Boundary Effect microphones have been around for some time now, and the standard PZMs (Pressure Zone Microphones) use piezo technology. The ATM87R, however, is a full‑blown condenser mic, giving it the potential to display a much smoother top end than conventional piezo designs. The ATM87R has a hemi‑cardioid (half‑space cardioid) polar pattern and, as the name implies, has been designed to cope with high SPLs, making it suitable for very dynamic signals. The ATM87R runs off 48V phantom power, and has a two‑position switch for flat response or low‑frequency rolloff to control ambient noise, recessed underneath the mic to avoid accidental operation. A 25ft cable is supplied, with a miniature TA3F connector on the microphone end and the usual standard‑sized balanced XLR male type on the other.
As with any boundary/pressure zone microphone, the symmetry and area of the mounting surface directly affects the sensitivity of the microphone at low frequencies. These microphones make use of reflected sound and need to be mounted on a flat surface like a table top or wall, with the front of the mic facing the sound source along the longer dimension of the mounting surface. Sensibly, the bottom surface of the ATM87R is made of a clingy rubber material which helps the mic to stay put and also dampens unwanted noises. Overall, the construction of the microphone is excellent, though the cable supplied, with its miniature connector, is a little flimsy.
I used the ATM87R on every session I did over a couple of weeks in the studio. On piano, used subtly, it gave a lovely warmth and sense of space without removing the stereo image of the other mics, and on drums it gave just enough of the room sound without the splashiness that can come with other PZMs. I even put the ATM87R directly in front of the bass drum on one session, getting excellent results. On flute and saxophone, the ATM87R gave such a tight sound (in a fairly dead area) that it was hard to believe a boundary microphone was being used. In a small home studio, I would think that the ATM87R would be most suited to acoustic guitars and drums — though anyone seriously thinking about making their own drum samples would find this microphone ideal for powerful 'roomy' sounds on rock tracks, or nice tight ambience for jazz and soul samples. When recording electric guitar through an amp, the ATM87R would always be useful as a room microphone, as it responds well to high SPLs and retains a nice, smooth top end.
In all, I was hugely impressed with this mic. Boundary/PZMs have always been regarded as slightly limited, specialist mics — but this one is different. If you are in the market for condenser mics, have a listen to these before making a decision — you'll be glad you did! John Verity