Fountek JP3 vs. Aurum Cantis G2Si
Copyright 2005 Troels Gravesen

Left: Aurum Cantus G2Si ribbon tweeter, alias Harwood UR2.0 (Europe). Right: Fountek JP3 ribbon.

A few notes and graphs on these two ribbons. Apart from a possible 1 dB difference in sensitivity from 2-7 kHz, these drivers are very much interchangeable. Even a small dip at 3.7 kHz, which is possibly derived from baffle geometry, is shared by the drivers. Both drivers are flat down to 1.5 kHz but I will not recommend going lower than 2.5 kHz. Use 3rd or 4th order filters.

Left: Red = Aurum Cantus G2Si-I, blue = Aurum Cantus G2Si-II, green = Fountek JP3 (original ribbon). 10 uF capacitor connected in series with driver during measurement.
Right: G2Si, driver I & II. Measurements with crossover seen below.

Crossover used for measurements.

Fountek JP3

Available from here:
GM Sound Denmark.
GM Sound - Produkt 2

Available from Madisound, US:,
price is 81-89 US$/ea depending on faceplate + postage.

Aurum Cantus:

This driver is called Harwood UR2.0 (peel off the label on the box and you will see "G2Si".
Price is 119 EUR/ea (2131 DKK/pair at my doorstep)


28-09-2005: Received this mail from Mark:

I was googling and found your article about replacement ribbon in Fountek. I have built a lot of ribbon speakers of different configurations. At the moment, I am into building ribbon microphones. The constructions of ribbon tweeters and microphones are very similar. If you don't mind I have a few tips. One of the biggest problems is to make a good corrugator. I machined mine on a mill with indexing rotary table. However, I found this device: It is not very good as a corrugator for microphones, where the foil is much thinner - I am working with 0.6-1.5um thickinesses. Basically, it just tears the foil. Another problem is a ribbon skewing. That is, the clearance in mics between ribbon and pole pieces is less 0.01", so the ribbon should be PERFECTLY straight. However, with something like thicknesses of 4um and up, this corrugator should work just fine. Make sure to get a metal one. The plastic is uneven in the middle. If you want to experiment with foils thinner than 11um household aluminium, look in older paper-in-oil capacitors. The thinnest I was able to find was 3.5um Illinois caps. The lower the voltage rating, the thinner material. Usually, it is about 6 um. Just unroll the thing, place on a clean glass, and clean with isopropyle alcohol. Do it outdoors. I heard it is not a good idea to breath odour from these babies.
Best regards, Mark

Thanks to Mark for the information.