Ever since the studio where I do my tracking (Mavericks in NYC) acquired a pair of vintage RCA BK-5A ribbon mics, I've become a big fan and have found a ton of uses for them. It's difficult to track down the production dates of RCA equipment, but the BK-5A was likely produced from roughly the mid 1950s into the later '60s. (There are photos of a very young Johnny Cash, circa 1957, singing into one; and the DJ in The Carpenters' 1976 video for "Calling Occupants of Interplanetary Craft" is using one.) The BK-5A looks like a Revolutionary War cannon with Art Deco details, but its unique qualities are more than skin-deep, as it has a hypercardioid polar pattern (most ribbons are figure-8), a frequency range of 50 Hz to 15 kHz, and was designed to withstand the SPL of gunshots during broadcast and film work. RCA did some interesting things with the chambers behind the ribbon to accomplish this ruggedness, and it seems to me that the challenge of designing a mic that can take a bullet has resulted in its unique sound. There is also a three-position low-end roll-off switch, and the BK-5A shipped with a tennis-ball sized, perforated-metal windscreen that, according to Bob Crowley of Crowley & Tripp, doesn't really do anything. Bob also told me that the BK-5A shares its transformer and a few other bits and pieces with the formidable RCA 77DX ribbon mic, and that, in his opinion, the BK-5A sounds similar to the 77DX in unidirectional mode.
What I love most about ribbon mics is their ability to deliver detailed imaging in the upper mids, those critical frequencies where so much of a recording's vital characteristics are. The BK-5A focuses on the same sonic area that an SM57 seems to focus, but the BK-5A captures details in that range that give it a transparency, realism, and detail I rarely get out of a dynamic mic. Anyone who has used a Royer R-121, for example, can attest to the detailed realism and imaging a ribbon can deliver-now imagine that without all the velvety lows and silky highs of the Royer, and you're getting the idea of what the BK-5A sounds like. Or, imagine an SM57 that doesn't get nasal or snotty but instead delivers 3D imaging and nuanced details. To my ears, that's the BK-5A.
For me, this is a thoroughly useful set of characteristics, since during mixdown I am often pulling out bottom end on tracks to make room for the bass, kick, or whatever is carrying the low end of the music. I also really like the lack of shimmering, sizzling highs for similar reasons, as tracks I've recorded with the BK-5A seldom compete with important high-frequency content. So, I've been using the BK-5A for tracks that I want to occupy the middle of the mix without getting in the way of the highs and lows.
For example, the nuances captured on violin were particularly impressive, with rosin, horsehair, and wood rendered in 3D, without any irritating upper harmonics. This violin sat right in the mix as I wanted it to. And I love the BK-5A as a room mic on drums; it captures all the sound I want, without competing with the overheads or the kick. The snare just punches through, giving me ambience where I want it. On a record I'm currently mixing, I've taken to squashing the BK-5A room mic with a compressor so it breathes with the beat. This technique creates a really useful sustained snare sound and extra action from the cymbals, but without the sloppy washed out sound that I sometimes get when using condensers in the same way. Throwing the BK-5A over the shoulder of the drummer gave me a crunchy, vintage sounding, lo-fi mono drum track, but didn't obscure any nuances of the drummer's performance.
I found another very interesting use for the BK-5A. In the vocal-mic shootout I did with NYC-based singer-songwriter Sarah Tolar, Sarah was giving killer performances through the BK-5A, but in the context of her warm, intimate record (lots of Steinway and upright bass), the BK-5A made Sarah sound like she was coming through a transistor AM radio. When she sang through an R-121, the tone was rich, detailed and sublimely warm, but her performance sounded disengaged in comparison. Sarah and I talked about it, and something in the midrange emphasis of the BK-5A was giving her information she just couldn't get from other mics that have more full-range sound. She is also a seasoned stage performer, quite used to SM58s and others mics of that ilk. In this case, I hung both mics, had Sarah monitor through the BK-5A, and then used the Royer for the record-a win-win situation that worked for the entire album. (If you try this with two ribbons, watch out as the magnets like to pull at each other. I don't know if this affects the performance of the ribbons, but I didn't hear anything.)
I've heard male vocals recorded with the BK-5A that work beautifully; it's ideal for a somewhat eerie, midrangy sound when something more lush isn't appropriate-great for a quasi-lo-fi vibe. In fact, anytime you want a limited frequency response, but don't want to sacrifice detailed imaging, the BK-5A is a great mic. I would never recommend the BK-5A to anyone buying his or her first mic-or to anyone rounding out a small mic collection-but I would tell anyone looking to add another color to an already well-rounded mic collection to try to get one. Buying a BK-5A is a bit of work, as you'll have to search eBay or another source, and possibly have the ribbon replaced. I should also mention that the later model BK-5B is, as Bob Crowley told me, only different in that it has a slightly altered vent behind the ribbon. Though the BK-5B literature listed a far wider frequency response, Bob feels there is no sonic difference between the BK-5A and 5B. Prices on eBay seem to hover somewhere between $750 and $1000.
Tape Op is a bi-monthly magazine devoted to the art of record making.