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Discussion Starter #1
I have been using the Rat Shack meter for a while to take measurements. Finally bit the bullet on a mic, UMM-6 calibrated by CSL.

My issue is that the bass does not graph when using this mic. I am convinced I have a bad setting in REW because using the REW SPL meter through the mic while running the generator shows SPL's of 75-85dB between 30hz and 50hz.

But the graph only shows 10-30dB.

I am certain that I have something set wrong but I can't find it.

When I run the same measurement with the Rat Shack meter it shows the bass is 5dB hot. And it sounds hot to my ears.

Anyone know what could be causing the bass to disappear from my graphs?
 

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Discussion Starter #3
Calibration file is loaded. The curve is -10 at 5hz then approaches zero by 20hz.

I'm not sure about unchecking the C Weighted SPL. In the mic/meter preference the input type is set to Mic or Z weighted.

In the SPL meter app I can select A or Z but when I calibrate the level it automatically goes back to C.
The SPL meter app is set to SPL, C, and S. When I try selecting Z or A it flips back on it's own.

Thanks for the help.
 

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Discussion Starter #4
It probably is something to do with the C curve but I can't figure it out.
I've uninstalled REW and reinstalled to clear things out. Cleared the log.

Preferences.
The Soundcard is SPDIF out as Default Output, no hdmi. UMM-6 in as Microphone.
Mic/Meter is unchecked C Weighted SPL Meter, loaded narrow band response 0 degree.

Here's a screen shot with the frequency generator running at 35.3hz and the SPL meter showing 85dB while the graph in the background shows -28dB or 57dB.
The SPL meter shows C selected. It won't let me select anything else. It reverts back to C when I run a calibration.

I'm stumped. :huh:
 

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The measurement looks like a plot of speakers only with the speakers set to "small", no contribution from a sub. What mode is the processor in when you measure?

Is the REW SPL meter showing the same levels as your RS SPL meter if you put it in the same place as the mic?

What does the RTA plot look like when you play the 35Hz tone?
 

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Discussion Starter #6
Agreed, it looks like there is no sub when using the UMM6 but it is there and is playing hot.

I took side by side measurements of the UMM6 versus the Rat Shack SPM. No smoothing.

The first graph is an overlay of the two. Both taken with the same volume settings with the mics sitting next to each other, 4" apart. Green is the SPM with C checked.

Second is the measurement using the SPM with C weight box checked.

Third is the UMM6, same settings on the preamp, re-calibrated SPL in the app, C weight box unchecked.

Fourth is an RTA using the UMM6 at 35hz, no averaging. Not sure what this tells us but hopefully someone else can explain it.

Each mic was used with their calibration files. The SPM just uses the standard file downloaded from here a few years ago when I started this journey.
 

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That's pretty strange. Could you attach the mdat file that has the RS and UMM measurements in it?

Does the UMM measurement come out the same if you switch to the other input channel (left if you were using right or vice-versa)?
 

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Discussion Starter #9
Ok, tried selecting Left and Right input as UMM default and UMM microphone, for four trial runs and it made no difference.

Also tried a run with invert checked, again no significant difference.

Then bumped the replay and record buffers up to 128k each with no significant changes.

What is really weird is when you look at the phase graphs between the two mics. The SPM looks reasonable to me. The UMM phase measurement is all over the place. Maybe this is part of the puzzle.
 

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Discussion Starter #11
No luck.

I've tried 44.1, and 48 in REW also played around with the sound card settings just for kicks. Set the card to output 44.1 and 48 combinations with REW set at both. No luck.

Also bumped up my ASIO buffer to 1024 samples.

Searched for driver updates on the mic. Zip.

It doesn't make sense. The reading look correct while the measurement is happening. While the measurement is happening the bars show output steady at -3dB and the input bouncing around -10 to -20dB on both the SPM and the mic measurements.
When I get to the graph the graph shows sound rolling off below 120hz on the UMM-6. :huh:
 

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Which version of REW are you using, the latest beta? Have you tried using the Java drivers rather than ASIO?
 

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Discussion Starter #13
REW V5.00 build 2142.

I've uninstalled and reinstalled it a few times. Also done the, delete preferences and shut down to reset things.

I do not see a selection on this version for ASIO versus Java, although I remember it from past versions. Maybe I'm not looking in the right spot. Should it be on the Soundcard tab? I can go into the M-Audio control panel to disable ASIO.

The card is an older Audiophile 96/24 that is updated with current drivers and control panel software.

I can't run sweeps today but will try some more tomorrow afternoon if possible.
 

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Discussion Starter #15
New Attempt. I'm about 30 seconds away from giving up entirely on the USB option.

V5.01 build 2863.

Used asio4all to add 6ms hardware buffer offset in order to get the mic to play nice with the sound card.

Graph has some volume now but it is still jibberish with an odd curve and phase issues.

Samples were taken at 48khz and 44.1khz with minimal differences.

In room manual measurement of 28hz - 40hz measured individually at 1hz increments is about 80dB.
 

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Looks like some kind of feedback loop happening. If you tap on the mic do you hear anything from the speakers? Are there any monitoring controls on the M-Audio control panel, or (if you are on win7/Win8) is 'Listen to this device' ticked on the properties for the mic?

Does the PC have any other audio output you could try, maybe a basic built-in card?
 

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Kyhl,



This pic shows that you have two soundcards that just won't play nice together .

I don't know why , but everything you've displayed shows results that are shifted upwards by one octave ( compared to the original event ) .

For instance ( in the pic above ) you outputted a signal of 35.4 hz through one, which the other measured as one octave higher ( just over 70 hz ) .

As John mentioned , try a different soundcard for output ( one that isn't PCI based ) , & is preferably working on the same buss type as your mic ( which is USB 1.1, I believe ) .

The Behringer UCA202 ( which is cheap ) might help you out .

:sn:
 

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Discussion Starter #18
Took some time off to cool my frustrations.

I see what you are saying about the measurements being shifted up an octave but I have no idea why that would happen with the USB mic and not with the SPM.

The computer is an XP machine that was built about a month before windows 7 came out and I haven't upgraded.

Tapping on the mic does not feed through to the speaker output.

There is almost no adjustment to the M-Audio Control panel.

I do not have the correct connections to connect to the sound card built into the motherboard and have no intention of buying them or anything else to experiment with this. Also don't feel like opening up the box to remove the current sound card and active the default only to put it back together because there was a 99.9% chance of receiving the same results. This is turning into the definition of insanity and I think I'm done unless a solution is suggested.

What I find most unfortunate is that I have used up all of the time I have allocated to upgrade my room just on this silly experiment which accomplished nothing. In two weeks I will have no more time to work on this until fall. It's very frustrating. So I think I'm done with this so I can actually accomplish something useful.
 

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Discussion Starter #20
Thanks for the support.

Please post here if you find a solution.

My solution was to take the mic to the range. I was running a pointing dog on a hunt test and blasted the mic with a round of 6's from a 12 gauge. It wasn't going to help my room anyway so I had to have fun with it somehow.

The dog ran awesome as expected for Dixieland Rusty bloodlines. She's a beast and that's what really matters. Was nice to be outside blowing stuff up, mic or birds. Made me feel better anyway.
 
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