Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 457 - AVS | Home Theater Discussions And Reviews
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post #13681 of 14559 Old 02-27-2015, 10:54 AM
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Originally Posted by markus767 View Post
Older UMIK-1's used a 12dB gain setting, the newer ones are set to 18dB.
So, given the headroom issue that the 18dB setting is causing, what is the recommended change to our standard procedure? Lowering the mic output setting in Windows?
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post #13682 of 14559 Old 02-27-2015, 11:07 AM
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Originally Posted by AustinJerry View Post
Ah hah! Do you mean this:



TBH, I have never paid much attention to the fact that Windows reports a 12dB gain for the mic. And since I have never changed the dip switch settings, I was unaware that the Windows gain setting display would change.

Now that I understand, I think it is certainly worth while to mention that, if a user is experiencing clipping, that the Windows gain setting display should be checked. If it doesn't display 12dB, than a link to the thread that shows hw to change the dip switches might be appropriate.

So, to close on the issues you have been experiencing, and now that you have verified that the mic has a 12dB gain setting, are you able to take a 90dB-level measurement without clipping?

Yes sir! exactly! that window shows the corresponding gain on the umik. HOWEVER, each time I changed the dip switches, I had to uninstall the umik driver (via properties tab on the umik recording device), then plug the mic back in and reinstall the driver (should happen automatically) before windows would recognize the new umik gain setting. kind of a PITA but this has been a very grueling but interesting experiment. I am now able to run 88db test sweeps without clipping when the umik is set to 12db gain, but I still don't have much headroom (i think about 3-4 db with the 12db gain on the umik). I'm sure I could get more gain by turning the windows mic volume down, but since I don't see much of a change in the graphs when using the 6db umik gain setting, I'm thinking I will use that one and then can get even more headroom if I need to by adjusting the windows mic volume down. Again, I primarily am going to be using rew to measure my subwoofer, so I would like to have as much headroom as possible to measure at loud volumes (over 100db). The only way I see this being possible is to use the 6db gain on the umik or lower (or a combination of the 6db gain in the umik AND lowering the windows mic volume to get more headroom). Thanks so much to everyone who has helped me so far! attached are the graphs of 6db vs 12 db gain on the umik , and 100 for the windows mic volume. not much difference, so why not use the lower gain setting to give me even more overhead!

I'm new to reading these graphs so if someone feels there is a large diff between them, then maybe I should go back to using the 12db umik gain setting.
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post #13683 of 14559 Old 02-27-2015, 11:11 AM
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Quote:
Originally Posted by AustinJerry View Post
So, given the headroom issue that the 18dB setting is causing, what is the recommended change to our standard procedure? Lowering the mic output setting in Windows?
either this, or lowering the umik gain setting seems to do the trick, or even a combination of both. if you lower the windows mic volume, it seems the spl meter stays accurate until you go down to 10 or lower on the windows volume. At that point, the spl meter seems to increase by 1db. also, if you lower the windows volume to 0, then the spl meter is inaccurate in rew. so, if recommending a drop in the windows volume setting, I would recommend not to go any lower than about 10.
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post #13684 of 14559 Old 02-27-2015, 11:27 AM
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Originally Posted by mattdub1 View Post
Yes sir! exactly! that window shows the corresponding gain on the umik. HOWEVER, each time I changed the dip switches, I had to uninstall the umik driver (via properties tab on the umik recording device), then plug the mic back in and reinstall the driver (should happen automatically) before windows would recognize the new umik gain setting. kind of a PITA but this has been a very grueling but interesting experiment. I am now able to run 88db test sweeps without clipping when the umik is set to 12db gain, but I still don't have much headroom (i think about 3-4 db with the 12db gain on the umik). I'm sure I could get more gain by turning the windows mic volume down, but since I don't see much of a change in the graphs when using the 6db umik gain setting, I'm thinking I will use that one and then can get even more headroom if I need to by adjusting the windows mic volume down. Again, I primarily am going to be using rew to measure my subwoofer, so I would like to have as much headroom as possible to measure at loud volumes (over 100db). The only way I see this being possible is to use the 6db gain on the umik or lower (or a combination of the 6db gain in the umik AND lowering the windows mic volume to get more headroom). Thanks so much to everyone who has helped me so far! attached are the graphs of 6db vs 12 db gain on the umik , and 100 for the windows mic volume. not much difference, so why not use the lower gain setting to give me even more overhead!

I'm new to reading these graphs so if someone feels there is a large diff between them, then maybe I should go back to using the 12db umik gain setting.
You should learn how to use the "Overlay" tab in REW. This would allow you to show both measurements at the same time, making it much easier to spot the differences.
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post #13685 of 14559 Old 02-27-2015, 11:30 AM
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Originally Posted by AustinJerry View Post
You should learn how to use the "Overlay" tab in REW. This would allow you to show both measurements at the same time, making it much easier to spot the differences.
does this help? blue line is 12db gain on umik, pink is 6db gain on umik. both with windows volume at 100 for the mic
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post #13686 of 14559 Old 02-27-2015, 11:55 AM
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(UMIK-1, HDMI)

I just tested with windows volume at 100 and at 0, and don't see any differences greater than the margin of error / natural variation.
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post #13687 of 14559 Old 02-27-2015, 11:57 AM
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Originally Posted by mattdub1 View Post
does this help? blue line is 12db gain on umik, pink is 6db gain on umik. both with windows volume at 100 for the mic
Yes, this makes it much easier to see the differences. Basicly these same until the high frequencies. Not sure why there be any difference. Perhaps someone else will have a theory.

Regardless, a lot of the measuring we do with REW is to compare "before" and "after" scenarios after making a change (adding treatments, moving a sub). The differences you are seeing are absolute differences. When you are measuring relative differences, you won't be changing the mic sensitivity, so any slight differences in absolutes don't really mean anything. Make sense?
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post #13688 of 14559 Old 02-27-2015, 11:58 AM
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Originally Posted by Soulburner View Post
(UMIK-1, HDMI)

I just tested with windows volume at 100 and at 0, and don't see any differences greater than the margin of error / natural variation.
So you are saying that the microphone output setting in Windows has no effect on measurements taken in REW? That seems to contradict what others have posted earlier. I need to run my own test.
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post #13689 of 14559 Old 02-27-2015, 12:05 PM
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Originally Posted by Soulburner View Post
(UMIK-1, HDMI)

I just tested with windows volume at 100 and at 0, and don't see any differences greater than the margin of error / natural variation.

differences in your graphs? or differences in the overhead while running the measurements? I'm attempting to gain more overhead when running the tests while keeping the graphs the same.

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post #13690 of 14559 Old 02-27-2015, 12:09 PM
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Originally Posted by AustinJerry View Post
Yes, this makes it much easier to see the differences. Basicly these same until the high frequencies. Not sure why there be any difference. Perhaps someone else will have a theory.

Regardless, a lot of the measuring we do with REW is to compare "before" and "after" scenarios after making a change (adding treatments, moving a sub). The differences you are seeing are absolute differences. When you are measuring relative differences, you won't be changing the mic sensitivity, so any slight differences in absolutes don't really mean anything. Make sense?
yes, I think it makes sense. basically, the differences in the graphs between the gain settings are unlikely to translate to a large real world difference when measuring my sub placement for example? Also, I ran a few more tests: I get 17db headroom at 6db umik gain with windows volume at 40. I get 10.8db headroom at 6db umik gain with windows volume at 100. I get the same overhead (10.8db) at 12db umik gain with windows volume at 40. Last, I get 2.9db headroom at 12db umik gain with windows volume at 100. all tests were run at 88db.
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post #13691 of 14559 Old 02-27-2015, 12:23 PM
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Originally Posted by AustinJerry View Post
So you are saying that the microphone output setting in Windows has no effect on measurements taken in REW? That seems to contradict what others have posted earlier. I need to run my own test.
OK, I ran a test, and the microphone output setting in Windows does not seem to have any effect on REW measurement levels. When I wrote that section of the Guide, I thought the setting made a difference. Since there have been a number of REW version upgrades since the Guide was released, perhaps REW had altered something internally. As soon as I receive other confirmations of this behavior, I will update the Guide appropriately.
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post #13692 of 14559 Old 02-27-2015, 12:30 PM
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Originally Posted by AustinJerry View Post
OK, I ran a test, and the microphone output setting in Windows does not seem to have any effect on REW measurement levels. When I wrote that section of the Guide, I thought the setting made a difference. Since there have been a number of REW version upgrades since the Guide was released, perhaps REW had altered something internally. As soon as I receive other confirmations of this behavior, I will update the Guide appropriately.
not even a slight variance? when I compare windows volume of 40 vs 100 on the 12db gain setting in the umik, there is barely any difference for me (which would match your account since you are using the 12db gain in the umik). But, when I compare windows volume of 40 vs 100 on the 6db gain setting in the umik, there is a slight difference. attached are the two comparisons. first is the 12db gain setting (windows volume 40vs100). second is the 6db umik gain setting (windows volume 40vs100).

EDIT: I will re-do the windows volume 40 vs 100 test for the 6db gain setting later when I get home. I may not have done these two measurements consecutively with the mic in the same place, so that may be the cause for the variance. Will update later after re-running the comparison graphs.
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post #13693 of 14559 Old 02-27-2015, 12:35 PM
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Originally Posted by AustinJerry View Post
So, given the headroom issue that the 18dB setting is causing, what is the recommended change to our standard procedure? Lowering the mic output setting in Windows?
The setting shouldn't cause any issues because the mic is level calibrated by miniDSP with that specific gain setting. My mic is set to 18dB and has its sensitivity factor set to -.7976dB. A mic with the 12dB setting should differ by about 6dB.

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post #13694 of 14559 Old 02-27-2015, 12:35 PM
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What does your RTA look like with no sweep?
I have never tried a RTA graph. New to the REW program and havent even thought of trying that, or knew what that test did.

At lunch I muscled up and moved my 200lb sub into my bedroom, which is roughly (didnt take measurements of room size) somewhere around 12 to 14 x 12 to 14 x 8ft tall. Its quite small. I hooked one sub up to a extra receiver I had laying around. The strange thing that I found was that with the door closed I had a very flat response from like 20-30hz down to 6-7hz. If I opened up the door I had a peak again around 8hz. Now I was doing this just to see if my living room is the cause for the bump down low. I had the sub in front of my dresser that has our tv on it. It was the only place I could put it in the room and the frequency response from like 40-50 on up took a big nose dive, which is definitely from just improper placement. But, that wasnt what I was trying to learn about. I really should have posted these graphs while at lunch but didnt have time. I can later if people want to see them? BTW I did put the mic in many different locations. A few of them right up to the cone of the driver.

With this peak I am getting when there is a entry way into a hallway or another room goes against everything I have learned as far as room gain from subs, especially sealed subs. My subs are sealed Cap S2's. With my small hallway opening to the front left of my living room going to the kitchen, I would have never thought of getting a bunch of gain anywhere down low, especially the one I get on my graphs.

With my talks with a Cross Spectrum tech, he said in some rooms a entry way to another room of hallway can cause a sudden rise in frequency response in the lower frequency range (he called it some name, that I cant remember. Maybe, thats what I have going on here. That graph with the door closed was silly flat down low unsmoothed. Soon as I opened the door any the hump came back.
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post #13695 of 14559 Old 02-27-2015, 12:38 PM
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Originally Posted by mattdub1 View Post
not even a slight variance? when I compare windows volume of 40 vs 100 on the 12db gain setting in the umik, there is barely any difference for me (which would match your account since you are using the 12db gain in the umik). But, when I compare windows volume of 40 vs 100 on the 6db gain setting in the umik, there is a slight difference. attached are the two comparisons. first is the 12db gain setting (windows volume 40vs100). second is the 6db umik gain setting (windows volume 40vs100).
I wasn't looking for tiny differences, Matt. I changed the output from 100% to 50% and was looking for a significant swing in the REW recording levels. I would not have noticed a small difference, but who cares?
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post #13696 of 14559 Old 02-27-2015, 12:39 PM
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Originally Posted by markus767 View Post
The setting shouldn't cause any issues because the mic is level calibrated by miniDSP with that specific gain setting. My mic is set to 18dB and has its sensitivity factor set to -.7976dB. A mic with the 12dB setting should differ by about 6dB.
The 18db gain setting on the umik is not allowing me any headroom and causes the mic to clip at 88db sweeps. only way I can run 88db sweeps without clipping is to turn down the windows volume setting or decrease the gain in the umik to 12 or 6db. Are you able to run an 88-90db sweep in rew with your windows mic volume at 100 and your umik set at the factory 18db gain?
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post #13697 of 14559 Old 02-27-2015, 12:40 PM
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The setting shouldn't cause any issues because the mic is level calibrated by miniDSP with that specific gain setting. My mic is set to 18dB and has its sensitivity factor set to -.7976dB. A mic with the 12dB setting should differ by about 6dB.
Makes sense. My sensitivity factor is approx. -6
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post #13698 of 14559 Old 02-27-2015, 12:40 PM
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The 18db gain setting on the umik is not allowing me any headroom and causes the mic to clip at 88db sweeps. only way I can run 88db sweeps without clipping is to turn down the windows volume setting or decrease the gain in the umik to 12 or 6db. Are you able to run an 88-90db sweep in rew with your windows mic volume at 100 and your umik set at the factory 18db gain?
Did you adjust the sensitivity parameter at the same time?
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post #13699 of 14559 Old 02-27-2015, 12:42 PM
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I wasn't looking for tiny differences, Matt. I changed the output from 100% to 50% and was looking for a significant swing in the REW recording levels. I would not have noticed a small difference, but who cares?
Did you get the same increase in overhead like I did when running the test sweeps with the windows mic volume at 50 instead of 100?
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post #13700 of 14559 Old 02-27-2015, 12:44 PM
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Did you adjust the sensitivity parameter at the same time?
you mean did I adjust the sensitivity in the cal file when switching between the 12 db and 6db umik gain? if so, then yes I did do that
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post #13701 of 14559 Old 02-27-2015, 12:45 PM
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With my talks with a Cross Spectrum tech, he said in some rooms a entry way to another room of hallway can cause a sudden rise in frequency response in the lower frequency range (he called it some name, that I cant remember. Maybe, thats what I have going on here. That graph with the door closed was silly flat down low unsmoothed. Soon as I opened the door any the hump came back.
This is correct. Open entry ways into adjoining hallways or rooms can influence the FR and decay. These adjoining spaces can act as resonators.

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post #13702 of 14559 Old 02-27-2015, 12:58 PM
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Did you get the same increase in overhead like I did when running the test sweeps with the windows mic volume at 50 instead of 100?
Didn't test this.

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you mean did I adjust the sensitivity in the cal file when switching between the 12 db and 6db umik gain? if so, then yes I did do that
Good.
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post #13703 of 14559 Old 02-27-2015, 12:59 PM
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[QUOTE=AustinJerry;32178881]Didn't test this.

Would you mind checking just to see if you get the same increase in headroom? Thanks
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post #13704 of 14559 Old 02-27-2015, 01:07 PM
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The UMIK-1 has two gain adjustments.

One is the gain set by the internal DIP switches, which change the gain applied to the analog signal from the mic element. It would be unusual to need to change those unless measuring particularly high or particularly low levels.

The other is set by the OS input volume setting. At an input volume of 100 (or 1.0, depending on how the volume is displayed) 24 dB of gain is applied to the digital data. At an input volume of zero, 31 dB of attenuation is applied to the digital data. REW by default adjusts the input volume to have 0 dB, i.e. no gain applied to the digital data. The setting needed for that depends on the operating system, for Windows 8 that gain setting is about 53.

If the UMIK has been selected in REW's input device and input settings REW reads the input volume setting and adjusts the SPL readings to take into account the corresponding gain or attenuation that has been applied to the digital data.
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post #13705 of 14559 Old 02-27-2015, 01:16 PM
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Originally Posted by JohnPM View Post
The UMIK-1 has two gain adjustments.

One is the gain set by the internal DIP switches, which change the gain applied to the analog signal from the mic element. It would be unusual to need to change those unless measuring particularly high or particularly low levels.

The other is set by the OS input volume setting. At an input volume of 100 (or 1.0, depending on how the volume is displayed) 24 dB of gain is applied to the digital data. At an input volume of zero, 31 dB of attenuation is applied to the digital data. REW by default adjusts the input volume to have 0 dB, i.e. no gain applied to the digital data. The setting needed for that depends on the operating system, for Windows 8 that gain setting is about 53.

If the UMIK has been selected in REW's input device and input settings REW reads the input volume setting and adjusts the SPL readings to take into account the corresponding gain or attenuation that has been applied to the digital data.
Thanks for the clarification, John. This has been a somewhat confusing issue.
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post #13706 of 14559 Old 02-27-2015, 01:29 PM
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Originally Posted by mattdub1 View Post
differences in your graphs? or differences in the overhead while running the measurements? I'm attempting to gain more overhead when running the tests while keeping the graphs the same.
I will try again tomorrow, and will look at more parameters. I only did a quick sweep and looked at FR by SPL before I was off to work. I may have misunderstood the implications of the volume setting. Granted, I wasn't running 90db sweeps (though my sub does hit very close to that thanks to DynamicEQ). I will push harder with the new X4000 but I am starting to see what you're saying. It tells me I have about 10db of headroom when I'm at -20 on the AVR. That should make it impossible to hit an average of 90db considering most of my graph is in the 70's except for the sub. Then again, I don't plan on ever using my system at those levels.
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post #13707 of 14559 Old 02-27-2015, 01:45 PM
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Originally Posted by JohnPM View Post
The UMIK-1 has two gain adjustments.

One is the gain set by the internal DIP switches, which change the gain applied to the analog signal from the mic element. It would be unusual to need to change those unless measuring particularly high or particularly low levels.

The other is set by the OS input volume setting. At an input volume of 100 (or 1.0, depending on how the volume is displayed) 24 dB of gain is applied to the digital data. At an input volume of zero, 31 dB of attenuation is applied to the digital data. REW by default adjusts the input volume to have 0 dB, i.e. no gain applied to the digital data. The setting needed for that depends on the operating system, for Windows 8 that gain setting is about 53.

If the UMIK has been selected in REW's input device and input settings REW reads the input volume setting and adjusts the SPL readings to take into account the corresponding gain or attenuation that has been applied to the digital data.
Thanks john. So it sounds like its OK to lower the windows mic volume setting as it won't affect the accuracy of rew measurements, correct? If so, and I want to be able to measure my subwoofer at loud levels, is there a suggested setting you would recommend between the umik gain and the windows mic volume? I am currently clipping at 88db tones through my l/r speakers only (no sub yet). Although, my graphs tell me I'm getting some peaks in the 40-50hz range so I'm guessing those 100db peaks are what's causing the clipping. Thx

Last edited by mattdub1; 02-27-2015 at 01:50 PM.
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post #13708 of 14559 Old 02-27-2015, 02:17 PM
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Originally Posted by jim19611961 View Post
This is correct. Open entry ways into adjoining hallways or rooms can influence the FR and decay. These adjoining spaces can act as resonators.

Have you seen the graphs I have posted in the last few days on this thread? Is this something I would want to smooth with a manual EQ?
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post #13709 of 14559 Old 02-27-2015, 02:47 PM
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Sorry if I gave wrong advice, it was just the advice I was given (not here, in the ULF thread). I couldn't measure over ~118db with the mic at 100, I turned it down to 80 and now I can measure to ~135db (and yes, I realize most folks have no need to measure that high but I was doing max output/compression sweeps on my T-18s).

Are you saying the measurements I've taken with the mic set to 80 are invalid somehow? If so, that sux.
I just thought of something - all you guys seem to be using the UMIK-1 with a sens factor....I'm using a UMM-6 that I have to calibrate the SPL each time I run REW. Maybe this is why changing the mic volume made such a drastic difference for me...?

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post #13710 of 14559 Old 02-27-2015, 02:49 PM
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I just thought of something - all you guys seem to be using the UMIK-1 with a sens factor....I'm using a UMM-6 that I have to calibrate the SPL each time I run REW. Maybe this is why changing the mic volume made such a drastic difference for me...?
Perhaps. But the Guide explains how to add a sensitivity factor to the UMM-6 calibration file as well. If you do this, you won't have to manually calibrate ever again.
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