Every microphone has some kind of characteristic in its favour - frequency response, subtle distortion, proximity effect, warmth, and so on (writes Rob Speight). A good engineer will use each trait to his advantage: "Every mic in my arsenal, including the beloved classics, has characteristics I love and some I dislike," explains Don Miller, owner of Kansas-based Airbourne Audio Productions.
Yet, microphone manufacturers will more often than not suggest a use. "Generally speaking, condenser microphones tend to do a better job with acoustic instruments in the studio than dynamic mics," explains Gregor Zielinsky, Grammy Award-winning Tonmeister and recording engineer.
"However, there are exceptions to this rule, and you will often find a Sennheiser MD 411 or MD 421 for brass or saxophone. Sennheiser's MKH Series, Neumann's KM Series and large-diaphragm microphones are ideal for recording acoustic instruments. Obviously, we are talking about a wide range of different instruments here, so we need to go down to 'instrument level' as it were and take a closer look at which microphone works best for which instrument - bearing in mind that every engineer has his or her own taste and that recording techniques will vary depending on the type of music, for example whether a violin is recorded for classical or pop music."
And that's what this is all about: sax and violins! Or, more broadly, brass and strings: two completely different types of instrument requiring quite different approaches. Weak pun, maybe, but all the same, a valid approach to the issues faced with capturing acoustic instruments.
"Recording strings and brass is tricky because you want to capture the presence of the instrument with a tool that does not over-accentuate the upper midrange 'bite' of horns or the rosin 'squeak' of a bow. In this application, the Telefunken AR-51 is a great complement to most of these situations, while the Telefunken AK-47 does things that border on the religious experience with the lower register brass instruments such as the baritone sax and trombone," evangelises CN Fletcher, US product development/EU operations manager at Telefunken.
"The AR-51 has the ability to capture strings without stridency, and horns that grab without 'biting your head off'. The AK-47, especially with the lower register brass instruments, has the capability to capture the 'air' of the instrument in a highly intimate manner without making the listener feel like they are being assaulted by them."
John Royer of ribbon mic specialist Royer Labs agrees: "Brass and stringed instruments can be challenging to reproduce, especially with their tendency to exhibit shrill or harsh-sounding highs. However, these instruments rarely present harsh or brittle highs at source - it is usually the practice of capturing them with a condenser or dynamic microphone that brings out the worst in them, demanding 'fixing' in the mixdown. The smooth frequency response of a quality ribbon microphone does not over-emphasise the high end of these instruments. Rather, they track them more like they actually sound."
To a greater or lesser degree, engineers and producers tend towards recording strings especially, and brass in certain situations, as transparently as possible, with as much air as possible around strings. Brass on the other hand can be close mic'd or given more space, and obviously a combination of mic choice, placement and environment are all equally important.
"A microphone for both strings and brass must have a wide dynamic range and must be very neutral, if you want to record the instruments as they sound in real life," explains DPA managing director Morten Stöve. "We recommend using mics with a flat frequency response for as little colouring as possible, such as the DPA 4015 or 4006.
"Most acoustic instruments, including brass and strings, produce complex waveforms that require microphones with a good transient response to be reproduced truthfully," says Milab Microphones marketing manager Mattias Strömberg. "For brass, SPL handling may be an important feature. It is also important to have versatile and compact mounting systems. Our rubber shock-mounts are specifically designed to have a low profile but still keep unwanted vibrations from reaching the microphone."
However, many other considerations also come into play: "In general, one has to decide if you prefer large- or small-diaphragm microphones," explains Thomas Stubics, product and marketing manager at AKG. "One of the most famous tube mics in the history of recording was, and still is, the legendary AKG C12. Its successor, the C 414 has become a studio since the early '80s."
The C 414 became so popular, obviously because of its sound, but also its huge 152dB dynamic range and SPL handling of up to 158dB.
"Personally, I prefer the MKH 800, MKH 8040, U87 but also the MD 421 for trumpets and trombones," continues Zielinsky. "The positioning of the microphone is as important as the microphone type itself. For example, if you prefer to have a close trumpet sound - because this enables you to hear the subtle attack of the instrument - you will usually have to battle with the effect that the sound becomes too aggressive once you come in very close with the mic.
"A simple yet effective trick is to move the microphone's main pick-up angle out of the main sound direction of the trumpet. With a mic like the MKH 8040, you can simply point the microphone slightly upwards. This will soften the sound but keep the closeness you want. Of course the distance between the instrument and the microphone is very important too. It will vary with the type of music you are recording and the sound you want to achieve. You may prefer a closer distance for jazz and rock ensembles, sometimes also for big bands, while greater distances are used with classical music and big bands, too."
"I've never heard anything better in a ribbon microphone than Royer's R-122, ever! I always use ribbon mics for their warmth and sweet high frequency response characteristics, but then there is something truly unique about the powered R-122's sound quality," enthuses Grammy Award winner Bruce Swedien.
CharterOak Acoustics president Michael Deming comments: "I have recorded quite a few orchestra sessions and the big-band sessions will typically use a full frequency response dynamic microphone such as the Sennheiser 441 on the trumpet section as it can handle the volume and EQ of the instrument in loud passages and still sound great. The microphone is also very versatile in terms of the possible EQ settings on the mic itself.
"For trombone I like to use a ribbon microphone, but too often the fixed figure-eight pattern will not work in a live situation with a 25-piece group in one room. For these instances I turn to a condenser with a similar sound, such as our S600 large-diaphragm front-address condenser, which has an EQ very similar to a ribbon but is much more suitable for picking up the trombone section. I might put a microphone on the bass trombone separately and mic the first for instruments with a stereo pair. It is always a good thing to have separate control of the bass trombone and baritone saxophone tracks. The sax can be picked up by a nice cardioid condenser. I have always had great results with our E700, SA538, Microtech Gefell UM70, AT4050 and many other similar microphones."
All good microphones should, of course, exhibit as low self noise as possible and in a studio environment, coupled with instruments that have such a wide dynamic range, this is doubly important: "Clearly dynamic range is of key importance in these areas where subtlety and nuance are crucial to players' performance; high SPL handling is also desirable where horn sections are concerned. The AT4047MP has remarkably low self noise to ensure that nothing stands in the way of capturing the pure sound of acoustic brass instruments, for example," explains Audio-Technica's UK marketing sales manager Harvey Roberts.
"Audio-Technica is also aware of the challenges that studio engineers face when miking horn and string sections. So in terms of usability, the multi-pattern options afforded by a AT4047MP and mid-side configuration of the stereo AT4050ST allow for real flexibility in working environments."
AKG also suggests a large-diaphragm microphone, but one that is the smallest large-diaphragm microphone on the market in the form of the M930. This has a dynamic range of 142dB(A) and a very low 7dB(A) noise floor making it ideal for both strings and brass. Additionally, the M296, with its small metal diaphragm has, "...an almost linear frequency response all the up to 20kHz guaranteeing orthophonic recordings both near and far field", according to Elisabeth Kühnast, Microtech Gefell sales engineer.
Yet, it is not just new and improved microphones that engineers want to use on a day-to-day basis. It takes a good few years for microphones to be seen as classics and every engineer will have their own preference. Tom Scott, sax player, composer, arranger and conductor, as well as band leader of the west coast jazz fusion ensemble The LA Express, says of the Milab DC98B that it is "the truest reproduction of horns and vocals I've ever heard". Emmy Award-winning film composer Brian Keane, meanwhile, enthuses about the CharterOak SA538: "I love our SA538! I use it in every string session. Nice full sound with a satisfying top end for both orchestral and bluegrass-style strings."
So, how do manufactures create classics, and do they look to the past to create them?
"A classic would be the MD421 for brass. I also consider the MKE212 a classic, though not as widely known," Zielinsky says. "This is an old pressure zone microphone that was launched in the 1980s. It produces a very warm and open sound on strings in orchestra and chamber music recordings. Many engineers love to use the old tube (valve) mics from Neumann with their special vintage sound and the U87 is an industry standard that can be found in studios all over the world."
In the early 1990s, Audio-Technica launched the AT4033, the worlds first mid-priced high-performance studio condenser. The microphone - the result of a three-year development programme - exploited modern engineering and production techniques to create the first microphone for under $1,000. "The AT4033 employed many design innovations to provide such a high performance at this price point. A specially contoured, vapour-deposited diaphragm, just 2 microns thick, ensured accurate high-resolution signal reproduction. Coupled with low noise, symmetrical, transformerless circuitry, this produced an exceptional transient response and low distortion output," explains marketing director Harvey Roberts. Phil Ramone once said of the microphone: "The 4033 is incredible. Once I put it up, I can never take it down." The microphone is still popular today and one of Audio-Technica's best sellers.
It must be remembered, the old adage 'fix it in the mix' is the worst thing anyone can ever say in a recording studio. Throw them out and reposition or replace the mic! Get the front end right and the rest will (usually) fall into place: "Especially for acoustic instruments, microphones must capture the sonic fingerprint in every detail and they must be able to catch the spirit of the performance into an electrical signal," Stubics says poetically.
Milab recently released the DC-96C, which carries on the heritage of its classic DC-96, released in 1967: "The DC-96 has become a very popular mic for drum overheads, acoustic guitar and piano - but also for string instruments thanks to its transparent reproduction and small size. The DC-96C is virtually identical to the DC-96B on the outside, but it has been completely redesigned on the inside. The self noise is down to 12dB, the transformer is gone, while sensitivity and SPL handling is up," enthuses Strömberg.
Sweden's Pearl Microphones, which also has a heritage dating back some 70 years, utilises a unique capsule design. The rectangular capsule achieves a very flat and resonance-free frequency response, which extends across most of the microphone's usable range: "Some of our models from the '70s are often used for recording acoustic instruments, especially the TC-4, DC 96 and DC 63. These microphones use our rectangular capsules which produce a well-known sound," explains Bernt Malmqvist, managing director at the company.
So, where now? If engineers know what they like, what is there still to be improved on? Are there classics still to be launched on an unsuspecting audio landscape?
"I don't think there is a limit," postulates Stöve. "Everything can be improved. Sometimes the technology even forces us to take a step in the opposite direction because of environmental changes or RF problems, for example. I do, however, think that the DPA range of studio microphones has made it pretty far. We still try to improve our products and lately we have introduced a transformerless version of our mic preamp with even better performance than the previous versions," he says enthusiastically.
Audio-Technica is equally optimistic: "We are known for our innovative approach to microphone design, and ongoing development. Emerging technology will continue to have an impact on design," says Roberts. "To take the case of the AT4080 and AT4081, 18 patents are pending on these models, evidence of the strides being made by the company in advancing what is a 'classic' design. Here, it is the combination not only of great tone but also of robust design and build - made possible by new manufacturing techniques - that has yielded benefits previously unthinkable."
Stubics agrees: "New useful features will allow one to focus on the most important thing and that is that art equals music equals emotions. These features will include technologies to allow musicians, engineers and producers to decide on the sound and behaviour of a microphone in the final mix and working with the electrical and mechanical interfaces will become much easier."
Deming and Zielinsky have different opinions: "Actually, this question is difficult to answer, as it is so closely interrelated with the questions of how a microphone is used and where it is positioned for which recording situation, style of music and sound style. A microphone on its own cannot make or break a recording," says Zielinsky.
Deming concludes: "I'm not sure to be honest. In the past few years we have seen capsules in different shapes - rectangles, triangles - we see different drilling and gold sputtering patterns, but we have yet to hear a drastic improvement over what we have been using for years in any of these new techniques. I have seen an improvement in grille design from Josephson Engineering that totally eliminates the potential for the resonance of this metal part, yet I have seen no improvements in dynamic or ribbon microphone design with the exception of some ribbons using +48VDC to power an amplifier section to boost output level. But, ribbons are still as they have always been, no top end and no output level, making them very difficult to get good results from except on very loud, very bright electric guitar tracks."