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Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 57

post #1681 of 2967
2/27/13 at 8:41am
I measured the left and right speaker with the subwoofer engaged. The mains are set to SMALL and crossed over at 100 Hz. I also bypassed the Anti-Mode device on the sub, a Hsu VTF MK-2, which is set to 25 Hz Max Extension mode.

The red line is the left speaker with 1/6 smoothing

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post #1682 of 2967
2/27/13 at 8:51am
[quote name="AustinJerry" url="/t/1449924/simplified-rew-

Is there anything in this discussion that needs to be added to the Guide?
[/quote]

Jerry, just a small corrrection needed on page 51, item #9. To access the Graph Axis LImits window, you must open the "Limits" button, not the "Freq Axis" button.
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post #1683 of 2967
2/27/13 at 9:02am
Quote:
Originally Posted by Pres2play View Post

Recalibrated the mic at 80 dBs and you were right. Here's the new reading...




Thanks. I'll test for the low frequency noise tonight using RTA, as you suggested. This would be helpful in the Guide.

 

Yes, that looks more reasonable.

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post #1684 of 2967
2/27/13 at 9:06am
Quote:
Originally Posted by Pres2play View Post

Jerry, just a small corrrection needed on page 51, item #9. To access the Graph Axis LImits window, you must open the "Limits" button, not the "Freq Axis" button.

 

Fixed, thanks for pointing this out.

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post #1685 of 2967
2/27/13 at 9:08am
I forgot to mention my room dimensions: 18.5' x 10.5 x 9 feet

My main seating area is against a wall and midway along the lenght of the room, which I am told is the worst spot in the room for sound.
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post #1686 of 2967
2/27/13 at 9:25am
Quote:
Originally Posted by Pres2play View Post

I forgot to mention my room dimensions: 18.5' x 10.5 x 9 feet

My main seating area is against a wall and midway along the lenght of the room, which I am told is the worst spot in the room for sound.

 

Anything against a wall places you in the peak of a room mode, which might account for the uneven response below 200Hz.  Without moving any furniture, you might experiment by taking several measurements at spots directly in front of your MLP, say at 1ft increments.  I recommend a left+right+sub(s) measurement, 15-300Hz, no smoothing.  The objective is to see if the sub response is any smoother further away from the wall.  If that is indeed the case, then you have a choice--rearrange the seating, or figure out how to address the issue by a different (more difficult) method.

 

Have you posted any room pics or a room layout?

 

 

You have a peak just above 100Hz, which coincides with the 108Hz 2nd mode of the room width.  To make this peak better, you would need to move the seating 2.5ft forward.  The other issues in your response curve could be associated with the placement of your front speakers, which a diagram would help in the analysis.

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post #1687 of 2967
2/27/13 at 9:29am
Quote:
Originally Posted by Pres2play View Post

I measured the left and right speaker with the subwoofer engaged. The mains are set to SMALL and crossed over at 100 Hz. I also bypassed the Anti-Mode device on the sub, a Hsu VTF MK-2, which is set to 25 Hz Max Extension mode.

The red line is the left speaker with 1/6 smoothing


What is the blue line? Do they both have 1/6 smoothing? How does it look with the Antimode?

You should post this graph with just the low frequencies (15-200hz) with no smoothing to analyze your LF response better.
Quote:
My main seating area is against a wall and midway along the lenght of the room, which I am told is the worst spot in the room for sound.

Horrible spot for you MLP. mad.gif Can you post a diagram and pics of your room?
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post #1688 of 2967
2/27/13 at 12:05pm
I'll post a room diagram tonight. There's a closet at the opposite end of the room that limits my seating arrangement.

The Axial Standing Waves chart is interesting. I don't fully understand harmonics, but having the chart and the graphs together should makes things a little clearer.

I'm hoping to have the left+right+center measurement tomorrow. But maybe I should hold off on that until I remove all the 2x4-feet sound panels from the walls.
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post #1689 of 2967
2/27/13 at 12:13pm
Quote:
Originally Posted by Alan P View Post

What is the blue line? Do they both have 1/6 smoothing? How does it look with the Antimode?

You should post this graph with just the low frequencies (15-200hz) with no smoothing to analyze your LF response better.
Horrible spot for you MLP. mad.gif Can you post a diagram and pics of your room?

The blue line is the right speaker. It's my first graph, so bare with me. And both curves have 1/6 smoothing.

I will definitely post a graph of the low frequencies, with and without Anti-Mode. I'm also curious (and anxious to buy a more powerful sub if I can learn to measure FR accurately)
Edited by Pres2play - 2/27/13 at 12:24pm
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post #1690 of 2967
2/27/13 at 12:25pm
Quote:
Originally Posted by Pres2play View Post


I'm hoping to have the left+right+center measurement tomorrow. But maybe I should hold off on that until I remove all the 2x4-feet sound panels from the walls.

 

I would hold off on making big changes until you have a better understanding of where the issue are.  IMO, your focus should be on the area under 200Hz.  The 2x4 sound panels affect higher frequencies, and are likely not influencing the lower frequencies at all.

 

Adding subs, however, is almost always a good idea.  Also keep in mind that if you have two subs, two identical subs always are better than mismatched subs.

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post #1691 of 2967
2/27/13 at 3:57pm
Quote:
Originally Posted by Pres2play View Post

I forgot to mention my room dimensions: 18.5' x 10.5 x 9 feet

My main seating area is against a wall and midway along the lenght of the room, which I am told is the worst spot in the room for sound.
When you say that your seating is along the "length" of the room, do you mean your couch is against one of the 18.5' walls?
Quote:
Originally Posted by Pres2play View Post

The Axial Standing Waves chart is interesting. I don't fully understand harmonics, but having the chart and the graphs together should makes things a little clearer.
For the moment, don't worry your room's length and height modes, since you don't have multiple rows and aren't using a riser. With all the listeners seated straight across and at the same height, look to solve problems with your room's width modes. This way, you'll be addressing the modes that cause seat to seat differences across your couch.

Yes, you'll still have height and length modes, but they should be the same in all seats (same distances from front wall, back wall and ceiling). If you can fix those too, nothing like it. But for the moment, if you can at least get consistent response (not great response) across your seating area, then the room correction system in your receiver will thank you.

If Audyssey sees the same peaks and dips in all seats, then it won't have to decide which problems to fix and which ones to leave alone (problems that don't show up in enough seats). Sometimes, placement alone can't solve all the modal issues. In that case (e.g., can't move couch away from back wall), the best you can hope to do (after treatments) is make things easier for electronic room correction to do its job.
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post #1692 of 2967
2/28/13 at 1:19am
Guys, here's a drawing and layout of the room. Sorry I forgot to provide distance to each speaker. I'll write that in later today.



Not in the drawing are the shelves surrounding the Sub and Left Surround speaker. It's a bit hard to see, but the Anti-Mode device is resting on top of the Hsu sub. On the left is the UMM-6 mic on a boom stand, and behind that is the Left Surround speaker resting on some books. Below the books are two budget subs currently not in use.



And here's the 55" Pio and front speakers. In this picture the mains are toed-in quite a bit. I thought it would help send early reflections into the two OC 705 panels behind the plasma, but that only deaden the sound so I straightened the speakers and removed the panels from that location. Sounds better without the panels there.



In this pic, the Left Surround is almost hidden by the couch. (I will have to fix that). A heavy curtain covers two windows facing the building courtyard. And, of course, you see two more sound panels above the shelves, which work really well up there.


Edited by Pres2play - 2/28/13 at 2:39am
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post #1693 of 2967
2/28/13 at 1:23am
Quote:
Originally Posted by AustinJerry View Post

I would hold off on making big changes until you have a better understanding of where the issue are.  IMO, your focus should be on the area under 200Hz.  The 2x4 sound panels affect higher frequencies, and are likely not influencing the lower frequencies at all.

Adding subs, however, is almost always a good idea.  Also keep in mind that if you have two subs, two identical subs always are better than mismatched subs.

I agree, no big changes just yet. I need to spend a week or two making measurements and learning REW. I think even two subs would not help me if I don't know where to place them.
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post #1694 of 2967
2/28/13 at 2:07am
Quote:
Originally Posted by sdurani View Post

When you say that your seating is along the "length" of the room, do you mean your couch is against one of the 18.5' walls?
For the moment, don't worry your room's length and height modes, since you don't have multiple rows and aren't using a riser. With all the listeners seated straight across and at the same height, look to solve problems with your room's width modes. This way, you'll be addressing the modes that cause seat to seat differences across your couch.

Yes, you'll still have height and length modes, but they should be the same in all seats (same distances from front wall, back wall and ceiling). If you can fix those too, nothing like it. But for the moment, if you can at least get consistent response (not great response) across your seating area, then the room correction system in your receiver will thank you.

If Audyssey sees the same peaks and dips in all seats, then it won't have to decide which problems to fix and which ones to leave alone (problems that don't show up in enough seats). Sometimes, placement alone can't solve all the modal issues. In that case (e.g., can't move couch away from back wall), the best you can hope to do (after treatments) is make things easier for electronic room correction to do its job.

That's correct, the main couch is against one of the 18.5' walls. I'ld like to keep it where it is, so the family won't have to navigate around it to go to the closet.

Thanks for your advice. So you're saying I should work with width modes first. How do I do that exactly, without Audyssey for now.
Edited by Pres2play - 2/28/13 at 2:43am
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post #1695 of 2967
2/28/13 at 5:38am
Quote:
Originally Posted by Pres2play View Post


I agree, no big changes just yet. I need to spend a week or two making measurements and learning REW. I think even two subs would not help me if I don't know where to place them.

 

That is a wise approach.  Placement is extremely important, not only for the subs, but for all the speakers.  And the way to find the best placement is by measuring, which is why we are honing our REW skills.

 

Your listing room is not without its challenges, but there are always things to do that will result in improvement.

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post #1696 of 2967
2/28/13 at 5:43am
Quote:
Originally Posted by Pres2play View Post


That's correct, the main couch is against one of the 18.5' walls. I'ld like to keep it where it is, so the family won't have to navigate around it to go to the closet.

 

 

I can see that moving the couch forward in a small room would have its challenges.  However, in the interest of understanding the sonic characteristics of the room, you should at least measure several spots further out into the room just to see how the response changes.  Once you have this knowledge, you will understand your choices better.  There are few listening rooms that don't involve trade-offs among aesthetics, convenience, and best sound.

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post #1697 of 2967
2/28/13 at 6:27am
Quote:
Originally Posted by Pres2play View Post

I think even two subs would not help me if I don't know where to place them.
Quote:
Originally Posted by AustinJerry View Post

That is a wise approach.  Placement is extremely important, not only for the subs, but for all the speakers.  And the way to find the best placement is by measuring, which is why we are honing our REW skills.

Hi Pres2play, instead of moving the sub around I find it easier to place the sub at the MLP (and rise it as well close to ear level) and move the mic around the room.
Quote:
Originally Posted by AustinJerry View Post

I can see that moving the couch forward in a small room would have its challenges.  However, in the interest of understanding the sonic characteristics of the room, you should at least measure several spots further out into the room just to see how the response changes.  Once you have this knowledge, you will understand your choices better.  There are few listening rooms that don't involve trade-offs among aesthetics, convenience, and best sound.

Hi Jerry, can Pres2play get the same result by moving the main speakers further back instead of moving the couch forward?
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post #1698 of 2967
2/28/13 at 9:13am
Quote:
Originally Posted by Pres2play View Post

So you're saying I should work with width modes first.
Yes. IF you can't use placement to address all the peaks & dips, then your next best bet is to make those peaks & dips the same across the seating area, making it easier for your receiver's room correction system to improve the response at all seats.
Quote:
Originally Posted by Pres2play View Post

How do I do that exactly, without Audyssey for now.
This doesn't just apply to Audyssey, it will be useful no matter which room correction system you have (MCACC, YPAO).

There are several things you can try, measuring each to see what works best in your room. Try moving your single subwoofer to the midpoint of room width, either behind your TV stand or behind the couch. If you get another sub, then you can try placing them at the quarter points of room width (4' 7.5" from the side walls). And if all else fails, you can always resort to nearfield bass (place a sub on either side of your couch), the idea being to hear less of your room and more of your subs. You can further help minimize width modes by placing your L/R speakers 37" in from the side walls.

On a separate note, I would move the surround speakers to the back tri-corners of the room (where the back corner meets the ceiling). This will help make the surround field a little more diffuse and ambient, while still maintaining clear left-vs-right surround separation.
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post #1699 of 2967
2/28/13 at 9:48am
Quote:
Originally Posted by AustinJerry View Post

That is a wise approach.  Placement is extremely important, not only for the subs, but for all the speakers.  And the way to find the best placement is by measuring, which is why we are honing our REW skills.

Your listing room is not without its challenges, but there are always things to do that will result in improvement.

Thank you, Jerry.
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post #1700 of 2967
2/28/13 at 9:53am
Quote:
Originally Posted by AustinJerry View Post

I can see that moving the couch forward in a small room would have its challenges.  However, in the interest of understanding the sonic characteristics of the room, you should at least measure several spots further out into the room just to see how the response changes.  Once you have this knowledge, you will understand your choices better.  There are few listening rooms that don't involve trade-offs among aesthetics, convenience, and best sound.

Yes, absolutely makes sense. Even if I select a spot where the sound gets worse, I am learning the best placement, which has been basically my only method up till now. REW should really help going forward. Lots of measurements to make with couch moved around.
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post #1701 of 2967
2/28/13 at 10:10am
Quote:
Originally Posted by JChin View Post


Hi Pres2play, instead of moving the sub around I find it easier to place the sub at the MLP (and rise it as well close to ear level) and move the mic around the room.
Hi Jerry, can Pres2play get the same result by moving the main speakers further back instead of moving the couch forward?

That's not a bad idea, move the couch temporarily and place the sub in that spot. If I find a way to stabilize the box at different heights, I will give it a go.

The mains are about a foot from the wall. That keeps them well in front of the plasma screen to help reduce sound reflection. But hey, no harm in trying. I'll add it to my "to-do" list. Good stuff JChin.
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post #1702 of 2967
2/28/13 at 10:22am
Quote:
Originally Posted by Pres2play View Post

Quote:
Originally Posted by AustinJerry View Post

I can see that moving the couch forward in a small room would have its challenges.  However, in the interest of understanding the sonic characteristics of the room, you should at least measure several spots further out into the room just to see how the response changes.  Once you have this knowledge, you will understand your choices better.  There are few listening rooms that don't involve trade-offs among aesthetics, convenience, and best sound.

Yes, absolutely makes sense. Even if I select a spot where the sound gets worse, I am learning the best placement, which has been basically my only method up till now. REW should really help going forward. Lots of measurements to make with couch moved around.

 

FWIW, I wouldn't get too carried away with moving a bunch of furniture around for FR below 200Hz.  I know some may disagree with this but when I did my sub crawl, I found little to no change in the FR regardless of how furniture was positioned in the room relative to the mic position (e.g. I even checked with the mic placed directly behind a couch as opposed to having the couch completely removed from the room).  At this stage, you are looking for directionally correct changes so until you find the best alternative location, I wouldn't knock yourself out moving everything around! wink.gif

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post #1703 of 2967
2/28/13 at 10:37am
Quote:
Originally Posted by sdurani View Post

Yes. IF you can't use placement to address all the peaks & dips, then your next best bet is to make those peaks & dips the same across the seating area, making it easier for your receiver's room correction system to improve the response at all seats.
This doesn't just apply to Audyssey, it will be useful no matter which room correction system you have (MCACC, YPAO).

There are several things you can try, measuring each to see what works best in your room. Try moving your single subwoofer to the midpoint of room width, either behind your TV stand or behind the couch. If you get another sub, then you can try placing them at the quarter points of room width (4' 7.5" from the side walls). And if all else fails, you can always resort to nearfield bass (place a sub on either side of your couch), the idea being to hear less of your room and more of your subs. You can further help minimize width modes by placing your L/R speakers 37" in from the side walls.

On a separate note, I would move the surround speakers to the back tri-corners of the room (where the back corner meets the ceiling). This will help make the surround field a little more diffuse and ambient, while still maintaining clear left-vs-right surround separation.

Hi, Sdurani. My system does not have room correction and I don't want to bypasss the DACs on my new Oppo player just yet. I will try the different placement you suggested, and if can find proper hardware for mounting my book shelves in the corners I will try that too. (It might be easier to replace the surrounds with speakers that are wall mountable).
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post #1704 of 2967
2/28/13 at 11:52am
Quote:
Originally Posted by jkasanic View Post

FWIW, I wouldn't get too carried away with moving a bunch of furniture around for FR below 200Hz.  I know some may disagree with this but when I did my sub crawl, I found little to no change in the FR regardless of how furniture was positioned in the room relative to the mic position (e.g. I even checked with the mic placed directly behind a couch as opposed to having the couch completely removed from the room).  At this stage, you are looking for directionally correct changes so until you find the best alternative location, I wouldn't knock yourself out moving everything around! wink.gif

I'll try the mic in a bunch of locations first. Thanks.
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post #1705 of 2967
3/1/13 at 1:44am
Quote:
Originally Posted by AustinJerry View Post

Anything against a wall places you in the peak of a room mode, which might account for the uneven response below 200Hz.  Without moving any furniture, you might experiment by taking several measurements at spots directly in front of your MLP, say at 1ft increments.  I recommend a left+right+sub(s) measurement, 15-300Hz, no smoothing.  The objective is to see if the sub response is any smoother further away from the wall.  If that is indeed the case, then you have a choice--rearrange the seating, or figure out how to address the issue by a different (more difficult) method.

Have you posted any room pics or a room layout?




You have a peak just above 100Hz, which coincides with the 108Hz 2nd mode of the room width.  To make this peak better, you would need to move the seating 2.5ft forward.  The other issues in your response curve could be associated with the placement of your front speakers, which a diagram would help in the analysis.

Let me see if I can read the Axial Standing Wave chart correctly. I can move the seating forward 2.5 feet, OR 7.5 feet to reduce the peak? Is that what the chart is telling me?

Also I extended the chart by a few multiples. Would I be correct in assuming that the circled frequencies will be reinforced by the room, more so than the others?



Edited by Pres2play - 3/1/13 at 2:12am
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post #1706 of 2967
3/1/13 at 7:45am
Pres, just to clarify, the length of the room is usually entered, and referred to as the dimension from the screen to the back wall. I'm getting a little mixed up when I read the posts in terms of length and width. I think you are saying that the main listening position is against the back wall at the midpoint and that back wall has a dimension of 18.5'. That would mean the width of your room is 18.5', not 10.5'. Is that correct?
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post #1707 of 2967
3/1/13 at 7:48am
Quote:
Originally Posted by Pres2play View Post


Let me see if I can read the Axial Standing Wave chart correctly. I can move the seating forward 2.5 feet, OR 7.5 feet to reduce the peak? Is that what the chart is telling me?

Also I extended the chart by a few multiples. Would I be correct in assuming that the circled frequencies will be reinforced by the room, more so than the others?


 

Not Pres, but that is correct.  I don't see what difference it makes.

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post #1708 of 2967
3/1/13 at 8:02am



It doesn't really make a difference. I was just trying to follow the recommendations of moving forward 2.5' to get into the 108 Hz null and saw in the width part of the Axial Standing Waves chart. It just took me a couple of double checks of looking at the sketch and the chart to follow. There are some references to focusing in on width modes and that's where I had trouble following.
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post #1709 of 2967
3/1/13 at 8:07am
Quote:
Originally Posted by Pres2play View Post


Let me see if I can read the Axial Standing Wave chart correctly. I can move the seating forward 2.5 feet, OR 7.5 feet to reduce the peak? Is that what the chart is telling me?

 

 

If you examine a specific standing wave, then the standing wave is at its maximum SPL at the top of the arc, and at its minimum SPL at the bottom of the arc.  So, for example, look at the primary standing wave of the 18.5' wall, which is 31Hz.  If you sit in the center of your couch, then you will be sitting in a null WRT the 31Hz mode, i.e. you should not be able to hear a 31Hz tone.  However, at this same sitting position, you are at a peak of the standing waves for the 10.5' wall, so you would hear 54Hz, 108Hz, 163Hz, 217Hz, etc. emphasized at this position.  With the couch against the back wall, sitting in the center spot would not be very good.

 

There are two ways to use the standing wave model to produce smoother results.  First method is speaker placement.  If you place a speaker in a standing wave null, then you excite that null and reduce its effect.  So, for your two front speakers, placing them at the 1/4 and 3/4 dimensions of the 18.5' wall, i.e. at 4.5' and 13.5' would help the 61Hz mode.  And placing the same speakers 1.25' in front of the wall would help the 217Hz mode, placing them 1.75' in front of the wall would help the 163Hz mode, and placing them 2.5' in front of the wall would help the 108Hz mode.  You need to look at your overall frequency response measurements to decide if any of these placements address response issues, and then decide if you can live with moving the speakers.

 

For a single sub, the model suggests placing it in the middle of the front wall, which would help the 31Hz mode.

 

Placement to address modes associated with the ceiling height are more difficult.

 

The next thing you can do is to sit in a spot that minimizes room mode effects.  Sitting in the center of the couch is usually best for imaging, but be aware that you would be sitting in a 31Hz null.  Moving the couch away from the wall would likely improve sound significantly, with 1.25', 1.75', and 2.5 ft being the three distances to try.  I would simply measure these three distances first to see what improvement you might expect.

 

Does this make sense?

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post #1710 of 2967
3/1/13 at 8:36am
I would love to use that standing wave software, but I don't know where to begin.

This is a VERY rough floor plan I put together with paint. It's not to scale, but I think it illustrates the issues I have reasonably well:



Basically, the purple bits are my speakers, the yellow bits are where we sit, and you can see how open things are. Is my best bet to run the software multiple times, once for the width where it's open to the dining room, one where it's restricted by the wall? Similarly for the length, should I do a run including the stub wall, and another using the wall on the near side of the stairs, and perhaps a third using the other stairway wall? I guess I'm subject to more modes this way than in a simple rectangular room?
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