# Ruler flat measurements-please help



## JS20000 (Jun 28, 2013)

I have just acquired a Dayton UMM-6 USB microphone for use with tuning my system. I am feeding the output to the system through a Turtle Beach USB-to-Toslink (optical) adapter to a DAC. My laptop (Toshiba C855D) is the source-it is running Windows 8. My microphone is calibrated (the calibration file is loaded into REW). The SPL levels are reading appropriately. Whenever I attempt to measure a sweep, the measured curve is completely flat and I have checked my control panel settings to make absolutely sure there is no monitoring selected. Is it measuring the response of the soundcard instead of the system? I have the input set up for the Dayton microphone and the output for the USB adapter so what else is there? This is very frustrating as I've spent the better part of two hours retracing everything.


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## JS20000 (Jun 28, 2013)

Another thing I failed to mention is that I can make RTA measurements in real time and make adjustments but I can not measure any sweep responses for my parametric eq adjustments-they all turn out like I said; flat.


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## JS20000 (Jun 28, 2013)




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## JS20000 (Jun 28, 2013)

I have attached a graph with my measurements-they're separated.


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## JS20000 (Jun 28, 2013)

I solved the problem: the sweeps were too fast for the microphone to measure. I set the sweep rate to 1M and everything measures as it should.


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## JS20000 (Jun 28, 2013)

I attempted to continue with more measurements today and it's back to goofing up again. I have followed the procedure to the letter and kept all the settings the same-what is with this ? I honestly do not see what I am doing differently. Can anyone answer this for me? I'm about to give up on this software and return this microphone because I've just about had it.


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## JS20000 (Jun 28, 2013)

I have tried everything: shutting down and starting up the laptop with the USB mic connected/disconnected, adding a loopback cable on the "mic in" and headphone jacks, turning the enhancements on and off, etc. I know this mic works with REW. Is it because the laptop is running Windows 8? It measures with the RTA feature just fine but it will not do any sweeps without flatlining at 107db (regardless of where my target level is set). Is it just a bad mic? The calibration file loads into REW every single time I open the thing. I sat around and waited almost two months for this mic to get back in stock and then this happens. I thought this forum was full of experts-am I the only one that's going to be posting on this thread?


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## PassingInterest (Mar 29, 2009)

I take exception with post number four, but I'm okay with the others.
I'm kidding, of course.

So, the problem at this point is your flat-lining at 107 dB?
You may need to adjust the input level (mic level) in the Windows mixer.
Right Click the speaker icon, lower right on the screen.
Select Recording Devices.
Select active input and adjust the input level, so you are not over-driving the sound card's input level.

I hope this helps.


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## JS20000 (Jun 28, 2013)

That didn't work-it's still maxing out. I tried minimizing the input levels, which gave me low signal level warnings and I compensated by simply raising the volume but the exact same result. If I select the UMM-6 as default, there is no input level control so you would have to use microphone master volume on the laptop as your control input mixer. I can only get a good input signal at 80-90db SPL and have the output and input match (at -24db) with the input mixer control in the "settings" menu between .8 and 1.00.


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## PassingInterest (Mar 29, 2009)

You may be maxing out the mic itself.

Nope, scratch that. The spec for the umm-6 states:
*Maximum SPL for 1% THD @ 1000 Hz: 127 dB *


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## PassingInterest (Mar 29, 2009)

I wish I had the same equipment, so I could experiment. But right now, I'm not sure what the problem is.

When you flat-line at higher levels, do you _only _decrease the output level to get it to work again--changing nothing else? I just want to try to eliminate any other variables. 

If you didn't unplug, re-plug or anything else, but _only _tweaked the output, that is one avenue to pursue (output level/input over-load). 

If you unplug, then re-plug the USB device, the device driver might not load completely every time, so the device may appear to be dead on the screen. 

Also, with _some _USB devices, you need to use the _exact _same USB port that you used the first time, or the device drivers won't load--not completely. It's a weird Windows thing.

I don't know if any of that info helps, but it could be some things to check.


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## JS20000 (Jun 28, 2013)

The mic is not maxed out; I have tested with SPL levels almost down to the noise floor as well as ridiculously high SPL levels and get the same result. I will call these people at Dayton to see if it is a driver issue. If it's a driver issue, why does it even work at all? It simply does not want to cooperate with the frequency sweep measurements.


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## PassingInterest (Mar 29, 2009)

JS20000 said:


> If it's a driver issue, why does it even work at all?


I have a different setup.

Sometimes, when I plug in my USB soundcard, the drivers don't load properly and I get results that look like the soundcard is dead.

When that happens, I unplug and re-plug the USB soundcard and then it works and I get good graphs.

This does not seem to explain why RTA would work, but not an FR sweep.

Post a good graph, so we can see what it looks like when it is working.


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## JS20000 (Jun 28, 2013)

Here is a graph of the SPL measurements for the brief moment the microphone was working:


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## PassingInterest (Mar 29, 2009)

That graph looks pretty normal. Is it current, so it is working now, or is it an older graph?

If it is working now, why not try a full 20Hz - 20kHz sweep, if you are testing your mains?

Or, perhaps the graph needs to be adjusted to display more of the results.


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## JohnM (Apr 11, 2006)

To get a flat measurement nearly always means you are either (1) measuring a loopback connection or (2) you have saved one of your actual measurements at that position as a cal file so more measurements at the same position are 'corrected' to flat by the incorrect cal file. Some things to check:

- You should not have a soundcard cal file loaded if you are using a USB mic, so if you have one, remove it
- The mic must be selected as the input in the REW soundcard preferences

To investigate in more detail you will need to post the mdat file for one of your measurements.


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## JS20000 (Jun 28, 2013)

That is an old graph and it is part of a full range sweep. It was flatlining at 107db; I changed the resolution of the sweep to 1M and I got this graph. I closed the program and reopened it the next day with the same settings and it is back to flatlining.


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## JS20000 (Jun 28, 2013)

Here's the .mdat text file for that measurement:

SPL measurement data saved by Room EQ Wizard V4.11
Source: Microphone (2- UMM-6), MICROPHONE (Master Volume), Right channel, volume: 1.000
Format: 1M Log Swept Sine, 1 sweep
using mic/meter cal file:
C:\Users\owner\Downloads\1380937.txt
Dated: Sep 7, 2013 9:06:38 PM
REW Settings:
C-weighting compensation: Off
Target level: 75.0 dB
Note: audio_1
Measurement: Sep 7 21:06:38
Frequency Step: 0.3364485 Hz
Start Frequency: 19.998121 Hz


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## JohnM (Apr 11, 2006)

I need the actual .mdat file to be able to investigate the measurement (the file you get when you use File -> Save Measurement or click on the floppy disk icon to save the measurement).


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## JS20000 (Jun 28, 2013)

Alright, here goes...


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## JS20000 (Jun 28, 2013)

Here's one of a flat measurement:


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## JohnM (Apr 11, 2006)

Very odd, the flat lines look like loopback measurements but the input data says UMM-6...

You do appear to be using a very old version of REW though? Files come up as saved by 4.11, best updating to the latest V5.01 beta version from here, which has additional support for USB mics like the UMM-6. A word of warning though, Dayton's cal files for the UMM-6 appear very irregular, the curves should be fairly smooth, I doubt the accuracy of their cal.


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## JS20000 (Jun 28, 2013)

I had the option to install the beta version but I did not because I was convinced the beta version still had bugs. I'll download the beta version and see how that works out.


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## JS20000 (Jun 28, 2013)

The new version cleared everything right up-the newer version compensates for the UMM-6's sensitivity. Thanks for the help.


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