Amplifier design parameters required for a good match for high (16+) ohm speakers?

Thanks for the responses. 

I am using a Dynaco ST-70 (35wpc) into Contrast Model One As3 speakers having a rating of 16ohms and 92dB sensitivity.  I believe the sensitivity rating might be a little high, even considering that 92dB equates to 89dB with an 8ohm speaker. I have no knowledge about the impedance across the frequency range, however the manufacturer states that it does not vary much.

I guess then, when considering an amplifiers rating into an 8ohm load, one should half that rating into a 16ohm load as a way of assessing that amplifiers ability to provide enough power for a particular circumstance.  

I might add that Ralph of Atmosphere refurbished my ST-70. 



 

@jroberson @robersonj2 did any of those get notifications?

Rodman, Thanks much for your input and the link. I can't believe I did not find this review myself. It seems that the input impedance of this amp is not the reason I didn't find it as enjoyable using a Schiit SYS passive pre as with my Jolida active pre. Bass was lacking with the SYS.

I have always know that he tube rectifier in the original ST70 was a weak link. Though I would not want to replace with SS rectification. This was why I spent so long looking for a high impedance speaker to use with it. I was also looking to find one with greater than 92dB sensitivity. I have been using the 16 ohm taps with the Contrasts. I have used the 8 ohm taps with other 8ohm speakers, however approached use with them with caution as they all drop below 4ohms in the bass region. I never considered these speakers ideal for this amp.

Rodman, my ST-70 has the 5AR4 rectifier tube made by GE, and the 7199 driver tubes made by Conn in USA. Currently using JJ EL34 output tubes. I know the JJ EL34 could be replaced with a smoother tube. Any particular Mullards you might recommend?

Ralph, I am using the 16ohm output with the Contrasts, which are rated at 16ohms. I am not sure about actual impedance within the bass frequencies. 

Pasting youtube video

 

testing response