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noobie question :)

sergeauckland

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Do you feed the ECM8000 into a laptop and, if so, how do you do that? I have one with an XLR out. Also, do you know how much changed with the calibration? Mine isn't and I don't have a serial number.
I use a Lexicon Ionix U22 interface that provides the 48v phantom power and gain. That feeds a laptop with either REW or ARTA or whatever other measuring software I might need. I also use the interface for recording.

As to calibration, I did that myself against a calibrated Earthworks microphone, and derived the curve which REW or ARTA use. Somewhat tedious to do but I thought necessary for my application which was to equalise my speakers pseudo-anechoically to +-1dB. The mic is OK uncalibrated for checking in-room responses as calibration errors of a couple of dBs are of little consequence, but those are of the same order as I was trying to correct so thought I'd do it properly, and learn something at the same time.

S
 

RayDunzl

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The vertical axis is in dB SPL. What you're seeing is the self-noise of the UMIK-1 in the RTA window of REW with nothing playing (using a 48kHz sampling rate). USB packet noise typically results in an 8kHz spike. Everything else belongs to the UMIK-1. It has a lot of circuitry built into its housing so that spectrum is to be expected.

Here's my UMIK-1 in my echoic chamber:

1573433286394.png


18hz - Air conditioning
60-300 - pc fans, refrigerator, floor fan on a variac about 20 feet away
300-1000 - ambient
1000Hz+ spikes - electronic in the UMIK1 or its connections or the REW just sees it.

None of this is very important when using it to measure in-room speaker output, usually at 80 or more dB.

If the spikes bug you with a 1000Hz tone being measured, use 957Hz or some other choice so the harmonics don't overlap multiples of 1kHz
 
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RayDunzl

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How can SPL be negative?

0dB SPL is a reference level which is not the absence of sound, but close to the lower limit of you hearing anything under perfect conditions.

Negative decibels represent a fraction of that sound level, Positive decibels a multiple of it.
 

MediumRare

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0dB SPL is a reference level which is not the absence of sound, but close to the lower limit of you hearing anything under perfect conditions.

Negative decibels represent a fraction of that sound level, Positive decibels a multiple of it.
That makes a lot of sense. It's almost like celcius then in that the 0/100 are set at sort of commonsense useful levels.
 
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