The one on the far left goes straight into an amp, an mpf102 source follower into a TDA2003, well I think it's a source follower, might have the signal off the drain, opps, I'm not altogether sure, but anyways it goes straight into the amp and give acceptable output with minimum noise. It shares the same resistance accross the tabs as the one in the middle which doesn't give acceptable results at all and has a very high noise floor and not very good sound. They are both about 20 ohms.
The one on the far right is about 10-11k across the tabs and is very noisy as well and only just gives a signal into the same amp.
So I'm wondering if some sort of small signal amp, 0ne or two transistors, might help to get some good signal from the two that don't so far. Would an electret type amp circuit, feeding 1.5V to one of the tabs work with a little work on the impedance that they hit.
Any ideas on how to approach this would be appreciated, The frquency response is something I'm not worried about and would prefer a narrow one but the noise floor and good earthing are important.
Incidentally the far right one has had a holder and springs made up and attached to an old speaker frame. Looks kinda twenties, eh?