Is this “flat” in theory or in actuality? It would make it easier to calibrate for other programs if we knew more about what we had. Can you provide a frequency plot (MLSSA or equiv?) Those Panasonic capsules arent what they say in datasheets, and Im a wee bit dubious of anything based on TL084 being pristine by any means.
Pardon my ballbusting, but audio is a sneaky b*tch, and without real-world data I woulndt believe any claim made by any mfg.

The mic looks damn cool. Ala Dave Royer pipe-bomb.

A few thoughts:

a) Guys- Lighten up…this isn’t rocket science…it’s simply a project for somebody interested in acoustics who cannot justify the expense of “pro” gear.

b) Panasonic published a data sheet for the capsule which includes a very flat response plot from the low 20′s to over 20khz. If you choose not to believe the published specs, well, ok. What can I say? Now, it’s entirely true that the response could be altered by the capsules (mis)application, but a fair bit of attention went into addressing that. The data sheet is here:

http://www.hpfriedrichs.com/downloads-projects/wm60a.pdf

c) Somebody used the phrase “pristine” with regard to the tl084 capabilities or lack thereof. Input bias current, input offset current, input offset voltage, open loop gain, gain bandwidth product, slew rate, settling time, CMR, PSR, output impedance, et al, are among the parameters used to characterize an op amp. Note that “pristine” is an audiophile word, not an engineering term. I chose the ’084 because it performs reasonably well, and is both cheap and ubiquitous. But if you don’t like the TL084, pick a different op amp! That’s the nice thing about homebrew gear. It’s what you decide to make it. :)

d) Someone drew my attention to a minor error in the amp schematic. This has been corrected and uploaded to my site.

Pete
AC7ZL

eric,

see:
http://www.hpfriedrichs.com/images-projects/audio-mscheme.gif

The drawing does not illustrate the principle as well as it should, but here’s the trick: when you cut the pcb trace linking the ground terminal to the case, make the cut toward the terminal end of the trace, (not the case end).
this will leave a very tiny pcb “nub” on which you can solder your new ground wire.

I admit to having worked this under a low-power stereo microscope, using a dremel bit with a real fine point on it.

If you try to solder directly to the microphone case, you probably won’t be successful.

If you study the frequency response of the Panasonic datasheet, you notice the following on the diagram:
* the y-axis has got large values, upto +20 dB and -30 dB, that’s why it shows flat for most of the spectrum!
* if they reduced their scale for the Relative Response, it would show the minor variations!
* if you guys are concerned about flat response mics, there will always be slight variation, there is no perfect mic!
* if it’s really absolutely flat, it won’t be cheap!!

Hi,i need a good flat response mic for audio testing.Can someyone help? eg Make and model.Preferrably in South Africa.Wilhelm