Old-time microphone shoot-out with an elderly Martin acoustic guitar,

We recently made some recordings of some of our oldest microphones, tracking a 125 year-old Martin 0-18 acoustic guitar. The guitar is very special – it was build in 1900 before Martin began selling guitars with steel strings*, and has a very lightly-built Adirondack spruce top and rosewood back and sides. It would have originally been fitted with gut strings and now has a set of Aquila 900 nylon replica gut and silk. I love the warm tone of this elderly little guitar.

The microphones in question are all quite ancient too, with the exception of the BerZerker from Extinct Audio which we put up for reference. The recordings are below with a description of the microphones. Most are ribbon microphones but we added an STC dynamic into the mix too. All were run directly into a UA Apollo 8 preamp and recorded into Logic with no further processing except that the tracks are normalised when bounced down.

1. Melodium Type R, serviced with new ribbon.

2. National model VM-11 (a replica of an RCA PB type) serviced with new ribbon

3. Extinct Audio Berzerker vocal microphone, new.

4. STC 4021C with VIE grill. This 15 ohm low impedance mic is connected via an Extinct Audio matchbox.

5. RCA PB144 with original ribbon in place.

6. National VM-1 serviced with new ribbon.

7. Toshiba Type C with new ribbon.

8. Siemens ELM 24/III cleaned and serviced with new ribbon.

All of the recordings have merit although some of the older mics have higher noise levels than one would expect from a modern microphone. The VM11 was particularly hissy. As one would expect, the BerZerker had by far the highest output level and needed substantially less gain than the other microphones. I was especially impressed with how good the STC 4021 sounded in this context, and the Siemens mic was impressive too considering it is now around 95 years old.

Finally, we made a mid-side recording with the Siemens ELM24/III as mid and the Melodium type R as side. This has a little bit of reverb and compression added for fun.

And so it is fairly easy to make nice sounding recordings with very old microphones, although it helps if they are properly maintained and serviced. For those interested, the pieces of music is roughly “Birds flew over the spire” by Gary Ryan. You can hear a much better performance by Beatrix Novak here. She’s a better guitarist but we’re better at fixing microphones. 🙂

*This started in 1902, according to Guitar World.

Pimp my microphone!

Here are some upgraded, modified and generally pimped mics that we have put together for customers.

In each case the microphone gets a new ribbon, upgrade transformer and a few other tweaks, along with a shiny new badge.

I will leave the reader to guess the identities of the donor mics. 
🙂

Ribbon mic patents

Here are some more ribbon microphone related patents, both US and British, from the 1930s, 40s & 50s.




The diagram (above) is from one of the patents, and may be the first tube ribbon mic!

Harry Olson, Marconi, July 1932.  
Improved ribbon mic with tube amp and better housing. Possibly the first tube ribbon mic! 
Olson, Marconi, May 1933. 
Directional microphone with velocity and pressure components connected in series.
Otto Kolb, September 1933. 
Ribbon mic with 1 to 1.5 micron ribbon and holes in the pole pieces for improved air way.
Andrew Swickard, Bell Telephone Labs. July 1936. 
Ribbon microphone with both velocity & pressure sections
Thomas Julian, GEC, March 1944. 
Improvements in ribbon microphones.
Horace Duffell, Radio Gramaphone Development, June 1947
Adustable magnet pole pieces. 
William Cragg, Standard Electric Corp. December 1945. 
Velocity microphone with ribbon supported along its edges
Helmuth Eckardt, Bell Telephone Labs, May 1949. 
Describes a 3-zone ribbon to eliminate distortion and improve frequency response. 
Donovan Shorter & Hugh  Harwood, BBC, March 1953
Improved ribbon microphone design. Looks very much like the STC / Coles 4038!

Melodium 42B rebuilt

A few weeks ago we received this rather forlorn looking box of Melodium bits for service!

Melodium 42B stripped down to parts

The good news was that all the important parts were there, and despite some corrosion, the magnets and the transformer were on good shape, which meant that this vintage gem could be restored to some of its previous beauty.

Melodium 42B repaired and re-ribboned

The mic was stripped down and all the parts cleaned up in the ultrasonic bath. Then the magnets and some other bits were painted to stop the rust returning, and the motor reassembled. Dino (the owner) wanted to retain the vintage look of the mic, so the grills were straightened, de-rusted and then given some clear lacquer rather than being refinished. New grill cloth gives some protection against pops and wind blasts.

Then it was put back together and a new cable fitted with XLR output. And of course a new ribbon. The mic looks pretty damn cool!

Thanks to Dino Jakobsen of The Why Project.

BBC R&D reports on ribbon mics

The good old BBC have made many of their research and development reports available through their website, spanning 1944 through 1996.

Below are links to some of the reports that relate to ribbon microphones. In many cases there is a lot of interesting technical data. The rest of the articles can be accessed here.

1945
The Crosley ribbon velocity microphone.

1947
Tannoy Ribbon Microphone

1953
Lustraphone VR53 ribbon microphone

The design of the PGD and PGS ribbon microphones.

The EMI microphone Type 2351E.

Tannoy microphone Type MD. 422.

1956
Design of the PGD and PGS Ribbon microphone Part 2

1958
RCA BK5

1961
Reslo RB

1965
Beyer M160

(Thanks to Santiago Ramos for sending the links.)

More bad magnets

These rather disturbing photographs are of bad magnets inside a T-Bone RB500 ribbon microphone.
Failed magnets in a T-Bone microphone

The coating around the magnets had peeled away, allowing the rare earth magnets to oxidise and expand. This process of course destroys the ribbon too. The magnets can be replaced, but may not be worth the expense.

I have seen a few microphones that look like this, and the worrying aspect is that it seems to happen spontaneously, possibly because the coating on the magnets was not of high quality, or perhaps they were scratched or cracked on installation.

Nearly all manufacturers now use neodynium magnets for their microphones, and I fear a epidemic in the future.

Many thanks to Andrea Cappellato for sharing the photos of his microphone.