There is a good chance that you will like the sound better without them. But if you don’t then put them back on.

There is also some discussion around what to do if you have a lousy speaker with poor off-axis response. Some, including Dr. Toole in his text, will say then an option exists to absorb side-reflections then. As I said however (and Dr. Toole does the same in the next breath), that if you know you have a speaker with poor off-axis response, then you want to remedy that first. The strategy should not hinge on what tod o with a poor speaker. Further, published listening tests show that even when off-axis response is poor, many people prefer to hear it than not. So that is two reasons to not chase this often mandated goal.

3b) Front wall should have absorption. The nice effects I talked about don't apply here since both ears hear the same reflection so nothing is added perceptually. So put absorption there.

3c) Floor should have absorption. If you go blindly this way, this appears to be an impossible thing to do right. Why? Any absorber should be broadband, i.e. go down to a few hundred hertz. If not, it will then apply the equiv. of an equalizer to the off-axis sounds you are trying to absorb instead of blocking them. Typical thickness you need is 3-4 for inches for an absorber. I suspect few of you want to put such an absorber on the floor! Fortunately psychoacoustics and listening tests save us. That data shows that timbre changes we hear as a result of "floor bounce" is from 500 Hz and up. Good news about that is that a thick carpet on thick padding will get us there or close enough. So be sure to put a carpet on the floor. This will also help with #4 below.

3d) Back wall. For the same reason as #3b, you should put absorption there.

3e) Ceiling. It is not well understood but somehow our perception of ceiling reflection is not the same as floor even though they are symmetrical with respect to their effect on what we hear. The recommendation there is an optional one in the form of a diffuser.

4) Keep an eye on overall amount of absorption you have in the room. This is where RT60 comes in. Measure it and look at the value in 500 Hz frequency range. Target range is 0.2 to 0.4. If you are building a new room, you can fairly predict its level using Sabine's formula. Here is an example of me doing the simple math and arriving at similar measured value in a room: http://www.avsforum.com/t/1453370/do-bass-traps-produce-noticeable-audible-difference/150#post_23051964. Note again that this is approximate math and no precision is required. If you want a rule of thumb, you want around 25% of the surfaces covered. Keep in mind the large surface such as your wall to wall carpet can amount for a lot of this. If you add a ton of panels around the room on top of this, you may cross the line and have the room be "dead." That word was picked for a reason: there is nothing good about a dead sounding room! So be very careful in chasing spike in ETC and constantly adding absorption. You will likely wind up with a dead room that will not only not be so good for enjoyment of your content but is a lousy place to live and converse in. Be especially careful of everyday living room. If they are fully furnished, the RT60 may already be in target area. Get good speakers and you may not have to do a thing about mid to high frequencies there!

That said, for multi-channel sound in dedicated rooms, you can go toward the lower end of the scale (e.g. 0.2). But don't go beyond. One of the worse offenses of DIY room treatment is too much absorption due to fear of reflections being "bad." Opt for the higher range for music.

That’s it really. Take this as a primer as you read more depth research papers and books. There is no better start and validation than Dr. Toole’s book: http://www.amazon.com/Sound-Reproduction-Acoustics-Psychoacoustics-Loudspeakers/dp/0240520092/ref=sr_1_1?ie=UTF8&qid=1370189955&sr=8-1&keywords=toole+floyd. Put that in your cart now and you will learn more about audio than spending years reading forum posts. With the primer above, then the text will make more sense to you. Read it multiple times. I have. It is not a novel where you read it once and it all sinks in.

As you see, I have provided the complete answer. And as a bonus, reduced the set of measurements we need. And the core measurement that is used, frequency response, is something everyone understands. To the extent we don't follow it and continue to seek complicated measurements whose data we don't quite understand and propose vague strategies on what to do with them, then we show that we are not looking for simplicity as you say. More below.
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AFAICS there has been almost zero information posted on how to choose the acoustic model, but a lot of discussion about which expert is 'right' and which is 'wrong'.
There is zero information about "acoustic mode" from the answer I provided because the whole question is wrong. You don't need an antiquated model that was designed for production of sound for a different audience and objectives. By continuing to ignore the reasoning behind both factors, you invite the confusion to the table that you mention.

I can't think of a more silly statement to make to a novice than, "pick your acoustic model." It is like telling a person wanting to buy a car to pick their ignition timing before they can drive it! It is even worse in that the people who advocate this message, have no listening test to offer for efficacy of them. Only an appeal to one's (incorrect) intuition that you must dislike reflections. Leading people to build overly dead room. They make it worse by then advocating that people not even measure how dead their room is by claiming RT60 is not valid. So the person keeps going those reflections as if to trim each blade of grass in their yard by hand.

The result is pages after pages of this thread with the wrong and redundant discussion of "you still have more reflections at X milliseconds." How many times do we need to see that back and forth anyway? Why no objection to that? Imagine sitting in my shoes knowing how wrong the whole approach is, and seeing it being discussed as if it is 9 out of 10 commandments smile.gif.

You can sit through a 2-day course by Dr. Toole where he teaches the teachers to go and design rooms at CEDIA. Not once does he say "pick your acoustic model." Not once does he say "use ETC." What he does do is emphasize the role of the speaker. What he does do is teach you the fundamentals of acoustic science; how there are two domains: below transition frequencies and above. How below transition the frequency response measurement rules. How above, psychoacoustic rules and not some simplistic view that reflections which runs counter to many research studies. He will tell you the history of LEDE rooms and what is wrong with following those footsteps and not in so kind words smile.gif. All of it is backed impeccably by research. It is not meant to be the last word in acoustics and he says outright that this is his biased with an opinion built over 40 years of being in this field. All is not known. But a lot is known that leads us to excellent reproduction systems at home.

But we don't want to go there. And instead, keep asking for an acoustic model. A question that is long obsoleted but we don't want to acknowledge that, lest we invalidate a lot of what we have said in these forums. We won't spend $30 on a book that teaches us far more than anything we could read online. Even, when a summary of the book's message is provided per my post above, we prefer to continue asking the wrong question of acoustic model. So it is clear we are shopping for a specific answer, not "the" answer. The specific answer must fit our preconceptions of acoustic science even though we acknowledge in the next breath that we don't know the answer by asking which acoustic model to use. Either you know it and you make a case for it or accept advice from top experts in the industry who do Keith. You can't have it either way.

This thread is the best one I have seen on this topic. It is a shame now that we have gotten to the last chapter, what to do with the data, we are either shy about discussing it, or the vocal majority votes for one point of view and just sails past any objections to their stance. I show how ETC can show incorrect data by some 28 dB and it does not even phase people. Folks continue as if that was not even said let alone backed by research-quality listening test/measurements. I show how the mathematics of how ETC works, and how physics of speakers completely put its results in doubt. Yet post after post still talks about what to do with its spikes. How do we expect to get anything done to help people if we can't rationalize this type of interchange?

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post #3346 of 12230 Old 06-08-2013, 10:46 AM
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At the heart of the matter is no amount of information really will tell you what a modal sounds like in a direct sense. The basic information regarding models has already been said redundantly throughout the web. I think there should be an assumed meeting point somewhere between those seeking it and those possessing it. For those seeking it, I think you owe it to the discussion to do the educational part yourself to the point where the basics are grasped. You cant expect those possessing it to have to repeat the long and arduous chore of repeating the basics in every thread.

The bickering you speak of is a natural consequence of personal subjectivity in regards to what one likes as a personal preference and different interpretations of the available facts. The more generalized the inquiry, the more this will be the case. Questions like "what model should I choose" is a bit like asking "what color should be my favorite". It just invites unnecessary controversy.

What I think is the most constructive scenario for discussion of room models is clarification of the specifics of a given model and how that may play out in a certain situation (or particular room).

edit: The most important and revealing knowledge is obtained from actual listening. Those of you serious about this might consider that half an hour of listening to a room treated a particular way will provide more info than 100 hours (perhaps smile.gif ) of blogging. If I were starting out and unsure which direction to go, I would find people who have done actual models, find out where they are, find those closest, and strike up a conversation with them. In my experience, most people are more than happy to share what they have built, and extend invitation fairly readily once the ice is broken. This may take some time and effort, but considering what you do to your room may very well be what constitutes what your room sounds like for a decade or more to come, I view the effort as one with enormous returns and little investment.

Yes that would be the best I believe. I have 2 invites for Seaton subs already (5hours north in Seattle) but some successfully treated rooms I think would hold more value in experience

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post #3347 of 12230 Old 06-08-2013, 11:43 AM
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edit: The most important and revealing knowledge is obtained from actual listening. Those of you serious about this might consider that half an hour of listening to a room treated a particular way will provide more info than 100 hours (perhaps smile.gif ) of blogging.
That would be good but such a room does not come by easily. It would need to be configurable both ways so that you can perform a (preferably blind) test of each configuration. Listening to one room with one set of equipment and then listening to another with a different set of equipment, room size and configurations will not yield an answer. Fortunately such tests have been done and results readily available such as this from Dr. Toole's book:

'It was in this room [reference listening room being built at NRC research institute] that experience was gained in understanding the role of first reflections from the side walls. The drapes were on tracks, permitting them to easily be brought forward toward the listening area so listeners could compare impressions with natural and attenuated lateral reflections (see Figures 4.10a and 8.8). In stereo listening, the effect would be considered by most as being subtle, but to the extent that there was a preference in terms of sound and imaging quality, the votes favored having the side walls left in a reflective state. In mono listening, the voting definitely favored having the side walls reflective. See the discussions in Chapter 8, and Figures 8.1 and 8.2, which show that attenuating first reflections seriously compromises the diffusivity of the sound field and the sense of ASW/image broadening."
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The bickering you speak of is a natural consequence of personal subjectivity in regards to what one likes as a personal preference and different interpretations of the available facts. The more generalized the inquiry, the more this will be the case. Questions like "what model should I choose" is a bit like asking "what color should be my favorite". It just invites unnecessary controversy.

Please forgive me for being direct but what you say Jim simply is not supported in research. Testers overwhelming vote like above and it is nothing like random selection of colors. Here is related back up from Dr. Toole's private presentation:

"In double-blind listening tests where listeners compare music with and without the side-wall reflections, the results consistently indicate a preference for the reflections.

Listeners given the opportunity to adjust the sound level of the reflection to maximize “preference,” chose levels that were above the levels of natural room reflections. "


I can cite more references but it honestly feels like I am trying to tout the benefits of meat to vegetarians smile.gif. There seems to be no openness to accepting proper research here. Simply put, people interested in the performance of audio in their room need to start with the position that they fit the groups tested above and will have a preference for having side reflections than not. And therefore these room models are wrong as a result. That is what the science tells us. Let's not put that aside and side with our own notions and pass them as the statement of what it is.

Now if you have listening tests that state otherwise, that show completely random choice such as picking colors, let's see them. I have debated this topic numerous times and that data is never put forward but maybe this is my lucky moment smile.gif. In absence of that, let's at least acknowledge that our views are seriously undermined by people with impeccable credentials that have tested such things.

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post #3348 of 12230 Old 06-08-2013, 12:18 PM
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Please forgive me for being direct but what you say Jim simply is not supported in research. Testers overwhelming vote like above and it is nothing like random selection of colors.

I can cite more references but it honestly feels like I am trying to tout the benefits of meat to vegetarians smile.gif. There seems to be no openness to accepting proper research here. Simply put, people interested in the performance of audio in their room need to start with the position that they fit the groups tested above and will have a preference for having side reflections than not. And therefore these room models are wrong as a result. That is what the science tells us. Let's not put that aside and side with our own notions and pass them as the statement of what it is.

Now if you have listening tests that state otherwise, that show completely random choice such as picking colors, let's see them. I have debated this topic numerous times and that data is never put forward but maybe this is my lucky moment smile.gif. In absence of that, let's at least acknowledge that our views are seriously undermined by people with impeccable credentials that have tested such things.

First of all, I said "a bit like", not "exactly like". Additionally, if the research you refer to was as an exact science as your presenting it to be, then everyone one should like the same kind of room and acoustics, and clearly people do not.

In the context that I meant it, the colors are:

LEDE / RFZ
NE (non-environment)
FTB (Front to back)
Svana's philosphy ( http://www.hifisentralen.no/forumet/akustikk-og-rom/54859-svana-s-acoustics-philosophy.html )

Plus a myriad of individual approaches blending different colors together.

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post #3349 of 12230 Old 06-08-2013, 12:28 PM
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That would be good but such a room does not come by easily. It would need to be configurable both ways so that you can perform a (preferably blind) test of each configuration. Listening to one room with one set of equipment and then listening to another with a different set of equipment, room size and configurations will not yield an answer. Fortunately such tests have been done and results readily available such as this from Dr. Toole's book:

'It was in this room [reference listening room being built at NRC research institute] that experience was gained in understanding the role of first reflections from the side walls. The drapes were on tracks, permitting them to easily be brought forward toward the listening area so listeners could compare impressions with natural and attenuated lateral reflections (see Figures 4.10a and 8.8). In stereo listening, the effect would be considered by most as being subtle, but to the extent that there was a preference in terms of sound and imaging quality, the votes favored having the side walls left in a reflective state. In mono listening, the voting definitely favored having the side walls reflective. See the discussions in Chapter 8, and Figures 8.1 and 8.2, which show that attenuating first reflections seriously compromises the diffusivity of the sound field and the sense of ASW/image broadening."

Simply drawing curtains wont turn an optimized RFZ room into a NE, or any other room. Dr. Toole's research reveals exactly, but nothing more than he states, so listeners could compare impressions with natural and attenuated lateral reflections. While many would benefit from a clear idea of what this difference is, it is not in any way like comparing optimized rooms of different models.

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post #3350 of 12230 Old 06-08-2013, 12:46 PM
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Do you guys think my receiver's calibration microphone would work well in measuring frequency response for REW? It would save me cash by not having to buy that Behringer microphone. Thank you.
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post #3351 of 12230 Old 06-08-2013, 01:27 PM
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The saga continues...

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post #3352 of 12230 Old 06-08-2013, 01:29 PM
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Do you guys think my receiver's calibration microphone would work well in measuring frequency response for REW? It would save me cash by not having to buy that Behringer microphone. Thank you.

Not really. It doesn't have a calibration file, so the measurements you would get would not be accurate.
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post #3353 of 12230 Old 06-08-2013, 02:21 PM
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Quote:
Originally Posted by jim19611961 View Post

Simply drawing curtains wont turn an optimized RFZ room into a NE, or any other room. Dr. Toole's research reveals exactly, but nothing more than he states, so listeners could compare impressions with natural and attenuated lateral reflections. While many would benefit from a clear idea of what this difference is, it is not in any way like comparing optimized rooms of different models.

precisely. the study attenuates the first-order sidewall reflections while ignoring the later arriving (lateral) diffuse sound-field in such studies. looking at one component in isolation and ignore the system/total response as a whole. is toole supposed to be some sort of expert on LEDE? where is the documentation that toole/olive performed in LEDE/RFZ rooms - which rooms specifically did they test in? i was hoping this would have been answered by now.
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post #3354 of 12230 Old 06-08-2013, 02:32 PM
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Originally Posted by amirm quoting Toole 
In stereo listening, the effect would be considered by most as being subtle, but to the extent that there was a preference in terms of sound and imaging quality, the votes favored having the side walls left in a reflective state.
So the effect was subtle, and to the extent there was a preference, it was in favor of side reflections. Would that be 51% in favor of this subtle difference or what? We would need to know what percentage of people actually had a preference, and of those who did have a preference, how many preferred reflections and how many preferred no reflections. Toole doesn't supply any of those details in his book to support his statement. It doesn't really sound like "Testers overwhelming vote like above" as amirm asserts, does it?

By the way, just so everyone has the full context, at the end of the quoted paragraph, Toole concedes that "this is definitely a case where personal opinion is permitted." Somehow, amirm always manages to omit important information like that when it doesn't support his agenda.
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and just how large were these "drapes" used in the study??

regarding treatment of our rooms here, the sidewall absorption is surgically placed to limit the amount of overall absorption within the room (or ideally why reflectors are used to redirect the reflection away from the listening position - which does not remove energy from the room)). how much later arriving energy was inadvertently attenuated by the over-sized drapes in the study?

suddenly, it's not a study of the attenuation of sidewall reflections vs allowing sidewall reflections ... it's the attenuation of sidewall energy AND faster decay times vs allowing sidewall reflections with normal decay times. is that truly apples to apples?

regardless, such a study has no bearing on the comparison to LEDE/RFZ as the later-arriving/laterally arriving/exponentially decaying diffuse sound-field was not induced. it's an attempt to inspect one component in isolation while ignoring the remaining factors of the response.

totally flawed.
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post #3356 of 12230 Old 06-08-2013, 03:58 PM
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Just a quick Reflection, pun intended, on IR measurements.

I have what is essentially an LEDE purpose designed and built room, please see the thread link to review the full plans of the room. However the plans are short the recently installed ceiling teatments that I just managed to complete a year late. smile.gif

After reading all these comments on IR and reflections I decided to look at my room and nearly "died" when I saw what was happening in the first few mS. Everything else was what I had expected and designed for.

So I decided to post the results just to show how easy it is to worry about reflections that have nothing to do with the room design and in my case are a function of the three leather Bello seats. I will post the rooms full REW results in a later response to hear what is the general opinion of the rooms performance.

The following two IR graphs show the response at the MLP with no "dummy" sitting in the central of three chairs.





The following are with the seat dummy.





I will be interested in the users comments on these graphs.

The first peak at approximately 150uS is not a room reflection it is something to do with the 1038 Genelecs response as it appears no matter how close the mic is to the speaker and if I measure the speaker in another room. The reflection increase of approximately -12dB at approximately 10mS is from the rear QRD and is as designed.

The initial window is at least -15dB and reaches -20dB and is terminated at 10mS with the -12dB reflections from the rear QRD

Just goes to show you need to be very careful when analyzing where the reflections come from.
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post #3357 of 12230 Old 06-08-2013, 04:05 PM
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I will be interested in the advanced users comments on these graphs.

I guess that rules me out.
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post #3358 of 12230 Old 06-08-2013, 04:08 PM
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I guess that rules me out.

Don't be so modest.wink.gif

All opinions and views are welcome. You embarrassed me into removing the word "advanced".
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post #3359 of 12230 Old 06-08-2013, 04:33 PM
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Just a quick Reflection, pun intended, on IR measurements.

I have what is essentially an LEDE purpose designed and built room, please see the thread link to review the full plans of the room. However the plans are short the recently installed ceiling teatments that I just managed to complete a year late. smile.gif

After reading all these comments on IR and reflections I decided to look at my room and nearly "died" when I saw what was happening in the first few mS. Everything else was what I had expected and designed for.

So I decided to post the results just to show how easy it is to worry about reflections that have nothing to do with the room design and in my case are a function of the three leather Bello seats. I will post the rooms full REW results in a later response to hear what is the general opinion of the rooms performance.

The following two IR graphs show the response at the MLP with no "dummy" sitting in the central of three chairs.


I will be interested in the users comments on these graphs.

The first peak at approximately 150uS is not a room reflection it is something to do with the 1038 Genelecs response as it appears no matter how close the mic is to the speaker and if I measure the speaker in another room. The reflection increase of approximately -12dB at approximately 10mS is from the rear QRD and is as designed.

The initial window is at least -15dB and reaches -20dB and is terminated at 10mS with the -12dB reflections from the rear QRD

Just goes to show you need to be very careful when analyzing where the reflections come from.

You want to terminate the ISD gap at 20ms - 28ms or so. 9.5ms is too short IMO.

As far as that early reflection energy, show us a close up of the first 5-10ms of the ETC.

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post #3360 of 12230 Old 06-08-2013, 04:47 PM
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You want to terminate the ISD gap at 20ms - 28ms or so. 9.5ms is too short IMO.

As far as that early reflection energy, show us a close up of the first 5-10ms of the ETC.

Here you go. I assume this is what you are looking for?



Or did you mean this?



The reflections at 1.4mS are coming from adjacent chairs.

I cannot terminate at 20mS and choose to deliberately terminate at 10mS due to MY room design constraints/size, speaker layout and I didn't want QRD's etc. at all sorts of weird angles just to get the reflection path to 20 feet.

I realize this is not "ideal" but it seems to sound fine.
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