Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 85 - AVS Forum
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Old 04-10-2013, 02:10 PM
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Quote:
Originally Posted by Pres2play View Post

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Originally Posted by sdurani View Post

For those who have JavaScript enabled, see animated gif below.

Radiation pattern of a typical loudspeaker.



Keep an eye on the changing frequency and compare it to the directivity balloon.

Easy to spot which direction is the front of the speaker, since the directivity in that direction doesn't change.

Can you explain exactly what we're seeing?

 

What he said!
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Old 04-10-2013, 03:24 PM
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Quote:
Originally Posted by Pres2play View Post

Can you explain exactly what we're seeing?
If you were to surround a loudspeaker with a sphere of tiny microphones, you could measure how loud the speaker was in every direction simultaneously, trying test tones at various frequencies: 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz, etc.

The graph is that sphere, with volume level being shown as distance from centre. The further out the pink data points, the louder the speaker is in that direction; the outer edge of the sphere being the loudest the speaker can go.

As the frequency goes up (listed in the top box of the graphic), the speaker becomes more directional. The lower the frequency goes, the more omni-directional the speaker becomes. The increase in directionality isn't because the speaker gets louder in the front, but instead because it gets quieter in every other direction.

Notice that when you are on-axis to the speaker (front of the sphere in the graph), the volume doesn't go down as frequency rises. But if you are off-axis (above, below, behind, to the side), the speaker becomes quieter. In the low frequencies, it is like a lantern. At the higher frequencies, it is like a flashlight.

The reason I posted it was to show that even when a speaker is pointed away from a wall, there can still be enough sound radiating from behind the speaker to cause a boundry cancellation.
Saril likes this.

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Old 04-10-2013, 03:25 PM
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Quote:
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Originally Posted by kbarnes701 View Post



 

 

EDIT again: thinking some more about this, when I am outside in a huge open space or field, as I am every day, if someone is standing in front of me, with their back turned towards me, and they speak, I can still hear them. Not as clearly of course, but I can definitely still hear them.

 

Are you sure it isn't just sound coming out the port in the rear?   eek.gif

ROTFLMAO :)  Brilliant!!

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Old 04-10-2013, 06:07 PM
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Quote:
Originally Posted by Pres2play View Post

Hi. The problem has been there from the beginning. I guess I only noticed it now thanks to my growing familiarity with REW.

No one has answered my post about the HDMI input on the Oppo player. I may have to resort to pulling out my receiver to see if it's the player, the laptop or REW setup.

hello
Could it be something with the trigger level on the sub when set to automatic?
When sending a LFE signal, the management in the Oppo should add 10dB, so signal is stronger than a redirected signal to the main. Maybe in case of the direct LFE, the sub triggers and with the redirected main speaker, it does not.
I use the front HDMI on an Oppo BDP-103, but connect it to an AVR with HDMI. So I do not use the signal management in the Oppo.
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Old 04-11-2013, 01:42 AM
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Hey, thanks. I switched out the OPPO and used my Yamaha AVR to make the measurements. Sadly, it looks like the OPPO is not handling bass management through the HDMI input. I'm still wating to see if someone in the OPPO thread can verify this. Unless you have the HDMI output also hooked up in the OPPO, the way you have it, I would not use the OPPO the way it is, with the analog output, to run REW.

Here's a new graph with the laptop connected to the Yamaha. It looks much better now. I still get some high peaks when I measure the sub separately so you may have a point about the LFE channel. Something to look into.

This curve looks way too smooth. I'll have to double-check the smoothing.


OLED Display: Samsung S9C
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Old 04-11-2013, 06:50 AM
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^^^Can you click the legend in your pics so we can see the smoothing (assuming it's 1/6 above) and which channel(s) are included?  Be sure to put something descriptive in the measurement title so it shows up in the legend.  The whole LFE channel thing seems to be overcomplicating your bass measurements.  Could you just take a measurement of the L or R channel with the speaker unplugged?  Then you'll just be left with your redirected bass response.  Getting the sub location as right as it can be in your room should be your first priority.

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Old 04-11-2013, 06:51 AM
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That certainly looks a lot better, and is more of what I expected in the low end.  I agree it does look quite smooth, especially since you are not running any EQ.  I will be interesting to see if you get a useful answer back from the Oppo forum.

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Old 04-11-2013, 06:33 PM
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A question for you guys. Do i run audyssey to get the distance first then turn it off to measure or do I factory reset the avr to measure. If I factory rest , I would have to add distance. I have three PSA xv15s. I plan to work on my bass first. My receiver is onkyo 709.

Thanks

Dan
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Old 04-11-2013, 06:58 PM
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Jerry, the image below (which I've posted on the 105 thread) shows that the Oppo is receiving 5.1 LPCM signal from my laptop, so we know the laptop settings are okay.



As you know, Bob P. verified that bass management is working in the Oppo. To test it again for myself, I measured the left speaker with the subwoofer turned OFF (red). Then I measured the left speaker with the power amp turned OFF and sub ON (green). Finally, I measured the left speaker with the amp and subwoofer ON (purple), which I've offset for clarity and comparison. All have 1/6 smoothing, and 100 Hz crossover.



It appears bass management is, indeed, functioning correctly; the red and green traces together match the purple curve above. The issue I was having, was trying to measure the left speaker and sub response separately. Instead of using the method above, I was making measurements using output 1 with output 4 in the timing reference box. As Turboman indicated, selecting output 4 may trigger the LFE channel. What do you think?

Also, the graph shows a good dip at 30 Hz, which I hope I can fix with multiple subs. I think this a very fair and accurate FR for my room. I can work from here to make improvements.

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Old 04-11-2013, 07:24 PM
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Quote:
Originally Posted by Pres2play View Post

Jerry, the image below (which I've posted on the 105 thread) shows that the Oppo is receiving 5.1 LPCM signal from my laptop, so we know the laptop settings are okay.



As you know, Bob P. verified that bass management is working in the Oppo. To test it again for myself, I measured the left speaker with the subwoofer turned OFF (red). Then I measured the left speaker with the power amp turned OFF and sub ON (green). Finally, I measured the left speaker with the amp and subwoofer ON (purple), which I've offset for clarity and comparison. All have 1/6 smoothing, and 100 Hz crossover.



It appears bass management is, indeed, functioning correctly; the red and green traces together match the purple curve above. The issue I was having, was trying to measure the left speaker and sub response separately. Instead of using the method above, I was making measurements using output 1 with output 4 in the timing reference box. As Turboman indicated, selecting output 4 may trigger the LFE channel. What do you think?

Also, the graph shows a good dip at 30 Hz, which I hope I can fix with multiple subs. I think this a very fair and accurate FR for my room. I can work from here to make improvements.

I think everything looks fine. However, I still think your overall sound quality would be improved, and the setup would be simplified, if you were using an AVR with room correction (like Audyssey), rather than using the Oppo as a pre-pro. Just my opinion.
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Old 04-11-2013, 07:30 PM
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Originally Posted by mp5475 View Post

A question for you guys. Do i run audyssey to get the distance first then turn it off to measure or do I factory reset the avr to measure. If I factory rest , I would have to add distance. I have three PSA xv15s. I plan to work on my bass first. My receiver is onkyo 709.

Thanks

Dan

No need to do a factory reset. Once you have run Audyssey, your speaker distances and trims will be set. If your objective is to measure the overall audio quality in your listening room, then measure with Audyssey turned on. If the measurements indicate that there are issues to be addressed, then post the measurements here and you will receive all sorts of feedback and suggestions.

When you post your results, make sure you include some details about your setup, e.g. the type of equipment you have, a brief description of your listening room, including pictures if possible, etc.
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Old 04-11-2013, 07:47 PM
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Will do. Thx. Hope my mic works.
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Old 04-12-2013, 06:23 AM
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Quote:
Originally Posted by Pres2play View Post


It appears bass management is, indeed, functioning correctly; the red and green traces together match the purple curve above. The issue I was having, was trying to measure the left speaker and sub response separately. Instead of using the method above, I was making measurements using output 1 with output 4 in the timing reference box. As Turboman indicated, selecting output 4 may trigger the LFE channel. What do you think?
 

You do not need anything in the timing reference box at all when measuring the combined speakers plus sub. Bass management will cause the sub to play. IOW, if you have L or R or C speaker selected, then the timing reference box needs to be empty. This will then give you whichever speaker you have selected plus the redirected bass. If you want to test the speakers without the sub, then physically disconnect the sub or switch it off. If you want to test the sub alone, select Output 4 (and again with the timing ref box blank). 

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Old 04-12-2013, 07:38 AM
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Question. I plan to run the REW tonight. I am going to work on the subs first. I gain matched them few days ago. I have three PSA xv15s

Since I am trying to optimized their locations first, do I run one first with the other two off? Then look at the FR, then add the other subs see what it does? And move them around? Or just run all three and see what the FR looks like?

After I have optimized the sub locations, I was going to run right, left, center with subs to see what the cross over looked like. It's currently at 80
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Old 04-12-2013, 09:17 AM
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Measure with all 3 subs ON - it's the interaction you want to optimize. Move the subs around until you get the smoothest response.

Measure the sub + either FL or FR, not both FL/R.

AVR: DENON 2113ci
FL/R: Klipschorn
CC: Klipsch RC64ii
SUR: Polk LS F/X x 4
SUB: PSA XS15 x 4 (Soon to be replaced with dual T-18s!)
DISP: Mitsubishi WD-73740
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Old 04-12-2013, 09:21 AM
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Also, make sure you run (at least the first mic position of) Audyssey first to confirm that your sub levels are in the acceptable range (+/-3db).

AVR: DENON 2113ci
FL/R: Klipschorn
CC: Klipsch RC64ii
SUR: Polk LS F/X x 4
SUB: PSA XS15 x 4 (Soon to be replaced with dual T-18s!)
DISP: Mitsubishi WD-73740
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Old 04-13-2013, 01:17 PM
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Hi guys.

after epic 8 hrs of moving three 70 pound subs around, i wanted to shoot someone. I hit a wall and want to see if you guys can help me out



room: L shaped. See pics

front wall width: 20 ft 6 inches,
main seating width: 15 feet,
length: 19 feet and 2 inches
height: 9 feet and 6






My gear: Axiom epic 80, AVR onkyo 709, PSA xv 15x3

running 7.3

have two GIK monster bass traps. ignore those panels. they are 1 inch fiberglass. from what i read, they are worthless. plan to get broadband panels after this.
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Old 04-13-2013, 01:35 PM
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Here is my findings:


for subs(red) and sub FR FL(green)

This is best I could do with the subs. Cant smooth out that dip at 37 no matter what i try to do. the cross over is at 120 fronts, which was the best. Keep the audyssey distance of 10.5, which was the best



waterfall for sub




The dip at 37 must be room mode but cant be width or the length. maybe height? i even tried to stack two subs, didnt help.


i need some major bass traps according to the waterfall
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Old 04-13-2013, 01:39 PM
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how do i attach the mdat file. its says its not allowed
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Old 04-13-2013, 01:47 PM
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15 to 20000hz





impulse

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Old 04-13-2013, 03:17 PM
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Quote:
Originally Posted by mp5475 View Post

how do i attach the mdat file. its says its not allowed

You'll have to use a service like Dropbox or Yousendit to post a link.
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Old 04-13-2013, 03:53 PM
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Quote:
Originally Posted by mp5475 View Post

Question. I plan to run the REW tonight. I am going to work on the subs first. I gain matched them few days ago. I have three PSA xv15s

Since I am trying to optimized their locations first, do I run one first with the other two off? Then look at the FR, then add the other subs see what it does? And move them around? Or just run all three and see what the FR looks like?

After I have optimized the sub locations, I was going to run right, left, center with subs to see what the cross over looked like. It's currently at 80

 

@MP5475

 

 

- The room mode calculator doesn’t show any modes at 37Hz, although the model’s usefulness is suspect with an odd-shaped room (i.e. not rectangular).

 

- To make the graphs easier for us to read, change the vertical scale to something like 40-100dB, such that the labels on the left are in increments of 5dB.  This also makes the graph look a little better.  Remember to include a note in the graph title with regards to what is being measured (e.g. Left front + subs).  The legend at the bottom is too small to read.

 

- You don’t say where you ended up placing the subs.  The room pictures, while useful, don’t give us enough information.  I suggest you draw up a quick floor plan showing where your speakers are placed, where the seating is, and what the wall dimensions are.  Here is an example (doesn’t need to be this detailed):

 

 

 

 

- The waterfall isn’t too bad.  You show 300ms and 600ms, but we have agreed here to use 450ms to post measurement.

- The ETC graph shows a lot of reflections, typical of a room with few treatments.

- As Jkasanic recommends, set up an account on a file-sharing site like http://www.dropbox.com, upload the MDAT file, and post the link.

 

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Old 04-13-2013, 05:29 PM
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A 37 Hz mode implies something that's a multiple of about 7.6' (1/4-wave). What are the dimensions of the L? As AustinJerry said, a dimensioned room drawing would help, although that is almost certainly some sort of room mode (cancellation).

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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Old 04-13-2013, 05:52 PM
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Something wrong with REW on mac. Cant do capture anymore even though i did this afternoon. i screen captured

Here is redone SPL and waterfall

Blue line: sub FR FL Red: Sub




Will work on the room diagram
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Old 04-13-2013, 05:56 PM
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Old 04-13-2013, 06:01 PM
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Sub water fall following the guide

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Old 04-13-2013, 06:08 PM
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Quote:
Originally Posted by mp5475 View Post

how do i attach the mdat file. its says its not allowed

You can compress it:

 

 

lastbutnotleast.mdat.zip 1,922k .zip file

 

 

 

or just add .txt to the filename and tell everyone to remove it:

 

 

lastbutnotleast.mdat.txt 2,773k .txt file

 

 

 

or use DropBox. smile.gif

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Old 04-13-2013, 06:15 PM
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room layout.

sorry for crappy drawing




i tried put a sub front left but it worsened the 37 dip and created a nasty dip at 70

tried to place sub along the entire front wall but anything to the left was really bad.
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Old 04-13-2013, 06:18 PM
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Quote:
Originally Posted by LastButNotLeast View Post

You can compress it:


lastbutnotleast.mdat.zip 1922k .zip file



or just add .txt to the filename and tell everyone to remove it:


lastbutnotleast.mdat.txt 2773k .txt file



or use DropBox. smile.gif


good idea
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Old 04-13-2013, 06:43 PM
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Quote:
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@MP5475




- The room mode calculator doesn’t show any modes at 37Hz, although the model’s usefulness is suspect with an odd-shaped room (i.e. not rectangular).
Can you try the mode calculator again, but with 15 feet as the width?

Sanjay
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