Marik
Well-known member
I remember an argument from last year about Chinese ribbon mics where I was claiming that loading the ribbon microphones affects mostly the low end and somebody else (was it Rossi?) was saying that it affects top end.
The last few days I was measuring a bunch of transformers, including Chinese stock, Cinemag, Lundahl, and my own wound toroidal transformer. The test revealed why we had the differences in our findings.
For the measurements I was using a "Vector Impedance" section of my HP 4274A LCRZ meter. The beauty is it measures the whole ribbon/transformer system up to 100KHz. It also measures the phase angle. The results were very interesting and highly enlightening, explaining many processes in ribbon microphones, as well as the reason the stock Chinese mics lose the high frequencies with loading.
For the test I used a medium ribbon motor structure (very similar to the Nady RSM4 and alike). With the stock ribbon of about 4-6um, and stock transformer the impedance between 100Hz and 500Hz drops from 868 Ohm to 396 Ohm, then stays there till 3KHz and then from 5KHz to 50KHz raises from 413 Ohm to 1.8KOhm, reaching 3.9KOhm (!!!) at 100KHz.
For comparison, with the same ribbon, but with my own wound toroidal transformer the impedance drops from 314 Ohm to 107 Ohm between 100Hz and 1KHz, then stays there until 10KHz, raising from 136 Ohm on 30KHz, to 290 Ohm on 100KHz.
Both Lundahl and Cinemag did not have that huge impedance spike on the top of the range, either. Cinemag was measuring little better than Lundahl, but then again, it is a lower ratio transformer. In fact, to be of the same quality transformer it should've been measuring MUCH BETTER. IMO, its very low permeability DU core is unusable for ribbon transformers and results in a very high Pri DCR (0.11 Ohm, whcih translates into high noise), and still low Pri. inductance.
The thinner ribbon (1.5um) with the same transformers measures much better both impedance-wise and in term of phase.
With my transformer it stays flat @224 Ohm from 1KHz to 10KHz, then just slightly raising to 295 Ohm at 100KHz.
For comparison, Lundahl LL2912 was flat @309 Ohm from 1KHz to 10KHz, and then raising to 455 Ohm at 100KHz. It had worse phase characteristics.
Hopefully, that was helpful.
Best, M
The last few days I was measuring a bunch of transformers, including Chinese stock, Cinemag, Lundahl, and my own wound toroidal transformer. The test revealed why we had the differences in our findings.
For the measurements I was using a "Vector Impedance" section of my HP 4274A LCRZ meter. The beauty is it measures the whole ribbon/transformer system up to 100KHz. It also measures the phase angle. The results were very interesting and highly enlightening, explaining many processes in ribbon microphones, as well as the reason the stock Chinese mics lose the high frequencies with loading.
For the test I used a medium ribbon motor structure (very similar to the Nady RSM4 and alike). With the stock ribbon of about 4-6um, and stock transformer the impedance between 100Hz and 500Hz drops from 868 Ohm to 396 Ohm, then stays there till 3KHz and then from 5KHz to 50KHz raises from 413 Ohm to 1.8KOhm, reaching 3.9KOhm (!!!) at 100KHz.
For comparison, with the same ribbon, but with my own wound toroidal transformer the impedance drops from 314 Ohm to 107 Ohm between 100Hz and 1KHz, then stays there until 10KHz, raising from 136 Ohm on 30KHz, to 290 Ohm on 100KHz.
Both Lundahl and Cinemag did not have that huge impedance spike on the top of the range, either. Cinemag was measuring little better than Lundahl, but then again, it is a lower ratio transformer. In fact, to be of the same quality transformer it should've been measuring MUCH BETTER. IMO, its very low permeability DU core is unusable for ribbon transformers and results in a very high Pri DCR (0.11 Ohm, whcih translates into high noise), and still low Pri. inductance.
The thinner ribbon (1.5um) with the same transformers measures much better both impedance-wise and in term of phase.
With my transformer it stays flat @224 Ohm from 1KHz to 10KHz, then just slightly raising to 295 Ohm at 100KHz.
For comparison, Lundahl LL2912 was flat @309 Ohm from 1KHz to 10KHz, and then raising to 455 Ohm at 100KHz. It had worse phase characteristics.
Hopefully, that was helpful.
Best, M