# What should be my volume level on my processor?



## trcns (Sep 15, 2015)

This is the first time I will be using REW, I have M-Audio Avid MobilePre MkII connected to McIntosh MX 121 processor. There is a volume on M-Audio Avid MobilePre MkII and on MX 121. Questions which volume should set to what?


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## Lumen (May 17, 2014)

Welcome to HTS!
First, the M-Audio USB interface should be connected to a computer/laptop, not your AVR. Second, you will need a microphone like this one from Parts Express. There's a handy hookup guide on this page and REW user guides on this page. Happy measuring!


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## trcns (Sep 15, 2015)

I went through this setup documentation. The third image reflects my setup. External card M-Audio connected via usb and audio/line out connecting to Processor via XLR.


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## Lumen (May 17, 2014)

trcns said:


> ...which volume should set to what?


Okay, I go one step further...
Your interface has reasonably good frequency response so you can probably skip Step-6 of REW's Online Help Manual but you'll want to read Step-7 to get your answer (repeated here for convenience: 

_*Check Levels Procedure*

"Open the Soundcard Preferences panel and choose whether to set the levels using your subwoofer or a main speaker, making the appropriate selection in the drop-down box in the Levels panel. This tells REW whether to use a subwoofer or speaker calibration signal. If you have connected the soundcard output directly to your subwoofer or to an equaliser that is connected to your subwoofer then choose Use Subwoofer to Check/Set Levels here, if you are connected to an AV processor input you can use the subwoofer or main speaker settings. 

Press the Check Levels... button and follow the instructions on screen. The test signal defaults to an RMS Level of -12 dBFS. If connected to an AV processor, start with the volume fairly low and increase it until the meter is reading around 75 dB. The exact level is not critical. If connecting directly to an equaliser such as the BFD, use the Sweep Level control to change the level of the generated signal. In either case, the final Sweep Level will be used for subsequent measurements - remember to use the same AV processor volume setting whenever measurements are made. 

If input levels are low DO NOT KEEP MAKING THE TEST SIGNAL LOUDER. Input levels should be set through the volume controls on the input path, not the output, using very loud test signals is likely to damage your speakers and your ears."_


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## trcns (Sep 15, 2015)

Thanks, This portion matches my question "Press the Check Levels... button and follow the instructions on screen. The test signal defaults to an RMS Level of -12 dBFS. If connected to an AV processor, start with the volume fairly low and increase it until the meter is reading around 75 dB." 

Now one more question;

I have two subwoofers, should I measure them separately or together?


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

Together.

Regards,
Wayne


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## trcns (Sep 15, 2015)

I am really very sorry, but I am having really tough time in understanding to Calibration part.

I saw several video's where They calibrate the Sound card. But I cannot get it, Loop Back connector I understand, does it include any where connecting a Microphone or Just one loopback wire and nothing else.

If just a loop back connector only then where do we calibrate the MIC. EMM-6 comes with Calibration file, I have a DBX RTA-M mic when and how do I calibrate it?


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

You don’t calibrate the mic. You load its calibration file into REW under Preferences -> Mic/Meter tab.

Regards,
Wayne


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## trcns (Sep 15, 2015)

I was to calibrate the mic my self, since it did not come with calibration file, does one common Calibration file work for all microphones of one particular model/brand?


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## rab-byte (Feb 1, 2011)

No each mic should have its own calibration file. You should be able to find it with the mic's serial number on the manufacturer's website.


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## Lumen (May 17, 2014)

Here's some more info for your mic.
The loopback connection is used for timing measurements. You won't need it for frequency/impulse response and related graphs.


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## trcns (Sep 15, 2015)

I just bought DBX RTA-M Mic, which did not come with calibration file. So I called DBX and asked for the calibration file, for which they answered that there is no specific file for every Microphone, there is only one generic file for all there mic's. 

My question is, should I worry about having dedicated file for this mic? I bought it day before yesterday, so for now its easy to return, but it will be difficult to return a week from now.

In-case, if I have to return it, which mic should i go with ECM-8000 or EMM-6? Which one is better?


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## Lumen (May 17, 2014)

Cross spectrum Labs will calibrate the mics for a fee, but it's not required. Even an iPhone or Radio Shack SPL meter will do the job. More expensive microphone's and precise calibration are needed for high frequency tasks. They are simply not necessary for the type of room/speaker measurements performed for room correction. So the answer to your question is: personal preference.


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## trcns (Sep 15, 2015)

I have the SPL Meter and iphone as well, would you please point me to right documentation for Microphone calibration? Thanks.


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

trcns said:


> My question is, should I worry about having dedicated file for this mic?


It all depends on what your objectives are in using REW. If you’re merely interested in seeing or equalizing low freq response, then the Radio Shack meter Lou mentioned is all you need.

If you’re interested in getting “before and after” graphs to give you an idea what your receiver’s room correction is doing, then you can use the dbx mic with the company’s generic calibration file, as well as any other measurement mic with a generic calibration file. 

However, if you intend to do any manual equalizing of the main-channel speakers, I’d recommend a calibrated mic from Cross Spectrum. You certainly don’t want to do any equalizing based on an inaccurate graph. See the graphs on this page that shows how much off-the-shelf mics can vary in response from one sample to the next.




> In-case, if I have to return it, which mic should i go with ECM-8000 or EMM-6? Which one is better?


Cross Spectrum has quit recommending ECM8000 mics due to unacceptable inconsistencies from one sample to the next. So, you want the EMM6, even if you don’t need a calibrated mic.

Regards, 
Wayne


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## Lumen (May 17, 2014)

Thanks for the clear explanation, Wayne! :T
I learned some things there.


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## trcns (Sep 15, 2015)

Thanks Wayne. At least I know what to do next.

The goal is to buy the best and never use it, even half of its potential.

I contacted the Cross Spectrum, I will try returning the DBX back and will buy EMM-6 from Cross Spectrum..

Audio/Video is an expensive hobby, and I am trying to learn it as much as I can, that's why in my other post I asked for a training on Room WQ. I am going through the user manual, but its not the same as instructor let training. It take way longer to clear the concepts and I really appreciate your and Lumen's help.


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## trcns (Sep 15, 2015)

So I returned the DBX mic and purchased EMM-6 Premium+ from Cross Spectrum. Hopefully Mic issue is addressed.

Now While calibrating the sound card, I have 

"Device Output" and "Device Input" 

And Than "Timing Reference Output" and "Timing Reference Input"

I have M-Audio MobilePre external Sound card with two inputs and two outputs, Looping the Output1 with the Input1.

Question is;

If I want to use Timing Reference while analyzing the room, should I also loop it as well when I am calibrating the Sound card?


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## jtalden (Mar 12, 2009)

No, there in no need or capability in REW to calibrate the reference channel.


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