Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 432 - AVS Forum
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post #12931 of 12947 Old Yesterday, 12:18 PM
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^
looks good to me

is it a deliberate target curve? it looks like -6dB from 1kHz to 20kHz and a few dB rise below that
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post #12932 of 12947 Old Yesterday, 12:20 PM
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Originally Posted by SherazNJ View Post
jerry,
I used to blocking technique just to see which one is causing the high reflection and if the material is useful. So I placed the panel right on top of center speaker half way out and took reading. Spike was still there. Then I moved the panel all they way forward on top of the speaker. Took the reading and behold. All spikes gone. See the attached image. This confirms that the material can absorb. Also since the spike didn't go away when panel was half covering, it shows that the reflection is coming from ceiling further down (I think).
I had a pesky reflection that was bouncing off the ceiling, and then off the back wall to the MLP. When you have a multiple-surface reflection, you are no longer dealing with the first point of reflection, so do what Jim recommends--move the panel around until you find the source. It always feels good when you narrow down a reflection, doesn't it?

Don't forget the back wall. The ceiling and back wall treatments provided the most improvement for me, with the side wall treatments only producing marginal improvement.
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post #12933 of 12947 Old Yesterday, 12:24 PM
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Originally Posted by GibsonES300 View Post
I've been working through this thread while trying to improve my room and system with REW and MiniDSP.

I would love some feedback about where I am so far.

Magnepan 1.7, DWM woofer, Rythmik F15HP

I appreciate any and all feedback.
Where you are depends on what your goals are.

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post #12934 of 12947 Old Yesterday, 12:24 PM
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Quote:
Originally Posted by GibsonES300 View Post
I've been working through this thread while trying to improve my room and system with REW and MiniDSP.

I would love some feedback about where I am so far.

Magnepan 1.7, DWM woofer, Rythmik F15HP

I appreciate any and all feedback.
Welcome to the thread. Looks quite good, as the d00d says. Nice work. Please describe how you are using the MiniDSP, i.e. what MiniDSP do you have, what channels it is used on, what plug-in you are using etc. I am interested because I just finished my own MiniDSP project to time-align four subs using a 2x4 box.
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post #12935 of 12947 Old Yesterday, 12:25 PM
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Shouldn't that go in the miniDSP thread?

Downloadable FREE demo discs:
http://www.avsforum.com/t/1475769/de...ently-authored 

Did you really need to quote that entire post in your reply?
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post #12936 of 12947 Old Yesterday, 12:36 PM
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The target curve was deliberate. It just sounds nice to me.

I'm using a 2x4 unbalanced MiniDSP. It's running the 2.1 plugin and handling the hand-off between the 1.7's and Rythmik. I've been pretty pleased with how it works. I may look into the new Dirac unit they're releasing to get these results on the rest of my channels. My only gripe with the 2x4 is the .9V limit on the output.

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post #12937 of 12947 Old Yesterday, 12:40 PM
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Quote:
Originally Posted by AustinJerry View Post
If you find the source of the reflection, but the treatment isn't effective enough to get it below -20dB, either get more effective treatments, or be happy with the way it is.
Which one is considered an effective material? Guide points out R-30 pink stuff. I don't assume they come in panels?
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post #12938 of 12947 Old Yesterday, 01:05 PM
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Originally Posted by SherazNJ View Post
Which one is considered an effective material? Guide points out R-30 pink stuff. I don't assume they come in panels?
I dont mean to present riddles, but what material is best depends on:

1) The space available
2) Down to what frequency your trying to absorb
3) The size of the surface

Pink Fluffy is best in the sense that it absorbs the lowest when there is enough available space (12"+).

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post #12939 of 12947 Old Yesterday, 01:28 PM
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Originally Posted by jim19611961 View Post
I dont mean to present riddles, but what material is best depends on:

1) The space available
2) Down to what frequency your trying to absorb
3) The size of the surface

Pink Fluffy is best in the sense that it absorbs the lowest when there is enough available space (12"+).
Thx for that. I was disputing in my mind weather the stuff I have is effective since I saw spikes going down but not much. Then at one point, it took out the whole spike (see image at 19.20m). So then it seems like that it is working. I just don't understand why I'd see some spikes reducing to only a few dbs (like 3-4db)????? I thought that its the material but then some spikes are completely gone below -20. I'm all confused about these materials Why would they take out small spike and now whole? Could it be also the angle wave is interacting with panel?
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post #12940 of 12947 Old Yesterday, 01:52 PM
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Quote:
Originally Posted by SherazNJ View Post
Thx for that. I was disputing in my mind weather the stuff I have is effective since I saw spikes going down but not much. Then at one point, it took out the whole spike (see image at 19.20m). So then it seems like that it is working. I just don't understand why I'd see some spikes reducing to only a few dbs (like 3-4db)????? I thought that its the material but then some spikes are completely gone below -20. I'm all confused about these materials Why would they take out small spike and now whole? Could it be also the angle wave is interacting with panel?
Dont confuse absorption with reflection. Using panels as per the blocking method inherantly has very high angles involved. Your panel, in such a case, is redirecting (reflecting) the sounds away from one place to another at least as much as its absorbing anything.

The other thing involved is that a panel on a wall is much further from the source than a blocking panel at the speaker. At the wall, the sound has had some time to spread out, requiring you cover a larger surface area for effectiveness, particularly as the frequency in question is lower.

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post #12941 of 12947 Old Yesterday, 03:36 PM
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Originally Posted by jim19611961 View Post
Dont confuse absorption with reflection. Using panels as per the blocking method inherantly has very high angles involved. Your panel, in such a case, is redirecting (reflecting) the sounds away from one place to another at least as much as its absorbing anything.

The other thing involved is that a panel on a wall is much further from the source than a blocking panel at the speaker. At the wall, the sound has had some time to spread out, requiring you cover a larger surface area for effectiveness, particularly as the frequency in question is lower.
Ah that makes a lot more sense now. Each time I was moving panels, I could see up/downs changing.

So guys, here is the before and After. I still couldn't get rid of reflection around 4-4/12 . What do you guys think?
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post #12942 of 12947 Old Yesterday, 04:39 PM
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Ah that makes a lot more sense now. Each time I was moving panels, I could see up/downs changing.

So guys, here is the before and After. I still couldn't get rid of reflection around 4-4/12 . What do you guys think?
Floor?

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post #12943 of 12947 Old Yesterday, 06:02 PM
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Floor?
I have basic carpet on floor. Will be putting blackest black carpet later. As of now no panels on floor but I did test by putting three panels off floor. I didn't cover area of center speaker from speaker to next 6 feet. May be that's causing it.

Another point I wanted to ask is how one can determine determine if too much reflection is absorbed? I have read in many places that we do want some reflection to keep room alive. So does that mean that we can leave some reflection above -20? Or it means to leave reflections below -20 and anything above is BADDDDDDD?
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post #12944 of 12947 Old Yesterday, 06:41 PM
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So when you tried the blocking technique, there was no direction that alleviated that massive early reflection? That is really nasty.
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post #12945 of 12947 Old Yesterday, 06:43 PM
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Originally Posted by SherazNJ View Post
I have basic carpet on floor. Will be putting blackest black carpet later. As of now no panels on floor but I did test by putting three panels off floor. I didn't cover area of center speaker from speaker to next 6 feet. May be that's causing it.

Another point I wanted to ask is how one can determine determine if too much reflection is absorbed? I have read in many places that we do want some reflection to keep room alive. So does that mean that we can leave some reflection above -20? Or it means to leave reflections below -20 and anything above is BADDDDDDD?
You may be over-thinking this. You need to identify the major reflections, find a treatment that eliminates the reflection, and then sit back and decide whether the room sounds better or not.
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post #12946 of 12947 Old Yesterday, 11:08 PM
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So when you tried the blocking technique, there was no direction that alleviated that massive early reflection? That is really nasty.
I watched "Into The Storm" today. What a great movie to test the system. I am very happy with how bass responded. Very good indeed. Can't say the same for speakers yet.

Jerry, when I covered center speaker from top by placing the panel on top of it, it eliminated every single reflection but covering ceiling is not helping so far. That's why I'm constantly questioning my material. Can someone please share a good material to use? Jim said that pink stuff (R-30) are good for low bass. What is an effective material I can use?
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post #12947 of 12947 Old Today, 03:15 AM
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Originally Posted by SherazNJ View Post
Another point I wanted to ask is how one can determine determine if too much reflection is absorbed? I have read in many places that we do want some reflection to keep room alive. So does that mean that we can leave some reflection above -20? Or it means to leave reflections below -20 and anything above is BADDDDDDD?
An ETC doesn't tell you what frequencies make up the reflection. Furthermore lower frequency reflections don't show up as sharp spikes so there's a mismatch in how high and low frequencies get represented in the graph. A spectrogram can give a better picture.

Anyway, probably more important is acoustical symmetry. Make sure first strong reflections from the left and right speaker arrive at the same time. This can remove a lot of ambiguous localization cues.

If this is fixed then I would move on to eliminating very early reflections <2ms. Plants, furniture, coffee tables, chairs with high backs, equipment racks between the speakers, floor reflection, etc.

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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