Yet another C12 clone

[kilmister]

Great info Ricardo. Thanks!

Distance I've told isn't accurate cause I haven't measure it. It is definitely more than 1 meter and less than 3 meters. IIRC lab guy has told me he prefers to use greater distance than 1m to avoid proximity errors in measurements. I'll ask this when I see guy next time.

Cheers,
Paavo

 

[ricardo]

IIRC lab guy has told me he prefers to use greater distance than 1m to avoid proximity errors in measurements.

There are proximity errors at 1m and proximity errors at 3m.  Both can be seen in the audio range.

But if you don't measure the distance, you are just guessing.  Because 1m is standard, there is much experience on how specific types of mikes should look. eg Shure SM81, one of the 2 most extended cardioids in the known universe measures flat to 20Hz at 1m.  But actually its roll-off is 50Hz.

Other cardioid measurements showing flat to 20Hz were measured by the Marketing VP.

Have a look at the DPA website for a good discussion of this.

 

[kilmister]

There are proximity errors at 1m and proximity errors at 3m.  Both can be seen in the audio range.

Ah yes of course.

I'll ask if I may have access to lab again to play with measurings and will take few photos from the lab also.

Cheers,
Paavo

 

[ricardo]

I'll ask if I may have access to lab again to play with measurings and will take few photos from the lab also.

If you do, ask if they will show you how to get raw impulse responses of the speaker with both reference mike and your mike.

I would be interested to see some 1 second WAV files.  2012 derives this as part of the process.  Record the 2012 settings.

Don't forget to do back response too (assuming you are measuring a cardioid).

 

[kilmister]

I would be interested to see some 1 second WAV files.  2012 derives this as part of the process.

Do you mean recording test sweeps from output of 2012 or does it export files directly to 1.44Mb floppy or RS-232? I googled for the user manual but nothing bumped up.

Cheers,
Paavo

 

[ricardo]

I would be interested to see some 1 second WAV files.  2012 derives this as part of the process.

Do you mean recording test sweeps from output of 2012 or does it export files directly to 1.44Mb floppy or RS-232? I googled for the user manual but nothing bumped up.

The B&K 2012 is a sophisticated Time Delay Spectrometer.  It uses ..

• Linear frequency sweep to
• derive an Impulse Response which is then processed to get
• complex 'anechoic' frequency response

A more modern method is Prof. Angelo Farina's log sweep method which is now enshrined in his Aurora plugins for Audition.  I worked out the theory for this around 1990 to measure response & THD in the theoretically shortest possible time for production testing.  But the computing power, and especially good A/Ds, were too expensive at the time.

Google the relevant keywords.