Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 364 - AVS Forum
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post #10891 of 12050 Old 08-04-2014, 08:03 AM
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Probably would, Jim, but you know my aversion to DIY panels. Temporarily, I have left the extra panel in place on top of the GIK 242 panel, which has tamed the reflection. As soon as I understand why the 242 panel isn't doing the job, I'll figure out a permanent solution. I plan on trying to cover the frame today.

Actually, I'm feeling pretty good that I actually identified the source of the reflection. I had always assumed the back wall had been effectively treated. It just proves how difficult reflections can be, and gives me a renewed respect for the job you have done in your listening room.
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post #10892 of 12050 Old 08-04-2014, 02:27 PM
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Originally Posted by jim19611961 View Post
Jerry, if you really want to kill the rear wall reflections, I would put 12" of pink fluffy there.
For my rear wall I used the 3.5" of Roxul SafeNSound and it seems pretty effective. I made the panels myself but maybe just thicker less dense panels would work for AustinJerry?
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post #10893 of 12050 Old 08-04-2014, 02:55 PM
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For my rear wall I used the 3.5" of Roxul SafeNSound and it seems pretty effective. I made the panels myself but maybe just thicker less dense panels would work for AustinJerry?
What you used or what Jerry has are either one, up to killing a 8K reflection. My money is still on the seams.

The only reason I brought up fluffy is if Jerry gets to the point where the GIK panels wont do the job and he has to replace them with something. I either forgot or didn't know about his aversion to DIY.

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post #10894 of 12050 Old 08-05-2014, 08:52 PM
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I'm about to embark down the rabbit hole of room treatments. I'm adverse to making panels due to the lack of tools, skills and time. Like Jerry, I prefer to purchase pre-fabricated and professionally made units.

Recently came across a company called Foam Factory in Michigan. Price seems reasonable compared to the competition such as Auralex.

Going to start with their bass absorbers. Can someone let me know if their test results here:http://www.usafoam.com/acousticfoam/...-Absorbers.pdf look okay?

Thinking of using the male/female broadband absorbers to address the first reflection issues. The ETC graph for the center channel looks really bad as shown in the attachment.


Would like some opinion on Foam Factory's datasheet here:http://www.usafoam.com/acousticfoam/...-Absorbers.pdf if it will do. Considering to address the glass coffee table in front of the center then re-measure.

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post #10895 of 12050 Old 08-05-2014, 09:35 PM
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My recommendation would be to browse the GIK Acoustics site before you make any decisions. Read this comparison of GIK traps vs. foam traps: http://www.gikacoustics.com/comparin...44-bass-traps/.

Foam has a terrible reputation as an acoustic control. If I am reading the product offerings correctly, a foam treatment is more expensive than a comparable GIK 242 broadband trap. GIK also has a consulting service that will assist you in developing a plan for treatments, and the service is free of charge.

Other sites to look at are ATS Acoustics and RealTraps, although RealTraps is on the expensive side.

I agree, that ETC measurement is one of the worst I have ever seen. Compare it to Jim's.
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post #10896 of 12050 Old 08-05-2014, 09:38 PM
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Originally Posted by jim19611961 View Post
My money is still on the seams.
Sorry to disappoint, Jim, but I fixed the reflection without ever testing whether the seams were causing the issue. The end justifies the means, so when the reflection was fixed, I returned to relaxing and enjoying the improved sound.

Still some work to do, but I am getting there...

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post #10897 of 12050 Old 08-06-2014, 05:57 AM
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Quote:
Originally Posted by AustinJerry View Post
Sorry to disappoint, Jim, but I fixed the reflection without ever testing whether the seams were causing the issue. The end justifies the means, so when the reflection was fixed, I returned to relaxing and enjoying the improved sound.

Still some work to do, but I am getting there...

So, you left the blocker in place, yes?

One thing to point out here though. In the 3-4ms range, your reflections are louder (look more closely at your before after graphs on the previous page). 5-10db louder. While they don't exceed -20db significantly, I question whether this is a good solution.

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post #10898 of 12050 Old 08-06-2014, 06:08 AM
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Originally Posted by AustinJerry View Post


Here it is for quick reference.

You have a nice downward slope to 6ms bottoming out to -30db. Excellent to this time point. This is absent in your revised graph above.

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post #10899 of 12050 Old 08-06-2014, 06:58 AM
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Originally Posted by jim19611961 View Post
Here it is for quick reference.

You have a nice downward slope to 6ms bottoming out to -30db. Excellent to this time point. This is absent in your revised graph above.
Surely this can't be caused by the addition of additional treatment on the back wall, could it? Might it be a measurement anomaly? The additional treatment is likely to be a different substance than the GIK material, could that cause the measurement difference?
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post #10900 of 12050 Old 08-06-2014, 07:11 AM
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Originally Posted by AustinJerry View Post
Surely this can't be caused by the addition of additional treatment on the back wall, could it? Might it be a measurement anomaly? The additional treatment is likely to be a different substance than the GIK material, could that cause the measurement difference?
You can rule out measurement anomalies by taking measurements multiple times with and without your additional panel. All I have to work with is the measurement data you are providing. But based on that, your additional panel while solving one problem, creates others it looks to me.

But it does make sense to some degree given the additional reflections are earlier in time, and the additional panel is closer to your mic as well. If the add'l panel is creating new reflections, this is where (in time) one would expect to see them.

Not knowing what the material of the new panel is made of makes assessing how it should behave impossible to guess.

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post #10901 of 12050 Old 08-06-2014, 07:32 AM
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The additional panel is an ATS Acoustics 2" thick panel (substance unknown), which has a plywood backing. The GIK 242 panel underneath it is a 3" thick panel with an open back with an air gap between it and the wall.

I suppose the next step is to remove the extra panel, test your theory on the edges causing the reflections, and if the result is positive, re-mount the 242 panels rotated 180 degrees. This is all a bit more work that I had hoped to avoid, but after all, we are looking for the best solution, correct? I purchased a small roll of pink fluffy earlier in the week just in case I had to resort to Plan B.

If that still doesn't work, my next step would be to swap out the 242 panels with 244 panels temporarily to see if the thicker panels make a difference.
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post #10902 of 12050 Old 08-06-2014, 07:42 AM
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Originally Posted by AustinJerry View Post
The additional panel is an ATS Acoustics 2" thick panel (substance unknown), which has a plywood backing. The GIK 242 panel underneath it is a 3" thick panel with an open back with an air gap between it and the wall.

I suppose the next step is to remove the extra panel, test your theory on the edges causing the reflections, and if the result is positive, re-mount the 242 panels rotated 180 degrees. This is all a bit more work that I had hoped to avoid, but after all, we are looking for the best solution, correct? I purchased a small roll of pink fluffy earlier in the week just in case I had to resort to Plan B.

If that still doesn't work, my next step would be to swap out the 242 panels with 244 panels temporarily to see if the thicker panels make a difference.
If a 8K reflection is what we are trying to solve, the 242 panels should be as good as the 244 panels at doing that. Going back to data you provided previously, if the reflection shows on the 8K IR and not on 4K IR, then we are looking for a fairly small surface.

The wavelength of 8K is 1 2/3", btw.

The 244 panels might provide reflection control a bit deeper (lower) though. Would have to see filtered IR at 500hz to see if your present panels are doing that job or not.

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post #10903 of 12050 Old 08-06-2014, 08:39 AM
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OK, I'll do some testing/re-arranging tomorrow. Stay tuned, and thanks for the advice.
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post #10904 of 12050 Old 08-06-2014, 10:12 AM
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Well, my back "wall" may be a special case, IDK, but as I've mentioned a few times when treatment there was recommended to me (it's bareness being so obvious): reflections were noticeably (REW) and audibly worse with panels there. Who'da thunk it? Not the knowledgable people who had a casual look to give me advice. So the back wall is panel-free, wasted a fair bit of time and purchased a few unneeded panels for there, just couldn't believe they made things worse...it's a bit mentally hard to undo work/money spent.

I could have sworn that I measured reflections coming from the back wall (string method), but once I had treated the other walls, those reflections weren't there anymore. This is probably something that people who have done this numerous times have noticed...the lesson for me being not to try to do the whole thing in one shot (I didn't actually, as far as getting panels), but to re-do the reflection measurements/ETC/etc. after the most obvious stuff (first reflections) are treated. Which I don't think I did, I just did the simple measurements again to see if I was on the right track, I didn't actually "change the plan" after the first phase. We all know about plans and military endeavors like room treatment...

Anyway, my question is: do those of you with a UMIK-1 use the foam thing over the microphone? I don't, I thought those things were just for when near your mouth to prevent some breathing/"wind" noise. Do you think the microphones are calibrated with it on? It would be easy enough to test the difference with it on and off...another thing for the list next time I do REW. I already have a dust cap for the UMIK-1, so I don't need it for that.
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post #10905 of 12050 Old 08-06-2014, 11:19 AM
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Well, my back "wall" may be a special case, IDK, but as I've mentioned a few times when treatment there was recommended to me (it's bareness being so obvious): reflections were noticeably (REW) and audibly worse with panels there. Who'da thunk it? Not the knowledgable people who had a casual look to give me advice. So the back wall is panel-free, wasted a fair bit of time and purchased a few unneeded panels for there, just couldn't believe they made things worse...it's a bit mentally hard to undo work/money spent.

I could have sworn that I measured reflections coming from the back wall (string method), but once I had treated the other walls, those reflections weren't there anymore. This is probably something that people who have done this numerous times have noticed...the lesson for me being not to try to do the whole thing in one shot (I didn't actually, as far as getting panels), but to re-do the reflection measurements/ETC/etc. after the most obvious stuff (first reflections) are treated. Which I don't think I did, I just did the simple measurements again to see if I was on the right track, I didn't actually "change the plan" after the first phase. We all know about plans and military endeavors like room treatment...

Anyway, my question is: do those of you with a UMIK-1 use the foam thing over the microphone? I don't, I thought those things were just for when near your mouth to prevent some breathing/"wind" noise. Do you think the microphones are calibrated with it on? It would be easy enough to test the difference with it on and off...another thing for the list next time I do REW. I already have a dust cap for the UMIK-1, so I don't need it for that.
I think your story is a case and point that knowing with out a doubt where a problem exists must be known before permanent and expensive treatment is applied. General and casual recommendations are merely that, general and casual. At the end of the day, if its your room, its up to you to know. The rest of us are not there.

IMO, the only way to be certain of the cause of a problem is to take measurements before, put up a temporary solution, and remeasure. Neither string, nor modeling nor seemingly good advice is a substitute for this. If advice given seems good, then test it by measurement. I always have spare R19, OC703, and large boards around for rigging temporary solutions to things and trying them out.

But here is a casual and general recommendation Take some R19, put it in a big bag, and stick it in different locations. After taking an initial reading, watch how your measurements change. I have discovered SEVERAL fixes to things that never would have fit the doctrine of generally applied theory in this way.

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post #10906 of 12050 Old 08-06-2014, 12:14 PM
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Originally Posted by cfraser View Post
Well, my back "wall" may be a special case, IDK, but as I've mentioned a few times when treatment there was recommended to me (it's bareness being so obvious): reflections were noticeably (REW) and audibly worse with panels there. Who'da thunk it? Not the knowledgable people who had a casual look to give me advice. So the back wall is panel-free, wasted a fair bit of time and purchased a few unneeded panels for there, just couldn't believe they made things worse...it's a bit mentally hard to undo work/money spent.

I could have sworn that I measured reflections coming from the back wall (string method), but once I had treated the other walls, those reflections weren't there anymore. This is probably something that people who have done this numerous times have noticed...the lesson for me being not to try to do the whole thing in one shot (I didn't actually, as far as getting panels), but to re-do the reflection measurements/ETC/etc. after the most obvious stuff (first reflections) are treated. Which I don't think I did, I just did the simple measurements again to see if I was on the right track, I didn't actually "change the plan" after the first phase. We all know about plans and military endeavors like room treatment...

Anyway, my question is: do those of you with a UMIK-1 use the foam thing over the microphone? I don't, I thought those things were just for when near your mouth to prevent some breathing/"wind" noise. Do you think the microphones are calibrated with it on? It would be easy enough to test the difference with it on and off...another thing for the list next time I do REW. I already have a dust cap for the UMIK-1, so I don't need it for that.
Interesting that things got worse. I certainly wouldn't expect treatments to make reflections worse. No change, maybe, but not worse (unless the treatments were poorly made with something that is reflective).

In my case, I had reflections from the back wall that were actually coming from the ceiling, i.e. a "secondary" reflection. I had to treat both the ceiling first reflection point as well as the back wall, and the improvement was significant. As Jim says, applying theory doesn't always result in actual improvements--reflections are complex and difficult to isolate. Based on recommendations from all the experts who have participated in this thread, including Jim, Markus, J, and others, the best way to isolate reflections is to stick a temporary absorption material in a spot and re-measure. Certainly use this approach before purchasing expensive panels, drilling holes in the walls, etc.
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post #10907 of 12050 Old 08-06-2014, 12:21 PM
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Quote:
Originally Posted by jim19611961 View Post
Here it is for quick reference.

You have a nice downward slope to 6ms bottoming out to -30db. Excellent to this time point. This is absent in your revised graph above.
Jim, I have published incorrect information, sorry. The ETC measurement that you liked, with the nice downward slope, is labeled "No Blocking", when actually it should be labeled "Block Above", i.e. it shows reflections coming from the ceiling. So, I was focusing strictly on that single reflection coming from the back wall that I didn't realize that I could benefit from some additional ceiling treatments.



So, based on this revelation, I am inclined to augment the ceiling treatments before re-visiting the back wall, which could be "good enough" as it is. Your thoughts?

Edit: Of course, I still have that pesky ceiling fan which could be causing some problems...
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post #10908 of 12050 Old 08-06-2014, 12:45 PM
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Jerry,

Now I am thoroughly confused

Lets start again.

1) ETC L
2) ETC R

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post #10909 of 12050 Old 08-06-2014, 12:50 PM
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Don't forget to consider what you might want to do with respect to future Dolby Atmos soundtracks. Ceiling treatments might need to take into consideration the use of "Dolby enabled" up-firing speakers, which intentionally use ceiling reflections to provide the overhead audio. I.e. you might want to be able to move the absorbers that you mount on the ceiling.

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post #10910 of 12050 Old 08-06-2014, 12:54 PM
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Sorry that I have confused you. During my "blocking" exercise, I measured each speaker (left, right, center) by placing a panel to block reflections from the right, from the left, from behind the MLP, and finally from above, i.e. ceiling reflections.

The measurement that you used as and example of desirable reflections (except for the single spike from the back wall) was the center speaker with ceiling reflections blocked.

Does this make it any more clear?
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post #10911 of 12050 Old 08-06-2014, 01:00 PM
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Don't forget to consider what you might want to do with respect to future Dolby Atmos soundtracks. Ceiling treatments might need to take into consideration the use of "Dolby enabled" up-firing speakers, which intentionally use ceiling reflections to provide the overhead audio. I.e. you might want to be able to move the absorbers that you mount on the ceiling.
I have been closely following the Atmos discussions, and based on what I have heard so far, I am not a candidate for Atmos. I want my listening room optimized for music listening, not for action-oriented movies. Even if I were interested in Atmos, I am absolutely not a fan of the upward-firing strap-on speakers. I would install either surface-mounted or in-ceiling speakers (which might involve re-locating ceiling treatments, as you say).
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post #10912 of 12050 Old 08-06-2014, 01:11 PM
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Sorry that I have confused you. During my "blocking" exercise, I measured each speaker (left, right, center) by placing a panel to block reflections from the right, from the left, from behind the MLP, and finally from above, i.e. ceiling reflections.

The measurement that you used as and example of desirable reflections (except for the single spike from the back wall) was the center speaker with ceiling reflections blocked.

Does this make it any more clear?
I understand what you said you did, but I no longer understand which graph applies to what, or what the spike in question pertains to as to where in the room that spike is coming from.

This would be easier if you were here, or I were there

Or perhaps I am not getting it cause I just got up from a nap

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post #10913 of 12050 Old 08-07-2014, 08:16 AM
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Here are the results of new REW ETC measurements taken this morning. My objectives were:

1. Re-assess a reflection originating from the back wall behind the MLP. This wall is well-covered by GIK 242 panels, but the blocking technique reveals that there is still a reflection coming from the wall. As a temporary solution, I have placed a second treatment on the back wall, two ATS Acoustics 2'x4' panels I had lying around. In the measurements, the label "with extra panels" refers to having the ATS treatments in place as well.

2. Remove the "Extra panels" and test Jim's hypothesis that the edges of the 242 panels might be the source of the reflections. I cut several strips of pink fluffy and taped the strips over the vertical joint first, and then the horizontal joint, and measured both.

3. Finally, Jim commented that one of the ETC measurements from earlier in the week showed significantly better reflection control than the others. This measurement was labeled "block above", which means a panel was placed to temporarily block reflections from the ceiling direction. I re-measured the effect of blocking ceiling reflections today.

Measurement 1: Center channel with "extra panels" in place -



Measurement 2: Center channel with "extra panels" removed -



Measurements 3 and 4: Use pink fluffy to cover edges of the 242 panels -








Measurement 5: With "extra panels" in place, measure center channel, blocking ceiling reflections -




Conclusions:

1. The pink fluffy had no effect on reducing the reflection from the rear wall (sorry, Jim).
2. The extra panels are effective in reducing the reflection from the rear wall, and should stay in place (at least until a better solution presents itself).
3. Blocking ceiling reflections seems to produce desirable results. This suggests that additional treatment on the ceiling might be worthwhile to consider.

Adding additional ceiling treatments is tricky. First of all, it is difficult to place temporary treatments on the ceiling to assess effectiveness. Second, there is no way to reduce the reflection from the ceiling fan, other than to relocate or remove the fan. I am unwilling to do either, so I will live with one undesirable reflection. So, if I decide to proceed, I will order the treatments, install them, and then cross my fingers while I take a new measurement. If the expected improvement is not there, I am out the expense, and have a couple more holes in the ceiling. Such is the joy of hunting reflections...
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post #10914 of 12050 Old 08-07-2014, 08:55 AM
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Jerry,

Good detective work.

If you look carefully, you will see some things did change with the pink fluffy vertical coverage. Not the reflection your hunting, but one at 5ms and another around 5.4ms. This is a clue that the reflection your after is 1.0 - 1.46ms later than the vertical area, which means farther away. So the pink fluffy did help, just not in the area of primary interest

On the horizontal pink fluffy test, there is a change also. Look at the 4.5ms spike. See how it altered some?

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In addition to the speakers, maybe where the wall meets the ceiling may be a place of interest.

--- --- ---

This illustrates a helpful tool. That is, when you change something in the room and remeasure, if what you hoped would change didn't, look for what DID change. Another technique is to put a flat reflector in some given place, and look for the timing of the anticipated spike. This will help isolate a spot in terms of its timing and hopefully guide you to the spot your really looking for.

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Last edited by jim19611961; 08-07-2014 at 09:35 AM.
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post #10915 of 12050 Old 08-07-2014, 09:52 AM
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[QUOTE=jim19611961;26367401]Jerry,

Good detective work.

If you look carefully, you will see some things did change with the pink fluffy vertical coverage. Not the reflection your hunting, but one at 5ms and another around 5.4ms. This is a clue that the reflection your after is 1.0 - 1.46ms later than the vertical area, which means farther away. So the pink fluffy did help, just not in the area of primary interest


In addition to the speakers, maybe where the wall meets the ceiling may be a place of interest.

--- --- ---

[QUOTE]

Regarding the speakers and the wall/ceiling intersection, not sure why you are proposing this might be a reflection source. First of all, the "extra panels" fix the reflection I am looking at, and they don't extend that far up. Also, when hunting reflections, I always apply the "angle of incidence equals the angle of reflection" rule. How could a signal coming from the center channel reflect off of something that high up, and then down to the mic? Unless, of course, it is hitting the ceiling first, and then the back wall, and then down to the mic. Which leads me to the finding you failed to comment on--do you think blocking ceiling reflections (measurement 5) produced significant enough improvements to warrant experimenting with added ceiling treatments? This might address the speaker and wall/ceiling intersection issue as well?

Here are the treatments I might add:



Once the panels are in place, I need to figure out how to treat the small rectangle in the center that the panels don't cover. I might have to resort to a (gasp!) DIY treatment. And there is still the reflection from the underside of the ceiling fan, which is unfortunately untreatable, because any treatment would cover the LED lighting kit on the bottom (which is important).

Jim, your thoughts?
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post #10916 of 12050 Old 08-07-2014, 10:00 AM
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[quote=AustinJerry;26369465][QUOTE=jim19611961;26367401]Jerry,

Good detective work.

If you look carefully, you will see some things did change with the pink fluffy vertical coverage. Not the reflection your hunting, but one at 5ms and another around 5.4ms. This is a clue that the reflection your after is 1.0 - 1.46ms later than the vertical area, which means farther away. So the pink fluffy did help, just not in the area of primary interest


In addition to the speakers, maybe where the wall meets the ceiling may be a place of interest.


--- --- ---

Quote:

Regarding the speakers and the wall/ceiling intersection, not sure why you are proposing this might be a reflection source. First of all, the "extra panels" fix the reflection I am looking at, and they don't extend that far up. Also, when hunting reflections, I always apply the "angle of incidence equals the angle of reflection" rule. How could a signal coming from the center channel reflect off of something that high up, and then down to the mic? Unless, of course, it is hitting the ceiling first, and then the back wall, and then down to the mic. Which leads me to the finding you failed to comment on--do you think blocking ceiling reflections (measurement 5) produced significant enough improvements to warrant experimenting with added ceiling treatments? This might address the speaker and wall/ceiling intersection issue as well?

Here are the treatments I might add:



Once the panels are in place, I need to figure out how to treat the small rectangle in the center that the panels don't cover. I might have to resort to a (gasp!) DIY treatment. And there is still the reflection from the underside of the ceiling fan, which is unfortunately untreatable, because any treatment would cover the LED lighting kit on the bottom (which is important).

Jim, your thoughts?
Yes. Your proposal for addl ceiling absorption looks promising.

FYI, When I approached my ceiling treatment, I started as you are putting up single panels. Before long, I realized that there was benefit in just treating the entire ceiling space between me and the speakers resulting in a 12'x15' ceiling cloud.

As far as the ceiling/wall intersection, the 45 degree angle of the trim up there looks like a possible reflection point to me. But admittedly, looking at pictures of your room is an imprecise way of guessing on my part. A 3D perspective is difficult.

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post #10917 of 12050 Old 08-07-2014, 10:15 AM
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Thanks for the feedback, Jim. I think it is worth a try with the additional ceiling panels. I'll place the order today, and should have them installed late next week. I'm hoping for a measurable improvement. Once the new panels are in place, it will be a simple exercise to stuff some pink fluffy around the base of the fan to see if that little open rectangle needs attention as well.

I can see the finish line!
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post #10918 of 12050 Old 08-07-2014, 10:19 AM
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Quote:
Originally Posted by AustinJerry View Post
Thanks for the feedback, Jim. I think it is worth a try with the additional ceiling panels. I'll place the order today, and should have them installed late next week. I'm hoping for a measurable improvement. Once the new panels are in place, it will be a simple exercise to stuff some pink fluffy around the base of the fan to see if that little open rectangle needs attention as well.

I can see the finish line!


In my case, the finishing line keeps moving

As I moved the ETC firstly to -20db, then to -25db, then to -30db, I felt like there were noticeable improvements in sound. Particularly in soundstage and low level detail. Unfortunately, along with this, things got more dead as well, and had to impliment my Haas Kickers to compensate. Just something to keep in mind as you continue to reduce reflection magnitudes.

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Last edited by jim19611961; 08-07-2014 at 10:28 AM.
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post #10919 of 12050 Old 08-08-2014, 08:05 AM
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Originally Posted by markus767 View Post
New REW beta 22 is out with substantial improvements and fixes for the EQ tool:
http://www.hometheatershack.com/foru...tml#post865057
Any impressions on the new beta? I can't grab it while at work.
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post #10920 of 12050 Old 08-08-2014, 08:08 AM
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Originally Posted by HDgaming42 View Post
Any impressions on the new beta? I can't grab it while at work.
The bugs I had reported to John have been fixed. Now you can use PEQ up to 20kHz. It was limited to 10kHz before.

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
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