Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 121 - AVS Forum
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post #3601 of 12050 Old 06-15-2013, 03:34 PM
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Originally Posted by ggsantafe View Post


OK - looks like I have excessive ringing at 15, 38 & 65hz. What strategies can I adapt to address these issues - you mention strategic placement of treatments - is this a hit or miss proposition? treat then measure, etc. Are any of these frequencies more important to address than the others? Can I expect any improvement by re-positioning subwoofer and/or MLP? I know this thread can get quite technical at times and blows right past my level of comprehension.

Right now my learning curve has progressed to taking REW measurements, and learning how interpret the results (with much help from thread participants) and I'm looking for some basic suggestions to progress in my understanding of the acoustic properties of my room. I didn't think I'd ge this far, so I'm not ruling out further improvement - I'm just trying to get a grasp of the potential solutions, techniques. Appreciate any insight that can be offered.

 

Absorption bass traps are most effective when placed at the intersection of two (or three) walls.  The intersection could be in a corner between the back wall and a side wall, for example.  Or between a wall and the ceiling.  Corner-mounted bass traps straddle the corner forming a 45 degree angle.  There are special tri-corner traps that fit where three walls intersect.  There are broad-band bass traps that do a good job over 40-120 Hz, rolling off above 120Hz.  There are also specialty traps that are tuned for a specific frequency (membrane traps).

 

I recommend that you visit several of the web sites for companies that sell room treatments (e.g. RealTraps, GIK Acoustics).  You will find quite a few technical papers, videos, etc. that will educate you on how to approach room treatments.  And, of course, you could go the DIY route.  There are a number of threads here on AVS that focus on how to build your own treatments.

 

Here is a picture of some of my bass traps (in the far corner, along the intersection between front wall and ceiling, and on the ceiling itself).  Does WAF come into play for you?

 

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post #3602 of 12050 Old 06-15-2013, 03:35 PM
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Originally Posted by AustinJerry View Post

It really doesn't make any difference, but I think we are talking apples and oranges.

I was talking about the "rise time" setting.

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post #3603 of 12050 Old 06-15-2013, 03:47 PM
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OK, I just finished an exercise in which I used the string technique to measure the length of each of five first reflection paths for both my front left and my front right speakers.  The reflection paths are shown with dotted lines in the diagram.  (The ceiling path is not shown, but I have the measurement).  In the bottom right corner is a table showing the string lengths for each path.

 

 

Now look at a recent ETC graph for the right front speaker:

 

 

There is not a single reflection that matches any of the distances I measured.  What the heck am I doing wrong?  I am totally frustrated.

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post #3604 of 12050 Old 06-15-2013, 04:40 PM
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Forget the math and use a blocking method to find the reflection areas. IME, a two-man job, though.
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post #3605 of 12050 Old 06-15-2013, 05:54 PM
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Originally Posted by AustinJerry View Post

There is not a single reflection that matches any of the distances I measured.  What the heck am I doing wrong?  I am totally frustrated.

ideally you should be utilizing hardware loopback to take into account propagation delays and sourcing from the true acoustic center. with this setup, the direct signal spike would correspond at the actual arrival time (flight path), not at T=0 (T = 0 should correspond to the signal generation at the speaker).

are you factoring (adding) in the direct signal flight path distance? for the string method you need to know the total time of flight, not just the "delta" between the direct signal and the arrival of the indirect signal.

for the first significant reflection at ~4.8ft, you need to add the direct signal distance (speaker --> mic) to get the total time of flight for that indirect reflection. that reflection does NOT have a total flight path of 4.8ft.

and the early clutter (1-3ms) needs to be addressed as well. either alignment issues in the speaker or edge diffraction.
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post #3606 of 12050 Old 06-15-2013, 07:52 PM
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Local, please be patient with me--I seem to be suffering a mental block.  And also, recall that there is no way to have a hardware loopback when using the USB mic and HDMI.

 

So, I stretch the string from the front of the right speaker to the point on the side wall that I identified as the first point of reflection (by using a mirror), and then extend the string to the MLP.  I measure the entire length of the string, which is 17' 4".  The speaker is exactly 10' from the MLP.  I now open the most recent measurement file and generate the ETC graph for the front right speaker.  Using the technique of holding down the CTRL key, pressing the right mouse button, and dragging the cursor horizontally, REW provides a readout showing a distance to a reflection.  I marked the screen shot with the REW-calculated distances, e.g.  7', 11.2', etc.

 

What is the relationship between the distance REW is showing and the distance I calculated with the string?  Do I add 10' to the REW distances?  If that is the case, then it is conceivable that the peak marked 7' is the 17' 4" that I measured with the string (4" could be easily my margin of error).

 

But I can't seem to match any of the others....

 

Edit:  The 15' REW distance could be the opposite-wall reflection @ 25.9'.  And it's possible that the 4.8' REW distance could be a reflection off the side of my DSX Wide speaker.  That leaves the 11.2' and the 13.1' reflection.  Time for the pink fluffy again?

 

Edit 2:  Also note that because of the symmetry of my listening room setup, I could have two reflections coming from different walls appearing at the same spot on the ETC graph.  For example, left front to left side is exactly the same distance as right front to right side (and both of those reflection points are currently untreated).

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post #3607 of 12050 Old 06-15-2013, 08:57 PM
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Originally Posted by AustinJerry View Post

Local, please be patient with me--I seem to be suffering a mental block.  And also, recall that there is no way to have a hardware loopback when using the USB mic and HDMI.

So, I stretch the string from the front of the right speaker to the point on the side wall that I identified as the first point of reflection (by using a mirror), and then extend the string to the MLP.  I measure the entire length of the string, which is 17' 4".  The speaker is exactly 10' from the MLP.  I now open the most recent measurement file and generate the ETC graph for the front right speaker.  Using the technique of holding down the CTRL key, pressing the right mouse button, and dragging the cursor horizontally, REW provides a readout showing a distance to a reflection.  I marked the screen shot with the REW-calculated distances, e.g.  7', 11.2', etc.

What is the relationship between the distance REW is showing and the distance I calculated with the string?  Do I add 10' to the REW distances?  If that is the case, then it is conceivable that the peak marked 7' is the 17' 4" that I measured with the string (4" could be easily my margin of error).
JMHO but you're doing more work than you need to by measuring all those paths. Let REW take you to the reflection point not the mirror. Take your first peak for instance, which shows as 4.8' from T=0. That means it took 4.8' more than the direct signal to arrive at the mic. Adding that to the 10' it took for the direct signal yields 14.8'. Tie off a 14.8' length of string to speaker (best guess at acoustic center) and the mic and then see where it hits a surface (or is within a couple inches of a surface). Put some pink fluffy at that spot and remeasure to see if it attenuated that spike.

This will be as accurate as you can get with the string method without being able to measure with loopback. If that's not successful then try the blocking method or use blocking in combo with the string to help resolve the path.
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post #3608 of 12050 Old 06-16-2013, 06:01 AM - Thread Starter
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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.


Sorry for the extremely late reply, but I too am using Def Tech speakers (BP7000's for L/R, C/L/R 3000 center, BPVX surround, and BP7001 currently used as surround back but will be experimenting with using them as wide speakers when I upgrade to my next Pre-Pro) and by using my front wall as bass trapping (20' wide room using one layer of R30 insulation, hung vertically from ceiling to floor, which gives me a 9.5" thick x 20' wide trap, plus doubled up layers in each corner for 18" thick corner traps) and also placing a QRD 1D diffuser behind each BP7000 speaker, I've been able to attain my goal and have my reflections and bass response tamed with no EQ above my 100hz crossover. wink.gif

It is absolutely doable. With this being said, however, I bought the BP7000's before getting serious into building a dedicated theater/listening space and before selecting this acoustical model. (LEDE/RFZ in my case)

I don't believe I would purchase the Def Tech's if I knew then what I know now, not only because it is more difficult to achieve the LEDE model with bi-polar speakers but also because when you take away the built in subs that the Def Tech's offer (assuming you also have at least 2 other actual subs you can use for better placement and better quality bass) you're left with a bi-polar speaker that costs a lot of money for what you get.

I'm happy with my BP7000's but my next speakers, if/when I can afford them, will probably be Wilson Watt/Puppy or Legacy and will surely be direct radiating.

There are a lot more placement opportunities and things to experiment with by using direct radiators and if you are truly trying to attain the LEDE model and are using proper acoustical treatments, direct radiating speakers are the way to go.

Bi-Polar speakers have advantages, too, and at the time I bought the BP7000's they were definitely the right speaker for me.

I'm very happy with them now that I have them placed properly, have proper treatments that are also installed properly, have properly utilized EQ, and have external subs to use in addition to the BP7000's but it was a ton of work and a huge learning curve to get this far with these speakers and this model.

But it absolutely can be done as I not only did it, but I'm extremely happy with the result and am not in any major hurry to change my speakers. smile.gif

--J

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post #3609 of 12050 Old 06-16-2013, 06:10 AM - Thread Starter
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Originally Posted by AustinJerry View Post

^ Should I add this to the Guide?

Those mirror tiles are an AWESOME idea!!

I'll have to go to my local Lowe's and see if I can find something similar. (HD is more than an hour away)

Also, as for the guide, whenever someone asks about acoustical models, which one to pick, etc, I always refer them to the EEtimes article you linked to recently. I even refer to it in the first or second post in this thread, but without the specific link. I should probably go edit the post and add the exact link.

It would be great if you add that article to the guide because I have yet to find a better article describing the basics of the models and their differences. The article isn't a complete guide, of course, but it's perfect for what it is meant to be which is an introduction to the different models so one can choose which model to research further after learning the basic differences of each model.

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post #3610 of 12050 Old 06-16-2013, 06:18 AM - Thread Starter
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Originally Posted by AustinJerry View Post

Quote:
Originally Posted by sdrucker View Post

 


Maybe it belongs in a separate guide: 'how to pick an acoustic model and select treatments to address issues that are barriers to it working optimally', with REW as the measurement tool?

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.

I don't get to speak often enough in this thread due to the designer of this world only allotting 24 hours per day but when I finally do, I talk way too much! biggrin.gif

I've never been accused of not giving enough information or details in my posts though! wink.gif

I love that title, BTW.

--J

PS I do think two documents would be helpful. One focusing on setup and basics and the other on all the advanced stuff and tidbits, tips, examples, etc. That post above outlining the string method was brilliant and was composed much more clearly and completely (and with pictures, too!) than I could ever hope to achieve. Just a thought though.

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post #3611 of 12050 Old 06-16-2013, 06:45 AM - Thread Starter
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Originally Posted by kbarnes701 View Post

Quote:
Originally Posted by sdurani View Post

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Originally Posted by kbarnes701 View Post

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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Originally Posted by jkasanic View Post

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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Originally Posted by AustinJerry View Post

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 jlpowell84 View Post

Jerry, are these models and their philosophies in full descriptive theory in this thread prior or elsewhere? I would love to learn about them.

In picking a room model, since it's highly doubtful one will have the opportunity to try out more than one or even visit rooms designed for LEDE, NE, Ambechoic, etc and spend any quality time there, you have to take a bit of a leap of faith.

I wouldn't let not knowing which model to choose stop you from getting started.

Up to a point, most all models have many/most things in common.

No matter which model you choose, you need to do the following:

First you should get the best speaker and listener placement figured out. This should be done with no treatments and no EQ. You want the best response possible while also achieving symmetry and still allowing for proper placement of surround/surround back speakers if you intend on focusing more on multichannel music/movies, but at a minimum, the L/R speakers should be placed optimally combined with the best MLP.

Optimally means you should focus on the best overall frequency response to begin with (remember, this is before treatments and EQ), along with the soundstage width you prefer, making sure to keep the height, width, and front wall to front of speaker distances all different. You should pick a spot with as few reflections, as little SBIR, and as few nulls as possible, but mainly focus on frequencies above the crossover assuming you'll be using separate subwoofers. Note, even with using external subwoofers which will have their own separate placement, remember a crossover isn't a brick wall filter and the speakers and subs have to work with each other, not against each other. Also, common crossovers are 80hz which is still well below the transition frequency and below specular reflection territory in all rooms so Modes/Nodes/SBIR is still very important, and shouldn't be dismissed altogether thinking that the subs and their placement will fix all the problems. Everything has to be designed/placed to work together.

Next, you will need to integrate your subs using all the known and often discussed methods to integrate them with your main speakers.

Then you can start introducing treatments, starting with bass trapping. The reasons you want to introduce bass trapping first is because most of the bass traps folks in this thread will use are going to be broadband and will themselves alter the frequency response and specular reflections. If you added reflection panels first and other broadband acoustical panels to get the room tamed and get to the decay levels you want to achieve, then start adding bass traps, you'll quickly find you're making your room too dead and will have to remove and probably also change the position of many panels. You can save money (buying less panels) and time by focusing on bass traps first.

Only after you have the frequencies under 300hz tamed as much as possible for an even decay rate and relatively flat frequency response with no major nulls and if possible no major peaks (but no matter what, you need to get rid of the nulls via placement of subs, speakers, and MLP plus bass traps as no amount of tweaking or EQ will help you here) should you move forward.

At this point, (again, this is for any/all acoustical models) you want to take a look at your efforts and see how they've all paid off in REW, doing another before/after test. You should already see a lot of improvement at this point, but when looking at the ETC, which is what we focus a lot on in determining the different acoustical models and how the corresponding ETC should look for each model, you need to make sure that all the high gain early reflections up to around 20ms are tamed to -20db or below and ALSO (this is where a lot of people fail) that there are no spikes or masses of dips in that response from the direct signal to about 20ms. You may have all your reflections under -20db out to 20ms but it should also look smooth and be densely populated. If you have sparse reflections with peaks and the peaks are at -20db while most of the rest of the response is -25db or even -30db, this isn't good either. You want the ETC to be smooth, densely populated, and no major peaks/nulls out to around 20ms.

Only at this point do you really need to be concerned with implementing an acoustical model.

By the time you've accomplished all the common goals listed above, you'll hopefully have a better idea of how the changes you make alter the sound of the room and your listening experience and enjoyment, plus in your down time when not physically working on the room or making measurements, hopefully you'll have had time to research the different acoustical models more.

By the time you get to the point of really needing to nail down how you'll finalize your room, you'll probably realize where you'll want to take it and how you'll accomplish it. wink.gif

So go ahead and get started, and be sure to share your results. There is no reason to wait until you're 100% sure whether you're going with LEDE/NE/Ambechoic, etc, before treating your room and making it sound 10 times better than it does now. You'll learn a lot in the process and have a much clearer understanding by the time you're to the last step and as long as at that time you are able to make a decision on a model and stick with it, you won't have to undo or redo anything so you'll have had just that much more time to enjoy your system and all the improvements along the way.

Hope this helps.

--J
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post #3612 of 12050 Old 06-16-2013, 07:25 AM - Thread Starter
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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.


No they won't. But they will drastically EQ the room and alter the balance by taking the highs and upper midrange right out!

I've never heard of broadband drapes!

But what do I know, as I was just called silly among other things.

It's funny how many people I've talked to that literally have this poster on "ignore" yet he wonders why nobody responds to him.

It's also funny to me how he touts his "methods" as science yet dismisses ALL of the many many proven models such as those you've listed above that are based on true science some of which have been around for decades and are still the most popular models implemented today, some of which are also implemented regularly by a few of the folks he mentions on a regular basis when quoting them out of context and without having a full understanding of acoustics and psychoacoustics by researching on his own (note most of his content is simply copied/pasted from other people) and having thoughts of his own. Instead, unless the information was presented by Toole, it's wrong.

Remember, this guy was asked to leave early on. He agreed to do so. He never did. To me, that makes him a liar and he is obviously not a man of his word.

He obviously has an agenda here and although I haven't been direct up to this point and have largely bit my tongue and tried to stay out of it hoping most people would be able to see through him on their own, I'm tired of this thread being hijacked by him and quite frankly, ruined, so I'm asking all of you to please ignore him.

If you agree with most of what this poster (or should that read poser) says, that's fine. It's not what he says that I have a problem with so much as it is that he is in a thread that has a specific purpose, title, and goals, yet is constantly preaching to us that we are wrong, shouldn't be doing this or that, and isn't offering any constructive or helpful advice at all.

Quite frankly, I'm tired of it. It derails the thread, infuriates several of the more knowledgeable people here, and it must be a turnoff to all the folks who are coming here to be less confused not more confused.

I hate reading all the bickering and this is the one and only time I will personally contribute to it.

He is more than welcome to start his own thread debating the merits of what this thread is trying to teach.

He is NOT welcome here any more. I urge each and every one of you to put him on ignore and most definitely not respond to him. Maybe he'll get the hint and go away. If we continue to engage him, he'll only post more and cause more harm.

What he's done in the last few posts (I'm so far only up to the post I've quoted as I'm behind) is like telling someone who is looking to buy a boat and is trying to figure out which one to buy that they shouldn't buy a boat at all because boats can only be used in the river and they should instead buy a car because it can be used on the road, there are more roads, and they can go more places!

Again, this thread is for a specific topic. It's in the title. Any posts not relating to this topic or posts that are simply created to cause chaos and destruction should be reported to the moderator from here on and should NOT be responded to directly.

If you find yourself agreeing with the things this member says, kindly take it to PM or another thread so as not to derail this discussion any longer.

Remember, we DO believe in using the waterfall, ETC, etc in this thread and realize there is no such thing as RT60 for small acoustical spaces. We do NOT advocate only paying attention to the FR thinking that flattening it will solve all our problems nor do most of the members in this thread think that by doing so will make it "good enough" in the time domain, for instance. For most of us here, it will never be good enough, as this is as much of a hobby and learning experience as actually watching films and listening to music.

There is no need to comment on this post and there will be no further comment on this topic from me. I refuse to engage in childish behavior beyond this post.

Again, please do not respond to this member in this thread and please report all off topic and out of line posts to a moderator.

Thank you,

--Jason

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post #3613 of 12050 Old 06-16-2013, 07:33 AM - Thread Starter
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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.

BEAUTIFUL!!!

How does it sound? What made you decide to choose this model? I think that will be helpful for those in this thread that are still on the fence.

I'm going to read your build thread right now and will be back with more comments, but for now, all I can say is GOOD JOB!! biggrin.gif

Speaking for everyone here, we'd really like to know more about the choices you made, what you had before, the decisions you made (the why's behind them), obstacles you had to overcome, and if you are happy with the results.

Anything else you can share here is very welcomed.

If I can be of any assistance to you, please let me know, and again, job well done!

Looking forward to reading your thread now. wink.gif

--J

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post #3614 of 12050 Old 06-16-2013, 07:46 AM - Thread Starter
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Hey guys, would this question be better suited in another thread? It seems good here since we are dealing with measuring our rooms and dealing with reflections and treating them.

I believe Sdrucker is running DT Mythos speakers, so perhaps he will comment.

Based on the many discussions of DT speakers with integrated powered subs, they pose a different challenge than more conventional designs, i.e. separate speaker/sub configurations.  Having said that, there is ample evidence that these speakers can perform well as long as you learn from other owners.  My opinion would be to seek guidance on one of the dedicated Definitive Technology speaker threads.

My dedicated room just so happens to have a full Def Tech setup and I'm using BP7000's for my mains.

I have performed numerous setups and tests (and have results saved and can share upon request) using the built-in Supercube Reference subs with the LFE input and external EQ (AS-EQ1 for MultEQ XT32 and/or DSP1124P - currently using the DSP1124p only) and also with the standard small setting and "only" my other two subs (currently Epik Empire - soon will be changing to PSA Triax, JTR S2, or Seaton F2), also I've used the same standard/small setting and tried varying the volume on the backs of the BP7000's to alter the crossover slope to my advantage which has helped a lot. I'm currently testing by using the BP7000's as large with LFE+Main and so far, believe it or not, due to all the processing, setup, placement, treatments, and options between the BP7000's and my external EQ, I'm actually getting the best sound ever with this!!

My next experiment, starting today or tomorrow will be keeping the large and lfe+main setting, but using the LFE inputs again so I can directly EQ the built in subs and vary the volume to offload some more of the huge effort my Epik Empire's have to give to fill my huge 4500 cu ft room.

Def Tech's can be great fun and have a TON of configurability but if you're using the built in subs along with extra/separate subs, phase match is key to getting them to play well together.

By doing what I'm doing now though, I'm able to get a rising bass response from crossover to 25hz or so while all the other channels are perfectly flat so I have the best of both worlds with multichannel (stuff with an LFE track) and 2-channel with a naturally rising bass response that has bass built into and as part of the main/large speaker system.

I responded to the request for info on using DT speakers with a LEDE model but I am over a week late tongue.gif so sorry about that.

If there are more questions regarding integrating DT speakers with these acoustical models, since the same info would apply to any speaker that is bi-polar and/or has built in subs, I'm fine with keeping it in this thread, as long as we can actually help you and the question relates to acoustics and integrating the speakers instead of a question that is speaker specific which would obviously be better suited in the thread for that speaker.

Were the questions answered re: DT speakers or are there more? I'm happy to help. wink.gif

--J

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post #3615 of 12050 Old 06-16-2013, 07:54 AM - Thread Starter
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Originally Posted by AustinJerry View Post

I believe Sdrucker is running DT Mythos speakers, so perhaps he will comment.

Based on the many discussions of DT speakers with integrated powered subs, they pose a different challenge than more conventional designs, i.e. separate speaker/sub configurations.  Having said that, there is ample evidence that these speakers can perform well as long as you learn from other owners.  My opinion would be to seek guidance on one of the dedicated Definitive Technology speaker threads.

Yes I have asked on the definitive forum. Joe from Definitive responded,
"1. Room treatments are always a good thing to consider. Slap echo in particular can be tamed with the right combination of treatments. Cloth drapes and other window treatments can really help, and throw rugs are good too. Even something as simple as adding a bookcase stuffed with 50 cent books from the library sale, plus a couple of decorative pillows placed on top, can help tame a "ringing" room and make dialog intelligibility / high frequencies sound much nicer. Treating the room can make even a mediocre sound system sound better.
2. There are companies that specialize in room treatments too. But be careful not to over-do it! A certain amount of reflection is actually very helpful for mid-range sounds (dialog intelligibility in particular). If you have ever been in an over-damped room, you'll know just what I mean. A custom guy I used to do business with built a dedicated theater for a customer... and they wound up ripping out all the acoustic treatment and starting over, because the room sounded so dead, and his expensive gear sounded dull. Anechoic chambers are great for testing loudspeakers, but bad for listening to them. Here is a link to a web site that has some acoustic solutions / advice / products. http://gikacoustics.com/acoustic-advice/
3. The speaker/ sub placement and your main listening position placement (couch, loveseat etc) are twin sides of the room acoustics coin. Moving your speakers / sub by 6 inches or a foot can make a big difference. If that is not an option due to domestic tranquility considerations, moving the couch by a similarly small amount can be every bit as effective. If your main listening position is in a null vs. your current speaker / subwoofer combination, no amount of money spend on a new sub will make the bass sound great there. The cancellation issue will still exist. Experiment as much as you can... but don't wind up spending the night on the couch because you have found the perfect solution
4. A pretty solid body of research suggests that forward-focused bipolar speakers, the technology we have in the BP 8000 series speakers, is helpful in dialog intelligibility. I wouldn't suggest using wall dampening treatments immediately behind a pair of our BP towers, but then again, wall dampening seems to work best up higher anyway. If ringing high frequencies are the issue, "higher-up" and "front of the room" are two rules of thumb that seem to be helpful. Dampening all the walls will make your sound bad."

The Mythos line afaik are all forward firing drivers. Just from a 101 perspective, which I am currently in, it seems they can be contradictive because of the rear firing drivers and the reflections produced, or am I missing something?. But I guess if treated right (diffusion I would guess) perhaps they can be effective.

Here is what I can do. Once My UMM-6 comes in and I get aquatinted with REW then I can go to my dealer who sold me my speakers and he will let me bring home some Studio monitor 65's which would be the replacements for the towers. Then I could compare them side by side with measurements.

Numbers 2 and 3 offer some good advice.

Number 1 - not so much. The books/bookcase as a diffuser idea was debunked long ago, I believe. Don't do that. You're introducing something that would be difficult to design properly (impossible??) and only after you're done, with a lot of work and a bunch of $.50 library books you'll never read, but have to store or dispose of, will you know if it made any actual improvement. Plus, $.50 here and there, especially for as many as I believe he's recommending or I would think would actually/possibly do "something" would be much more than a few properly implemented DIY room treatments that you can properly model and measure.

Number 4 - I own Def Tech Bi-Polar speakers, so I can't say I disagree, but I will agree that not everybody agrees. wink.gif Make sense? lol.

Mythos are standard front firing speakers. They aren't bi-pole. They do have built in subs though, although not nearly as powerful, and I wouldn't call them subs. They are more like adjustable lower mid-range and upper bass speakers. Since they do have this feature, it is worth discussing, but not in the context of which I believe you're asking re: bi-pole, etc.

What exactly are your concerns? Read my last several posts and see if I've answered your questions/concerns as again, I've implemented a proper design and while there were challenges and it was tough, I did ultimately accomplish it. That was with BP7000's, their flagship speaker with built in Supercube Reference subs. If I can do it, you can do it. smile.gif

Feel free to ask specific questions and we'll try to help.

As for comparing both speakers, if you have the ability to do so at little/no cost, go for it!!

Which model's specifically will you be comparing? What do you have now? What are you hoping the results will be/what are you looking to achieve?

Hope this helps,

--J

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post #3616 of 12050 Old 06-16-2013, 07:59 AM - Thread Starter
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Is anyone else not getting email notifications of new posts from AVS or is it just me?

Its hopeless for me, Ive been onto AVS now for almost a week on this. I just don't get any updates of the threads I subscribe to! Its very had to participate like this.....rolleyes.gif

I don't use email notification for anything as I subscribe to a lot of active threads and get on AVS at pretty much the same time every day, or if not the same time, at least in the same order of regular things I do in my life.

I keep a tab opened in my browser at all times, always logged in, and it stays on the "My Subscriptions" page so all I have to do is click "Subscriptions" at the top of the window and it will update the list.

From there I just go down the list of each thread I'm subscribed to, each day, clicking, "show first unread post" and when I'm all done I just click "Subscriptions" again to see if I'm all caught up or if more posts have come in while I was reading everything.

Once nothing more shows up, I go to bed. wink.gif

That's how I do it and keep my email clean and clutter free (well.... at least from AVS)

Just a suggestion. Feel free to take it or leave it, of course. Sorry the email notification isn't/wasn't working for you though.

--J

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post #3617 of 12050 Old 06-16-2013, 08:11 AM
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OK, I just finished an exercise in which I used the string technique to measure the length of each of five first reflection paths for both my front left and my front right speakers.  The reflection paths are shown with dotted lines in the diagram.  (The ceiling path is not shown, but I have the measurement).  In the bottom right corner is a table showing the string lengths for each path.




Now look at a recent ETC graph for the right front speaker:




There is not a single reflection that matches any of the distances I measured.  What the heck am I doing wrong?  I am totally frustrated.

Let me put forth something I do that may help here.

First, I take a full band smoothed ETC (black). Then I cover a piece of wall and take another (orange). Then I overlay the two.



Where the graphs are different clearly shows the exact timing of the covered piece of wall, in this case 10-16ms. This takes using string and measuring out of the equation. This simplifies things in that your focusing on one peak area at a time.

So when looking to find a particular peak, using the above method will tell without doubt whether you found it or not. Use a panel that only absorbs here. A panel with a scatter plate may redirect and/or complicate the data.

I realize I am showing things in Omnimic, not REW. IN Omnimic, I can lay down the first measurement, plot it, and look at the second one in real time while the measurement is taking place. I am only guessing if REW will let you do this in real time also. If not, you can still compare after the fact by overlaying the new graph to the old one. Just takes longer this way.

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post #3618 of 12050 Old 06-16-2013, 08:14 AM - Thread Starter
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Originally Posted by jim19611961 View Post

At the heart of the matter is no amount of information really will tell you what a model sounds like in a direct sense.

Questions like "what model should I choose" is a bit like asking "what color should be my favorite". It just invites unnecessary controversy.
Quote:
Originally Posted by jim19611961 View Post

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

LEDE / RFZ
NE (non-environment)
FTB (Front to back)
Svana's philosphy

Plus a myriad of individual approaches blending different colors together.
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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.
Jim, if no amount of description will give us an idea of what an acoustical model sounds like, if the mere act of asking which model to choose is just an invitation to unnecessary controversy, if there are several different studio models AND a myriad of combinations of those models to choose from, if simple experiments with reflections at home will not in any way allow us to compare different models, then how is someone reading this thread supposed to reconcile all that with the OP saying that we need to...
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Originally Posted by jevansoh View Post

PICK A MODEL - List your model
I'm not going to ask which model to choose, since that would just invite... well, you know. But I hope you don't think it is as unreasonable to ask how one goes about choosing an acoustical model for oneself (again, not asking which one). I was hoping for an answer earlier when Jerry was asked how he came to choose his specific model, but he simply replied that that's what he chose and he wasn't necessarily recommending it to others.

Is there something wrong with explaining how or why a particular choice was made, so that other might benefit from the selection process? Seriously Jim, how is someone supposed to PICK A MODEL when you can't describe what it sounds like and no one explains why they chose their specific model?

Not Jim, but read my last several posts (from today) for more information/insight.

I picked LEDE as my model because after researching all the different models and reading a lot of textbooks and forums over on Gearslutz, and being mostly interested in the quality and presentation of 2-channel in my room, as although I listen less to music than I watch movies, I'm more critical of my music listening sessions than of my movie's sound and based on the shape/size of my room, the fact that I felt I could actually "achieve" the model (It's fine to pick the model that Blackbird studios uses, but can you implement it without a huge room, forklifts, and a million dollars? NO.) I figured I'd give it a go.

By the time I was done with the initial round of research I realized most models had most things in common up to the point you decide what to do with the ISD Gap (if, where, and how to terminate it and what is to follow) so I got 80% there (as you and everyone else can too) without it being imperative that I continued to follow the LEDE design if I didn't like how things were shaping up until I got to the point of no return when designing/creating my ETC response.

That's how I did it. I didn't have other listening rooms to go to. I live in a small town in Ohio, on the river bordering KY and WV and the closest (and only ONE) member I've ever seen anywhere near me is over an hour away, and everyone else is 2-3 hours drive or more. There are no recording studios here either.

So all I had to go on was research and my own interpretation of what the different models would give me based on comments in the forums (much more discussion on room acoustics over at Gearslutz) and in the texts I read on the different models.

Everyone will get most of the way there by following the steps I made several posts back as most goals are the same up to a point.

Picking a model isn't totally abstract either. The size of your room and budget along with how much effort you're willing to put into it and what you're designing for (2-channel or multi-channel or combo of both) and your listening habits will a lot of times dictate what you end up being "able" to do.

Most of the time this is a modified LEDE (modified by length of ISD gap and/or use of diffusers/reflectors to get the termination - could be other things, too) or NE design in homes.

If you're all about movies and have a small room, NE is for you.

If you're all about 2-channel and/or have a larger room and want to experience psychoacoustic effects and make your room sound larger and more spacious than it physically is, then LEDE is for you.

I think people are getting stuck because they see this as daunting only because it's new. But on other forums, such as Gearslutz and HT Shack, it's not new.

Lot's of people implement acoustical models all the time. There just aren't lots of examples here on AVS and any time something is new, it's exciting along with being frightening at the same time.

The good news is, if you're reading this, then your hobby is learning and spending time on AVS as much as (or possibly more than) listening to music/watching movies anyway, and all the same treatments can be reused if you don't like the outcome and wish to change models.

Plus, remember, the first 80% is going to be the same no matter which model you choose, and I promise you, as you're implementing the first 80%, and as you continue to read and learn and hear the differences that first 80% gets you, your goals will become more defined as you'll understand a lot more by going through the process. By the time you have to make a decision you'll be much more comfortable.

So don't try to plan out everything now, before doing "anything" or you'll get overwhelmed and get NOTHING accomplished.

Take it one step at a time, get to 80%, and ask again, if you need to, once you're at that point, which model you should go with. wink.gif

Hope this helps,

--J
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post #3619 of 12050 Old 06-16-2013, 08:32 AM - Thread Starter
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Quote:
Originally Posted by jim19611961 View Post

Quote:
Originally Posted by AustinJerry View Post

I asked the same question a week ago, and received this response from Jason.

http://www.avsforum.com/t/1449924/simplified-rew-setup-and-use-usb-mic-hdmi-connection-including-measurement-techniques-and-how-to-interpret-graphs/3150#post_23371051

More in depth response smile.gif

Only point I differ about is At 20ms or so you will see a reflection as close to around -12db as possible followed by DENSE reflections that decay smoothly over time into the noise floor. As I understand things, -12db for the termination is a minimum, not a hard number. I have read different papers that suggest -12 to -6db range. Here is one:

http://jgbouska.tripod.com/audio/d_davis_lede_audio_1987_p1.pdf

If you look at figure 4 on page 4, his example graph clearly shows the "kicker" well above -12db.

To clarify, yes, -12db is MINIMUM. Thanks for catching that.

The more the better, however, I'm not sure if you were to get, let's say, a -6db gain termination followed by the dense return/tail being closer to -12db and falling that that would be better than something closer to -10db (for instance) followed by the dense tail that is closer in db. Does that make sense?

I don't know for sure which is best, BTW. It isn't the easiest thing to change/experiment with. wink.gif

-12db for the termination, whether using a HAAS kicker or not though is absolutely the minimum and I suppose the ultimate goal would be as strong as possible right up to the 0db point of the direct sound, but the chances of having that much delayed energy available while still taking care of all the high gain early reflections is slim to none, especially if using absorption and in a small room.

You'd have to use reflection only and have a good size room with little loss and exact placements for every piece of the puzzle with engineered treatments to even approach that, so for the folks in this forum, just starting out, if we can achieve the minimum -12db termination followed by a dense and decaying return of specular reflections, we're doing pretty darn good!

At that point, one could always try to improve things, but at least you'd have the model nailed down and can experiment from there, possibly replacing the broadband absorption with engineered bass traps and reflection only for specular reflections. That's getting ahead a bit though. wink.gif

--J

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post #3620 of 12050 Old 06-16-2013, 08:39 AM - Thread Starter
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Quote:
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Quote:
Originally Posted by AustinJerry View Post

Not really. It doesn't have a calibration file, so the measurements you would get would not be accurate.

Cool. I will not use my receiver's calibration mic then. Instead, I will use my Aperion SPL Meter as it seems the software is tailored towards SPL meters by having a calibration for the C-weighted measurement.

I have an HDMI cable running from my computer to my receiver, so my receiver is acting as my sound card. Do you guys think I still need to create loopback connection, as I do not have a microphone preamp. The microphone is connected to my computer but the audio is coming from my receiver.

I see no problems using your cal mic or SPL meter to get started with REW.

Either would be fine for learning how to use the software and also for relative measurements (to see the effect of changes you've made between measurements) but you shouldn't use either mic for absolute measurements (to show exactly how your room is performing) or make any major decisions based on information/results you get with those mics.

If you're waiting on a backordered UMM-6 for instance, and are eager to get started, I say go for it!

There is no reason to use the loopback method for what we're teaching here and in fact it is impossible as of right now if you are using a USB mic and/or HDMI connectivity.

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post #3621 of 12050 Old 06-16-2013, 09:01 AM - Thread Starter
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Quote:
Originally Posted by markus767 View Post

And Toole agrees - I don't know why one poster lately tried to make it look like he wasn't:

"In measurements of refl ections, we need to measure the spectrum level of
refl ections to be able to gauge their relative audible effects. This can be done
using time-domain representations, like ETC or impulse responses, but it must
be done using a method that equates the spectra in all of the spikes in the
display—for example, bandpass fi ltering. Examining the “slices” of a waterfall
would also be to the point, as would performing FFTs on individual refl ections
isolated by time windowing of an impulse response.
All of this is especially relevant in room acoustics because acoustical materials,
absorbers and diffusers, routinely modify the spectra of refl ected sounds.
Whenever the direct and refl ected sounds have different spectra the simple
broadband ETC or impulse responses are not trustworthy indicators of audible
effects." ("Sound reproduction", p 257)

To this point, an illustration:



Black = full band ETC
Orange = 1K ETC
Green = 4K ETC

(all 200us smoothing)

Kept it simple here for ease of discerning. But the full band (which is what the vast majority use the majority of the time) is quite different than what is happening at 1k and 4K. If you really feel your ISD gap is really -20db, then take a look at 1K and then see. In my case, the 1K returns average 5db higher than the full band ETC. Those of you aiming for a -20db ISD gap really need to do it down to at least 1K if not lower. The filtered IR in REW can do this (although I am doing it in Omnimic for this example).

A HUGE +1 to Markus and Jim.

I cannot overstate how important it is to use filtered ETC measurements. I posted a detailed step-by-step in reply to one of Jerry's posts on how to do this in REW. Maybe he can repost it separately as I believe it was in a post with a lot of other info and tips/tidbits.

If you aren't looking at a filtered response you aren't accurately using the ETC and can compare it to measuring only 10khz to 20khz for example (not exact numbers) as the ETC (full band / unfiltered) is biased to the higher frequencies which is why it is absolutely necessary to filter it.

I'm glad folks are realizing the importance of this.

--J

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post #3622 of 12050 Old 06-16-2013, 09:04 AM - Thread Starter
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I have several questions regarding how the impulse measurements are being presented.  Jim uses OmniMic, which is somewhat different than REW.

My first question is regarding smoothing.  The REW users in this thread have been presenting unsmoothed ETC graphs.  Data smoothed to .2ms is considerably different, as shown below:













The smoothed graph shows no peaks higher than -20dB, which certainly tells a different story than the graph I have been using.  Which is the one we should be using for our discussions?

Second question is regarding how Jim presents his comparison of unfiltered and filtered ETC graphs.  I don't see a way in REW to overly filtered and unfiltered graphs.  Anyone know how to do this?

Do not smooth. Filter yes. Smooth no. Just as you need to see as much info in the frequency response as possible to truly get a picture of what's going on and how to treat it, you need the same resolution in the ETC.

It's good to filter, in fact it's necessary. There is no reason to add additional smoothing to this process simply to find high gain specular reflections.

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post #3623 of 12050 Old 06-16-2013, 09:15 AM
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To clarify, yes, -12db is MINIMUM. Thanks for catching that.

smile.gif
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Originally Posted by jevansoh View Post

The more the better, however, I'm not sure if you were to get, let's say, a -6db gain termination followed by the dense return/tail being closer to -12db and falling that that would be better than something closer to -10db (for instance) followed by the dense tail that is closer in db. Does that make sense?

Makes sense. What your describing here is the terminator to "tail" relationship. I dont know what is best for the later, but the former must be robust enough to trigger the Haas effect. In my experience, I couldnt really notice the Haas trigger (terminator) doing whats its suppose to until a strength of -10 or -8db, and prefer -6db.
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Originally Posted by jevansoh View Post

I don't know for sure which is best, BTW. It isn't the easiest thing to change/experiment with. wink.gif
smile.gif

Ive had good luck in experimenting with the terminator strength, playing with it at levels from -15db to -5db. The tail is a different story.
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Originally Posted by jevansoh View Post

-12db for the termination, whether using a HAAS kicker or not though is absolutely the minimum and I suppose the ultimate goal would be as strong as possible right up to the 0db point of the direct sound, but the chances of having that much delayed energy available while still taking care of all the high gain early reflections is slim to none, especially if using absorption and in a small room.

I havent seen a recommended termination level above -5db. 0db? I guess one could try that. I would guess at the least you would notice more image broadening. One thing to be careful with WRT really strong terminators is the effect on the FR curve. At 0db, you would be effectively adding 3db at those frequencies that the terminator employs. At a -6db terminator, your only adding 0.97db.
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You'd have to use reflection only and have a good size room with little loss and exact placements for every piece of the puzzle with engineered treatments to even approach that, so for the folks in this forum, just starting out, if we can achieve the minimum -12db termination followed by a dense and decaying return of specular reflections, we're doing pretty darn good!

Getting a strong terminator shouldnt be a problem in small room if your relying on a specular reflection to produce it. As for the decay, I dont know if you would want to do this specularly., or how you would do it and also be able to spread it out over time. This is where diffusers are handy.

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At that point, one could always try to improve things, but at least you'd have the model nailed down and can experiment from there, possibly replacing the broadband absorption with engineered bass traps and reflection only for specular reflections. That's getting ahead a bit though. wink.gif

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post #3624 of 12050 Old 06-16-2013, 09:18 AM - Thread Starter
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I do not think, by any stretch of the imagination, that I have achieved a 'perfect' NE room. In fact I know I have not. But I have limitations on what I can achieve, as do most of us, and I am so far pleased with what I have. I will continue to try to make improvements where I can, over time and am indeed experimenting with different speaker/sub placements soon (thanks Sanjay for all your help).

Keith, have you started experimenting with the Behringer yet?  Just curious if it is as easy and worthwhile to implement as you had envisioned?

Not Keith but I bought the Behringer DSP1124p along with the Midi to USB interface so it works with REW and automatically transfers the EQ settings in REW to the dsp so I never have to touch the million+1 buttons on the front of the dsp from a user here on AVS in the classifieds for around $60 and it was the absolute best investment I've ever made.

I've been able to totally get rid of my Audyssey XT32 (was using the AS-EQ1 for that since I only have XT built in my Denon AVR-5805CI) and only use the DSP1124p.

You get 12 filters and can save 10 different EQ curves.

With the Mini-DSP you only get 6 filters.

It's a great investment and I wouldn't be without it.

Highly recommend it. You can let REW automatically calculate the filters and transfer them over, similar to how Audyssey operates, but unlike Audyssey, you can totally tweak those filters after you measure to see the actual result and how it compares to the simulated/calculated result REW shows (it's normally very close unless dealing with a true null that can't be fixed with EQ of any kind) and then you can create a house curve and totally flatten your response. You can easily create (up to 10) different EQ settings for movies or music (one with a bump in the lows and one without for instance) and different house curves, even different EQ's for use with different crossovers which makes it very easy to do comparisons to find out what you ultimately like the best.

If you don't get the Behringer, at least get some type of Parametric EQ as EQ is an absolute necessity for the frequencies below the crossover (even if you have perfect treatments/bass traps, if for nothing else, to create a rising response in the low end / your own house curve) but once you properly treat your room, you should no longer need Audyssey for the mid-high frequencies.

Look in the classifieds and on eBay as these show up pretty often. Don't pay more than $100 shipped, for everything including the Midi controller though, as these aren't nearly as rare as many other items.

--J

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post #3625 of 12050 Old 06-16-2013, 09:23 AM
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Do not smooth. Filter yes. Smooth no. Just as you need to see as much info in the frequency response as possible to truly get a picture of what's going on and how to treat it, you need the same resolution in the ETC.

It's good to filter, in fact it's necessary. There is no reason to add additional smoothing to this process simply to find high gain specular reflections.

--J

I disagree. Smoothing is a good tool when doing graph comparison.

It depends on what your after.

If you want to know the true strength of your reflections then no, dont smooth. But comparing two unsmoothed ETC's is tedious, and difficult to draw conclusions from in a broad sense. In a narrow sense, like looking at one particular peak, then yes, I would use unsmoothed ETC's.

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post #3626 of 12050 Old 06-16-2013, 09:31 AM - Thread Starter
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Originally Posted by jkasanic View Post

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Originally Posted by kbarnes701 View Post

 
I do not think, by any stretch of the imagination, that I have achieved a 'perfect' NE room. In fact I know I have not. But I have limitations on what I can achieve, as do most of us, and I am so far pleased with what I have. I will continue to try to make improvements where I can, over time and am indeed experimenting with different speaker/sub placements soon (thanks Sanjay for all your help).

Keith, have you started experimenting with the Behringer yet?  Just curious if it is as easy and worthwhile to implement as you had envisioned?

I did but I have been sidetracked recently by a) wanting to watch some movies to cut down my backlog, b) more recently, spending a lot of time researching how to install my new projector and screen (!!) and c) carrying out some experiments this week, following advice by placement-Meister Sanjay, with moving my speakers a little and my subs (a fair bit). 

What I discovered with REW/Behringer to date is that yes, it is easy. Just play with the filter creation in REW and upload via a permanently connected midi interface to the Behringer. Very easy. Then use REW to measure the effect of the new filters. That is where I stopped for now. It will take some trial and error but I have to say that even on my first go, I managed to flatten the bass curve a little around the splice - but not so much that it was audible on listening tests. As the Behringer has a defeat switch it was easy to get my lovely assistant to switch the thing in and out, and since the Behringer is in a different room I could even do a blind AB test. This may prove useful later when I return to PEQ with more vigour. I will return to it, but for now I shall be concentrating first on moving the speakers/subs, measuring and then re-running Audyssey and measuring again (and re-doing the sub distance tweak too assuming the new speaker/sun placements are beneficial). Once that is done, I have to instal the PJ and then calibrate it etc etc. Much to do over the next two weeks, or 'fortnight' as we Limeys call it smile.gif

Keith, I got very behind in this thread and am just now catching up (had no idea how backed up I was until I saw I had over 400 messages to read and respond to!)

Sorry I didn't get back with you regarding the BenQ w1070. Am I to understand you've already made a decision/purchase? What did you end up going with? Which screen?

Also, where is the discussion regarding your new speaker/sub placement? I've missed more than I thought apparently. frown.gif

If you're interested, I'll chime in and help in any way I can. Again, sorry for the delayed and/or non-responses and although I'm done promising I'll be better next time at responding faster (as that has already come back to bite me as although my intentions are always good, this little thing called life outside AVS keeps getting in the way!) I sure will try. I "plan" to be around AVS all day today as I am reading up on new subs myself and am all caught up on everything else, except this particular thread which I'm working on now.

Thanks, and I don't know if I'm the one to credit or blame, depending on how you look at it, for your new projector/screen purchase, but I'm sure you'll be thoroughly impressed and will finally have a true theater in your home! I always forget that you were still watching on a TV and think you'll absolutely love a big screen, especially in a room that's dedicated to nothing but movie watching! It's almost a crime that you didn't have a bigger screen before now. wink.gif

--J

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post #3627 of 12050 Old 06-16-2013, 09:53 AM - Thread Starter
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I agree.  The technical discussions have been very interesting, and I feel an agreement on the definition of the LEDE/RFZ model is close at hand. 

I believe we have a reasonable understanding on how to identify early reflections. What is not so clear is how to select the right treatment, and measure the success of the treatment.  Also, we have not really discussed diffusion/redirection--materials, how-to, measurements, etc. 

This is the exact point I was hoping to get to when I envisioned this thread.

I'm happy it looks like we're about there. Finally! biggrin.gif

Now, I'm finding myself a bit overwhelmed to be honest. I need a bit of guidance.

I don't have the time to write a whole book taking a room from empty/blank slate and detailing each step of the way the entire progression from designing and building the room to the final outcome of a textbook LEDE room.

There are already better books than I could right on these topics anyway.

So, I guess I'm asking where to start? We've covered a lot of ground in the thread already and there is a lot of great info, but unfortunately, a lot (most?) of it is buried and hard to find between all the posts from the salesman that is trying to debate and dismiss every word I type and then all of the bickering that follows.

Plus, due to the time I have available and the unfortunate consequence of not being able to keep up on a daily basis but then once a week or so posting 20-30+ posts in a row that most people probably skip I'm not sure I'm being very effective.

This is where your organizational skills (of which I am honestly jealous of, Jerry) can come in very handy.

Can you guys help me get on track? Maybe an outline of what you'd like to see, or at least where you'd like to begin?

Can we work on getting all the information I've already posted in a more clear and concise form or document then ensure we're all (or at least mostly) on the same page and ready to proceed?

I have a lot more information to share but I'm not quite sure what we're ready for or how to go about it other than just creating more of the same novella type posts I'm sure I'm known for at this point.

Suggestions are very welcome.

--J

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post #3628 of 12050 Old 06-16-2013, 09:58 AM - Thread Starter
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I think the next step is prioritizing the LEDE / RFZ criteria.

The following is my opinion, not consensus necessarily based on papers or experiment.

Often times, even after deciding on the model, in this case LEDE / RFZ, as it applies to ones typical listening room for listening purposes (not control room), compromises have to be made. Having a priority hierarchy helps to preserve the most important things while steering one towards compromising (when necessary) the most on the lesser criteria.

1) Isg gap

I feel meeting, and preferably exceeding the minimum value of -20db (at least down to 1K), is the most important. Presumably the overall goal is better sound, and giving the direct response the time (20ms or greater ideally) it needs to be discerned, cues identified by our brains, and minimal aberrations to the FR response is paramount. If what the direct response is trying to do is compromised, then everything else is also.

2) Terminator

Its not LEDE / RFZ at all without this feature.

3) Diffuse Tail

I agree 100% with the information in points 1 and 2 here. This is the first step into beginning to create the actual LEDE model and where the different criteria of all the different models will change.

It also assumes that several other things have already been done and are completely understood and that we're mostly to that point, such as Modal problems taken care of, SBIR taken care of, proper speaker placement, seating positions, etc, and that we have a clear idea of where we're headed.

I guess the question is, are we ready for this?

Is the consensus that we should now, at this time, start focusing on points one and two of this post?

I just need a little direction here. I think we all do. I'm here to serve not to dictate so please help me help you.

Thanks,

--J

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post #3629 of 12050 Old 06-16-2013, 10:16 AM - Thread Starter
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Once you know the criteria, and the most critical features of it, then we can look at how to go about things.


IMO, in small rooms, I am of the philosophy that you cant ever have too much bass trapping. I have yet to see an example of where too much has been used to a detrimental effect, whereas the lack of it or insufficient amount of it is quite common. Anywhere corners meet is a potentially good place. Particularly where three corners meet.


In small rooms, high gain early reflections need absorbing. Redirection is a good option IF your willing to splay your walls (something most people dont want to do). And diffusion I am not a fan of for high gain early reflections, but it definitely has its place for later lower level ones.


Now the rest of it is particular to each room. What you have to ask yourself at every wall surface is whether:


1) absorption

2) diffusion

3) redirection


(Our three most common tools)


...is going to best preserve or compromise your isd gap. An untreated wall can be taken as redirection, so look where each untreated wall surface is redirecting the energy from each speaker and see if it intrudes on the isd gap. See if its far enough away where diffuse energy will arrives late enough. Or reflect it in a more beneficial direction. By looking at all your walls in this manner, what treatment is necessary become self apparent.


Along with this, you have to decide how your going to terminate, and how to get the path length long enough. If your fortunate enough to have the walls behind the listening area 11' or 12' distant, then things are much easier since a single bounce from them will arrive back at the listening area after 20ms. In this case, diffusion would be a prime candidate. If your not fortunate, and your back wall is less than 11', certainly if its less than 9 ' or 10', your left with a dilemma. Your either going to have to have a isd gap less than 20ms or your going to have to bounce the energy around at least twice. I cant say for sure which is the better or more feasible choice for all rooms. This must be addressed on a case by case basis.

Well, let me be the first case then!  At first, I was planning to use R30 Roxul insulation panels in the corners behind my false wall as well as at the floor and ceiling joints.  Then it was suggested that I consider covering the entire wall.  In this case, I believe I've gone from just bass trapping to absorbing across the entire stage.  You mention that you can never have too much bass trapping...does this still apply?  The floor plan below shows the basic elements of my listening space.  L, C and R speakers are behind the false wall and the sub is placed directly underneath the C speaker.  I have not shown the surrounds in this layout but there are 4 in-ceiling at the moment.  I've considered upgrading the surrounds (even downgrading from 7.1 to 5.1) but decided I wanted to undertake SQ optimization first as I don't find them objectionable per se while listening to multi-ch content:







As you can see, I have a far from ideal listening space with respect to ISD Termination.  After watching several hours of film at approx. 1.5x SW, I'm not opposed to moving the MLP slightly more forward which should help a little but I doubt enough to get me to > 20ms.

Here was my proposal on adding the Roxul (which I would like to understand if it's still a good idea or if I should just concentrate on the edges and tri-corners?):




 I'm willing to treat areas outside of the false wall but these obviously require a little more WAF which means I'll likely be buying panels that either blend in with the decor (so as to be invisible) or add to it (e.g. decorative panels).  Either way, I've lost my low cost DIY approach being applied behind the false wall!  Suggestions?

Although it is very possible to design for "too much bass trapping" in implementation, I've yet to see it done.

However, if you are using broadband velocity based trapping (fuzzy insulation) then you aren't really using true "bass trapping" at all and as you are taming the bass you are also sucking all the life out of the room as it's having an even more pronounced effect on the higher frequencies.

To keep it cheap and simple, if you have enough room, you can do what I did and treat the whole front wall (behind my false screen wall - all hidden) with R30 insulation and depending on how much room you have back there and how much trapping you need, you can orient it so that it is 9.5" thick or 15" thick. Then simply cover it with plastic so you don't over absorb the mids and highs and now you are using it strictly as a bass trap. You may want to do even more in the corners (double up the layers, for instance, which is exactly what I did).

So remember, when discussing bass trapping, if you are only using insulation (of any kind) it is broadband and affecting much more than just the bass.

These are the types of issues that we need to discuss and get taken care of first, before trying to implement the final details of the LEDE model, because you won't have the energy to use to terminate the ISD Gap if you've absorbed it all by using broadband (uncovered) insulation as bass traps as they trap everything, not just the bass, unless properly modified.

As for small rooms needing absorption, well... All rooms probably need some type of absorption but that doesn't have to be determined by the size of the room alone.

In small rooms and rooms where you aren't able to alter the construction by creating splayed walls, you can easily use large reflectors (Mine are simply 5/8" Drywall which is cheap at under $10.00 for a 4x8' panel and very massive so they make a perfect specular reflector) cut, sized, and placed to create an ISD Gap and then put bass trapping IE: R30 insulation behind the reflector without overdamping the highs. Two birds. One stone. wink.gif

By only surgically placing absorption in small rooms and reflecting the paths TWICE, you can increase your ISD Gap and have the best of both worlds because as long as you don't over absorb you'll still have enough energy to work with for the termination and return.

--J

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post #3630 of 12050 Old 06-16-2013, 10:28 AM - Thread Starter
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Perhaps you missed it, but these models were talking about only are vaild for 2 channel audio. If only 5% of your listening is this, then I am not sure if the work, time and expense is going to be a great return for you.

But dealing with the bass response as a separate issue is valid for anything audio. Do you have measurements of your room? Can you either repost them or link me to them?

Well, I certainly realized the models are for 2-channel audio. Add the open floor plan that I have to the fact that most of my listening is in Multi-channel, I guess I should opt out of trying to do anything WRT achieving a particular model.

This doesn't meant I can't optimize my treatments for improved bass response and reduced early reflections, it just means I am never going to achieve what you did. Depressing.

Jerry, there is no reason to give up!

We all have to make compromises. I doubt anyone here (including me) is going to have a perfect textbook example and actually get their rooms certified.

However, my motto is that if you design and strive for perfection you'll achieve satisfaction.

He already showed you two ways you can achieve relatively good ISD Gap/termination.

It is absolutely doable. Perfect it is not, but I have looked at your room many times and if I thought it wasn't doable or even extremely unlikely that you could achieve it I assure you I would've told you so before now.

Don't give up. There's nothing to be alarmed about.

However, the more posts I'm reading and further I'm catching up, I'm not quite sure we're all quite "there" yet and don't want to get too ahead of ourselves.

I've realized we all desperately need your help and organizational skills to help design a guide/outline of the order in which we should do things, start from the beginning, and on a case by case basis try to help the participants of this thread meet their goals.

There aren't that many of us and each of the specific things we help one poster with should translate mostly to another poster.

Some have no treatments, some are undertreated, overtreated, etc. A lot of folks are overwhelmed and several more are looking for guidance.

We're all over the map here.

I made a post (one of about a hundred so far it feels like) earlier today outlining, step by step, how we should begin and how we get to the 80% point.

I think that needs to be expanded upon and be made part of the guide/101 and when we're mostly to that point, then start worrying more about the termination in detail.

Very few of the posters here seem to be ready for that. In fact I think it's you and one other guy! wink.gif

In the mean time, I'm more than willing to answer specific questions and help out on an item by item and case by case basis if you are in fact ready to proceed and don't want to wait on most others to catch up.

I'd greatly appreciate any effort you can make depending on your interest and time available to help get a guide together based on the information I've posted today and what we've discussed before, because although a lot of the information is in this thread now, it's all over the place and people are reading different parts at different times and are in different places and we really need to get everyone on the same page or at least have an understanding of what the proper steps are, as defined earlier today by me, and can then explore and further discuss implementing each stage of the design.

By the time we're to the 80% point I honestly believe people will be much more comfortable in picking a model and sticking with it, seeing it through.

Let me know what you think.

--J

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