Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 684 - AVS Forum | Home Theater Discussions And Reviews
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post #20491 of 20501 Old Today, 11:27 AM
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Quote:
Originally Posted by mharris2007 View Post
Hi Jerry. I have the front left two on one channel of the minidsp, the front right on another, the rear left on its own, and the rear right on its own. I will get more measurements with the polarity and post it here. Thanks so much for your help.

Matt
Post the MDAT file for downloading as well, please.
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post #20492 of 20501 Old Today, 04:18 PM
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My 1st post in this thread. I got Cross Spectrum umik-1 and also made some acoustic panels based on DIY poster thread.
I am trying to measure the difference with acoustic panels in place vs without. Since these are thin panels (2" + 1" airgap) there is likely no difference in sub response but posting that also to understand how improve the in room response for the sub.

Any help with interpreting the data would be much appreciated. Since these are my 1st ever measurements I am not even 100% sure if I did them right (hopefully!).

Images attached.

Link to mdat files
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Last edited by rawhit; Today at 04:24 PM. Reason: Link to mdat files
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post #20493 of 20501 Old Today, 04:41 PM
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Quote:
Originally Posted by rawhit View Post
My 1st post in this thread. I got Cross Spectrum umik-1 and also made some acoustic panels based on DIY poster thread.
I am trying to measure the difference with acoustic panels in place vs without. Since these are thin panels (2" + 1" airgap) there is likely no difference in sub response but posting that also to understand how improve the in room response for the sub.

Any help with interpreting the data would be much appreciated. Since these are my 1st ever measurements I am not even 100% sure if I did them right (hopefully!).

Images attached.

Link to mdat files
That looks really good to me. I like what you've done.

I think you just need to reduce your volume level and redo the measurements (maybe -20dB). You want the waterfalls to fully decay by 300ms.

Your bass response looks a little low. You want the subwoofer level to at least match the main speakers. Many of us prefer it 3-6 (or even 9) dB hot.

Last edited by Marc Alexander; Today at 04:46 PM.
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post #20494 of 20501 Old Today, 05:59 PM
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Quote:
Originally Posted by rawhit View Post
My 1st post in this thread. I got Cross Spectrum umik-1 and also made some acoustic panels based on DIY poster thread.
I am trying to measure the difference with acoustic panels in place vs without. Since these are thin panels (2" + 1" airgap) there is likely no difference in sub response but posting that also to understand how improve the in room response for the sub.

Any help with interpreting the data would be much appreciated. Since these are my 1st ever measurements I am not even 100% sure if I did them right (hopefully!).

Images attached.

Link to mdat files
Sorry, I don't agree with Marc.

Couple of housekeeping suggestions:

- There is no need to have six separate MDAT files. You can conduct multiple REW measurements within the same file. Saving six measurements in one MDAT, rather than have six individual MDAT files is much more efficient.

- You need to describe what each measurement represents, i.e. subs+mains, subs only, etc. Otherwise, how are we going to know what the measurements are? It looks like you have provided four measurements that have subs+some other speaker, and two measurements that are sub only. Just a guess.

First, let's look at what looks like the Subs+mains:



There are huge swings in the freq response below 200Hz. Sub response falls off a cliff below 50Hz. What sub(s) do you have?

Now let's look at a good waterfall. Note the waterfall vertical scale is 60-110, which coincides with your measurement level (which maxes at 100dB). Time window is 450ms. These are the ways we present waterfall graphs, if you read the guide.



The waterfall is not terrible, but since the frequency response is so bad, it is hard to make a conclusion. Now the ETC graph:



Significant reflections higher than -20dB. Not good. Finally the sub response:



Not good at all.

You have your work cut out for you. Sorry if I have been blunt.
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post #20495 of 20501 Old Today, 06:57 PM
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Quote:
Originally Posted by Marc Alexander View Post
That looks really good to me. I like what you've done.

I think you just need to reduce your volume level and redo the measurements (maybe -20dB). You want the waterfalls to fully decay by 300ms.

Your bass response looks a little low. You want the subwoofer level to at least match the main speakers. Many of us prefer it 3-6 (or even 9) dB hot.
Thanks Marc. For the next round, will lower the levels to -20db. These measurements were taken with AVR volume at 0db and no bass boost.

Quote:
Originally Posted by AustinJerry View Post
Sorry, I don't agree with Marc.

Couple of housekeeping suggestions:

- There is no need to have six separate MDAT files. You can conduct multiple REW measurements within the same file. Saving six measurements in one MDAT, rather than have six individual MDAT files is much more efficient.

- You need to describe what each measurement represents, i.e. subs+mains, subs only, etc. Otherwise, how are we going to know what the measurements are? It looks like you have provided four measurements that have subs+some other speaker, and two measurements that are sub only. Just a guess.

First, let's look at what looks like the Subs+mains:



There are huge swings in the freq response below 200Hz. Sub response falls off a cliff below 50Hz. What sub(s) do you have?

Now let's look at a good waterfall. Note the waterfall vertical scale is 60-110, which coincides with your measurement level (which maxes at 100dB). Time window is 450ms. These are the ways we present waterfall graphs, if you read the guide.



The waterfall is not terrible, but since the frequency response is so bad, it is hard to make a conclusion. Now the ETC graph:



Significant reflections higher than -20dB. Not good. Finally the sub response:



Not good at all.

You have your work cut out for you. Sorry if I have been blunt.
Thanks Austin. Lot of useful comments and I definitely have a lot more reading to do. Few quick comments.
  • I will collate the measurements into single mdat file.
  • The 1st two graphs are of only the front right speaker, red one is with room treatment and green without room treatments. The subwoofer was switched off. My mains do fall off sharply at around 40-45hz as you noted.
  • Was trying only compare a single speaker with and without room treatment to see if waterfall plot shows more damped response with quicker fall off in time domain.
  • The subs are Seaton submersive HP+ master and slave crossedover at 90hz. One reason for the anomaly could be that my AVR (aging denon 4311ci) is set to have low freq mode as LFE+main so may be the AVR is trying to blend in and distribute the low freq to both sub and main .

    I will take some measurements with low freq mode as LFE only for complete hand over to sub.
  • Will also take some measurements below 100hz with sub+mains playing together to check if it helps smooth out the response.
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post #20496 of 20501 Old Today, 07:55 PM
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Jerry I wanted to know if I'm on the right track here, I'm trying to get good in room bass response. They are all self explanatory I think. Thank you, I have mdat files in my REW folder but don't know how to post them in a single file, not to take up a lot of room here I just dropped the jpgs below. I just wanted to let you know I'm getting acquainted with Win10 instead of my obsolete 8.1...

To help understand what I was doing I originally did the SDT for music only with L+R mains but then the C+subs didn't look so good, so I tried to get the best of both worlds with optimizing with the SDT for both music and movies.
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Last edited by ahblaza; Today at 07:59 PM.
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post #20497 of 20501 Old Today, 08:01 PM
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I will learn how to just put these in a folder to just open and view instead of all of the above. Sorry
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post #20498 of 20501 Old Today, 08:01 PM
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Quote:
Originally Posted by rawhit View Post
Thanks Marc. For the next round, will lower the levels to -20db. These measurements were taken with AVR volume at 0db and no bass boost.


Thanks Austin. Lot of useful comments and I definitely have a lot more reading to do. Few quick comments.
  • I will collate the measurements into single mdat file.
  • The 1st two graphs are of only the front right speaker, red one is with room treatment and green without room treatments. The subwoofer was switched off. My mains do fall off sharply at around 40-45hz as you noted.
  • Was trying only compare a single speaker with and without room treatment to see if waterfall plot shows more damped response with quicker fall off in time domain.
  • The subs are Seaton submersive HP+ master and slave crossedover at 90hz. One reason for the anomaly could be that my AVR (aging denon 4311ci) is set to have low freq mode as LFE+main so may be the AVR is trying to blend in and distribute the low freq to both sub and main .

    I will take some measurements with low freq mode as LFE only for complete hand over to sub.
  • Will also take some measurements below 100hz with sub+mains playing together to check if it helps smooth out the response.
A measurement of right speaker without the sub is quite useless for general information.

Seaton subs are very good subs. The sub response curve indicates to me that you don't have the subs dialed in properly yet. As for the setting on the 4311, there is nothing wrong with that AVR. I still have a 4311 in the bedroom, and it is a fine AVR. Your speakers should be set to "small" with a crossover ~80Hz, and the setting in the 4311 should be "LFE" and not "LFE+Main".

If you want to show a meaningful graph of bass response, measure subs+center, 15-300Hz, at 85-90dB measurement level, and leave the response curve unsmoothed.
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post #20499 of 20501 Old Today, 08:06 PM
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Quote:
Originally Posted by ahblaza View Post
Jerry I wanted to know if I'm on the right track here, I'm trying to get good in room bass response. They are all self explanatory I think. Thank you, I have mdat files in my REW folder but don't know how to post them in a single file, not to take up a lot of room here I just dropped the jpgs below. I just wanted to let you know I'm getting acquainted with Win10 instead of my obsolete 8.1...

To help understand what I was doing I originally did the SDT for music only with L+R mains but then the C+subs didn't look so good, so I tried to get the best of both worlds with optimizing with the SDT for both music and movies.
That is a ton of measurements. Several look quite good. Clearly moving the sub resulted in a nice improvement. I don't quite understand what you were changing for the other measurements, but surely you can tell which measurement looks the best. Stick with that one. The bass looks really nice!

Edit: I just realized SDT means the sub distance tweak. For some reason, I was confusing it with STD! . I would stick with the SDT that makes the sub+center look the best.
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post #20500 of 20501 Old Today, 08:58 PM
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Thanks, and no I wasn't transmitting STD's. I initially optimized the bass response with the mains as I was concerned with music only at the time but was able to get some really good results with a bit of a compromise using C+ subs and the SDT, so I'm satisfied with bass response for now and realized how important it is to find the best location for the subs. Thanks for all that you do Jerry, without your diligence with that guide none of my efforts would have been possible. I really wanted to see what I was hearing and now will relax for a while and enjoy the fruits of my labors till the next phase.

Best Regards
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post #20501 of 20501 Old Today, 09:54 PM
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Quote:
Originally Posted by rawhit View Post
Thanks Marc. For the next round, will lower the levels to -20db. These measurements were taken with AVR volume at 0db and no bass boost.


Thanks Austin. Lot of useful comments and I definitely have a lot more reading to do. Few quick comments.
  • I will collate the measurements into single mdat file.
  • The 1st two graphs are of only the front right speaker, red one is with room treatment and green without room treatments. The subwoofer was switched off. My mains do fall off sharply at around 40-45hz as you noted.
  • Was trying only compare a single speaker with and without room treatment to see if waterfall plot shows more damped response with quicker fall off in time domain.
  • The subs are Seaton submersive HP+ master and slave crossedover at 90hz. One reason for the anomaly could be that my AVR (aging denon 4311ci) is set to have low freq mode as LFE+main so may be the AVR is trying to blend in and distribute the low freq to both sub and main .

    I will take some measurements with low freq mode as LFE only for complete hand over to sub.
  • Will also take some measurements below 100hz with sub+mains playing together to check if it helps smooth out the response.
Quote:
Originally Posted by AustinJerry View Post
Sorry, I don't agree with Marc.
AustinJerry is the expert here who wrote the guide! I am still learning from information he has posted years ago.

I am impressed by what you have done "so far", for a first time user using UMIK-1 and REW. The waterfall overlay [showing the effects of your treatments] in particular shows you are learning your way around REW!

In hindsight I probably should not have used the phrase "looks good". I was offering some encouragement and advice. I had not loaded your mdat and was viewing on my phone.
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