Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 178 - AVS Forum
Forum Jump: 
 9Likes
Reply
 
Thread Tools
post #5311 of 10745 Old 10-15-2013, 11:05 AM
AVS Special Member
 
jkasanic's Avatar
 
Join Date: Dec 2006
Posts: 1,135
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Liked: 57

Keith's waterfall is shown with the default settings in REW with the exception of the time range extended to 450ms (from 300ms):

 

 

The noise floor has traditionally been approx. 40dB with "legacy" REW kits but we've found with the USB mics that people are seeing anywhere from 50-55dB in a "quiet" room.  For this reason, we've tried to increase the dB of the measurements to at least 30dB above the noise floor (so closer to 85dB measurements) as well as adjust the noise floor up to the minimum threshold reported by USB mic users (50 dB).  As a compromise (and knowing Keith, also to dispel any concerns about an even better looking waterfall being the result of using a higher noise floor) when presenting his graphs, Keith has elected to show down to 45dB instead of what he actually measures (which I believe is closer to 50dB with his UMM-6).  This gives the appearance of presenting his waterfall in a more conservative light than using 50dB as the noise floor.  My last RTA actually showed closer to 56 dB as my noise floor!

 

The only other presentation difference I can think of could be related to the width of the image capture or the preview size used to display it in the forum.  I always use 900px as the capture width (I think 871 is the default) and I preview my waterfalls with the 500x1000px large option.  If you instead use a url address to present photos (instead of uploading them directly) then I'm not sure if you're presented with the same preview sizes or not which might explain why some users have larger previews than others.

 

EDIT:  Remember that Keith's graph is unsmoothed but after EQ and his room is heavily treated so you'd really want to see his response/waterfall prior to any room treatments or EQ to see the benefits each is having on his response and decay times.  It actually looks to me to be more like 83-92 dB range (peak between 55-60Hz and null around 250Hz?) from 15-300Hz for a +/- closer to 4.5.

jkasanic is offline  
Sponsored Links
Advertisement
 
post #5312 of 10745 Old 10-15-2013, 11:42 AM
Advanced Member
 
bao01's Avatar
 
Join Date: Dec 2012
Posts: 649
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 24
The guide shows 0, 90, 150 for X, Y, Z. I followed the guide.

It can't be +/- 4.5 dB because it's greater than 2 lines (each line is 5). It is at least 12, maybe 13 or 14 between peak and valley.

B&W 802 Diamond mains, B&W HTM2 Diamond center, B&W 804 Diamond surrounds, Parasound HALO A 51, Krell KAV-300i , Integra DHC-80.3 pre-pro, two JL Audio Fathom f113 subs, Panasonic TC-P65VT50 65" plasma
bao01 is offline  
post #5313 of 10745 Old 10-15-2013, 11:53 AM
AVS Addicted Member
 
kbarnes701's Avatar
 
Join Date: Jan 2008
Location: Main Listening Positon
Posts: 16,546
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 515 Post(s)
Liked: 1239
Quote:
Originally Posted by jkasanic View Post
 

Keith's waterfall is shown with the default settings in REW with the exception of the time range extended to 450ms (from 300ms):

 

 

The noise floor has traditionally been approx. 40dB with "legacy" REW kits but we've found with the USB mics that people are seeing anywhere from 50-55dB in a "quiet" room.  For this reason, we've tried to increase the dB of the measurements to at least 30dB above the noise floor (so closer to 85dB measurements) as well as adjust the noise floor up to the minimum threshold reported by USB mic users (50 dB).  As a compromise (and knowing Keith, also to dispel any concerns about an even better looking waterfall being the result of using a higher noise floor) when presenting his graphs, Keith has elected to show down to 45dB instead of what he actually measures (which I believe is closer to 50dB with his UMM-6).  This gives the appearance of presenting his waterfall in a more conservative light than using 50dB as the noise floor.  My last RTA actually showed closer to 56 dB as my noise floor!

 

The only other presentation difference I can think of could be related to the width of the image capture or the preview size used to display it in the forum.  I always use 900px as the capture width (I think 871 is the default) and I preview my waterfalls with the 500x1000px large option.  If you instead use a url address to present photos (instead of uploading them directly) then I'm not sure if you're presented with the same preview sizes or not which might explain why some users have larger previews than others.

 

EDIT:  Remember that Keith's graph is unsmoothed but after EQ.  It actually looks to me to be more like 83-92 dB range (peak between 55-60Hz and null around 250Hz?) from 15-300Hz for a +/- closer to 4.5.

 

All correct. Noise floor of 45dB 'cosmeticises' the graph a little less. I’d say +/-4.5dB was closer to the mark too. also note that the bottom goes to 15Hz on the graph - really we should ignore the stuff below 20Hz. This ties in with my approx +/-3dB across the full spectrum, 1/6th smoothed.  Here is the same info but with a 50dB floor: (this is 450ms)

 

 

 

Looks better now doesn't it? :)

 

And here it is with a 55dB floor and 300ms:

 

 

So you pays your money and takes your choice :)

 

TBH, we can barely hear frequencies below 20Hz anyway, so when they are 35dB down, I cease to worry about them. I've given up obsessing over trying to get 'perfect' looking graphs and these days am concentrating on issues I can actually hear!  I think it is easy to get carried away and to start looking at graphs as though they are an end in themselves.

kbarnes701 is online now  
post #5314 of 10745 Old 10-15-2013, 11:54 AM
AVS Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 4,725
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 307 Post(s)
Liked: 176
Quote:
Originally Posted by bao01 View Post

The guide shows 0, 90, 150 for X, Y, Z. I followed the guide.

It can't be +/- 4.5 dB because it's greater than 2 lines (each line is 5). It is at least 12, maybe 13 or 14 between peak and valley.

Don't get hung up on details. More important is the bigger picture. Looking at the frequency response of a single point in space is just one piece of the puzzle.

Important for good low frequency reproduction is low point-to-point variance, minimum phase behavior, low modal ringing and smooth frequency response. Obsessing about one single criteria doesn't result in good sound.

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
markus767 is online now  
post #5315 of 10745 Old 10-15-2013, 11:55 AM
AVS Special Member
 
jkasanic's Avatar
 
Join Date: Dec 2006
Posts: 1,135
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Liked: 57
Quote:
Originally Posted by bao01 View Post

The guide shows 0, 90, 150 for X, Y, Z. I followed the guide.

It can't be +/- 4.5 dB because it's greater than 2 lines (each line is 5). It is at least 12, maybe 13 or 14 between peak and valley.

 

Sorry, the lower limit is closer to 78 dB (not 83 dB as I posted earlier).  As for the other discrepancies, I'm guessing Jerry made some revisions to the guide that were not noted in the thread as we were going along.  For those of us that have been here since the beginning (sounds ominous and makes me feel old), we don't go back and read every revision of the guide.  HST, I'm not sure why Jerry deviated from the default REW settings unless that is something that was posted over at HTS and he was just being consistent with their standards.

 

EDIT:  To Markus' and Keith's point, stop getting hung up on the minor details.  Work on getting your sound stage balanced and take measurements with the MLP in the midpoint of the room if that's feasible.  Just curious, did you do this when you moved the subs to the 1/4 and 3/4 points along the wall or did you leave your MLP offset the 4'?

jkasanic is offline  
post #5316 of 10745 Old 10-15-2013, 11:55 AM
AVS Addicted Member
 
kbarnes701's Avatar
 
Join Date: Jan 2008
Location: Main Listening Positon
Posts: 16,546
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 515 Post(s)
Liked: 1239
Quote:
Originally Posted by bao01 View Post

The guide shows 0, 90, 150 for X, Y, Z. I followed the guide.

It can't be +/- 4.5 dB because it's greater than 2 lines (each line is 5). It is at least 12, maybe 13 or 14 between peak and valley.

 

The point is, it doesn't matter. FR to +/- 5dB unsmoothed (20Hz - 20kHz) is actually damn fine in the real world - and ringing that is 35dB down at 20Hz is also fine because it will be inaudible. It's easy to get obsessed with the graphs and forget why we take the measurements. 

 

+ what Markus said. You have to look at all the parameters together. A lot of people go nuts to get a FR graph that is flat 20-20Khz. Yeah, it looks great. But they can't actually hear anything better than +/3dB anyway, and the FR is the least interesting graph we can make. The waterfall is at least as important, and maybe more so, as are the ETCs.

 

In the graphs I posted above in reply to Joe, see how the different presentations can make them look very different? That's why it is important to get the parameters correct.

kbarnes701 is online now  
post #5317 of 10745 Old 10-15-2013, 12:04 PM
Advanced Member
 
bao01's Avatar
 
Join Date: Dec 2012
Posts: 649
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 24
I quote myself smile.gif
Quote:
Originally Posted by bao01 View Post

But again, i keep asking myself: what is audible to the average human ear???
I'm sure this info is out there. If the human ear can not discern +/- 10 dB peaks and dips that are 1/24 or even 1/12 octave in duration, then why do we care?

Basic question: for a given REW SPL graph, what types of peaks and dips can the average human ear detect???

I take graphs with a grain of salt i think.
Who really knows what sounds good to each of us?

B&W 802 Diamond mains, B&W HTM2 Diamond center, B&W 804 Diamond surrounds, Parasound HALO A 51, Krell KAV-300i , Integra DHC-80.3 pre-pro, two JL Audio Fathom f113 subs, Panasonic TC-P65VT50 65" plasma
bao01 is offline  
post #5318 of 10745 Old 10-15-2013, 12:08 PM
Advanced Member
 
bao01's Avatar
 
Join Date: Dec 2012
Posts: 649
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 24
Quote:
Originally Posted by jkasanic View Post

Just curious, did you do this when you moved the subs to the 1/4 and 3/4 points along the wall or did you leave your MLP offset the 4'?

I thought i was clear:
Quote:
Originally Posted by bao01 View Post

Wow - you have a really good memory.
You are exactly right.
The room is 28.4 ft x 22.2 ft and the TV and main spkrs are along one of the 28.4 walls but offset to the right by 4ft.
The center of TV and MLP are 10.2 ft from right wall instead of 14.2 feet from right wall.
I have not yet tried moving the entire system 4 ft to the left like Feri, Sanjay and others have suggested.
I will try that soon.


What i did do is move the two subs all along the 28.4 ft front wall - i tried all sorts of combinations, including 1/4 and 3/4.
My goal at that time was to see if 66 Hz dip would go away and it did not, no matter what.
I was only looking at SPL graph only, not waterfall.

But i need to redo the tests because i was not methodical and have a feeling i mucked some of the measurements up.
I never adjusted sub distances in the prepro as i was moving/graphing.

After futzing with front wall, i started moving the right sub all along the rear 28.4 ft wall and got best results there - i will post a diagram of best result.

I just care about MLP but if you care about two or more seats, all of these web sites indicate mid point of opposite walls is best which is sort of where i am now.

http://www.harman.com/EN-US/OurCompany/Innovation/Documents/White%20Papers/multsubs.pdf
http://www.aperionaudio.com/blog/dual-subwoofers-for-your-home-theater
http://www.audioholics.com/subwoofer-setup/subwoofer-placement-the-place-for-bass-part-1/subwoofer-placement-the-place-for-bass-part-1-page-6
http://forum.blu-ray.com/showthread.php?t=48286
http://www.bgcorp.com/PDFs/Better%20bass%20through%20multiple%20subwoofers.pdf

B&W 802 Diamond mains, B&W HTM2 Diamond center, B&W 804 Diamond surrounds, Parasound HALO A 51, Krell KAV-300i , Integra DHC-80.3 pre-pro, two JL Audio Fathom f113 subs, Panasonic TC-P65VT50 65" plasma
bao01 is offline  
post #5319 of 10745 Old 10-15-2013, 12:09 PM
AVS Special Member
 
mogorf's Avatar
 
Join Date: May 2009
Location: Budapest, Hungary
Posts: 4,244
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 89 Post(s)
Liked: 99
Quote:
Originally Posted by bao01 View Post

I quote myself smile.gif
I take graphs with a grain of salt i think.
Who really knows what sounds good to each of us?

+1. I'm waiting to see you pictures of your rearranged room bao, with all the speakers and subs set up to utilize all available space, not just a corner of that beautiful room. wink.gif
mogorf is online now  
post #5320 of 10745 Old 10-15-2013, 12:11 PM
AVS Special Member
 
jlpowell84's Avatar
 
Join Date: Dec 2012
Location: Eugene, OR
Posts: 3,889
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Liked: 208
Quote:
Originally Posted by jkasanic View Post

Keith's waterfall is shown with the default settings in REW with the exception of the time range extended to 450ms (from 300ms):




The noise floor has traditionally been approx. 40dB with "legacy" REW kits but we've found with the USB mics that people are seeing anywhere from 50-55dB in a "quiet" room.  For this reason, we've tried to increase the dB of the measurements to at least 30dB above the noise floor (so closer to 85dB measurements) as well as adjust the noise floor up to the minimum threshold reported by USB mic users (50 dB).  As a compromise (and knowing Keith, also to dispel any concerns about an even better looking waterfall being the result of using a higher noise floor) when presenting his graphs, Keith has elected to show down to 45dB instead of what he actually measures (which I believe is closer to 50dB with his UMM-6).  This gives the appearance of presenting his waterfall in a more conservative light than using 50dB as the noise floor.  My last RTA actually showed closer to 56 dB as my noise floor!

The only other presentation difference I can think of could be related to the width of the image capture or the preview size used to display it in the forum.  I always use 900px as the capture width (I think 871 is the default) and I preview my waterfalls with the 500x1000px large option.  If you instead use a url address to present photos (instead of uploading them directly) then I'm not sure if you're presented with the same preview sizes or not which might explain why some users have larger previews than others.

EDIT:  Remember that Keith's graph is unsmoothed but after EQ and his room is heavily treated so you'd really want to see his response/waterfall prior to any room treatments or EQ to see the benefits each is having on his response and decay times.  It actually looks to me to be more like 83-92 dB range (peak between 55-60Hz and null around 250Hz?) from 15-300Hz for a +/- closer to 4.5.

So do you think my spl calibration could be off if my RTA was hanging right at 35 db with my UMM 6?
jlpowell84 is offline  
post #5321 of 10745 Old 10-15-2013, 12:12 PM
AVS Special Member
 
jkasanic's Avatar
 
Join Date: Dec 2006
Posts: 1,135
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Liked: 57
@bao01: The mic position was not clear to me before only because after having moved the subs to the 1/4 and 3/4 points, I would've used that opportunity to take a measurement with centered MLP. As you've noted already, it was not a methodical process so I would suggest you try again.
jkasanic is offline  
post #5322 of 10745 Old 10-15-2013, 12:16 PM
AVS Special Member
 
jkasanic's Avatar
 
Join Date: Dec 2006
Posts: 1,135
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Liked: 57
@jlpowell84: wrt the SPL calibration, I can tell you that using the subwoofer cal in REW results in about a 5-6dB lower reading than using the speaker cal with sub turned off both measurements taken using my ratshack meter. I wonder if calibrating REW to the Audyssey mic post 75 dB level calibration would be more accurate?
jkasanic is offline  
post #5323 of 10745 Old 10-15-2013, 12:17 PM
AVS Special Member
 
jlpowell84's Avatar
 
Join Date: Dec 2012
Location: Eugene, OR
Posts: 3,889
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Liked: 208
Quote:
Originally Posted by jlpowell84 View Post

So do you think my spl calibration could be off if my RTA was hanging right at 35 db with my UMM 6?

Also with that said can I use the left speaker calibration to set it as opposed to the sub? I remember it said sub in the guide but I believe my radio shack meter is about 10db down in the bass department.
jlpowell84 is offline  
post #5324 of 10745 Old 10-15-2013, 12:17 PM
Advanced Member
 
bao01's Avatar
 
Join Date: Dec 2012
Posts: 649
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 24
Quote:
Originally Posted by mogorf View Post

+1. I'm waiting to see you pictures of your rearranged room bao, with all the speakers and subs set up to utilize all available space, not just a corner of that beautiful room. wink.gif

Quote:
Originally Posted by jkasanic View Post

The mic position was not clear to me before only because after having moved the subs to the 1/4 and 3/4 points, I would've used that opportunity to take a measurement with centered MLP. As you've noted already, it was not a methodical process so I would suggest you try again.

All in good time, my dear chaps ... all in good time.
smile.gif

(this stuff is exhausting)

B&W 802 Diamond mains, B&W HTM2 Diamond center, B&W 804 Diamond surrounds, Parasound HALO A 51, Krell KAV-300i , Integra DHC-80.3 pre-pro, two JL Audio Fathom f113 subs, Panasonic TC-P65VT50 65" plasma
bao01 is offline  
post #5325 of 10745 Old 10-15-2013, 12:19 PM
AVS Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 4,725
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 307 Post(s)
Liked: 176
Quote:
Originally Posted by bao01 View Post

Who really knows what sounds good to each of us?

This is totally unrelated to the topic at hand. What "sounds good to each of us" is entirely subjective. It describes preference. Sound reproduction is (or should) be about reference. The creator of a recording gets to decide what "sounds good", not the reproduction chain.

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
markus767 is online now  
post #5326 of 10745 Old 10-15-2013, 12:21 PM
AVS Special Member
 
jlpowell84's Avatar
 
Join Date: Dec 2012
Location: Eugene, OR
Posts: 3,889
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Liked: 208
Quote:
Originally Posted by jkasanic View Post

@jlpowell84: wrt the SPL calibration, I can tell you that using the subwoofer cal in REW results in about a 5-6dB lower reading than using the speaker cal with sub turned off both measurements taken using my ratshack meter. I wonder if calibrating REW to the Audyssey mic post 75 dB level calibration would be more accurate?

I have a tool kit DVD from Mark Seaton that has some -20db noise for each channel individually. Perhaps I can just do it 6-7 db higher than it reads and then double check with the -20db noise? How exactly would you calibrate REW using the audyssey mic? Does it recognize it?
jlpowell84 is offline  
post #5327 of 10745 Old 10-15-2013, 12:30 PM
Advanced Member
 
bao01's Avatar
 
Join Date: Dec 2012
Posts: 649
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 24
Quote:
Originally Posted by markus767 View Post

This is totally unrelated to the topic at hand. What "sounds good to each of us" is entirely subjective. It describes preference. Sound reproduction is (or should) be about reference. The creator of a recording gets to decide what "sounds good", not the reproduction chain.

I admit that i am very new to this graphing activity. I am just wondering how much effort someone should put into getting better graphs?
Is the effort commensurate with the perceived delta in SQ?
I think there will be very different answers from different sorts of people.
A 60 year old person may not hear much of a difference and may not care (i am not 60 smile.gif )
Someone in there twenties may go to great lengths and declare: "wow - this graph sounds soooo much better than that graph".

I don't want to catch graphitis smile.gif

B&W 802 Diamond mains, B&W HTM2 Diamond center, B&W 804 Diamond surrounds, Parasound HALO A 51, Krell KAV-300i , Integra DHC-80.3 pre-pro, two JL Audio Fathom f113 subs, Panasonic TC-P65VT50 65" plasma
bao01 is offline  
post #5328 of 10745 Old 10-15-2013, 12:30 PM
AVS Addicted Member
 
kbarnes701's Avatar
 
Join Date: Jan 2008
Location: Main Listening Positon
Posts: 16,546
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 515 Post(s)
Liked: 1239
Quote:
Originally Posted by bao01 View Post

I quote myself smile.gif
Quote:
Originally Posted by bao01 View Post

But again, i keep asking myself: what is audible to the average human ear???
I'm sure this info is out there. If the human ear can not discern +/- 10 dB peaks and dips that are 1/24 or even 1/12 octave in duration, then why do we care?

Basic question: for a given REW SPL graph, what types of peaks and dips can the average human ear detect???

I take graphs with a grain of salt i think.
 

 

Then wtf are you doing in this thread???????? 

 

Quote:

 Who really knows what sounds good to each of us?
 
That's the wrong question so it can't be answered - at least not in the way you mean.  Nobody knows exactly what you hear, obviously. But that isn't a relevant issue. Audio reproduction is a science. As such, it has basic parameters. One of these is that the reproduction equipment is able to reproduce what the content creator put in at the other end, unchanged. Whatever the content creator created is what we are aiming to reproduce - whether it is a Wagner concert, a Pink Floyd gig or <shudder> a folk music group. If your equipment is good enough it should be capable of reproducing that created content with precision and accuracy. And this is why we measure - so that we can see where we are deviating from the original. We want to deviate as little as possible of course and to that end we need to ensure we have players and amps that can play flat throughout the audible spectrum (really easy), speakers that are capable of reproducing the audible spectrum in its entirety, with no frequencies emphasised or de-emphasised and with appropriate dispersion characteristics etc (not very easy at all) and rooms that add nor take away anything from the final sound that reaches our ears (almost impossible). Measuring allows us to approach this lofty goal. It is the sole way to be sure what we are hearing. Whether what you hear is, you believe, good or not isn't an issue - that is entirely subjective and just as I might think Miles Davis is absolute heaven to listen to, you may think it is hell. But it's irrelevant in this context - all that matters is that we are both hearing what the recording engineer put onto the master in the first place.
kbarnes701 is online now  
post #5329 of 10745 Old 10-15-2013, 12:35 PM
AVS Addicted Member
 
kbarnes701's Avatar
 
Join Date: Jan 2008
Location: Main Listening Positon
Posts: 16,546
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 515 Post(s)
Liked: 1239
Quote:
Originally Posted by jlpowell84 View Post
 
Quote:
Originally Posted by jkasanic View Post

@jlpowell84: wrt the SPL calibration, I can tell you that using the subwoofer cal in REW results in about a 5-6dB lower reading than using the speaker cal with sub turned off both measurements taken using my ratshack meter. I wonder if calibrating REW to the Audyssey mic post 75 dB level calibration would be more accurate?

I have a tool kit DVD from Mark Seaton that has some -20db noise for each channel individually. Perhaps I can just do it 6-7 db higher than it reads and then double check with the -20db noise? How exactly would you calibrate REW using the audyssey mic? Does it recognize it?

He doesn't mean 'use the Audyssey mic' - he means use the Audyssey cal level of 75dB.

 

Gee, some people make this hard work. Just use the speaker level test in REW, turn the knob on the AVR until your SPL meter reads about 80-85dB, set REW to the level on the SPL meter and you're done. It takes about 20 seconds.

kbarnes701 is online now  
post #5330 of 10745 Old 10-15-2013, 12:39 PM
AVS Addicted Member
 
kbarnes701's Avatar
 
Join Date: Jan 2008
Location: Main Listening Positon
Posts: 16,546
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 515 Post(s)
Liked: 1239
Quote:
Originally Posted by bao01 View Post
 
Quote:
Originally Posted by markus767 View Post

This is totally unrelated to the topic at hand. What "sounds good to each of us" is entirely subjective. It describes preference. Sound reproduction is (or should) be about reference. The creator of a recording gets to decide what "sounds good", not the reproduction chain.

I admit that i am very new to this graphing activity. I am just wondering how much effort someone should put into getting better graphs?
Is the effort commensurate with the perceived delta in SQ?
I think there will be very different answers from different sorts of people.
A 60 year old person may not hear much of a difference and may not care (i am not 60 smile.gif )
Someone in there twenties may go to great lengths and declare: "wow - this graph sounds soooo much better than that graph".

I don't want to catch graphitis smile.gif

 

You do it till you are happy with the end result. Only you know when that point has been reached. The graphs are your guide and your support, not an end in themselves.

 

If you measure your room and you see a 20dB peak at 100Hz, then you don't need 'golden ears' to know something is wrong. You probably knew something was wrong anyway - but you didn’t know it was a 10dB peak at 100Hz. Now you do, so you can now set about fixing it. Same with modal ringing and reflections. You can’t fix a problem until you know what it is. And then you can measure again, after the fix has been applied, and see how far you have got. And so on until you are happy. 

kbarnes701 is online now  
post #5331 of 10745 Old 10-15-2013, 12:47 PM
AVS Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 4,725
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 307 Post(s)
Liked: 176
Quote:
Originally Posted by bao01 View Post

I am just wondering how much effort someone should put into getting better graphs?

None if he doesn't understand what those graphs really mean.

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
markus767 is online now  
post #5332 of 10745 Old 10-15-2013, 12:53 PM
AVS Special Member
 
jlpowell84's Avatar
 
Join Date: Dec 2012
Location: Eugene, OR
Posts: 3,889
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Liked: 208
Quote:
Originally Posted by kbarnes701 View Post

He doesn't mean 'use the Audyssey mic' - he means use the Audyssey cal level of 75dB.

Gee, some people make this hard work. Just use the speaker level test in REW, turn the knob on the AVR until your SPL meter reads about 80-85dB, set REW to the level on the SPL meter and you're done. It takes about 20 seconds.

Ok I see. You know what is a familiar world of terminology and processes to you is like an ocean of unfamiliar to others. I will try my best to ask the right questions. I tend to learn by asking questions but I will make a conscious effort to think it through and trial and error myself. You know 10 months ago I didn't know what a crossover was. smile.gif
jlpowell84 is offline  
post #5333 of 10745 Old 10-15-2013, 12:54 PM
AVS Special Member
 
mogorf's Avatar
 
Join Date: May 2009
Location: Budapest, Hungary
Posts: 4,244
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 89 Post(s)
Liked: 99
Quote:
Originally Posted by markus767 View Post

None if he doesn't understand what those graphs really mean.

...And the measurement techniques either! Markus, you have desperately asked folks here about this issue:

Quote

"...That's probably the 3rd time I'm asking: Did you measure multiple points within the listening area? Humans tend to have two ears, none of which is mounted where you've put your mic..."

Unquote

...but you never seem to get a good answer...mad.gif
mogorf is online now  
post #5334 of 10745 Old 10-15-2013, 01:02 PM
AVS Addicted Member
 
sdurani's Avatar
 
Join Date: Oct 2001
Location: Monterey Park, CA
Posts: 18,751
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 492 Post(s)
Liked: 609
Quote:
Originally Posted by jlpowell84 View Post

I am not opposed to rotating the room at all. Best would be to have the tv center essentially where I had that sub right?
That would be optimal, with your seating (your ears) going no further back than your 11.5' left wall. I think you'll soon discover that your room does not suck (quite the contrary).

Sanjay
sdurani is online now  
post #5335 of 10745 Old 10-15-2013, 02:28 PM
AVS Special Member
 
jlpowell84's Avatar
 
Join Date: Dec 2012
Location: Eugene, OR
Posts: 3,889
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 73 Post(s)
Liked: 208
Quote:
Originally Posted by sdurani View Post

That would be optimal, with your seating (your ears) going no further back than your 11.5' left wall. I think you'll soon discover that your room does not suck (quite the contrary).

Yea it will make my tiny 50" plasma seem bigger too smile.gif
jlpowell84 is offline  
post #5336 of 10745 Old 10-15-2013, 02:45 PM
AVS Addicted Member
 
kbarnes701's Avatar
 
Join Date: Jan 2008
Location: Main Listening Positon
Posts: 16,546
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 515 Post(s)
Liked: 1239
Quote:
Originally Posted by jlpowell84 View Post
 
Quote:
Originally Posted by kbarnes701 View Post

He doesn't mean 'use the Audyssey mic' - he means use the Audyssey cal level of 75dB.

Gee, some people make this hard work. Just use the speaker level test in REW, turn the knob on the AVR until your SPL meter reads about 80-85dB, set REW to the level on the SPL meter and you're done. It takes about 20 seconds.

Ok I see. You know what is a familiar world of terminology and processes to you is like an ocean of unfamiliar to others. I will try my best to ask the right questions. I tend to learn by asking questions but I will make a conscious effort to think it through and trial and error myself. You know 10 months ago I didn't know what a crossover was. smile.gif

 

I wasn't meaning to be snippy. We all knew nothing once. You are in the right place if you are willing to learn - there is considerable expertise here, all freely available.

kbarnes701 is online now  
post #5337 of 10745 Old 10-15-2013, 05:12 PM
AVS Special Member
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 6,815
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 229 Post(s)
Liked: 646

Wow, guys, I take a few hours of to go to the fitness center and a posting bomb goes off!  I can't tell whether everything has been resolved, or whether there are still issues.

 

First of all, the procedure to calibrate the mic in REW using an external SPL should not be that difficult.  Does any confusion remain?

 

Second, WRT the settings for the Waterfall graph, I opened my REW app on the laptop, and the Waterfall settings I am using are not the default settings in REW.  Here are my current settings vs. the default settings.

 

 

 

TBH, I don't know how I ended up with different settings, and also don't really understand how the settings make a big difference.  Here are two waterfalls generated from the same underlying measurement, one using default settings, and the other using my current settings:

 

 

 

So, what is the big difference, as long as we are using consistent settings to compare one waterfall against another for our own systems?  Question for the team:  should I edit the Guide and put in the REW default settings if this is what everyone is using?

 

The important things about the waterfall, IMHO, are:

 

- Setting the noise floor properly (which we consistently see as ~50dB when using USB mics).

- Taking measurements at least 35-40dB above the noise floor (I calibrate my mic to 90dB).

- Setting the horizontal axis to 20-300Hz (5Hz-300Hz for Keith ;)  )

- Adjusting the time window such that the resonances have fully decayed below the noise floor (300ms in a really good room, 450-600ms in a more typical room).

 

Have I missed anything?

 

I'm never going to the fitness center again....

AustinJerry is online now  
post #5338 of 10745 Old 10-15-2013, 05:51 PM
AVS Club Gold
 
sdrucker's Avatar
 
Join Date: Feb 2006
Location: Chicago, IL
Posts: 2,049
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 24 Post(s)
Liked: 120
Quote:
Originally Posted by AustinJerry View Post

Wow, guys, I take a few hours of to go to the fitness center and a posting bomb goes off!  I can't tell whether everything has been resolved, or whether there are still issues.

First of all, the procedure to calibrate the mic in REW using an external SPL should not be that difficult.  Does any confusion remain?

Second, WRT the settings for the Waterfall graph, I opened my REW app on the laptop, and the Waterfall settings I am using are not the default settings in REW.  Here are my current settings vs. the default settings.







TBH, I don't know how I ended up with different settings, and also don't really understand how the settings make a big difference.  Here are two waterfalls generated from the same underlying measurement, one using default settings, and the other using my current settings:







So, what is the big difference, as long as we are using consistent settings to compare one waterfall against another for our own systems?  Question for the team:  should I edit the Guide and put in the REW default settings if this is what everyone is using?

The important things about the waterfall, IMHO, are:

- Setting the noise floor properly (which we consistently see as ~50dB when using USB mics).
- Taking measurements at least 35-40dB above the noise floor (I calibrate my mic to 90dB).
- Setting the horizontal axis to 20-300Hz (5Hz-300Hz for Keith wink.gif   )
- Adjusting the time window such that the resonances have fully decayed below the noise floor (300ms in a really good room, 450-600ms in a more typical room).

Have I missed anything?

I'm never going to the fitness center again....

Wow, that changes my whole image of you...a fitness buff? I guess you need to keep your core flexibility up to lift those bass traps...tongue.gif. Disclaimer: I often read AVS on the elliptical tongue.gif

HST, YMMV but I actually think your current settings look a little better on the decay over 40 Hz than the defaults, specially 50-60 Hz if I read the plot on my iPad correctly. Maybe due to 30 vs. the default 51 slices, and the 300 vs. 500 ms Window? FWIW I use your Guide settings, and have chosen to run (and rerun) according to the current Guide revision.

I don't know if I can get away with > 85 db sine sweeps, as at least 35-40 db above the 54-57 db urban life noise floor in my room would mean sweeps as loud as 95 db eek.gif. That will go over real well w/neighbors and baby Kobi LOL... BTW he seems to like white noise for some reason. Beats me why..,

However, if we can agree to a theoretical 50 db floor as a minimum standard, and 450 ms as a baseline decay time, I'm good. Heck, maybe to really capture the essence of a room and avoid 'false positives' about decay being sufficient right at the USB standard, we should go Keith's route and use 45 db as the collective 'compromise' for publishing graphs. I can just see confusion as we move forward and start wondering if what was 'good enough' now isn't.

I know I felt that way when I initially picked up on using 600 ms and had waterfalls that decayed sufficiently above 40 db and 40 Hz...then saw the standards evolve and find that I had decay issues at 70 Hz....the room didn't change, just our knowledge..

Stuart

 

Denon 4311 with XT32 and Audyssey Pro

Oppo 93 and 103

Panasonic VT50

Sherwood R-972 with its version of the Trinnov Optimizer

MiniDSP 10x10 HD

PSB Imagine T2, Center, and Surrounds (as of 5/2014); HSU ULS-15 subs (2)

 

The Audyssey FAQ Guide can be found here:

http://www.avsforum.com/...

sdrucker is online now  
post #5339 of 10745 Old 10-15-2013, 06:05 PM
AVS Special Member
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 6,815
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 229 Post(s)
Liked: 646

What continues to bother me is that these parameter tweaks don't change the underlying data, they just change how the graph looks.  I don't really care whether we use a 40, 45, or 50dB lower limit as long as we agree on a standard and stick to it.

 

The 40dB headroom above the noise floor was a recommendation by Jason, IIRC.  Remember when he recommended measuring at 100dB?  I tried that, and it literally hurt my ears and had me concerned about damaging my speakers.  Of course, if that is too loud for your special circumstance, you need to live with it.

 

Edit:  And BTW, I value personal fitness very highly!

AustinJerry is online now  
post #5340 of 10745 Old 10-15-2013, 06:10 PM
AVS Addicted Member
 
sdurani's Avatar
 
Join Date: Oct 2001
Location: Monterey Park, CA
Posts: 18,751
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 492 Post(s)
Liked: 609
Quote:
Originally Posted by jlpowell84 View Post

Yea it will make my tiny 50" plasma seem bigger too smile.gif
And your soundstage wider. Like I said, I don't know if you use your system for music listening, but the symmetry will be hugely beneficial.

Sanjay
sdurani is online now  
Reply Audio theory, Setup and Chat

Tags
Dayton , Dayton Audio , Room Equilizer Wizard Rew

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off