B&O BM-5 Stereo Ribbon Microphone (Dynaco Model 200) Vintage [USED]

Condition

This microphone arrived in good working condition and had been stored in the plastic case for many years unused. However, the original cable and stand mount accessory are missing. Also, the top of the microphone was missing its original black plastic cover. There were no other accessories in the box.

As a result, we replaced the top cover with tension fit aluminum cap, which is firmly in place but can be carefully removed for future servicing, if needed. It so well-matched the original look of the microphone, I honestly feel it is an improvement to the original black plastic cap I have seen in pictures.

Furthermore, the general condition of the rest of the microphone is quite good, with no notable damage. The 90 degree turning mechanism and switches operate as expected. See pictures for some minor wear here and there.

We have also built a short adapter cable with a Switchcraft 5-pin DIN, Mogami Cable, Silver Solder, and Switchcraft Male XLRs with top/bottom ribbon element labeling for easy identification.

As far as we can surmise, the microphone is sounding exactly as it should. It has a unique sound from other ribbons because of its unique ribbon design. My understanding is it can be difficult to find these with the original ribbon intact!

That being said, it should be noted that these microphones are known for having a bit higher noise floor. This can be verified in various online forums. Modern software can probably be utilized to maximize the wanted sound. And some professional ribbon repair shops can upgrade these mics with larger, more powerful magnets which improve the noise specs.

Finally, the microphone does have a Dynaco label, and was sold as a model 200. The Dynaco label is lightly lifting at its edge. The case plastic is in decent shape. The foam in the bottom is not perfect and was loose inside, so some cardboard was inserted to make a spot for the pin-out notes for the mic, and the cable adapter. We also added a Cascade Ribbon Microphones yellow cloth to wrap around the elements for protection.

Description

The B & O Type BM 5 Microphone is a ribbon microphone (pressure-gradient microphone) for both mono and stereo recordings.

The B & O Type BM 5 Microphone is very well suited for stereo recordings of music, from both large and small orchestras. It has a wide dynamic range, smooth frequency response and low distortion, ensuring excellent sound quality for both tape-recorder and amplifier applications.

The BM 5 is designed for use with equipment having a balanced input. This feature, in connection with the relatively low impedance of this microphones, permits use of long extensions cables with no loss of sound quality.

The BM 5 is actually composed of two identical microphones mounted one above the other.

The upper microphone is detachable. When the upper microphone is removed, the lower microphone (Type BM 6) operates as a conventional monaural microphone.

The two individual microphones of which the BM 5 is composed may be rotated up to 90 degrees with respect to each other. The amount of relative rotation is indicated on a scale. 

Rotating the microphones as described permits altering the acoustic perspective of the sound picture, 90 degrees giving maximum width and zero degrees minimum width (mono).

The BM 5 carries two switches marked “M-T-O” and “+ / -“.

The “M-T-O” switch provides 3 functions:

• The “M” (music) position provides a flat frequency response and is used for recordings of music and voice in which the vocalist does not sing directly into the microphone. 
• The “T” (speech) position attenuates the lowest frequencies. This feature is necessary because of the inherent tendency of a ribbon microphone to over-emphasize the lo frequencies when used at a distance less than 3 ft from the sound source. The “T” position is used for close singing and speaking. In the “T” position, the microphone is compensated for a speaking distance of approximately 10-12 inches.
• The “O” (off) position mutes the mic output. 

The “+ / -“ switch has 2 positions.

• In the “+” position, the signals from the two microphones are in phase.
• Turning the switch from “+” to “-“ changes the phase of the lower microphone by 180 degrees.