Help with settings - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 23 Old 02-23-13, 08:47 AM Thread Starter
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Help with settings

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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post #2 of 23 Old 02-23-13, 09:43 AM
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Re: Help with settings


Hey Kyhl,

Did you uncheck the “C Weighted SPL” box when using the mic? Have you installed and loaded the mic’s calibration file?

Regards,
Wayne



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post #3 of 23 Old 02-23-13, 10:10 AM Thread Starter
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Re: Help with settings

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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post #4 of 23 Old 02-24-13, 09:09 AM Thread Starter
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Re: Help with settings

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.
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post #5 of 23 Old 02-24-13, 11:42 AM
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Re: Help with settings

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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post #6 of 23 Old 02-24-13, 04:57 PM Thread Starter
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Re: Help with settings

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.
Attached Thumbnails
Help with settings-mic-v-meter.jpeg  

Help with settings-rat-shack-rlsub.jpeg  

Help with settings-umm6-rlsub.jpeg  

Help with settings-rta-umm6-rlsub.jpeg  

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post #7 of 23 Old 02-25-13, 03:33 PM
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Re: Help with settings

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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post #8 of 23 Old 02-25-13, 05:29 PM Thread Starter
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Re: Help with settings

.mdats. Attached.

I remember trying switching the input channel with the UMM but will recheck it shortly just to make sure.
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post #9 of 23 Old 02-25-13, 05:46 PM Thread Starter
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Re: Help with settings

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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post #10 of 23 Old 02-26-13, 03:37 PM
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Re: Help with settings

The UMM-6 measurement is badly messed up. Try using 48 kHz sample rate to see if that helps.
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