Guidelines for nearfield measurement with UMIK-1

[bsexton]

I was taking measurements yesterday, trying to evaluate a center channel speaker I bought used.
I set the microphone up on a tripod, aimed the mic directly at the mid and tweet, from approximately 2 feet away.
Pure direct mode on Marantz receiver, -30db volume, graph shows the fundamental at 39.7 db
Used the regular calibration file
At some points in the measurement, it shows up to 189% distortion, with the lowest level at 67.2%

I'm guessing something went wrong with the mic, a measurement from earlier this year, a nearfield measurement of a subwoofer, at 102 db, only measured 3.7% at it's highet point.

Is my mic broken, or something messed up in settings?

 

[MediumRare]

Perhaps the level was too low. The -30 dB on the amp is not meaningful. Aim for 75 dB SPL when you check the level before doing the measurement. A good speaker should not go above 1% distortion at any point above 100 Hz at a near field SPL under 85 dB.

 

[Gerry Iaria]

I was taking measurements yesterday, trying to evaluate a center channel speaker I bought used.
I set the microphone up on a tripod, aimed the mic directly at the mid and tweet, from approximately 2 feet away.
Pure direct mode on Marantz receiver, -30db volume, graph shows the fundamental at 39.7 db
Used the regular calibration file
At some points in the measurement, it shows up to 189% distortion, with the lowest level at 67.2%

I'm guessing something went wrong with the mic, a measurement from earlier this year, a nearfield measurement of a subwoofer, at 102 db, only measured 3.7% at it's highet point.

Is my mic broken, or something messed up in settings?

I thought that Pure Direct was only 2 channels, please correct me if I'm wrong,