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|Building a Quality Microphone
Good recording is totally dependent on the quality of the microphones you use. Naturally, you cannot expect your recordings to sound good if the microphone picks up sound poorly. So, the beginning of a good audio chain is always the microphone. Many fine examples exist from various manufacturers, AKG, Shure, Neumann, audio-tecnica, earthworks, Rode,...just to name a few. And specific examples, such as Rode NT1, audio-technica AT4040, AKG C414, Neumann TLM103, Neumann U87, shure SM57, etc., all great mics for their intended purpose. These mics range from a few hundred to thousands of dollars. And, let's face it, if we could all afford a Neumann U87 we'd be all set. But, for most of us, we have to purchase something more affordable.
But, for those among us who might be handy with building things, there is another alternative. In the process of going that rout, I gathered a lot of information about building a surprisingly good, yet inexpensive microphone. So, read on, you too may be able to construct for yourself a versatile recording quality microphone.
If you look around the Internet for information on building microphones, sooner or later you will run across two things. One is information on using electret condenser microphone (ECM) capsules such as the Panasonic WM-61A, and applying the Linkwitz mod to it. The other is information on the Behringer ECM8000 measurement microphone. And, sooner or later, you'll find out that the two items overlap.
The Panasonic WM-61A condenser mic capsule is very inexpensive and provides excellent performance, especially if you apply the Linkwitz mod. The frequency response is flat from 20 to 20K hz! And, for most purposes it is quiet enough.
The Behringer ECM8000 measurement microphone is a very inexpensive phantom powered condenser microphone that performs well for the price right out of the box. However, since it is intended for measurement purposes and not recording, the designers have optimized it for the measurement task. It turns out to be fairly easy, although a delicate operation, to dramatically improve this mic, boosting it into the realm of far more expensive mics.
This is where things start to get interesting.
As it happens, Behringer builds the ECM8000 with a Panasonic capsule. I believe it is the WM-60A. And, it turns out that you can swap capsules and modify the mic's electronics to turn it into a much better mic!
Below is the schematic for the ECM8000 as Behringer builds it. If the schematic looks "busy", you are right. But, remember, Behringer designs these for measurement purposes, so a lot of those parts are designed for stability under any conditions. The good news, is that for recording we can get rid of about half of them!
The Modified Schematic
Below is the modified schematic for the ECM8000, which I would argue, is no longer an ECM8000 mic. I left things in the same relative positions so that you can easily spot removed parts. You will notice that the original 6 volt zener diode has been replaced with a 12 volt zener diode.
Note that if you remove R12 and R13, you need to replace them with jumpers,or the output will be disconnected from the XLR connector! Also, note that the stock ecm capsule has been replaced with a Panasonic WM-61A with the Linkwitz mod.
The Linkwitz Mod
The Linkwitz mod involves cutting the connection on the capsule between the case and the "source" connection. This is a delicate operation. You may very well ruin a few capsules before you get this right.
The Modified Mic
The modified mic is shown below! Note that I have modifed the brass tip of the mic to eliminate the flutes. It took about ten minutes on the grinder to accomplish this step, and it works much better! Looks better too, I think.
How does it sound?
Amazing! You will be very pleasantly surprised at how much better the mic sounds. In short, after the mods, it is a different microphone, and it sounds like a different microphone! After all, we are only using the output buffer/line driver from the original mic---everything else has been removed or replaced! The sound is much more open and cleaner. I'm already using mine for vocals, and achieving very clear and present vocal sounds! I have done some tests with acoustic guitar, and other instruments, and things look very promising indeed!
And It Gets Better!
As with many projects, I learned so much from modifying the ECM8000, that I designed and built a microphone from scratch to take this idea to the next level. Below is the schematic for my phantom powered ECM microphone. You will notice that the main difference is the 2K resistor from the source connection on the capsule to ground. In all my experimentation I've found this works the best. And the mic sounds amazing! Every time I use it, I marvel that a microphone this good can be built from a capsule costing a few bucks!...and a handful of other parts. It shouldn't sound this good!
I used to say, "Perhaps the ultimate"
What you see below is the schematic for what I used think may be the ultimate version of the phantom powered ECM mic (but see the next one further down below). The major modification with this version is the elimination of the zener diode! I've never liked zener diodes. They are extremely noisy devices, so having one in a microphone just doesn't sit right with me. The design below should give the same results as the schematic above, minus the zener diode noise!
Best So Far
Shown here is the schematic for the version of the circuit I prefer now. I cannot take credit for this circuit as there are several variations of it around the Internet. I simply substitute component values that I have found to work well. You will see right away that the circuit has a pleasing symmetrical look to it. And it has pleasing performance also!...sounds great, in fact. You'll find that the circuit gives good results for most circumstances. It still amazes me how much you can do with these inexpensive capsules!