Never do this!
While we are on the subject of what not to do: never touch the diaphragms! Hold the capsule by the edge only. The membranes are made of extremely thin material that can easily be stretched or deformed by touch.
Unbox the new capsule
First, clear your workspace to ensure that you have a clean surface to lay the capsule on.
Our capsules are wedged into their plastic cases with a short length of transparent plastic tube. This prevents them from rattling around during shipping.
The easiest way to remove the capsule from the box is to first remove the lid, carefully invert the box, and tap one edge of the box gently on a table. Once the capsule has emerged halfway from the box, gently remove it with your fingers, being careful not to touch the diaphragms.
Prying the capsule out of the box with a screwdriver is not recommended.
Open the microphone
Most imported large-diaphragm microphones open by spinning off the threaded base, near the XLR jack. Then, slide off the tube covering the circuit board.
In the case of the MXL 1006 pictured here, a second circuit board (which holds part of the battery-power circuit) had to be detached from the chassis first, to allow access to the screws holding the basket in place.
The white arrow marks the location of one of the screws holding the basket to the chassis.
Be sure to retain all the screws as you disassemble the microphone.
Make notes as you go
Such a photo is also useful if you accidentally break off another wire or component during handling. It is a critical reference if you end up troubleshooting your installation.
Many Cardioid microphones will have just two wires: one from the center of the front diaphragm, and a second from the side of the capsule.
All Multipattern microphones will have three wires: one from the center of both the front and rear diaphragms, and a third from the side of the capsule.
If the leads from the new capsule are soldered to the wrong points on the circuit board, the microphone will no longer function properly. Be sure you have recorded the location of the wires before you remove the original capsule.
Remove the original capsule
Carefully desolder the diaphragm leads from the circuit board. Use only as much heat as necessary. Be careful to avoid burning nearby components with the soldering iron.
The wire from the edge of the capsule can be left in place and re-used for the new capsule.
Once the diaphragm wires have been freed from the circuit board, unscrew the 2-4 screws holding the capsule to the saddle.
Then unscrew the termination wire from the side of the capsule.
Install new saddle
If your old capsule measured 34mm in diameter, the new capsule might fit the stock saddle. Hold the RK-47 in place to check for fit. Look through the holes or slots in the saddle to determine whether they line up with the holes in the outside rim of the new capsule.
If you need to replace the stock saddle, unscrew it from its mounting post.
If this is not possible, you will have to engineer a new saddle mount. A new post is included with the RK-47 capsule, should you need it.
Be sure the screw holding the saddle to the post is tight. Consider putting a drop of Loctite or glue on the screw head, to ensure that it does not come loose over the following years. If you use Loctite or any other adhesive, allow it to dry thoroughly before mounting the capsule, so that the fumes from the solvent in the adhesive do not affect the thin Mylar membranes of the capsule.
In this photo, the white saddle came with the microphone. The black saddle, shown here already installed on the stock post, comes with the RK-47 capsule.
Mount new capsule
Using one each of the the included 2mm machine screws and washers, carefully mount the RK-47 capsule to the new saddle.
Once one side is securely mounted, locate the original termination wire, or the new blue wire if you have soldered it in place. Using one of the included 2mm machine screws, attach the connection terminal at the end of the wire to the other side of the saddle.
Inspect the capsule alignment to ensure that it faces exactly 0° and 180° with respect to the microphone chassis. In most cases it is possible to gently twist the capsule mount to adjust the capsule position. Do not touch the microphone diaphragms.
If the microphone had only one diaphragm wire originally (this is often true of Cardioid microphones), the lead from the rear RK-47 diaphragm can either be clipped short or wrapped around the post to keep it out of the way. If the wire is retained and wrapped, or otherwise tucked out of the way, clip the bare end off first.
The benefit to retaining the rear termination wire is that the capsule can more easily later be rotated to enable use of the rear diaphragm, should the front diaphragm become damaged. Alternatively the microphone could be converted to Omni relatively easily, by wiring the rear diaphragm into the circuit.
Route the diaphragm wires through the capsule mount and chassis as the originals had been. Refer to the photo and notes made earlier.
Wiring notes for RK-87 Customers
The RK-87 has insulated backplates, like Neumann’s K87 capsule from the original U87. There are multiple ways to wire this capsule:
- For Cardioid-only use: it is unnecessary to attach the rear diaphragm or backplate to the circuit. Connect the front diaphragm’s wire, and use a single blue wire to connect the backplate half nearest the front diaphragm. (Whether to pass polarization voltage to the backplate or diaphragm depends on your mic’s design; if you reverse them, your mic will have reversed polarity with respect to correctly-wired microphones.)
- For multipattern use in a 3-wire microphone: ground the two backplate halves together via an external wire, then treat as any other K67 capsule.
- For multipattern use in a 4-wire microphone (such as the original U87): wire the two backplate halves separately so that they remain insulated from one another.
Attach the microphone basket to the chassis to protect the new capsule.
Optional: some microphone engineers recommend removal of the inner layers of metal mesh from the basket. This operation requires no special tools. A pair of strong needle-nose pliers and a wirecutter are sufficient. Work carefully to avoid deforming the outer layer of mesh. The layers are usually brazed together and must be separated to avoid damage.
Solder capsule wires to circuit
Inspect the solder joints to ensure that they are sound. Research cold solder joints for tips.
Final assembly and testing
Replace the body sleeve and bottom nut. Gently tip the microphone back and forth to listen for rattles. If a screw, washer, or bit of solder is loose inside the microphone, it could cause problems over time, and should be removed immediately.
Once you are confident the installation work is sound, connect the microphone to your favorite preamp, turn up the gain and enjoy the new microphone!