Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 447 - AVS | Home Theater Discussions And Reviews
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post #13381 of 13402 Unread 01-30-2015, 08:39 PM
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Got it (well close anyways) - attached is a bit of fun...I know I don't have a million dollar setup, but at least I have something I can begin to tweak. Any feedback hammer away at me.


OH EDIT - this is LEFT Main and SUB - which I just realized is only a starting point, I will get working on the right way to do all this...just relearning this all :-)




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post #13382 of 13402 Unread 01-30-2015, 09:13 PM
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First of all, you need to measure at a much higher level to get a meaningful waterfall graph. Did you calibrate your SPL before measuring or do you have a mic with a sensitivity factor?

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post #13383 of 13402 Unread 01-30-2015, 11:49 PM
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Originally Posted by toofast68 View Post
Got it (well close anyways) - attached is a bit of fun...I know I don't have a million dollar setup, but at least I have something I can begin to tweak. Any feedback hammer away at me.
There aren't any details about what you measured (sub only, left + sub, ???). Please follow the graphing methods laid out in AustinJerry's guide. A link to the guide is in his signature.
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post #13384 of 13402 Unread Yesterday, 04:12 AM
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Originally Posted by Alan P View Post
First of all, you need to measure at a much higher level to get a meaningful waterfall graph.
Levels in that waterfall look more than adequate to me, there's no benefit from using higher levels for waterfall measurements.
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post #13385 of 13402 Unread Yesterday, 07:29 AM
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Originally Posted by Alan P View Post
First of all, you need to measure at a much higher level to get a meaningful waterfall graph. Did you calibrate your SPL before measuring or do you have a mic with a sensitivity factor?
I am really struggling with this I guess...I did try to calibrate with my "old" SPL meter, but I must have screwed it up I guess. Also, I have a UMM-6 mic, pro calibrated by Cross Spectrum...I got a bit lost trying to figure out if I can calibrate using a sensitivity factor...I am hoping I can, seems silly that a super expensive mic relies on the calibration of a SPL meter....please give me any direction you think might help!


Thanks much!
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post #13386 of 13402 Unread Yesterday, 08:35 AM
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Originally Posted by toofast68 View Post
I am really struggling with this I guess...I did try to calibrate with my "old" SPL meter, but I must have screwed it up I guess. Also, I have a UMM-6 mic, pro calibrated by Cross Spectrum...I got a bit lost trying to figure out if I can calibrate using a sensitivity factor...I am hoping I can, seems silly that a super expensive mic relies on the calibration of a SPL meter....please give me any direction you think might help!


Thanks much!
If you go to the Dayton Audio website and input your UMM-6 serial number, you can download the original Dayton calibration file. If you open this with a text editor (windows Notepad or Wordpad will do) the first line will be the sensitivity information. Edit the Cross Spectrum Labs file (90 degree, narrow-band) to copy the first line from the Dayton file and insert it to become the first line of the CSL file. Now restart REW and select the edited file as the microphone correction and the sensitivity will be set automatically. I get a very good agreement between REW and my SPL meter doing this, and no longer have to perform manual calibration of the levels.
Hope the above is clear, regards, Mike.
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post #13387 of 13402 Unread Yesterday, 08:45 AM
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Originally Posted by AV_mike View Post
If you go to the Dayton Audio website and input your UMM-6 serial number, you can download the original Dayton calibration file. If you open this with a text editor (windows Notepad or Wordpad will do) the first line will be the sensitivity information. Edit the Cross Spectrum Labs file (90 degree, narrow-band) to copy the first line from the Dayton file and insert it to become the first line of the CSL file. Now restart REW and select the edited file as the microphone correction and the sensitivity will be set automatically. I get a very good agreement between REW and my SPL meter doing this, and no longer have to perform manual calibration of the levels.
Hope the above is clear, regards, Mike.
Wow, now I am clear...and I just figured out why I was nutty...the first UMM I bought was from Dayton, and thus the sensitivity data was built in and of course ... I realized I should have bought from Cross, so this is my first time using the new mic and I just was super confused. NOW IT IS ALL CLEAR...back to work on this...but it will most likely be after the super bowl...thanks again to all!

Will report back when fixed.
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post #13388 of 13402 Unread Yesterday, 10:13 AM
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Originally Posted by JohnPM View Post
Levels in that waterfall look more than adequate to me, there's no benefit from using higher levels for waterfall measurements.
I think what people may have been concerned about is that with (some of) the USB mics, the noise level in a common home room (untreated etc.) can show as ~50dB. It looks like he wasn't measuring a helluva lot over that. That was assuming his levels were calibrated etc., which it appears they weren't.
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post #13389 of 13402 Unread Yesterday, 11:24 AM
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Originally Posted by cfraser View Post
I think what people may have been concerned about is that with (some of) the USB mics, the noise level in a common home room (untreated etc.) can show as ~50dB. It looks like he wasn't measuring a helluva lot over that. That was assuming his levels were calibrated etc., which it appears they weren't.
Ive have also thought that. But at the same time, REW incorporates a tracking filter which I think JohnPM will point out allows accurate results well into the noise floor.

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post #13390 of 13402 Unread Yesterday, 02:32 PM
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Originally Posted by cfraser View Post
I think what people may have been concerned about is that with (some of) the USB mics, the noise level in a common home room (untreated etc.) can show as ~50dB. It looks like he wasn't measuring a helluva lot over that. That was assuming his levels were calibrated etc., which it appears they weren't.

Got my mic calibrated with the sensitivity file...levels look much better.


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post #13391 of 13402 Unread Yesterday, 02:34 PM
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Added this one as well, still not 100% sure I am posting the right stuff, but I got the legend now which should help


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post #13392 of 13402 Unread Yesterday, 02:38 PM
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Ive have also thought that. But at the same time, REW incorporates a tracking filter which I think JohnPM will point out allows accurate results well into the noise floor.
Sort of, it is mostly the effect of the FFT which is used to generate the plot. The 50 dB (say) 'quiet' reading on an SPL meter is the total level summing across all frequencies. The waterfall plot is analysing and plotting within bands typically a fraction of a Hz wide, so the noise level in the piece between 50 Hz and 50.4 Hz (for example) is typically 20 dB or so lower than the overall 'quiet' SPL.
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post #13393 of 13402 Unread Yesterday, 02:47 PM
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Looking like I should be posting the average...





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post #13394 of 13402 Unread Yesterday, 02:52 PM
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Originally Posted by JohnPM View Post
Sort of, it is mostly the effect of the FFT which is used to generate the plot. The 50 dB (say) 'quiet' reading on an SPL meter is the total level summing across all frequencies. The waterfall plot is analysing and plotting within bands typically a fraction of a Hz wide, so the noise level in the piece between 50 Hz and 50.4 Hz (for example) is typically 20 dB or so lower than the overall 'quiet' SPL.
Click image for larger version

Name:	rta.png
Views:	18
Size:	140.7 KB
ID:	515041

So, would an RTA with no source signal be the better noise floor measurement?

FYI, 46.5db was the RTA read for the attached graph.

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post #13395 of 13402 Unread Yesterday, 02:59 PM
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Looking like I should be posting the average...


Nope. The average is useless. Your original post was OK. What is causing that significant low frequency boost? Is this by design? It also shows as significant ringing below 50Hz.
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post #13396 of 13402 Unread Yesterday, 03:11 PM
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Nope. The average is useless. Your original post was OK. What is causing that significant low frequency boost? Is this by design? It also shows as significant ringing below 50Hz.
Ok thanks....as for the low frequency boost not sure...when I set this up a while ago it was ok...I most likely will rerun the setup and see if I can smooth it out.

As for the ringing....yeah I see that. I have a wall of bass traps up front, but nothing in the back walls. Due to my design (not very smart when I built the room) I really have no room for giant corner bass traps...

Is there any other way to try and tame that ? Would playing with the placement of the subs do anything ? Any other ideas, let me at it.
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post #13397 of 13402 Unread Yesterday, 03:23 PM
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The first step is to understand why the jumps almost 15db starting at 90Hz. If you were able to flatten out the bass, then the ringing would improve. Of course, if you are one of many who enjoy a house curve, then you will be faced with a trade-off between less bass or more bass. It takes quite a few traps to tame bass ringing. Take a look at the traps in my room (My Setup link in my sig). I use the intersection of walls and ceiling quite a bit. No worries about WAF here. Bass traps are always more effective at the intersection of two surfaces.
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post #13398 of 13402 Unread Yesterday, 03:28 PM
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Originally Posted by jim19611961 View Post
Attachment 515041

So, would an RTA with no source signal be the better noise floor measurement?

FYI, 46.5db was the RTA read for the attached graph.
Yes.
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post #13399 of 13402 Unread Yesterday, 03:41 PM
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The first step is to understand why the jumps almost 15db starting at 90Hz. If you were able to flatten out the bass, then the ringing would improve. Of course, if you are one of many who enjoy a house curve, then you will be faced with a trade-off between less bass or more bass. It takes quite a few traps to tame bass ringing. Take a look at the traps in my room (My Setup link in my sig). I use the intersection of walls and ceiling quite a bit. No worries about WAF here. Bass traps are always more effective at the intersection of two surfaces.
I will work on getting the bass to flatten, then see the effect on the ringing.

Since I have to worry about the WAF, I doubt I can do enough traps to help. At least I know what I need to work on. Thanks again!
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Quote:
Originally Posted by jim19611961 View Post
Attachment 515041

So, would an RTA with no source signal be the better noise floor measurement?

FYI, 46.5db was the RTA read for the attached graph.
Quote:
Originally Posted by JohnPM View Post
Yes.
Jerry, this looks like good info for your guide.

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post #13401 of 13402 Unread Yesterday, 11:54 PM
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Originally Posted by jim19611961 View Post
Attachment 515041

So, would an RTA with no source signal be the better noise floor measurement?

FYI, 46.5db was the RTA read for the attached graph.
Spectrum or RTA mode? "Adjusted RTA levels" or not?

Markus

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Originally Posted by toofast68 View Post
Looks like you got a 60Hz hum. Personally, I can't stand that. (My wife was amused/sympathetic when I pointed out a hum in our "theater" that is clearly audible to both of us when the stereo was turned OFF. Gotta figure that out.)

In terms of panels, I did some DIY using the information from here that passes a modicum of design sensibility. Similar techniques may be used to improve the appearance of corner traps.

Some of the panels from that thread are pretty amazing: Bond posters, show posters, etc. Comix panels would be neat. Imagine a '60s Bat-Man POW poster/acoustic panel

IIUC, the panels will help smooth the decay so that ringing is reduced and your bass will be tighter, although some think it ends up being too lean for movies.
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