Extinct Audio BM9A

Extinct Audio bring some fresh activity to their popular ribbon design!

If you want to know how good a piece of gear is, there are lots of questions you can ask. How does it perform on the test bench? What records was it used on? How does it sound in shootouts? Did that bald guy from SOS like it?

These are all valid criteria, especially the last one. But I’d like to propose another, under‑used metric. How often to people ask to borrow it? My mics enjoy plenty of action with friends and colleagues, and it’s no surprise that lots of people like to have a U87 on hand for a vocal session, for example. But the Neumann classic still comes a distant second in my league table of most‑borrowed mics.

Nine Lives

In SOS April 2018, I reviewed the Extinct Audio BM9 Viking, a passive ribbon microphone inspired by an old Bang & Olufsen design. I bought the review pair, and they’ve rarely been back in their boxes since. The BM9s get borrowed at least twice as often as any other mic, because they sound great on almost everything: drum overheads, guitar amps, brass, room miking, even lead vocals on occasion.

In fact, Extinct got so much right with the BM9 that all their subsequent products have essentially been variations on it. There’s the ruggedised Black Ops, the stereo Valkyr, and now the BM9A, a phantom‑powered version with a built‑in active buffer/gain stage. It’s outwardly identical to the passive version apart from the ’48V’ on the name badge (owners of both models might want to do something more obvious to differentiate them!). And, according to Extinct founder Stewart Tavener, it should sound exactly the same, except that it’s 22dB more sensitive.

Out & About

In a passive ribbon microphone, the transformer acts as an impedance converter, provides ‘free’ gain to boost the minuscule signal level coming from the ribbon element, and also balances the output. In an active mic, the output is electronically balanced instead, and this leaves more choices open relating to the transformer. Assuming part of the reason for making the mic active is to raise sensitivity, you can retain the same transformer and include a gain stage in the active electronics; or you can use a transformer with a higher turns ratio, with the active electronics being simply a buffer that stabilises the output and allows it to drive long cable runs. Or you could combine the two approaches.

The active BM9 uses exactly the same custom transformer as the passive version, designed and built in‑house, but married to an active output stage that provides 22dB gain.

Getting lots more gain from the transformer alone, though, requires a complete redesign using many more coils of thinner wire, increasing its capacitance and potentially changing the sound of the mic. Consequently, the active BM9 uses exactly the same custom transformer as the passive version, designed and built in‑house, but married to an active output stage that provides 22dB gain. It’s like having a passive BM9 with a Cloudlifter built in, and it does sound identical to the passive BM9 — with one caveat.

Transformer‑balanced mics can have a slightly symbiotic relationship with the preamp they’re feeding. A passive BM9 through a Neve 1073 might not always sound the same as a passive BM9 through an API 512, and so on. By contrast, the electronically balanced output stage in the BM9A should be relatively indifferent to preamp and cable loading. It’s also, of course, 22dB hotter, which can make a difference if you like to drive preamps hard and get a little saturation into the sound.

So, when I lent the active BM9s to a friend who often borrows the passive ones, he reported that they didn’t quite sound the same through his UA 610s, and I too managed to make them sound different by deliberately overdriving a vintage mic preamp. In the normal run of affairs, though, what you’re getting is exactly what it says on the tin: a BM9, just louder. It wasn’t broke, they haven’t fixed it, and it’s still a great mic!