Topic: Technical Question Re-Freq Response Plots

[stevetoney]

I was looking at the frequency response plots of the B&K 4022's in the yard sale...

http://taperssection.com/index.php/topic,98857.0.html

I'm curious about the fall-off on the right end of the plots.  In practical terms, is this fall-off actually heard on recordings such that it makes any difference?  When I look at similar plots on the Neumann cardiods, it doesn't appear that the drop off is as significant although Neumann doesn't take their plots out to as high a frequency. 

Just wondering because it seems to me that these higher frequencies are beyond human hearing anyway, aren't they?

Steve

[Church-Audio]

I was looking at the frequency response plots of the B&K 4022's in the yard sale...

http://taperssection.com/index.php/topic,98857.0.html

I'm curious about the fall-off on the right end of the plots.  In practical terms, is this fall-off actually heard on recordings such that it makes any difference?  When I look at similar plots on the Neumann cardiods, it doesn't appear that the drop off is as significant although Neumann doesn't take their plots out to as high a frequency. 

Just wondering because it seems to me that these higher frequencies are beyond human hearing anyway, aren't they?

Steve

In order to judge a roll off on a plot you have to understand its scale on the plot your looking at there is a different of about 2.5 db at 20k lol.... I would say that's pretty dam flat and not likely to be heard. The scale is magnified so you can see the real plot of the mic. Most company's use smoothing an algorithm designed to fool the reader into thinking something is flat when its not. The other trick most people use is a wide scale so it looks flat but with a wide scale a small movement in the line could be 10 db! B&K / DPA make some of the best mics in the world and they are one of the very VERY few companies that publish accurate frequency graphs for there products.

The other thing to look at is sensitivity ratings in your graphs one is rated at 7.1 mV the other is 7.8 mV I would say they are very well matched. Based on the graphs. The nice thing about B&K Is you can send the mics back to them for testing if the sensitivity numbers have changed you know something has happened to the mics in question. Now I am not talking .5 of a millivolt but if you go from 7.1 mV to say 4mV you know the mic has issues. And when your spending this kind of money a conditional sale should always be considered based on B&K'S re-examination of the mics to be purchased * used * IMO. And the resulting sensitivity numbers that come back from the tests.


Although anything above 20k is not something you can hear. I personally believe that there are harmonics above 20k that effect what you hear below 20k. So I think its important to have a mic that goes up to 25k or more if possible. That being said there are always issues with digital when you try and go up that high with out a filter. But that's another argument.

Chris

[JasonSobel]

yeah, the scale is real important when looking at these graphs.  as a comparison, here's the frequency plots that came with my gefells (matched pair):
http://www.turtleside.com/MG/0851-0852.pdf

as you can see, my mics are close to -10 dB at 20 kHz.
another thing to consider when mic companies publish specs is that they cane pick and choose the frequency cut-off points that they report in their general specs.

for example, the specs on the DPA (B&K) website say:
On-axis: 40 Hz - 20 kHz ±2 dB

ok, now clearly, the mics frequency response does not stop on a dime at 40 Hz.  many mic manufacturers like to report 20 Hz - 20 kHz as the frequencu response.  DPA made a marketing decision to call is 40 Hz - 20 kHz, because they are known for having "flat" mics and wanted to report their mics to be +/- 2 dB.  The frequency response down at 20 Hz is lower than -2dB, so DPA chooses not to report it.

on the other hand, some mic manufacturers would rather report a frequency range of 20Hz-20kHz, but they leave off the +/- whatever dB the response curve is at either end.  The written specs for my gefells is also 40 Hz - 20 kHz, but they don't report any +/- with it, as DPA does.

what it all comes down to, there's a lot of good info on these frequency response plots, but ultimately, how the mic sounds is what its all about

[Chuck]

What Chris and Jason are saying here is all true. While frequency graphs are cool to look at, they don't tell the whole story. Use them as a general guide when evaluating different microphones. As Chris said, averaging is a very common practice for manufacturers to use on these charts. Your ears will tell you more about a given microphone then most of the graphs that you see published.

[DSatz]

Steve, live music has very little energy above 16 kHz by the time it has traveled the distances from which we all typically record. And if you're recording amplified music, all that you would possibly be picking up at 16 kHz or above is noise and distortion anyway.

Nonetheless, the DPA response curves seem to be down only about 2 dB at 20 kHz--and if you look again at the Neumann curves with their tolerances taken into account they are no better. Yet no one (to my knowledge) ever complains about missing top end in the Neumann KM 140 or KM 184.

If you want microphones with range to higher frequencies--say 40 kHz--they are available from Schoeps, Sennheiser, Earthworks, and for that matter, DPA. But there isn't any credible evidence that this will make your recordings sound any better whatsoever, and no conventional playback system can handle such frequencies with fidelity.

The two best uses I know of for this capability are (1) for acoustical analysis of architectural models, in which a planned auditorium might be built at 1/10 scale and then test recordings made in the model and slowed down by a factor of 10 to analyze them--and (2) for slowing down bird song to a speed where the details can be appreciated by human ears. Some completely amazing things go on in bird song that are simply way too fast to hear in real time. But when you're recording music for human consumption in real time, anything above the audible range is generally garbage to begin with, and will only cause trouble if preserved.

--best regards