Tannoy Slendalyne Cardioid

This model is also known as the Houses of Parliament or HoP mic.

From the Xaudia blog:

Tannoy ribbon microphones were used in the British Houses of Parliament. According to Chris McClean's article for the Institute of Professional Sound, twelve 'brass barrel' microphones were fitted by Tannoy in 1951, and the system was further upgraded in the 1970s, again by Tannoy, with an installation that lasted until 1991. 

Here's the problem: I have seen several of these brass-barrel Tannoy mics on sale that claim to be ex-Parliament. Too many! Certainly more than twelve, and some at very inflated prices. Either Parliament kept a huge number of spares or this model was not exclusive, and was sold elsewhere. I have heard anecdotally of these being salvaged from church PA systems, and also being used in Canadian government buildings. The final clincher is that they were advertised in Hi-Fi magazines from 1962 onwards. For example, the following announcement appeared in Tape Recording magazine in May of 1962, accompanied by images of the HoP and Slendalyne Velocity models.

"A complete departure from previous exhibitions is forecast for the Tannoy Group who will be showing for the first time ever a range of microphones to be marketed under the "Slendalyne" label. Although they have manufactured microphones for internal use before, this company has never made their instruments available to the public before. First model is the Slendalyne single element ribbon cardioid microphone. This has a uni-directional characteristic giving a front-to-rear discrimination in excess of 15 dB over the entire audio range. Their second model, a velocity ribbon microphone, has a symmetrical figure-of-eight bi-directional characteristic making it suitable for indoor use in difficult acoustic conditions, and the moving coil microphone is of the pressure type ideal for outdoor use."

The article announces two new 'Slendalyne' ribbon microphones from Tannoy - a cardioid and a bidirectional version. Yet the cardioid version looks very much like the brass-barrel mic that was supposedly installed into the Houses of Parliament 11 years earlier! This sentence is particularly intriguing:

Although they have manufactured microphones for internal use before, this company has never made their instruments available to the public before."

The statement is not quite true as their earlier models were widely available. But this implies that these specific models had previously been supplied to select customers, and became available widely from 1962 onwards.

This microphone first appeared in the Hi-Fi Year Book of 1963.

TANNOY Products Ltd., West Norwood, London, S.E.27.

Slendalyne. Single Element Ribbon. Cardioid.

• Response 50 Hz- 12 kHz ± 3 dB.
• Sensitivity - 82 dB.
• Impedance. 600 ohms.
• Transformer fitted.
• High front to rear discrimination 15 dB.
• Price £25.

A summary of Tannoy directional ribbon mics at the Xaudia blog.

The Science Museum have a similar microphone in their collection, which they claim dates from 1972.