Hello, just passing through,
There are three versions of C4:
1. The old ones
2. The new ones
3. The even newer ones, which are like the new ones, except that they are charcoal grey and have a bug fix that was causing them not to play nice with the Zoom H4 portable recorder.
The difference between the old and the new versions, in terms of circuitry is vast. While all versions use the same heads, the newer mics have a completely new circuit. This originally came about due to an engineer in NYC who found the C4 omni to work particularly well for vocals - but was experiencing issues from time to time with the mic circuitry overloading. Now personally, I could sing all day into one of those mics and it wouldn't come near scorching, but context is everything and in this case it's not uncommon for the above mentioned engineer, one Louis Brown, to record sopranos from The Metropolitan Opera. You may wonder how it would come to be that a cat who regularly records such high level clients is employing a Studio Projects pencil mic, rather than the usual suspects, the Sennheiser MKH, Schoeps CMC**, Neumann KM***, etc. It turns out that he does use those mics, but came by the C4's when his tech picked up a pair to try out at the Manhattan School of Music. He liked how they sounded, so he ran them by Louis, who discovered that the C4 omni was the sound he was looking for. Ta-da. The Aristocrats.
I'm getting to the point, by the way. Thanks for staying with me here...
So, this whole SPL handling issue got to bugging me after hearing some of these beautiful recordings with an occasional SPLAT during a high transient, so I set out to fix the problem. In the old design, the limiting factor in SPL handling was the single output transistor. Very high transients would crash into the + rail resulting in a very undesirable clipping. Rather than modify the existing circuitry, I began working on an entirely new design with an output circuit that could handle a brutally high signal voltage. Along the way, I changed the pad circuitry from shunt capacitive to resistive, which makes for lower hiss and less phase distortion and I added another high pass filter cutoff, thereby getting rid of the "either-or" pad/high pass switch. The resulting topology is entirely different from any other condenser mic circuitry that I know of. My criteria for design was this:
1. High SPL handling.
2. Low circuit noise
3. Wide band linear frequency response.
4. High "in to out" signal ratio, which is important in "follower" type circuitry, where voltage gain can never surpass a gain of slightly less than 1.
5. Fast transient response
In comparing the specifications of my circuit to other pencil mics, I found that some models, such as the KM130 spec'd out similarly. The reason for this, I believe, is that given the type of mic: P48 power, solid state circuitry, vacuum deposited metal on mylar substrate for the diaphragm material, ~20mm diameter, there is a limit to how far one can push the design before resorting to high voltage circuitry, metal diaphragms, etc. In this case, the limiting factor in SPL handling is not so much the circuitry, as it is the diaphragm itself. With the C4's, I like to run the mylar fairly loose and close to the backplate for good frequency response and sensitivity. If I were to back off some of those parameters, we could go even higher in SPL handling, for instance, but would thereby compromise other desirable qualities of the mic as such. As it stands, the mic can now handle the divas, which is what we set out to do in the first place. But along the way, we also picked up a few dB in signal to noise, which pleases me to no end, especially in a small capsule mic. Other changes include a hypercardioid head, a simple mic clip rather than the shockmount - a piece that just did not turn out the way we wanted it to (Now Telefunken uses it for their "classic reproduction mic"), aluminum stereo bar with modular bushing to raise one mic above the other at precisely the correct height for coincident stereo recording and finally, a specially designed windscreen which I'm sure very few people notice, but I put a lot of work into that particular detail just the same...
Anyhow, that's the squid on the C4's if anybody else asks.
Cheers,
Brent Casey
Engineering and Design
PMI Audio Group
Topic: Studio Projects c4 - 2 versions? (Read 6479 times)