# Using REW to measure speakers



## GeorgeG (May 10, 2017)

Iv'e got REW up and running and am using it to measure and create FRD and zma files for crossover design. I have calibrated my EMM-6 mic and Audiobox twoi soundcard/analog interface and have started generating some SPL graphs with the mic 1M in front of the speaker baffle. How do I calibrate the absolute SPL db levels in my graphs? IOW, how do I get an accurate sensitivity level of my drivers (SPL output at a reference power level such as 2.83 volts)?

Thanks,

George


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## JohnM (Apr 11, 2006)

You will need an external SPL meter to use as a reference to calibrate REW's SPL reading.


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## GeorgeG (May 10, 2017)

Thanks John. Can you point me to where I can learn how to integrate my SPL reading with the software to get accurate absolute SPL levels?

Thanks,

George


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## JohnM (Apr 11, 2006)

Sure, process is described here.


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## GeorgeG (May 10, 2017)

Thank you . After I calibrate my absolute SPL level with an SPL meter do I calibrate again at any time during a multi driver measurement session. Example: woofer alone in enclosure and then tweeter alone in same enclosure, then a different speaker in the same set up. Or do I only calibrate every time I change the set up, say on a different day?

Thanks,

George


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## JohnM (Apr 11, 2006)

The calibration remains valid unless/until you change any of the gains in the input path.


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## GeorgeG (May 10, 2017)

JohnM said:


> The calibration remains valid unless/until you change any of the gains in the input path.


Thank you.


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## GeorgeG (May 10, 2017)

When using REW to measure driver impedance is this best done in the enclosure if available or in open air?

Also, when measuring frequency response in the enclosure in preparation for crossover design is it best to use an empty cabinet or have it filled with the target level of stuffing/foam?

Thanks,

George


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## JohnM (Apr 11, 2006)

If you are measuring impedance to determine driver parameters then options are free air and added mass or free air and sealed cabinet.

For frequency response in cabinet I'd be inclined to measure with damping material, but you'll probably get more informed answers in the DIY Speakers or DIY Subwoofers parts of the forum


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