Cadenza Ribbon Motor Modification...... a little more Gain & finding HF

[soundtom81]

After being a long time lurker and using the forum as my own personal information fiefdom :, I thought id better put a little something back

After rebuilding a very tired Cadenza Ribbon Mic Motor, it had little to zero magnetic field.
The magnets where replaced easy with 10mm diameter x 3mm thick countersunk [with a  3 mm hole the original plan was to drill and bolt in place ] Neodymium discs,

I had an idea to attempt to reduce the HF cut point  which was terribly low at around 5k [due to nearly 6cm distance front to back]  so i made a few short cuts for the sound pressure to travel 4mm holes -

Magnetic field stood at around 2,500 Gauss in the centre gap  - not happy with that :
another 1000 Gauss was found by adding some more discs 8mm X 1mm in 2 columns bringing it upto 3500 Gauss,
-more strength could be added I'm sure by sourcing magnets with less joints [or cutting down sizes] to fit the 18mm span.  [full aims to bring up the mag fields to 4200 Gauss]

mating the motor upto a rewound 1:35 rewound transformer the results were astounding  ;D
how astounding is yet to be frequency swept,  [I'll post the results when i have done them]

excuse the araldite  :-[- i was in a frenzied rush, the next one will be much tidier

 

[micaddict]

Welcome! 

Marik and others may chime in.

 

[ELM]

Nice work! I've got a pair of lustraphone vr64 with new transformers from xaudia. They sound good but the signal is very weak. Anybody tried to ad small super magnets to an old motor?
I might try it, you got me inspired!

 

[zebra50]

Nice work Tom!

With any / all of the old ribbons, keep in mind that the magnetic field is ultimately limited by the coercivity of the  steel pole pieces. Eventually they will saturate and say 'no more!'.

One big magnet will give you more than the same volume of little magnets. (And you can't chop down neodymiums.)

Stewart