# Noob caliberation question about HDMI out and usb in



## Justdhruv (Jun 4, 2011)

I am a total noob. I have played with REW a little bit. And i am learning
about using it from various sources: help files. forums etc.

i have installed a Infinite baffle subwoofer in my home theatre and i want to use REW to find the room modes. I intend to try to deal with the room modes with acoustic treatment only, to begin with. And later get in to some eq. I have already purchased the FBQ1000 for this purpose.

Before starting with any measurement, one has to calibrate the sound card and the mic.( for the mic i have the calibration file)

I have a Macbook Pro 17" which is running REW. For the output i am using a display port to HDMI adapter outputting to UMC-1 and the i have got a dayton emm-6 mic which is connected to the MBP through USB. as shown in the attached image.










The manual suggests that i connect the line out to the line in. Which does not seem possible in this case. I can however connect the computer's regular line out to line in.

The other option is that i can connected the LFE channel out from the UMC-1 to XLR mic in. But the LFE will be out putting only below 100 hz.

What are my options here. Any help will be greatly appreciated.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Welcome to the Forum!

You have at least a couple of issues here. A sound card calibration file requires a line in / line out loopback. This is an analog connection and it can’t be accomplished with an XLR-to-USB converter like your MicMate, or your display port-to-HDMI converter. Without the calibration file, you have no idea what the frequency response of these devices is, and if it’s not flat then REW cannot make allowances for it. This will lead to frequency response readings that are inaccurate.




> What are my options here. Any help will be greatly appreciated.


This thread covers the equipment requirements / options for REW, and shows wiring diagrams for connections:

REW Cabling and Connection Basics​
Regards,
Wayne


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## Justdhruv (Jun 4, 2011)

Thanks Wayne.
So this means that I should just use the laptop line and line out. And forget about the two interfaces for the calibration process.
I have a rode video mic. Maybe I can use that instead of the Dayton emm-6 
How does one make a calibration file for a mic?


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## Ile (Nov 23, 2010)

Justdhruv said:


> I have a rode video mic. Maybe I can use that instead of the Dayton emm-6
> How does one make a calibration file for a mic?


Video mic is directional so it's no good for room measurements and you need calibrated mic to make calibration file for a mic.

Use your dayton mic with calibration file + usb preamp and skip soundcard calibration. Good quality soundcard is pretty flat between 20-20 000Hz area and not so good ones have gradual roll off at low, high or both ends. 

You are looking for +-15db peaks and nulls caused by room modes around 30-100 Hz area, so it should be just fine without soundcard file.:T


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## Justdhruv (Jun 4, 2011)

thanks ile.

That was encouraging. I did a line out to line calibration. And indeed that sound card of the MBP has a flat response.

I have another problem though. REW is not able to use the usb powered mic.

I have a demo FuzzMeasure, and it is seeing it. The sound prefs of OS X can also see it and show the sound level. 

In fact once even REW was using it. But i cannot get it to use it again. Is there a setting i am missing. I am using "default device" setting for input.


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## Ile (Nov 23, 2010)

Justdhruv said:


> In fact once even REW was using it. But i cannot get it to use it again. Is there a setting i am missing. I am using "default device" setting for input.


If you can't find usb cards input from REW, leave it "default device" and try to set usb card as default from OS audio settings.


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