David Bock Talks Differences Between Vintage And Modern Microphones

David Bock on Bobby Owsinski's Production BlogAfter maintenance stints at such prestigious facilities as the Hit Factory in New York City and Ocean Way in Hollywood, Bock Audio Designs (formerly Soundelux) founder and managing director David Bock went from repairing vintage microphones to manufacturing them. David now utilizes his expertise to produce updated versions of the studio classics 251, U 47, U 47 FET, and U 67. In this excerpt from the Recording Engineer’s Handbook, David was kind enough to share some of his insights to the inner workings and differences between classic microphones and their modern counterparts.

Bobby Owsinski: “What actually makes a vintage microphone so special?
David Bock: There are a couple of things that go into that. The bottom line is that the ’50s were really the golden age of audio design. Those guys really did know what they were doing when they designed a lot of the key gear that people are still using. They used a lot of the correct techniques, and they had the luxury of decent materials and the time to research things properly.

There is a tone to these things that is harder and harder to duplicate. Not impossible, just harder and harder. They had tubes back then that are harder to get now. The available selection of materials was a lot greater back then. Then there’s the element of chance. Why would someone pay $20,000 for a 251? Well, maybe that particular 251 really does sound unique because AKG’s production was so sloppy and the capsules were so poorly machined that you’re bound to get one that excels beyond everything else and the rest are just kind of average. Now we have CNC machines that can make these tiny little holes on the capsule backplate all the same, which AKG really couldn’t do at the time.

As you were trying to build an updated version of a vintage microphone, were you trying to copy everything including the circuitry and trying to get that as close to the original as possible, or were you trying to just make it sound like the original without worrying how you got there?
The sound comes first, but that’s not the whole story. The first thing I had to do was try to find what makes the microphone sound the way it does. There were at least 15 points that you have to look at, it turns out, if you’re going to emulate the sound of a microphone. The first large problem is, “I want to copy the sound of a 251.” Well, which 251? I rented about ten 251s here in town [Hollywood], and you know what? There’s no such thing as a common 251. They’re all totally different. I could hear it and I could measure it.

Among some of them there is a common thread, though. Frequency response is the primary guidepost because all microphones have their own signature, but frequency-response curves don’t always tell you everything. You have to take frequency-response measurements not only far-field but also near-field, which strangely are not published and are completely critical to what we believe a microphone sounds like in the directional world. If you saw a proximity graph and a one-meter graph, you’d have a much better idea of what the microphone sounds like.

The dissection process continued through a lot of substitutions. You might take a power supply and substitute a different circuit topology and see what it changes, for instance. There are also a lot of measurements that you have to do. Our ability to test things today is definitely better than back when the classics were built, but it’s not completely conclusive and opens up a can of worms that says, “If I can’t measure it then I can’t hear it,” which I completely disagree with. If you worked only towards measurements, you end up with something that actually doesn’t sound particularly good compared to things that were designed with listening in mind.

Finally, there are listening tests. My primary listening test is to make a recording of a drum set in a large room. I’ve got a couple of key locations where I place the microphone to give me an idea about the close and distant pickup characteristics. That’s where you start hearing the differences. Microphone capsules are related to drums. If you took ten DW kits and you tuned them all the same, they’d still all sound different. There’s a parallel you could draw towards microphones. You could tune all the snare drums and toms the same and even use measurement devices to be sure that they’re the same, and yet the trained ear of an engineer can pick out the differences between them. We can lock onto things that are different about each one.

What’s the biggest difference in the way microphones are made today from the way the classics were made?
Mass production and availability of quality materials. Also, the need for profitability on a corporate level seems to affect how things are made a lot. I’ve seen the way Neumann microphones are built, and they’re very different from the way they used to be. Because of the way they built their microphones in the ’50s and early ’60s, [it] will allow me to be able to keep those microphones running for a long time. Not so with the newer microphones. They still make a great capsule, but they don’t make the microphone the same in terms of construction. They’re built for ease of production and lowest cost. It’s true almost across the board.

So if we were to make a broad statement, microphones are not made as well today as they were 50 years ago.
No, they’re not. Even if you had a “cost is no object” attitude, you still don’t even have the same metals available. The quality of brass is different now from what they used in the ’50s and ’60s, for instance, and an equivalent can’t be found.

With the way the business seems to be going with less and less emphasis on sonic quality, will there be enough people left to appreciate what you’re doing?
Anybody who is serious about the profession either evolves to a point where they say “I can use an SM57 for every track to make a record” or “I’d rather use a high-quality microphone to make a record.” You’re going to go one way or the other, and most people, if they stay in the business long enough, will usually gravitate to the more exclusive side.”

David Bock also appears as a guest on Episode #148 of my Inner Circle Podcast.

You can read more from The Mixing Engineer’s Handbook and my other books on the excerpt section of bobbyowsinski.com.

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