Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 498 - AVS | Home Theater Discussions And Reviews
Baselworld is only a few weeks away. Getting the latest news is easy, Click Here for info on how to join the Watchuseek.com newsletter list. Follow our team for updates featuring event coverage, new product unveilings, watch industry news & more!


Forum Jump: 
 459Likes
Reply
 
Thread Tools
post #14911 of 14939 Old Yesterday, 07:56 AM
AVS Special Member
 
3ll3d00d's Avatar
 
Join Date: Sep 2007
Location: London, UK
Posts: 1,209
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 624 Post(s)
Liked: 187
Quote:
Originally Posted by jim19611961 View Post
Agreed. I am oversimplifying a bit. Looking at the phase tells us about timing also. But GD alone does tell us certain things.

edit: if for no other reason, GD is easier to discuss because much more data and analysis exists in the study of GD than that of phase curves. At a layman level anyway.

Trying to discuss a phase curve is a can of worms I dont feel versed enough in to begin a discussion.
for sure, the different views are all valid. I was just pointing out the relationship with the phase response as that is important to know with respect to deciding what windows to apply when reviewing the data. IMV a frequency dependent window is the one to use here as that more closely corresponds to how you hear but you have to go outside of REW for that atm.
3ll3d00d is online now  
Sponsored Links
Advertisement
 
post #14912 of 14939 Old Yesterday, 08:05 AM
AVS Special Member
 
jim19611961's Avatar
 
Join Date: Mar 2011
Location: Texas
Posts: 1,634
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 306 Post(s)
Liked: 106
Quote:
Originally Posted by AustinJerry View Post
- Is the GD in my measurements bad enough that I should be taking some immediate actions?
At 50hz, not so much. At 200-1500, yes. Anything above 1 cycle (certainly 2), should be addressed.


Quote:
Originally Posted by AustinJerry View Post
- What actions can I take to identify/resolve the GD issues? Is this another "hunting down the reflections" exercise? Other approaches?
It might be

My Room
My Music
Rega - Apollo, Rega - DAC, Goldpoint Passive, Classe CA-100, miniDSP
Jenzen Next
jim19611961 is offline  
post #14913 of 14939 Old Yesterday, 08:14 AM
AVS Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 6,696
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1784 Post(s)
Liked: 628
Quote:
Originally Posted by jim19611961 View Post
Agreed. I am oversimplifying a bit. Looking at the phase tells us about timing also. But GD alone does tell us certain things.

edit: if for no other reason, GD is easier to discuss because much more data and analysis exists in the study of GD than that of phase curves. At a layman level anyway.

Trying to discuss a phase curve is a can of worms I dont feel versed enough in to begin a discussion.
You can't discuss one without understanding the other.

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 offline  
post #14914 of 14939 Old Yesterday, 08:16 AM
AVS Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 6,696
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1784 Post(s)
Liked: 628
Quote:
Originally Posted by 3ll3d00d View Post
for sure, the different views are all valid. I was just pointing out the relationship with the phase response as that is important to know with respect to deciding what windows to apply when reviewing the data. IMV a frequency dependent window is the one to use here as that more closely corresponds to how you hear but you have to go outside of REW for that atm.
Exactly why discussing GD in this thread doesn't make much sense. People only will start chasing ghosts.

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 offline  
post #14915 of 14939 Old Yesterday, 08:19 AM
AVS Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 6,696
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1784 Post(s)
Liked: 628
Quote:
Originally Posted by 3ll3d00d View Post
A speaker is a physical minimum phase device so it naturally has a GD that rises with frequency.
GD will be 0. It does not rise with frequency.

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 offline  
post #14916 of 14939 Old Yesterday, 08:19 AM
AVS Special Member
 
jim19611961's Avatar
 
Join Date: Mar 2011
Location: Texas
Posts: 1,634
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 306 Post(s)
Liked: 106
Quote:
Originally Posted by markus767 View Post
You can't discuss one without understanding the other.
Agreed. But if you buy in to the 1/2 cycle or 1 cycle idea, you dont have to fully understand it to to see if you have problem areas or not.

My Room
My Music
Rega - Apollo, Rega - DAC, Goldpoint Passive, Classe CA-100, miniDSP
Jenzen Next
jim19611961 is offline  
post #14917 of 14939 Old Yesterday, 08:22 AM
AVS Special Member
 
3ll3d00d's Avatar
 
Join Date: Sep 2007
Location: London, UK
Posts: 1,209
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 624 Post(s)
Liked: 187
Quote:
Originally Posted by markus767 View Post
GD will be 0. It does not rise with frequency.
I meant as frequency reduces (which is not what I wrote but still!). Zero would mean a constant slope to the phase response but I don't think that is the case is it?
3ll3d00d is online now  
post #14918 of 14939 Old Yesterday, 08:25 AM
AVS Special Member
 
jim19611961's Avatar
 
Join Date: Mar 2011
Location: Texas
Posts: 1,634
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 306 Post(s)
Liked: 106
Quote:
Originally Posted by markus767 View Post
Exactly why discussing GD in this thread doesn't make much sense. People only will start chasing ghosts.
What is imaginary or irrelevant about GD?

My Room
My Music
Rega - Apollo, Rega - DAC, Goldpoint Passive, Classe CA-100, miniDSP
Jenzen Next
jim19611961 is offline  
post #14919 of 14939 Old Yesterday, 08:32 AM
AVS Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 6,696
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1784 Post(s)
Liked: 628
Quote:
Originally Posted by jim19611961 View Post
What is imaginary or irrelevant about GD?
See 3ll3d00d post about smoothing and IR windows.

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 offline  
post #14920 of 14939 Old Yesterday, 10:36 AM
AVS Special Member
 
3ll3d00d's Avatar
 
Join Date: Sep 2007
Location: London, UK
Posts: 1,209
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 624 Post(s)
Liked: 187
Quote:
Originally Posted by AustinJerry View Post
I appreciate your responses, but I am no closer to understanding my measurements, or envisioning an action plan. Please comment on these questions:

- Is the GD in my measurements bad enough that I should be taking some immediate actions?
- What actions can I take to identify/resolve the GD issues? Is this another "hunting down the reflections" exercise? Other approaches?
Can you post the mdat (or a wav) somewhere?
3ll3d00d is online now  
post #14921 of 14939 Old Yesterday, 10:43 AM
AVS Special Member
 
lovingdvd's Avatar
 
Join Date: Jul 2002
Posts: 9,851
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 821 Post(s)
Liked: 142
Quote:
Originally Posted by jim19611961 View Post
At 50hz, not so much. At 200-1500, yes. Anything above 1 cycle (certainly 2), should be addressed...
I think what Jerry is asking (and I am wondering this myself) is addressed HOW?

From what I've read here GD can be a function of the speaker itself. Are all mid to high quality speakers designed so that GD is not an issue at least from the speakers themselves? If not, is there a spec from the manufacturer we can review to make sure we are not buying speakers that are subject to a GD issue? Or is it that any good quality speaker will not generally have GD issues in and of itself?
lovingdvd is online now  
post #14922 of 14939 Old Yesterday, 11:08 AM
AVS Special Member
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 9,751
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 2609 Post(s)
Liked: 1288
AustinJerry is online now  
post #14923 of 14939 Old Yesterday, 11:09 AM
AVS Special Member
 
jim19611961's Avatar
 
Join Date: Mar 2011
Location: Texas
Posts: 1,634
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 306 Post(s)
Liked: 106
Quote:
Originally Posted by lovingdvd View Post
I think what Jerry is asking (and I am wondering this myself) is addressed HOW?

From what I've read here GD can be a function of the speaker itself. Are all mid to high quality speakers designed so that GD is not an issue at least from the speakers themselves? If not, is there a spec from the manufacturer we can review to make sure we are not buying speakers that are subject to a GD issue? Or is it that any good quality speaker will not generally have GD issues in and of itself?
GD cant be treated as a cookbook recipe "If you have GD problems, do this".

I had a GD problem around 40hz several months back. I was reading 60+ms. Now it is about 15ms. What I did to fix it was very specific to my room and my speakers. Particularly how the subs integrated with my mains.

In Jerry's case, I cant be sure. I believe its reflection based.

In any case, the more you know about a subject, the better equipped you are to determine its value, whether it pertains to your system, and whether your willing to do something about it.

I really didnt intend to get pulled completely into this subject again. Ive brought it up before, and generally, folks here seem interested in other things more. Thats fine. But if your trying to better your system sound, I dont see how phase and timing can be left off the plate.

My Room
My Music
Rega - Apollo, Rega - DAC, Goldpoint Passive, Classe CA-100, miniDSP
Jenzen Next
jim19611961 is offline  
post #14924 of 14939 Old Yesterday, 11:21 AM
AVS Special Member
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 9,751
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 2609 Post(s)
Liked: 1288
Quote:
Originally Posted by jim19611961 View Post
GD cant be treated as a cookbook recipe "If you have GD problems, do this".

I had a GD problem around 40hz several months back. I was reading 60+ms. Now it is about 15ms. What I did to fix it was very specific to my room and my speakers. Particularly how the subs integrated with my mains.

In Jerry's case, I cant be sure. I believe its reflection based.

In any case, the more you know about a subject, the better equipped you are to determine its value, whether it pertains to your system, and whether your willing to do something about it.

I really didnt intend to get pulled completely into this subject again. Ive brought it up before, and generally, folks here seem interested in other things more. Thats fine. But if your trying to better your system sound, I dont see how phase and timing can be left off the plate.
I think what frustrates me the most, Jim, is hearing someone say that my system probably sounds like crap, and then not getting an offer to help me identify and resolve the issues. I know that if it were you, you would have a specific game plan for how the root cause might be identified. When I look at my room, it is not clear where to look for reflections that might be causing the problem. You have mentioned the front wall on several occasions, but my front wall is dominated by two windows with blinds, and a flat panel display. I am not sure what to do with those unalterable features.

I could use the blocking technique with a spare 2x4 panel that I have (assuming it absorbs reflections in the frequency range that is causing the issue).

Or I could look at bandwidth-filtered IR measurements for clues (although I still don't have a good grasp of how bandwidth-filtered IR's are used).

I also have some port plugs that can be used on the PSB Synchrony One speakers that alter the speaker from a ported design to a sealed design. Perhaps trying the port plugs might reveal whether the speakers are causing the issues.

See anything that might be a good approach?
AustinJerry is online now  
post #14925 of 14939 Old Yesterday, 11:48 AM
AVS Special Member
 
jim19611961's Avatar
 
Join Date: Mar 2011
Location: Texas
Posts: 1,634
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 306 Post(s)
Liked: 106
Quote:
Originally Posted by AustinJerry View Post
I think what frustrates me the most, Jim, is hearing someone say that my system probably sounds like crap, and then not getting an offer to help me identify and resolve the issues.
I can alleviate some of your frustration because I never said or implied this. I am a bit surprised you thought I was.

I said you had GD problems in the 200-1500hz range. And this was pointed out because you asked my opinion about it. How much and in what way does it affect how your system sounds? I dont know. How could I know?

What I do know is what the measured GD looks like, and what knowledgeable people besides me have said about it. What seems like a good reading and what does not.

I realize you have windows and a flat screen in the likely area that needs treating. I understand. If you cant treat it, dont. If you can, I think it will yield benefits.

I am pretty sure I HAVE offered to you what to do or what to try before. Here it is again. I would put as much pink fluffy (uncompressed) between the front speakers and the wall behind the mains as you can get. I would go as high as possible up to and including the ceiling. I would put it up as a temporary feature. String, bungie cord or what ever to hold it up in place for new room measurements.

I have other ideas, but I would start with this one.

I dont think standard blocking. mirror or string methods are going to be too helpful given the relatively low frequencies at work (200-250hz). The wavelengths here are 4' to 5'. Not easy to block or redirect.

My Room
My Music
Rega - Apollo, Rega - DAC, Goldpoint Passive, Classe CA-100, miniDSP
Jenzen Next

Last edited by jim19611961; Yesterday at 11:55 AM.
jim19611961 is offline  
post #14926 of 14939 Old Yesterday, 12:06 PM
AVS Special Member
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 9,751
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 2609 Post(s)
Liked: 1288
AustinJerry is online now  
post #14927 of 14939 Old Yesterday, 12:26 PM
AVS Special Member
 
lovingdvd's Avatar
 
Join Date: Jul 2002
Posts: 9,851
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 821 Post(s)
Liked: 142
Quote:
Originally Posted by jim19611961 View Post
...I had a GD problem around 40hz several months back. I was reading 60+ms. Now it is about 15ms. What I did to fix it was very specific to my room and my speakers. Particularly how the subs integrated with my mains...
Interesting Jim! Can you elaborate on what the issue turned out to be and specifically how you fixed it? Although it will pertain only to your room, seeing one specific example of what a fix can look like would be useful. Thanks.
lovingdvd is online now  
post #14928 of 14939 Old Yesterday, 12:35 PM
AVS Special Member
 
jim19611961's Avatar
 
Join Date: Mar 2011
Location: Texas
Posts: 1,634
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 306 Post(s)
Liked: 106
Quote:
Originally Posted by lovingdvd View Post
Interesting Jim! Can you elaborate on what the issue turned out to be and specifically how you fixed it? Although it will pertain only to your room, seeing one specific example of what a fix can look like would be useful. Thanks.
1) Reversing the phase on my main sub brought it from 60ms to 25ms.
2) Getting a mini-DSP for the sub allowed me to correct some overlap around 40hz where the sub and mains are crossing over. This brought the 40hz GD from 25ms to about 15ms.

My Room
My Music
Rega - Apollo, Rega - DAC, Goldpoint Passive, Classe CA-100, miniDSP
Jenzen Next
jim19611961 is offline  
post #14929 of 14939 Old Yesterday, 12:40 PM
AVS Special Member
 
3ll3d00d's Avatar
 
Join Date: Sep 2007
Location: London, UK
Posts: 1,209
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 624 Post(s)
Liked: 187
Quote:
Originally Posted by AustinJerry View Post
My guess is that whatever causes it appears in the 4-8ms range. If you apply v short FDW then the dip appears once you move to a 2 cycle window (at 250Hz this is 8ms long) and it seems to get stronger closer to 2 cycles than 1. You can see this in the spectrogram view in REW too, I've circled it in the spectrogram view. Your have a double dip by the looks of it and the spectrogram shows such holes early in the response (at ~3.8ms for the higher frequency one and ~8ms for the later one).

I don't think it's possible to analyse this further on paper (i.e. without knowing the room and being able to drill into it with more data) but maybe this gives you something to go on.
Attached Thumbnails
Click image for larger version

Name:	jerry.jpg
Views:	20
Size:	212.0 KB
ID:	750129  
3ll3d00d is online now  
post #14930 of 14939 Old Yesterday, 03:18 PM
AVS Special Member
 
JT78681's Avatar
 
Join Date: Apr 2012
Location: Austin, Texas
Posts: 1,990
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 564 Post(s)
Liked: 358
Quote:
Originally Posted by lovingdvd View Post
Yes however I wasn't asking about it being active. There's also a little toggle that must be selected.

Can you upload a screenshot of the ASIO control panel showing your mic and sound devices?

.
Sorry I know this sounds dumb, but I'm having some issues taking screenshots. I took a few snapshots I figure the more the better. I tried to take some better ones than before. The last picture is now the message I receive when I click on the measure button in REW.
Attached Thumbnails
Click image for larger version

Name:	IMG_0207.jpg
Views:	10
Size:	471.5 KB
ID:	750433   Click image for larger version

Name:	IMG_0206.jpg
Views:	10
Size:	284.3 KB
ID:	750441   Click image for larger version

Name:	IMG_0209.jpg
Views:	9
Size:	327.6 KB
ID:	750449   Click image for larger version

Name:	IMG_0208.jpg
Views:	12
Size:	483.7 KB
ID:	750457  

Receiver - Denon 4311CI
Speakers - Klipsch RF-82 II's, RC-62 II, RB-61 II's
Subs - Rythmik FV15HP's
JT78681 is online now  
post #14931 of 14939 Old Yesterday, 03:29 PM
AVS Special Member
 
Soulburner's Avatar
 
Join Date: Oct 2007
Posts: 1,196
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 194 Post(s)
Liked: 170
I get that often. I just have to go back in to ASIO Control Panel, then close it. Select your input and output devices again, and it should work. If it doesn't, close and reopen REW, disconnect the MIC, reconnect it then do the above steps again. It's finicky.
Soulburner is offline  
post #14932 of 14939 Old Yesterday, 03:41 PM
AVS Special Member
 
JT78681's Avatar
 
Join Date: Apr 2012
Location: Austin, Texas
Posts: 1,990
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 564 Post(s)
Liked: 358
Quote:
Originally Posted by Soulburner View Post
I get that often. I just have to go back in to ASIO Control Panel, then close it. Select your input and output devices again, and it should work. If it doesn't, close and reopen REW, disconnect the MIC, reconnect it then do the above steps again. It's finicky.
Thanks that's good to know that it can be finicky. Should my computer speakers volume be muted and the volume control for the Denon be the only one that's at 100%? Is the below okay?
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	7
Size:	110.3 KB
ID:	750617  

Receiver - Denon 4311CI
Speakers - Klipsch RF-82 II's, RC-62 II, RB-61 II's
Subs - Rythmik FV15HP's

Last edited by JT78681; Yesterday at 04:01 PM.
JT78681 is online now  
post #14933 of 14939 Old Yesterday, 06:52 PM
AVS Special Member
 
lovingdvd's Avatar
 
Join Date: Jul 2002
Posts: 9,851
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 821 Post(s)
Liked: 142
Quote:
Originally Posted by JT78681 View Post
Quote:
Originally Posted by lovingdvd View Post
Yes however I wasn't asking about it being active. There's also a little toggle that must be selected.

Can you upload a screenshot of the ASIO control panel showing your mic and sound devices?

.
Sorry I know this sounds dumb, but I'm having some issues taking screenshots. I took a few snapshots I figure the more the better. I tried to take some better ones than before. The last picture is now the message I receive when I click on the measure button in REW.
Try 5.12
lovingdvd is online now  
post #14934 of 14939 Old Yesterday, 08:44 PM
AVS Special Member
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 9,751
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 2609 Post(s)
Liked: 1288
Quote:
Originally Posted by 3ll3d00d View Post
My guess is that whatever causes it appears in the 4-8ms range. If you apply v short FDW then the dip appears once you move to a 2 cycle window (at 250Hz this is 8ms long) and it seems to get stronger closer to 2 cycles than 1. You can see this in the spectrogram view in REW too, I've circled it in the spectrogram view. Your have a double dip by the looks of it and the spectrogram shows such holes early in the response (at ~3.8ms for the higher frequency one and ~8ms for the later one).

I don't think it's possible to analyse this further on paper (i.e. without knowing the room and being able to drill into it with more data) but maybe this gives you something to go on.
Matt, I respect you for your depth of knowledge, and appreciate your feedback, but TBH I have read your response several times and cannot comprehend what you are saying. I mean no disrespect. Perhaps these concepts are over my head.
AustinJerry is online now  
post #14935 of 14939 Old Yesterday, 08:59 PM
AVS Special Member
 
lovingdvd's Avatar
 
Join Date: Jul 2002
Posts: 9,851
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 821 Post(s)
Liked: 142
Can you guys please have a look at my MDAT here: https://drive.google.com/open?id=0Bz...dWM&authuser=0 . It contains my pre-calibration sub only, post calibration sub only (via BFD) and post calibration sub plus L/R.

My take on it is as follows - I'm far from an expert so would like to know what you guys think:

1. The +13 dB peak is completely gone, thankfully. Side note: This nasty peak is what led me to see out a BFD years ago. When I first set up speakers in this room I thought my sub was bad - sounds so muddy and distorted. So I bought a new and highly regarded sub VTF3-MK2. Imagine my surprise when it sounded the same. That's when I researched and found REW and when I saw that I was like "there she is!". A BFD later and I was good to go.

2. Note that I purposely have my sub quite "hot". In addition, it has a house curve of +5 dB at 20 Hz down to +0 dB at 80 Hz. Still sounds very tight. As I posted a few days ago, if I try to balance it at the same SPL as the rest of the FR it sounds like the sub is completely missing...

3. Distortion looks completely fine - don't see any issues there. Right?

4. Waterfall shows great decay times. Considering this is an entirely untreated room that is great. Likely have this because it is a totally open room on one side.

5. ETC shows lots of issues; untreated room remember. I'm not concerned about it right now since I will be building a new room shortly. The purpose of this recalibration was because somehow my sub settings got changed and it didn't sound right, plus I wanted to sharpen my REW skills in preparation for getting an 88A when the new room is ready.

6. BIGGEST QUESTION: What do you guys thing is going on in the 110 Hz to 350 Hz range. It is so much lower than 350 Hz and up. My speakers are Pinnacle Gold Reference towers and are ported. They are each within a cabinet (with FR701 GOM in the front) that is big enough to fit them with about 6" of room in the front, side, back and top. Perhaps because these speakers are not meant to be placed into a cabinet doing so is messing up its response in the 110-350 Hz range?

7. Group delay (the subject of much discussion here lately) on the combined calibrated sub+LR looks looks pretty good, except for 60 ms at 162 Hz at mostly 25 ms and below, except for in the 225 - 350 Hz range as it peaks there near 50 ms and close to 100 ms at one point. Not sure what to do about it but not worth messing with given that I'll be rebuilding the room from scratch.

Other thoughts?

Thanks!
lovingdvd is online now  
post #14936 of 14939 Old Yesterday, 11:14 PM
AVS Special Member
 
3ll3d00d's Avatar
 
Join Date: Sep 2007
Location: London, UK
Posts: 1,209
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 624 Post(s)
Liked: 187
Quote:
Originally Posted by AustinJerry View Post
Matt, I respect you for your depth of knowledge, and appreciate your feedback, but TBH I have read your response several times and cannot comprehend what you are saying. I mean no disrespect. Perhaps these concepts are over my head.
well if this thread is for anything, it's for learning about things we don't understand

There are 2 ways to look at this; what does your data suggest about that dip? how do we analyse that data to look into the problem? I will try and write something on the latter tonight with some pictures to try to explain.

This leaves us with what the data says and what that means for you finding the root cause. As far as I can see, you really have 2 dips there which are caused by energy arriving after the initial impulse. It looks like the higher frequency dip (centred at ~265Hz) arrives after about 4ms while the lower frequency dip (centred at 240Hz or so) arrives after about 8ms. These should be taken as guidelines as it's hard to be v v precise here, nevertheless the 4-8ms window looks to be where your problem comes from. If you want to tackle this then you then need to narrow down what feature of your system could contribute a cancellation notch that arrives at the mic with that sort of delay after the initial impulse.

@jim19611961 is clearly going to be a better source of guidance for how to do that, my approach would be to get more data, something like; comparing measurements in the same spot from the L & R, moving the mic a particular distance on each axis (e.g. up/down/left/right/back/forward 1m) and comparing the resulting response, same approach but blocking on each axis instead.

A quick look at the other channels in that mdat suggests the same dips are evident but at sightly different frequencies. I suppose this might help you triangulate the possible locations.

Last edited by 3ll3d00d; Today at 01:05 AM.
3ll3d00d is online now  
post #14937 of 14939 Old Today, 01:18 AM
AVS Special Member
 
Soulburner's Avatar
 
Join Date: Oct 2007
Posts: 1,196
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 194 Post(s)
Liked: 170
Quote:
Originally Posted by 3ll3d00d View Post
This leaves us with what the data says and what that means for you finding the root cause. As far as I can see, you really have 2 dips there which are caused by energy arriving after the initial impulse. It looks like the higher frequency dip (centred at ~265Hz) arrives after about 4ms while the lower frequency dip (centred at 240Hz or so) arrives after about 8ms. These should be taken as guidelines as it's hard to be v v precise here, nevertheless the 4-8ms window looks to be where your problem comes from. If you want to tackle this then you then need to narrow down what feature of your system could contribute a cancellation notch that arrives at the mic with that sort of delay after the initial impulse.

@jim19611961 is clearly going to be a better source of guidance for how to do that, my approach would be to get more data, something like; comparing measurements in the same spot from the L & R, moving the mic a particular distance on each axis (e.g. up/down/left/right/back/forward 1m) and comparing the resulting response, same approach but blocking on each axis instead.
So you can find out the direction it's coming from, and treat that surface. That's really cool.
Soulburner is offline  
post #14938 of 14939 Old Today, 05:17 AM
AVS Special Member
 
jim19611961's Avatar
 
Join Date: Mar 2011
Location: Texas
Posts: 1,634
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 306 Post(s)
Liked: 106
Quote:
Originally Posted by AustinJerry View Post
Matt, I respect you for your depth of knowledge, and appreciate your feedback, but TBH I have read your response several times and cannot comprehend what you are saying. I mean no disrespect. Perhaps these concepts are over my head.
While not conclusive, an 8ms delay is consistent with your mains being 4' from the front wall and a 200hz dip.

Here is something else to try. If your 200hz issue is SBIR off the front wall, then moving the mains further from the front wall should make the problem move down in frequency, and moving them closer to the front wall should make it move up.

If the above proves to be the case, then this is some conformation that the front wall SBIR is the cause.

My Room
My Music
Rega - Apollo, Rega - DAC, Goldpoint Passive, Classe CA-100, miniDSP
Jenzen Next
jim19611961 is offline  
post #14939 of 14939 Old Today, 08:29 AM
AVS Special Member
 
Alan P's Avatar
 
Join Date: Jan 2003
Location: South Dakota
Posts: 4,891
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 1967 Post(s)
Liked: 1004
Quote:
Originally Posted by lovingdvd View Post
Can you guys please have a look at my MDAT here: https://drive.google.com/open?id=0Bz...dWM&authuser=0 . It contains my pre-calibration sub only, post calibration sub only (via BFD) and post calibration sub plus L/R.

My take on it is as follows - I'm far from an expert so would like to know what you guys think:

1. The +13 dB peak is completely gone, thankfully. Side note: This nasty peak is what led me to see out a BFD years ago. When I first set up speakers in this room I thought my sub was bad - sounds so muddy and distorted. So I bought a new and highly regarded sub VTF3-MK2. Imagine my surprise when it sounded the same. That's when I researched and found REW and when I saw that I was like "there she is!". A BFD later and I was good to go.

2. Note that I purposely have my sub quite "hot". In addition, it has a house curve of +5 dB at 20 Hz down to +0 dB at 80 Hz. Still sounds very tight. As I posted a few days ago, if I try to balance it at the same SPL as the rest of the FR it sounds like the sub is completely missing...

3. Distortion looks completely fine - don't see any issues there. Right?

4. Waterfall shows great decay times. Considering this is an entirely untreated room that is great. Likely have this because it is a totally open room on one side.

5. ETC shows lots of issues; untreated room remember. I'm not concerned about it right now since I will be building a new room shortly. The purpose of this recalibration was because somehow my sub settings got changed and it didn't sound right, plus I wanted to sharpen my REW skills in preparation for getting an 88A when the new room is ready.

6. BIGGEST QUESTION: What do you guys thing is going on in the 110 Hz to 350 Hz range. It is so much lower than 350 Hz and up. My speakers are Pinnacle Gold Reference towers and are ported. They are each within a cabinet (with FR701 GOM in the front) that is big enough to fit them with about 6" of room in the front, side, back and top. Perhaps because these speakers are not meant to be placed into a cabinet doing so is messing up its response in the 110-350 Hz range?

7. Group delay (the subject of much discussion here lately) on the combined calibrated sub+LR looks looks pretty good, except for 60 ms at 162 Hz at mostly 25 ms and below, except for in the 225 - 350 Hz range as it peaks there near 50 ms and close to 100 ms at one point. Not sure what to do about it but not worth messing with given that I'll be rebuilding the room from scratch.

Other thoughts?

Thanks!
1. Great!

2. I also have to run my subs quite hot to get the right "feel" from them. Mine are currently set 9db hotter than where Audyssey set them, 5000 cu. ft. space. Personally, I think the larger spaces require more SPL to get the same "feel" that you can get at lower SPLs in smaller spaces.

3. Agreed. But you need to measure higher to see when the distortion starts becoming an issue. I'm assuming you listen higher than you measured....maybe not.

4. Agreed.

5. Treating from reflections is great, but not always practical in a living room such as yours (and mine).

6. The only way to find out is top remove the speakers from the cabinets and re-measure.

7. I know nothing about GD, so can't comment.


Except for #6 , it's all looking pretty good IMO.

AVR: Denon 4520ci, FL/R: Klipschorn, CC: Klipsch RC-64ii, SUR: Polk LS/FX x4, FH: Klipsch RB-51ii x2, SUB: PSA T-18 x2, DISP: Mitsubishi WD-73740, BluRay: PS3 & BDP-S5100, Remote: URC MX-700
--------------------------------------------------
Getting Started with REW
Audyssey 101
Audyssey FAQ
Alan P is online now  
Sponsored Links
Advertisement
 
Reply Audio Theory, Setup, and Chat

Tags
Dayton , Dayton Audio , Room Equilizer Wizard Rew

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