Topic: DPA 4021 Frequency Response

[tedyun]

If you look at the specs of DPA 4021, it lists the on-axis frequency response as 40 Hz - 20 kHz:

http://tinyurl.com/dhwc6v

However, if you look at the frequency plots of the mics that Darktrain is selling on eBay, you can see that it has a pretty flat response from 20 Hz - 20 kHz:

http://tinyurl.com/c5wun9

(You have to cycle through the photos to see the charts)

Any ideas what account for this discrepancy?

TIA -- Ted

[audBall]

Just a guess as I'm not a DPA owner...

The range from 40hz to 20kHz is picked up "on-axis".  The lower regions of 20hz-40hz are more "omnidirectional" and can be picked up all around the microphone.  Sound is much less directional the lower the frequency gets.  Therefore, the mic will pickup the entire 20Hz - 20khz spectrum and both ranges listed in your post are correct.

[Roger Gustavsson]

Directional microphones are only flat at certain distance. In this case it is at 30 cm. You can see the frequency plots for other distancies here.

[JasonSobel]

the other thing you have to consider is how the frequency range is qualified with regard to tolerances.  In the case of DPA, the specs actually state 40Hz - 20 kHz +/- 2dB.  But the microphone frequency response doesn't just stop at 40Hz, DPA is implying that below 40Hz, the frequency response might be outside the +/- 2dB range.  As the actual frequency plots show, the mics do have a great bass response (which we all know from listening to these mics as well), but below 40Hz, the response might be at -3dB or -4dB (or more or less), and DPA chooses to not highlight the portions of the frequency response outside the +/-2dB tolerance.  Ultimately, that's probably a marketing decision.  DPA likes to market its microphones as having a very flat frequency response, so they'll only publish the 40Hz-20kHz portion of range that falls within +/-2dB.  The other marketing option is to publish a frequency range, but leave off the tolerances.  For example, the official specs for the Neumann km140 say 20 Hz - 20 kHz, but they don't say what the tolerances are.  If you look at that km140 frequency response graph, 20Hz is down at -11 or -12 dB.  But for Neumann, it was more important to market their mics as "20Hz - 20 kHz" rather than market their mics as having a super flat frequency response across the whole range.