Applet to create mic CAL file?

[pepar]

I know a CAL file is a renamed TXT file, but are there any applets that will allow me to manually enter the printout data and take care of the text formatting, spacing, etc, at the push of a button?

TIA!

[JohnM]

I seem to recall seeing an applet once that would let you use your mouse to in effect digitise an image of a plot to capture the plot's data values, needed to click on the axes and enter the axis values then click at various points along the curve to capture them. So long ago I have no idea where I saw it though, sorry.

[pepar]

Where can I find info on the format of a CAL file? I can probably make one myself if I could find out how.

TIA,
Jeff

[JohnM]

The file is plain text consisting of pairs of frequency and level values separated by spaces, tabs or commas. The first and last values in the file are used for all frequencies below and above the range of the data respectively.

• Each line of data must have a frequency value (which is in Hz) and a level value (which is in dB)
• The points can be at arbitrary frequency spacing, but each line must have a higher frequency than the one before and there must be at least 2 freq, level data pairs
• Only lines which begin with a number are loaded, others are ignored
• In comma-delimited files there must be at least one space after the comma
• Spaces before values are ignored

[pepar]

JohnM wrote:

The file is plain text consisting of pairs of frequency and level values separated by spaces, tabs or commas. The first and last values in the file are used for all frequencies below and above the range of the data respectively.

• Each line of data must have a frequency value (which is in Hz) and a level value (which is in dB)
• The points can be at arbitrary frequency spacing, but each line must have a higher frequency than the one before and there must be at least 2 freq, level data pairs
• Only lines which begin with a number are loaded, others are ignored
• In comma-delimited files there must be at least one space after the comma
• Spaces before values are ignored

Woo-HOOO! Thanks!

[JonP]

JohnM wrote:

I seem to recall seeing an applet once that would let you use your mouse to in effect digitise an image of a plot to capture the plot's data values, needed to click on the axes and enter the axis values then click at various points along the curve to capture them. So long ago I have no idea where I saw it though, sorry.

You're probably thinking of SPL Trace:
http://www.pvconsultants.com/audio/utility/spl.htm

It will let you trace over a picture of a frequency response graph, and generate a text file of the data points. Kind of tedious, but much better than trying to do it all by hand, if a graph is all you have. I think there's something else like this out there... but haven't seen it.

Now, everybody must remember the basic issue, that taking data from someone's graph of someone's mic would be perfect for HIS mic... but not neccicarliy YOUR mic. The only way to really be sure that you are truly compensating YOUR mic, is to bite the bullet and get it measured. Then YOU have YOUR cal file...

Look to the curves posted in other places on this site of how much variation you get in the different ECM8000's for instance. Using a generic cal file might be more helpful for Radio Shack SPL meter users, since they are VERY non-flat, and you're probably almost always improving things. But, in my opinion, for most other mics, you might make things worse.

That said... don't let it scare you off... The Berhingers, for instance, tend to vary more on the high end, we're mostly concerned with the low end. And even if you aren't totally accurate, having a general idea (and all of your measurements will be relatively accurate to each other, using the same setup) will allow you to do good work.