Linkwitz/Panasonic measurment mics

[888guitars]

Hi there I have failed in constructing mics from this idea of DIY measurment mics. I seem to have problems with getting them to sound much at all. Anyway if someone has done this and would like to sell them or make me a set of 2. Name your price. I'm not worried abot housing them as I have made several with bad sounding elements.

Let me know!

Nate

[J M Fahey]

Please post the schematic you are using.

[rjb]

Please post the schematic you are using.

I think he's referring to this (see heading "Microphone" about half way down the page).
It involves doing microsurgery on the mic capsule.
System Test

[888guitars]

Yup. I can do the "surgery" but the mics will be very anemic at best.

[J M Fahey]

Dear rjb, thanks.
I have built some variations of them, but I'd love to know which one is 808 actually having a problem with, so as to be able to provide precise instructions.
Thanks again.

[888guitars]

Here is the "MOD" page. I was maybe hoping this would at least work like my DOD measurment mic but have an XLR.

[J M Fahey]

I can do the "surgery" but the mics will be very anemic at best.

Dear 888
Sorry but your use of the conditional and future tense confuse me.
Have you done the mods or fear it won't work?
You also said

getting them to sound much at all

Does it mean they do not sound (or sound very weak and distorted) or simply they are not as loud as you imagine?
Also, this Linkwitz schematic includes a preamp, *maybe* the capsules work well and the problem is in the preamp itself.
Please describe your problem with a little more detail, and also post voltages measured on mic pin 2 and on op amp pin 1

*If* the mic works but looks "too deaf" in your opinion, it's fine.
It's been brutally padded down in sensitivity to make it stand 140dB SPL.
As you see, I am guessing too much, that's why I'd prefer to hear your somewhat more detailed description of the actual problem.
Good luck.

[888guitars]

I really would like to use a preamp from a line mixer to power them (phantom power) but if i must the battery will have to do.

I have a DOD mic that has a high threshhold for loud spl and was hoping for similar results. Again I like the idea of having it a XLR so i could use a mixer preamp.

[J M Fahey]

I'm starting to guess you want them for recording, not measurement purposes.
If that's so, I guess you are barking at the wrong tree.

[888guitars]

No not at all. I just want them to go into my mixer so i can feed them into my analyzer and also into anything else at the same time.

[Steve Conner]

The Linkwitz mod consists of changing the capsule's internal FET from a common-source amplifier to a source follower. By operating the FET with a gain of 1, the mic can stand higher SPLs before distorting.

If you want your capsule mic with 48V phantom power and a professional XLR output, that's a separate issue and I suggest you use something like Bill Wall's modified version of the Behringer ECM8000:
Http://www.directap.com/Microphones.htm

You could probably pick up a couple of ECM8000s pretty cheap on Ebay etc.

[J M Fahey]

Mmmmhhh, interesting, thanks for posting.
Please notice that Bill Wall's schematics have errors.
The "original Behringer" one dies above 3KHz , and he didn't understand how Behringer creates 2 balanced signals, so he drew that wrong also.
The Mic only sends signal to the XLR pin #2 , making the idea of having a balanced mic signal useless.
In his later Mods, he restores frequency response , but needlessly chops some parts which I guess were put there to make the mic less dependent on real world loads.
On the original mic, the output transistors are properly biased by a voltage divider in a reasonably stable way, and drop somewhat less than 4V each.
In his mod, they are current biased by the 100K resistors, which has 2 effects:
They probably (most certainly) saturate, introducing non linearity (maybe this explains the "new sound" which he likes so much) *and* current through the transistors depends on Hfe (beta) .
Since he does not speak about matching them, said matching is random, no more probable than throwing the Lucky Seven
3 times in a row.
Which anyway is not *that* important, since he still feeds the XLR connector with an unbalanced signal.
Personally, I would get a couple Behringers cheap, just improve capsules, apply the Linkwitz mod only and leave the rest as-is which certainly must work better than the circuit posted.
Uli Behringer may be "cheap" (not bad in my book) but certainly he's no fool.

[888guitars]

Thats probably what I will do Mr, Fahey. (Get the behringer mics) do the mod and be happy. I kind of wanted the satisfaction of a DIY mic.

[J M Fahey]

Fully agree.
*Big* problem for the home constructor (unless he has a fully equipped shop, including a lathe and such) is not the electronics job but the *mechanical* part.
Yes, you can epoxy together ball point pens, car antenna sections and such, but results usually look real crude, although sound may be perfect.
Keep us informed on your results.

[km6xz]

For recording sounds at moderately high levels little electret mics like those $1.50 Panasonic's are not bad for omni-polar response. They are particularly effective for binaural recording with a dummy head. Their small cross section area will result in pretty flat response but their high self noise, due also to their small cross-section. Used appropriately they can find a lot of uses in a studio.
Some pretty expensive mics use those cheap elements because there really are only 3 sources, and one of them does not sell to other companies. Panasonic is the largest producer of those elements, down to $0.20 in volume buys.