High Efficiency Speaker Asylum

Posted by marnold on October 09, 2002 at 09:24:15

In Reply to: Re: Power supply for Jensen F12NS field coil speakers posted by datubie on October 08, 2002 at 19:55:47:

I was much more worried about damage to and realignment of the voice coil than the winding part. If your field coils are like mine, they basically have the former built in as the pole piece and the support for the humbucking coil. Should be akin to spooling line onto a big fishing reel.

I finished the HV power supply and the second cabinet, so I now have a somewhat matched pair. They are nice, period. Some info I can pass on is that I am running 248V into the 5k coil for about 12W. The coil gets nominally warm after several hours of power, say maybe 100-105 deg F. The output appears to be about 4-5 dB higher than in the speaker with 250 ohm, 31V, 4W setup. More importantly, the detail seems more there, defined, clear, low level whatever. I think I will bump it to 15W and if all goes well try 18W which is the limit of my PS. Just to see what it does to the detail. There is no hum whatsoever. I haven't measured it, but the PS design software models 300 mV ripple in my HV supply and, absent signal, the speakers are absolutely silent. I am listening right now at a comfortable early morning level of ~70dB with an RMS input of 50 mV (0.325 mW).

Later,
Michael