Something old and something new – STC Coles 4038 and 4050

A good customer brought in his Coles 4050 stereo microphone for show-and-tell, which gave us a good opportunity to compare and contrast with some of the STC-Coles mics from the past.

STC4033, 4038 and Coles 4050 microphones
On the of the photo left is the imposing and impressive STC 4033, which contains both a ribbon mic and a ‘ball & biscuit’ dynamic element. These combine to give a cardioid pattern, which was difficult to achieve at the time. 
In the middle sits a 4038, which is perhaps the classic British broadcast ribbon – designed by and made for the BBC. This one was made by STC, and they are still made to the same design by Coles Electroacoustics. The soap-dish styling is dictated by the large horseshoe magnet inside.
The 4050 stereo mic is on the right, and looks very different again. It is a more modern styling but form still follows function, and strong neodynium magnets are used not only for the ribbon motor, but also to fix the mics to the stand mount. This allows free rotation and makes setting up for Blumlein pairs very quick and simple.
Frequency sweeps of 4050 (top, red & yellow) and 4038 (bottom red)

We ran a frequency plot of both halves of the 4050, and of the 4038.* Both mics sound very good, and although the old 4038 had a smoother top end roll off, the 4050 had an extended about +6 dB higher output and an extended frequency response. We were also very impressed with how well matched the two 4050 ribbons were – less than ±0.5dB across the range, and mostly much better than that.

The 4038 is prettier though!

* Taken at 30 cm distance. Please note that some of the bumps are due to our test chamber – there are issues with calibration when comparing a figure 8 ribbon with an omnidirection reference mic.

Thanks to John Gooding