# Mbox Windows REW



## HerOnAir (Nov 1, 2010)

Hello!
This is my first message. I am Hernán, I come from Argentina but I live in Germany. Please apologize my English. Since I've learned German it's very difficult to me, not to mix languages. I'm interested in REW and electroacustic measurements. I've work many years in Buenos Aires als FOH technician.
I wan't to buy new gear to make measurements, both room and live soundsystems. 
I own a Digidesign Mbox and a AKG C3000B microphone. 
I want to measure SPL and audio spectrum, RT60, etc.
I've thought that the Behringer DEQ 2496 was perfect to do the task, combined with a MM1 Beyerdynamic and a Voltcraft SL-200, but I've just read a post here where there was no so good opinions about it.
Previously I've thought of a Phonic PAA3, because of their transportability (no notebook is needed) but it seems to have many functions that the REW already have. Also "against" the PAA3 is that you can't correct curves, only with it.
The questions are: 
What would you advice me? 
How can I get good enough results without spending a lot of money?

In case that the Mbox would be usefull, how can I use it with REW?

I know that are many questions but, I hope you have time and lust to answer me,

Kind regards

Hernán Ferrari


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

Welcome to the Forum, Hernan!

It sounds like you’re interested in taking full range measurements. All you need to use REW is:

* A computer.
* A SPL meter such as the Voltcraft you mentioned.
* A USB audio interface. Your Digidesign should work, as long as it is compatible with the computer’s operating system.
* A mic that has been calibrated by a lab. The lab will generate a calibration file that you will load into REW. A calibration file corrects any deviance from flat that the mic has. This is important for accurate frequency response measurements. Otherwise the measurements will be a combination of the room’s response and the mic’s.

Unfortunately your AKG mic is not especially suited for measurements. Typically measurement mics are omnidirectional with a small element. So you will need a new mic. You might check with or recommended vendor Cross Spectrum Labs. I believe Herb will ship overseas, but contact him to make sure. He can sell you a custom-calibrated mic for as little as $70.

Regards,
Wayne


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## HerOnAir (Nov 1, 2010)

Hello Wayne, thank you for your advice and the welcome. You are very kind. I've read that you are an experienced professional in the field. 
In your experience, would you say that with that calibrated mic + mbox + SPL meter (Voltcraft) could I get satisfying results to correct a (not so big) live sound system? Would be the Behringer DEQ2496 a right tool to compensate curves?

What I have read is that Mbox uses ASIO drivers und REW (beacause of JAVA) can recognize only WDM drivers. I suppouse I'll have to feed the onboard sound card from my notebook with the Mbox analog out. In that case I should run Pro Tools and REW parallel. Have someone tried this before? Does it work? Should I calibrate my onboard soundcard? How?

As you can see, I still have many questions and thank to you I feel I'm getting closer! :T

Regards,

Hernán


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

> I've read that you are an experienced professional in the field.


 You’re saying that there’s someone in either Argentina or Germany who has heard of me? Wow, I don't know what to say... :T




> In your experience, would you say that with that calibrated mic + mbox + SPL meter (Voltcraft) could I get satisfying results to correct a (not so big) live sound system?


Yes, that set-up will work. The size of the sound system makes no difference.




> Would be the Behringer DEQ2496 a right tool to compensate curves?


I’ve never used that one, but basically a parametric equalizer gets the best results, and the DEQ has parametric filters. You would probably want to use REW’s RTA feature, that would allow you to view response and tweak filters in real time.




> What I have read is that Mbox uses ASIO drivers und REW (beacause of JAVA) can recognize only WDM drivers. I suppouse I'll have to feed the onboard sound card from my notebook with the Mbox analog out.


With the M-box you will not be using your computer’s onboard sound card. Typically the only issues with outboard sound card or USB interface have to do with it not being compatible with the computer. All connections between the sound card and the sound system will be analog.




> In that case I should run Pro Tools and REW parallel. Have someone tried this before? Does it work? Should I calibrate my onboard soundcard? How?


I know just enough about Pro Tools to be dangerous, but I don’t see how or why you would be using it parallel with REW. REW is primarily for calibrating and equalizing the sound system. Once that’s accomplished, it’s no longer needed. I have no idea what use REW would serve for recording and mixing audio tracks.

Regards,
Wayne


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## HerOnAir (Nov 1, 2010)

Dear Wayne, thanks again. I knew you through your articles wich I've just read as I decided to use REW. I'm glad to be in contact with you.

I'll try to tell you wich are my difficulties with REW and the Mbox: 
I've installed REW in my notebook wich is compatible with the Mbox and runs Windows XP.
I've connected my microphone to the Mbox with Phantom power.
I've try to use REW with the Mbox as input but it didn't work out. REW simply don't recognize the Mbox.
Then I've searched in this forum and I've found that REW works only with WDM drivers wich Digidesign simply haven't developed.

I would like to find a way in wich the Mbox can feed REW's input to make the RTA analysis. 

Thanks you I'm deciding to invest in Behringer's ECM8000 calibrated mic, wich offers Cross Spectrum Labs. 
The questions now is what else should I buy to make the measurements. It would be a pity to buy a new sound card just because Mbox won't work with REW but if is just imposible then I'll have to do it.

Another question is, if I buy the calibrated microphone then I would not need a calibrated SPL meter, or would I?

I've thought of the Berhinger DEQ because it has digital filters to do the "graphic" equalizing. Would you recommend another equalizer?

My idea to "mix" REW and Pro Tools was just to be able to have the Mbox as input and Preamp while REW is running. I have no idea how to use Mbox and REW. :help:

Thank you again! 

Regards

Hernán


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## JohnM (Apr 11, 2006)

According to Avid's website the drivers support ASIO and WDM. If you see the Mbox listed as an audio device in the Windows control panel Sounds and Audio Devices Properties, it has WDM drivers. What devices does REW show in the Soundcard Preferences Input devices list?


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## HerOnAir (Nov 1, 2010)

JohnM, you are right. The soundcard is recognized by Windows XP. In the Control Panel I can choose it as Main Out Device, but it seems that is not possible as Main Input Device (it is simply not on the list).
When I run REW, I can only find as Input:
"Primary Sound Driver"
"Default Device" other 
"SigmaTel Audio" wich is the onboard card.
Unluckly not a trace from Mbox...
I guess the guys on Avid-Digidesign haven't work so hard to make possible a full use of the card "outside" Pro Tools. What a pity!
Have you any idea if there is some "update" or "alternative drivers" available? Have you this "issue" before?
Thanks again to all you guys, I'm glad to find you!

Regards from rainy Germany,

Hernán


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## JohnM (Apr 11, 2006)

That's a nuisance. It would be worth an email to Avid or a post on their support forum to see if there is a driver available to allow access to the input. The Sigmatel onboard soundcard is probably also adequate for REW measurements, so worth trying that. I do plan to support ASIO drivers, but there is a fair amount to do to get that working reliably and some other development work ahead of it in the queue, so that's not a short term fix, sorry.


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## HerOnAir (Nov 1, 2010)

Dear John, thank you for your response. Again, you are right, I should write to Digidesign-Avid.

Right now, I'm thinking of buying a used Lexicon Omega USB sound card in Ebay. The reason is that it has SPDIF in/out wich is in fact a good option for me, because I use the digital input from my Sansui amplifier. Naturally, it has phantom power. So I guess it's a good way to patch "all" in the digital domain. I don't know if there is another card with phantom power and SPDIF in/out that works with 44.1/48KHz (I'm limited to those frequencies because of the amplifier's D/A).
If you had any idea of something similar/better I would like to here it. To you and Wayne, thanks again you're very kind.

Best regards,

Hernán


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## HerOnAir (Nov 1, 2010)

Hello, Hola, Hallo!
I've done some research and I found that the Tascam US-144MkII would be "better", because it doesn't need extra power. I've also read in this forum, that it isn't such a good idea to use SPDIF outputs...

So again, I'm a little bit confused. I thought that, if I connect all in the digital domain, I wouldn't have to deal with "frecuency response/distorsion" problems regarding of the microphone preamplifier wich in this case (tascam us-144mk2/lexicon omega) should be a decently one.

It seems that I haven't understand the whole process so clear, as I thought. 

My idea would be to measure/analize and make corrections with a digital grafik equalizer. So I thought that the correct way to connect the whole thing would be:

Microphone -> Analog Input + 48V USB Soundcard -> USB Laptop -> REW -> USB Soundcard SPDIF out -> SPDIF Input Digital Eq -> SPDIF out Digital Eq -> Digital Input Amplifier

I don't know how much audio quality would be lost if I make the analog connection between the USB Soundcard and the Digital Eq, but I would definitely use the Digital Input from my amplifier. 

So in this way I wouldn't know what and how to calibrate, outside the microphone wich I would buy with the "calibration file".

I hope your experience and advice can help me! :help:

Regards,

Hernán


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## JohnM (Apr 11, 2006)

The difficulty with using digital outputs is only with calibrating the overall system. In practice most soundcards offer very good low frequency extension and going through the loopback calibration process is more useful for picking up any setup problems than compensating for the minor level differences at very low frequencies. 

Audio quality at the "analog versus digital" level is not a concern for acoustic measurements, however, the huge variations imposed on signals by our rooms are several hundred times larger than anything you will encounter in the electronics of the system, whether they are analog or digital. 

In short, you can use anything that works, but a system that lets you make a confidence check by looping the output signal back into the input at some point is very helpful to check everything is set up correctly in the soundcard with no unwanted feedback loops.


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## HerOnAir (Nov 1, 2010)

Great point there John! 
So you are saying that once the soundcard is calibrated I wouldn't have to worry about the analog connections between the notebook and the equaliser in order to have accurate measurements because the "distorsion from room" is far larger than "the possible distorsion" from the electronic devices. In other words, once the microphone and the soundcard are calibrated the great amount of " electronic distorsion" in measurement is "compensated".

Following this reasoning I could buy a decent mic preamp just to do the task from entering the mic signal into the laptop and then it wouldn't be so "unaccurate" to feed my amplifier or the Berhinger DEQ2496 with the laptop's soundcard line output to do the measurements.

Once the measurements are done and the curve already compensated and saved, I could "go back" to the digital interconnection between Laptop -> DEQ -> Amplifier to get the best of audioquality.

Please correct me if I'm wrong!

Thank you again, that concept explained from someone that have the experienced was really illuminating!

Kind regards,

Hernán


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## laser188139 (Sep 19, 2009)

One way to verify the difference on your system, with your laptop, is to take a measurement driving the receiver through the analog connections, take a second measurement driving the receiver through the digital connection, and comparing the result. If you have receiver preouts, you could do this using the preout to avoid the room effects. The comparison of the two curves should give you an upper bound on the difference. 

When I did this on my system, I found no difference above 20Hz, the difference gradually increased to 2dB at 5Hz. Clearly, nothing at all to worry about.

Bill


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## HerOnAir (Nov 1, 2010)

Hi! I'm back!
I've decided to buy an ART Tube MP mic preamp, the ECM8000 by Cross-Spectrum Labs, the Behringer DEQ2496 and a "double" direct box to patch the line out from my laptop's soundcard into the DEQ.
Consecuently, I have to buy the cable to patch line out into the line from the soundcard. So I couldn't make the calibration yet.

I've not decided yet wich sound level meter to buy.
How important is its quality-precision? 
I guess a +/- 1,5 dB, Klass/Typ II device should be allright.

I wish to thank you all for your meaningful help!

Greetings from Saxony

Hernán


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