With capsules, electronic upgrade kits, and MXL donor bodies, I have about $500 in this pair of mics, and I can use them on almost anything and get an attractive recording.

These worked out really well.

Before installing the RK-12s, I rebuilt the electronics in each mic using Microphone-Parts Advanced upgrade kit as detailed in the previous entry. A switch was added under the board to provide for omnidirectional as well as cardioid patterns. The mini switch was set in a spot of urethane glue and tack soldered to ground at one corner.

With the switch closed, both front and back diaphragms are connected for an omni pattern. Switch open, only the front diaphragm is connected and a cardioid pattern results. The stereo pair of capsules is matched for level within 0.1 dB and is matched for frequency response as well.

Before closing the mics up, I glued a felt ring into the lower part of the mic shell, wrapped the capsule mounting post with a bit of felt, sort of like the base of a Christmas tree, and stuck a felt halo into the top of the headbasket to see if that would help with the 3 KHz resonance of the 990’s body - that hint of singing into a wineglass. I had earlier removed the inner layer of screen. It works. I changed C14 & C15 to 330 pF to complement the capsule’s top end. I like the sound, smooth and clean are the words that pop to mind. Great bass. Presence without screech or sibilance.

Back view.

Front view.

Damping pads.