RK-87 Microphone Capsule
The RK-87 is a true 34mm, dual-backplate large-diaphragm condenser capsule. It is based on Neumann's K87/K67.
The two backplates are electrically insulated from one another. Therefore this capsule is compatible with the original Neumann U87i, which requires a 4-wire capsule. The two backplates are easily connected externally for use in microphones that don't require a 4-wire setup.
Cardioid vs. Multipattern
The RK-87 can be used in Cardioid-only microphones, and in multipattern microphones.
For use in a Cardioid microphone, simply connect the front diaphragm and front backplate to the circuit. For multipattern operation in a 4-wire circuit (such as the U87i), connect both front and rear diaphragms, and both backplates independently. For use in a multipattern 3-wire environment, use a jumper to short the two backplates together.
We have selected the RK-87 to meet stringent performance specifications: the front and rear sides of the capsule match to within 0.3dB in sensitivity, and ±1.5dB in frequency response. This ensures the most consistent performance in Omni, and deep nulls in Figure-8.
|Capsule diameter:||34 mm|
|Diaphragm diameter:||26.7 mm|
|Capsule depth:||12.3 mm|
|Membrane composition:||3-micron Mylar, sputtered with Gold|
Capsule Mounts & Connections
Each capsule from Microphone-Parts.com includes a 10.5mm mounting post and all necessary screws for installation. Two backplate termination wires are included, with the tiny 2mm screws for attaching them. We also include our "supersaddle," which is easier to mount in many cases.
For recordists building a matched pair of microphones for critical stereo miking, we offer matched pairs of RK-87s. These capsules are matched by both sensitivity and frequency response; the two capsules' sensitivity differences for matched pairs is 0.3dB or less.
We recommend matched pairs only for microphones whose circuits are also matched. This is true of our MXL 990 circuit kit and MP-V57 PCB kits, and the S-series transformerless microphone kits, but is not generally true of any two inexpensive condensers (whether stock or modified). Contact us if you have questions or would like to discuss the matching process.
K87 vs U87
The "U87" is a microphone. The "K87" is a microphone capsule—in fact, it is the microphone capsule used in the U87 microphone. But it is not true that putting any K87 capsule (including the RK-87) into a microphone magically transforms the microphone into a U87.
Like all K87 (also known as K67) capsules, the RK-87 prefers to be used with a circuit that provides some high-frequency attenuation. The U87 circuit does this. The transformerless circuits sold on this site -- the MP-V57 PCB kit, the 990B PCB kit, the TL3 PCB kit -- all optionally provide high-frequency attenuation.
MXL's 2001 and V67 circuits provide a tiny amount of attenuation, as well.
For best results, use the RK-87 with a circuit that provides high-frequency attenuation. On a "flat response" circuit, the RK-87 capsule will likely sound too bright.