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Discussion Starter #1
Mic/ speaker calibration to flatline.

I would like to calibrate my UMIK-1 mic and KRK active speaker system in such a way , that the result could be seen as a flat line for the speaker. This setup I would then like to use to see the spectrum analysis of other mics in my collection. I hope it makes sense? Please help.
 

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Welcome to Home Theater Shack. Sounds like you might want to become familiar with our free but incredibly powerful software tool - Room EQ Wizard (REW). The download link for the latest beta version, which is definitely the one you want, is always the last post in THIS THREAD, and we have lots of experts on board who can help if you have questions.
 

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Thank you AudiocRaver, I actually became a member here because of REW. I would like to get some help in using REW to create a reference "flat" combination of existing equipment in order to measure other gear against. Kind of like a lab test. I do have a well designed recording studio and I started building mics a few years ago. They sound great, but to compare them against others would be interesting. If I could manage to generate such a "flat" reference curve I am looking at constructing a crude anechoic chamber for reference measurements.

I need some "setting" on REW where I can load a graph into and then use that graph as a reference "flat". Is there such a function on REW? In other words I want the "other side" of speaker calibartion, where a known speaker curve is available and I can calibrate a mic against that.
 

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With your sound card calibration file installed, but with NO mic calibration file installed, take a measurement of your reference mic with your mic and reference speaker (use only 1) in their reference setup.

Then, with that measurement selected on the main SPL & Phase panel:
Preferences > Soundcard > Make Cal > OK > OK > nameit.CAL > Save

Then install that file as the mic calibration file:
Preferences > Mic/Meter > Browse > select > Open

Verify that soundcard calibration file is installed correctly.

Now the calibration file you created is the reference curve for the speaker and mic combination in that setup.

This reference curve can also be applied to previously taken curves using the Change Cal button on a per-measurement basis, but it will only be valid for measurements taken in the same configuration with the same reference speaker.

For the best results:
  • Use the same speaker for all future measurements.
  • Position speaker and mic PRECISELY in the same positions in the same room with all surrounding surfaces and objects unmoved and unchanged.
  • Reduce/eliminate nearby reflective surfaces.
  • Close micing (1 to 3 ft) helps reduce disruption by room and surrounding objects, but makes precise repeatability of spacing and position/orientation more critical.
  • If you can create a small semi-anechoic space for measurement, like in a closet, that would be ideal.
  • Whatever your approach, precise repeatability of the acoustical environment is essential, and that means mm accuracy.
  • Start and end each measurement session with a re-measure of the reference mic to verify conditions have not changed.
  • Look at the impulse diagram for reflections that are disrupting the measurements.
  • Check the RTA view as a sanity check of your noise floor.
You get the idea, attention to detail and obsessive precision and repeatability will help you avoid frustration and get useful results. But then if you are building your own microphones, this is probably not news to you.

Good luck!:T
 

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Love the handle "TheAlien" :devil:

Welcome to Home Theater Shack! Thanks for joining!

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Discussion Starter #7
AudiocRaver, that is EXACTLY the answer I was hoping for. Precise and understandable. Thank you for the warm welcomes to the forum from the rest of you. I am on holiday in Cape Town at the moment, but will send photo's and graphs as soon as I have everything tested once back home. Keep well and may you have a good Xmas.
 

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Welcome welcome welcome :wave:
 
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