Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 709 - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 1745Likes
Reply
 
Thread Tools
post #21241 of 21671 Old 01-25-2017, 09:25 PM
Senior Member
 
buddhamus's Avatar
 
Join Date: Feb 2006
Location: Australia, Melbourne
Posts: 393
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 83
Quote:
Originally Posted by AustinJerry View Post
Are we talking about a 2x4? Both the input and output of my balanced 2x4 are set to zero. I would certainly leave the output settings at zero.
Yep 2x4 balanced. So output should be fine to set to 0. Nice!! I'm going to attempt to gain match my subs this week. As some of my subs are running out of steam before the others..... I've done level matching but still some subs are running harder than others.

Thanks again Austin!

Sent from my SM-G900I using Tapatalk
buddhamus is online now  
Sponsored Links
Advertisement
 
post #21242 of 21671 Old 01-25-2017, 09:27 PM
Senior Member
 
buddhamus's Avatar
 
Join Date: Feb 2006
Location: Australia, Melbourne
Posts: 393
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 83
Austin what MV do your normally listen at? Is it lower than reference? Is that why you don't have to adjust the input and output gains on the minidsp?

Sent from my SM-G900I using Tapatalk
buddhamus is online now  
post #21243 of 21671 Old 01-25-2017, 09:57 PM
** Man of Leisure **
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 15,123
Mentioned: 159 Post(s)
Tagged: 1 Thread(s)
Quoted: 6630 Post(s)
Liked: 3661
Quote:
Originally Posted by buddhamus View Post
Austin what MV do your normally listen at? Is it lower than reference? Is that why you don't have to adjust the input and output gains on the minidsp?

Sent from my SM-G900I using Tapatalk
I rarely run at reference. But when I set up my 2x4, as described in the guide linked in my sig, I ran tests to ensure that no clipping would occur at reference.
AustinJerry is offline  
 
post #21244 of 21671 Old 01-25-2017, 10:08 PM
Senior Member
 
buddhamus's Avatar
 
Join Date: Feb 2006
Location: Australia, Melbourne
Posts: 393
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 83
Quote:
Originally Posted by AustinJerry View Post
I rarely run at reference. But when I set up my 2x4, as described in the guide linked in my sig, I ran tests to ensure that no clipping would occur at reference.
Thanks Austin!

Sent from my SM-G900I using Tapatalk
buddhamus is online now  
post #21245 of 21671 Old 01-26-2017, 05:39 AM
AVS Forum Special Member
 
3ll3d00d's Avatar
 
Join Date: Sep 2007
Location: London, UK
Posts: 2,760
Mentioned: 97 Post(s)
Tagged: 0 Thread(s)
Quoted: 1569 Post(s)
Liked: 547
Quote:
Originally Posted by AustinJerry View Post
Why the MLP, Alan? A near-field measurement would minimize the resonating and vibrations you are talking about. If the sub is clipping, causing distortion, this would be easily measured near-field.
you'd most likely clip the mic with a near field measurement at levels high enough to cause a sub to be overloaded
3ll3d00d is online now  
post #21246 of 21671 Old 01-26-2017, 06:42 AM
AVS Forum Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 9,392
Mentioned: 78 Post(s)
Tagged: 0 Thread(s)
Quoted: 3654 Post(s)
Liked: 1304
Quote:
Originally Posted by 3ll3d00d View Post
you'd most likely clip the mic with a near field measurement at levels high enough to cause a sub to be overloaded
On the other hand, room effects wouldn't contaminate distortion measurements as much.

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 #21247 of 21671 Old 01-26-2017, 09:53 AM
AVS Forum Special Member
 
Alan P's Avatar
 
Join Date: Jan 2003
Location: South Dakota
Posts: 9,385
Mentioned: 50 Post(s)
Tagged: 0 Thread(s)
Quoted: 4705 Post(s)
Liked: 3333
Quote:
Originally Posted by AustinJerry View Post
Why the MLP, Alan? A near-field measurement would minimize the resonating and vibrations you are talking about. If the sub is clipping, causing distortion, this would be easily measured near-field.
Good point, Jerry.

I have only done distortion measurements from the MLP and assumed that is the location to be more concerned about, but I can see how taking nearfield distortion measurements could provide pertinent info as well.
Alan P is offline  
post #21248 of 21671 Old 01-26-2017, 09:55 AM
AVS Forum Special Member
 
3ll3d00d's Avatar
 
Join Date: Sep 2007
Location: London, UK
Posts: 2,760
Mentioned: 97 Post(s)
Tagged: 0 Thread(s)
Quoted: 1569 Post(s)
Liked: 547
Quote:
Originally Posted by markus767 View Post
On the other hand, room effects wouldn't contaminate distortion measurements as much.
either way you have a measurement with added, and unwanted, distortion
3ll3d00d is online now  
post #21249 of 21671 Old 01-26-2017, 09:56 AM
AVS Forum Special Member
 
Alan P's Avatar
 
Join Date: Jan 2003
Location: South Dakota
Posts: 9,385
Mentioned: 50 Post(s)
Tagged: 0 Thread(s)
Quoted: 4705 Post(s)
Liked: 3333
Quote:
Originally Posted by buddhamus View Post
Yep 2x4 balanced. So output should be fine to set to 0. Nice!! I'm going to attempt to gain match my subs this week. As some of my subs are running out of steam before the others..... I've done level matching but still some subs are running harder than others.

Thanks again Austin!

Sent from my SM-G900I using Tapatalk
Not sure what subs you have, but if you have subs that vary in performance by a wide margin, level matching at the MLP is what you want to do not gain matching (assuming the lesser subs are nearer the MLP). Afterwards, you may still have to dial down the lesser subs to keep them from reaching their limits at higher MV levels.
Alan P is offline  
post #21250 of 21671 Old 01-26-2017, 10:05 AM
Senior Member
 
buddhamus's Avatar
 
Join Date: Feb 2006
Location: Australia, Melbourne
Posts: 393
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 83
Quote:
Originally Posted by Alan P View Post
Not sure what subs you have, but if you have subs that vary in performance by a wide margin, level matching at the MLP is what you want to do not gain matching (assuming the lesser subs are nearer the MLP). Afterwards, you may still have to dial down the lesser subs to keep them from reaching their limits at higher MV levels.
Hey Alan, I have 4 x Submersives 1000w subs so they are all identical subs ... Funnily enough it's my nearfield subs that are running out of gas with the Farfields not even clipping while running 5db hot. Could be a placement problem... Hence why I wanna try and work this problem out. Thanks again!

Sent from my SM-G900I using Tapatalk
buddhamus is online now  
post #21251 of 21671 Old 01-26-2017, 10:20 AM
AVS Forum Special Member
 
Alan P's Avatar
 
Join Date: Jan 2003
Location: South Dakota
Posts: 9,385
Mentioned: 50 Post(s)
Tagged: 0 Thread(s)
Quoted: 4705 Post(s)
Liked: 3333
Quote:
Originally Posted by buddhamus View Post
Hey Alan, I have 4 x Submersives 1000w subs so they are all identical subs ... Funnily enough it's my nearfield subs that are running out of gas with the Farfields not even clipping while running 5db hot. Could be a placement problem... Hence why I wanna try and work this problem out. Thanks again!

Sent from my SM-G900I using Tapatalk
Ahhh, yes! Didn't realize you were the same guy posting graphs in the MBM thread.
buddhamus likes this.
Alan P is offline  
post #21252 of 21671 Old 01-26-2017, 10:26 AM
AVS Forum Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 9,392
Mentioned: 78 Post(s)
Tagged: 0 Thread(s)
Quoted: 3654 Post(s)
Liked: 1304
Quote:
Originally Posted by 3ll3d00d View Post
either way you have a measurement with added, and unwanted, distortion
Yep but my point was to do measurements that show what one wants to know. All too often people think that doing measurements would be an end in itself. The opposite is the case.

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 #21253 of 21671 Old 01-26-2017, 11:03 AM
Senior Member
 
turboman123's Avatar
 
Join Date: Jul 2011
Location: Switzerland
Posts: 374
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
Liked: 25
I have quite a resonant room, and I have been experimenting with subwoofer placement (1subwoofer). There are 2 practical possibilities: subwoofer in the left corner, or subwoofer in the right corner.
See enclosed the SPL diagrams (from the average of FL speaker and FR speaker). (Crossover frequency is 120Hz, which is recommended with my GoldenEar satellite speakers).
The subwoofer in the right corner position has stronger dips at around 100Hz and 150Hz.
The subwoofer in the left corner has a stronger dip at 40Hz.
See also enclosed the waterfall diagrams of the Front Right speaker (set to small).

I have following questions:
Can any improvements be made to the measurements?
Without changing the equipment: which position of the subwoofer would you recommend?
With a miniDSP EQ on the subwoofer channel, can a good improvement be expected, and which subwoofer position would be best with EQ?
With a miniDSP Dirac Live on all channels, can a good improvement be expected, and which subwoofer position would be best?
Any other recommendations? (I would exclude room treatment at this stage)
Attached Thumbnails
Click image for larger version

Name:	SWtest SPL.jpg
Views:	47
Size:	72.7 KB
ID:	1920889   Click image for larger version

Name:	FR SWleftcorner.jpg
Views:	45
Size:	108.1 KB
ID:	1920897   Click image for larger version

Name:	FR SWrightcorner.jpg
Views:	41
Size:	148.5 KB
ID:	1920905  

Last edited by turboman123; 01-26-2017 at 11:09 AM.
turboman123 is offline  
post #21254 of 21671 Old 01-26-2017, 12:06 PM
AVS Forum Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 9,392
Mentioned: 78 Post(s)
Tagged: 0 Thread(s)
Quoted: 3654 Post(s)
Liked: 1304
Quote:
Originally Posted by turboman123 View Post
I have quite a resonant room, and I have been experimenting with subwoofer placement (1subwoofer). There are 2 practical possibilities: subwoofer in the left corner, or subwoofer in the right corner.
See enclosed the SPL diagrams (from the average of FL speaker and FR speaker). (Crossover frequency is 120Hz, which is recommended with my GoldenEar satellite speakers).
The subwoofer in the right corner position has stronger dips at around 100Hz and 150Hz.
The subwoofer in the left corner has a stronger dip at 40Hz.
See also enclosed the waterfall diagrams of the Front Right speaker (set to small).

I have following questions:
Can any improvements be made to the measurements?
Without changing the equipment: which position of the subwoofer would you recommend?
With a miniDSP EQ on the subwoofer channel, can a good improvement be expected, and which subwoofer position would be best with EQ?
With a miniDSP Dirac Live on all channels, can a good improvement be expected, and which subwoofer position would be best?
Any other recommendations? (I would exclude room treatment at this stage)
1. Set smoothing to 1/24 or higher.
2. Measure at multiple positions within the listening area. The variance can be quite large.
3. Get a 2nd sub.

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 #21255 of 21671 Old 01-26-2017, 01:27 PM
** Man of Leisure **
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 15,123
Mentioned: 159 Post(s)
Tagged: 1 Thread(s)
Quoted: 6630 Post(s)
Liked: 3661
Quote:
Originally Posted by turboman123 View Post
I have quite a resonant room, and I have been experimenting with subwoofer placement (1subwoofer). There are 2 practical possibilities: subwoofer in the left corner, or subwoofer in the right corner.
See enclosed the SPL diagrams (from the average of FL speaker and FR speaker). (Crossover frequency is 120Hz, which is recommended with my GoldenEar satellite speakers).
The subwoofer in the right corner position has stronger dips at around 100Hz and 150Hz.
The subwoofer in the left corner has a stronger dip at 40Hz.
See also enclosed the waterfall diagrams of the Front Right speaker (set to small).

I have following questions:
Can any improvements be made to the measurements?
Without changing the equipment: which position of the subwoofer would you recommend?
With a miniDSP EQ on the subwoofer channel, can a good improvement be expected, and which subwoofer position would be best with EQ?
With a miniDSP Dirac Live on all channels, can a good improvement be expected, and which subwoofer position would be best?
Any other recommendations? (I would exclude room treatment at this stage)
Markus has provided several useful suggestions. Setting smoothing to 1/6 will mask the real response, which is likely to be worse than the screenshot you presented.

Neither placement is providing very good results, which doesn't surprise me. Corner placement is rarely the best, especially when it comes to managing room resonances, which your waterfalls reveal to be pretty bad. So, if you indeed have severe limitations WRT where subs can be placed, there is only so much you can do. If you want to explore how well PEQ will help, I encourage you to try PEQ for both placements--the more options you have, the more likely you will find something that provides some improvement. An 88A will also provide some improvement, but will not work miracles.

So it boils down to two of the most-often used pieces of advice: 1) Find a better spot for the sub, and 2) Consider adding one or more additional subs to smooth out the response. And, of course, room treatments will help with the bass resonances, but you seem to have ruled that out.
AustinJerry is offline  
post #21256 of 21671 Old 01-26-2017, 03:02 PM
Senior Member
 
turboman123's Avatar
 
Join Date: Jul 2011
Location: Switzerland
Posts: 374
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
Liked: 25
@markus and @Jerry
Thanks for the advice. I will reduce the smoothing and republish the results. I will also measure at multiple positions.

A further question:
I know that using multiple subs is a well known recommendation. However, in the last year or two, miniDSP has a Dirac Live solution which would be about in the same price range as an additional sub. Since I have a UMIK microphone, and also the capability to use REW, and lets assume the same price for a sub and a Dirac live, what has the best chance to provide an improvement: 2nd sub or Dirac Live?

Another question regarding REW:
Since I do measurement with a reference timing channel (center), then REW could know the phase difference between the two measurments with different sub position. Could REW simulate then the combined 2 sub output from the separate measurements?

Last edited by turboman123; 01-26-2017 at 03:11 PM.
turboman123 is offline  
post #21257 of 21671 Old 01-26-2017, 03:11 PM
AVS Forum Special Member
 
LastButNotLeast's Avatar
 
Join Date: Feb 2007
Location: 08077
Posts: 7,787
Mentioned: 33 Post(s)
Tagged: 1 Thread(s)
Quoted: 1497 Post(s)
Liked: 1099
What form of eq do you have available now?
Michael

Did you really need to quote that entire post in your reply?
Downloadable FREE demo discs: Demonstration Blu-Ray Discs (Independently Authored)
Welcome to AVS - Get out while you still can!
For most of the time, the here and now is neither now nor here. Graham Swift
LastButNotLeast is offline  
post #21258 of 21671 Old 01-26-2017, 03:13 PM
AVS Forum Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 9,392
Mentioned: 78 Post(s)
Tagged: 0 Thread(s)
Quoted: 3654 Post(s)
Liked: 1304
Quote:
Originally Posted by turboman123 View Post
lets assume the same price for a sub and a Dirac live, what has the best chance to provide an improvement: 2nd sub or Dirac Live?
Both together Are you looking for a multiseat solution or just a single seat?

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 #21259 of 21671 Old 01-26-2017, 03:15 PM
** Man of Leisure **
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 15,123
Mentioned: 159 Post(s)
Tagged: 1 Thread(s)
Quoted: 6630 Post(s)
Liked: 3661
Quote:
Originally Posted by turboman123 View Post
@markus and @Jerry
Thanks for the advice. I will reduce the smoothing and republish the results. I will also measure at multiple positions.

A further question:
I know that using multiple subs is a well known recommendation. However, in the last year or two, miniDSP has a Dirac Live solution which would be about in the same price range as an additional sub. Since I have a UMIK microphone, and also the capability to use REW, and lets assume the same price for a sub and a Dirac live, what has the best chance to provide an improvement: 2nd sub or Dirac Live?
I have the MiniDSP 88A with Dirac Live. It is a fine product that has state of the art room correction. However, room correction can only do so much, and there is no guarantee that it will solve all the issues with your bass response. And a second sub will always provide improved bass response, but only if you are able to position it in the best spot in your listening room. And a second sub does none of the other overall improvements you would get with Dirac live.

Recommending one solution over the other is a difficult request. I spend several years in a long journey looking for improved sound. It involved each of the recommendations you have been given so far. I now have four subs, and they are placed strategically in my room. I also have approximately twenty bass traps, and use Dirac Live as well as a MiniDSP 2x4. As you can see, each step I took involved additional analysis, and new solutions, and more cost. And, of course, I had Markus cracking the whip along the way, providing links to all sorts of obscure audio technical white papers. There is nothing easy about this journey.
AustinJerry is offline  
post #21260 of 21671 Old 01-26-2017, 03:23 PM
AVS Forum Special Member
 
LastButNotLeast's Avatar
 
Join Date: Feb 2007
Location: 08077
Posts: 7,787
Mentioned: 33 Post(s)
Tagged: 1 Thread(s)
Quoted: 1497 Post(s)
Liked: 1099
No, but it's much easier thanks to the efforts of you trailblazers.
THANKS!

Michael
AustinJerry likes this.

Did you really need to quote that entire post in your reply?
Downloadable FREE demo discs: Demonstration Blu-Ray Discs (Independently Authored)
Welcome to AVS - Get out while you still can!
For most of the time, the here and now is neither now nor here. Graham Swift
LastButNotLeast is offline  
post #21261 of 21671 Old 01-26-2017, 05:55 PM
AVS Forum Special Member
 
artur9's Avatar
 
Join Date: Mar 2013
Location: near philly
Posts: 1,690
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 547 Post(s)
Liked: 189
Quote:
Originally Posted by turboman123 View Post
I know that using multiple subs is a well known recommendation.
I avoided EQ for the longest time because it is possible to damage things if one doesn't know what one is doing. To compound matters, my experience with the MiniDSP 2x4 was less than stellar (it's been binned since).

Just using multiple subs and no EQ I did manage to get a pretty flat FR and decent waterfall. And the sound is very satisfying because it can go loud when it needs to.

Here's some old measurements I have without EQ. You can see that with 2 subs I get much flatter FR and extended low end. More subs make things even more extended, flatter and louder. The rockets in Interstellar never sounded so good!

Attached Thumbnails
Click image for larger version

Name:	2 subs only.jpg
Views:	199
Size:	44.8 KB
ID:	1921849  
artur9 is offline  
post #21262 of 21671 Old 01-27-2017, 03:07 PM
Senior Member
 
turboman123's Avatar
 
Join Date: Jul 2011
Location: Switzerland
Posts: 374
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
Liked: 25
Multisub simulation?
In a previous post, I had shown measurements of my fairly resonant room, and one of the recommendations was to use a multsubwoofer configuration. Presently I have only one subwoofer, and I am a bit hesitant to go to the expense of buying an additional subwoofer, with a risk that the improvement is maybe marginal.
So I wondered if it is possible to simulate a multisubwoofer configuration, from single subwoofer measurements.
REW in the "all SPL" view, "controls" can calculate the sum of two measurements, A + B. A simple A+B calculation of the SPL without considering phase will not give the right result. However, in the REW help guide from John Mulcahy, it is described:
"For meaningful results measurements that have impulse responses or phase data should be properly time aligned before they are combined ".
My understanding from this is, that phase can be taken into account. My understanding, and hope is, that this would be a way to simulate a multisub configuration, from single sub measurements.
I tried to search for this in this thread, but did not find anything at first sight.

So my questions are:
Would it be possible to make such a multisub simulation a reasonable prediction of a multisub configuration?
If yes, how to do this time aligning of data exactly?
turboman123 is offline  
post #21263 of 21671 Old 01-27-2017, 07:58 PM
AVS Forum Special Member
 
artur9's Avatar
 
Join Date: Mar 2013
Location: near philly
Posts: 1,690
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 547 Post(s)
Liked: 189
Quote:
Originally Posted by turboman123 View Post
Multisub simulation?
So I wondered if it is possible to simulate a multisubwoofer configuration, from single subwoofer measurements.
REW in the "all SPL" view, "controls" can calculate the sum of two measurements, A + B.
I think, maybe but probably incorrectly, that you may be able to do what you're thinking.

Assuming a timing reference, which I think you have, then summing of multiple measurements might work.

What I would think might work is
(1) Measure your sub with a timing reference.
(2) Move your sub to the location the second sub would occupy.
(3) Measure again with a timing reference.
(4) Do the A+B of those two measurements.

But I've not done anything with summing etc. There might be some time alignment work between (3) and (4).

P.S. An alternative would be to place the sub in the MLP and then move the mic to each possible location as per the sub crawl.
artur9 is offline  
post #21264 of 21671 Old 01-28-2017, 12:04 AM
AVS Forum Special Member
 
markus767's Avatar
 
Join Date: Apr 2009
Posts: 9,392
Mentioned: 78 Post(s)
Tagged: 0 Thread(s)
Quoted: 3654 Post(s)
Liked: 1304
Quote:
Originally Posted by turboman123 View Post
So my questions are:
Would it be possible to make such a multisub simulation a reasonable prediction of a multisub configuration?
If yes, how to do this time aligning of data exactly?
Follow the steps outlined by artur9.
You can go one step further and load those measurements into MSO and have the response optimized: http://andyc.diy-audio-engineering.org/mso/html/

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 #21265 of 21671 Old 01-28-2017, 11:18 AM
** Man of Leisure **
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 15,123
Mentioned: 159 Post(s)
Tagged: 1 Thread(s)
Quoted: 6630 Post(s)
Liked: 3661
Quote:
Originally Posted by buddhamus View Post
Hey Alan, I have 4 x Submersives 1000w subs so they are all identical subs ... Funnily enough it's my nearfield subs that are running out of gas with the Farfields not even clipping while running 5db hot. Could be a placement problem... Hence why I wanna try and work this problem out. Thanks again!

Sent from my SM-G900I using Tapatalk
FWIW, I ran some tests that might be of interest to you. First test was to check the output levels of the subs, measured at the MLP, using a REW 60Hz test tone played at -3dBFS, with AVR MV=0 and sub trim=0. The results are shown in the first thumbnail below. Note that all four subs are identical, and are meticulously gain-matched. Two subs are in the front of the room, and the other two are immediately behind the MLP. The first thing that you notice is the varying output levels, which shows the impact of the room and the sub placement. The right front sub is close to a couch, which is likely to be absorbing some of the low frequencies. Second thing to note is that the combined level of the subs at the MLP is 107dB, which is pretty loud (but I rarely play my system at reference).

Test 2 shows the results of REW measurements for a single sub with the mic placed near field. As Matt predicted, the mic clips at levels starting at -15dBFS, so two of the three measurements may be flawed. The next two clips show the output sweeps (notice measurement 3 shows the sweep distorting because of the clipping), and the distortion for each measurement level. Even though the THD at 20Hz is rather high at 23%, THD falls rapidly to 3.4% at 30Hz.

Test 3 shows a measurement at the MLP for all four subs, first at MV= -10 (a typical listening level for me), and then at MV=0 (reference). The 18.7% THD @20hz with MV=0 shows the extreme case, with THD rapidly falling off to 1.4% at 30Hz.

In all of these tests, the MiniDSP Input level and all four Output levels were set to zero. Watching the output meters on the 2x4, the max output reached -18 on the scale, which is right on the border between orange and red.

In summary, I did not find anything in these tests that would be cause for concern, especially since my listening levels are nowhere near as aggressive as the levels used in the test, and 20Hz content is equally rare. I welcome observations and comments from others regarding the results as well as the test methodology. And hopefully the tests will provide some guidance to @buddhamus WRT evaluating his own sub setup.
Attached Thumbnails
Click image for larger version

Name:	Clip1.JPG
Views:	31
Size:	37.6 KB
ID:	1925953   Click image for larger version

Name:	One sub sweep.jpg
Views:	38
Size:	78.8 KB
ID:	1925977   Click image for larger version

Name:	Clip2.JPG
Views:	29
Size:	34.2 KB
ID:	1925985   Click image for larger version

Name:	Four subs distortion.jpg
Views:	30
Size:	75.2 KB
ID:	1926001   Click image for larger version

Name:	Clip3.JPG
Views:	24
Size:	29.6 KB
ID:	1926009  

AustinJerry is offline  
post #21266 of 21671 Old 01-28-2017, 12:19 PM
AVS Forum Special Member
 
LastButNotLeast's Avatar
 
Join Date: Feb 2007
Location: 08077
Posts: 7,787
Mentioned: 33 Post(s)
Tagged: 1 Thread(s)
Quoted: 1497 Post(s)
Liked: 1099
Quote:
Originally Posted by AustinJerry View Post
Even though the THD at 20Hz is rather high at 23%, THD falls rapidly to 3.4% at 30Hz.
And this may help answer my question about "acceptable" levels of distortion.
My TV resonates at 25Hz, but below that it seems to behave.
Michael

Did you really need to quote that entire post in your reply?
Downloadable FREE demo discs: Demonstration Blu-Ray Discs (Independently Authored)
Welcome to AVS - Get out while you still can!
For most of the time, the here and now is neither now nor here. Graham Swift
LastButNotLeast is offline  
post #21267 of 21671 Old 01-28-2017, 12:29 PM
** Man of Leisure **
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 15,123
Mentioned: 159 Post(s)
Tagged: 1 Thread(s)
Quoted: 6630 Post(s)
Liked: 3661
Quote:
Originally Posted by LastButNotLeast View Post
And this may help answer my question about "acceptable" levels of distortion.
My TV resonates at 25Hz, but below that it seems to behave.
Michael
So, would you say that these results are reasonable or not?
AustinJerry is offline  
post #21268 of 21671 Old 01-28-2017, 01:03 PM
Member
 
MBrown2020's Avatar
 
Join Date: Aug 2013
Location: Wisconsin
Posts: 38
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 30 Post(s)
Liked: 11
Quote:
Originally Posted by AustinJerry View Post
I think there is room for improvement. Since you have only two sub outputs, are the two front subs equidistant from the MLP? If yes, then have you experimented with all available placement options for the subs? If no, then there could be an alignment issue. The response near what is likely the crossover point needs improvement. Have you tried the "sub distance tweak" to see if the response could be smoothed out?

I have attached a snapshot of my sub response for you to compare.
I did the sub tweak as best as I could do. I've noticed now there is a big dip round 17hz that wasn't there with the 2 subs and the combined left+right+subs has a huge peak round 40hz now with the added 3rd sub.
Attached Thumbnails
Click image for larger version

Name:	cent +subs.jpg
Views:	26
Size:	47.5 KB
ID:	1926369   Click image for larger version

Name:	l+rresponse.jpg
Views:	29
Size:	43.9 KB
ID:	1926377   Click image for larger version

Name:	Response_before_3rd_sub.jpg
Views:	29
Size:	56.9 KB
ID:	1926385  
MBrown2020 is offline  
post #21269 of 21671 Old 01-28-2017, 01:36 PM
** Man of Leisure **
 
AustinJerry's Avatar
 
Join Date: Jan 2003
Location: Austin, Texas
Posts: 15,123
Mentioned: 159 Post(s)
Tagged: 1 Thread(s)
Quoted: 6630 Post(s)
Liked: 3661
Quote:
Originally Posted by MBrown2020 View Post
I did the sub tweak as best as I could do. I've noticed now there is a big dip round 17hz that wasn't there with the 2 subs and the combined left+right+subs has a huge peak round 40hz now with the added 3rd sub.
You are right. I think the measurement without the third sub is better. But that could be just a placement issue, or time alignment. I assume you have time-aligned the three subs before taking the measurement?
AustinJerry is offline  
post #21270 of 21671 Old 01-28-2017, 01:41 PM
Member
 
MBrown2020's Avatar
 
Join Date: Aug 2013
Location: Wisconsin
Posts: 38
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 30 Post(s)
Liked: 11
Quote:
Originally Posted by AustinJerry View Post
You are right. I think the measurement without the third sub is better. But that could be just a placement issue, or time alignment. I assume you have time-aligned the three subs before taking the measurement?
What do you mean by time-aligned? Audyssey was completed using the pro kit before I started tweaking the distances of the subs and that was the smoothest I could get it.
MBrown2020 is offline  
Sponsored Links
Advertisement
 
Reply Audio Theory, Setup, and Chat

Tags
Dayton , Dayton Audio , Room Equilizer Wizard Rew



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