Amplifier design parameters required for a good match for high (16+) ohm speakers?
Most SS amp will output half the wattage @16ohm than @8ohm, you
need to check if a amp has enough output power to drive the 16ohm speaker to
desired
loudness/SPL. https://www.crownaudio.com/how-much-amplifier-power |
As long as the amplifier has enough power that it won’t be clipping into the 16 ohm load, it should work just fine, unless there is some other mis-match going on. I have made speakers that are user-configurable as either a 4 ohm load or a 16 ohm load. As long as the amps weren’t pushed into clipping, to the best of my knowledge all of my customers who tried it both ways preferred the 16 ohm configuration. I have been told by multiple amplifier designers that distortion is lower into a high impedance load. At least one amplifier designer, Ralph Karsten of Atma-Sphere, recommends high impedance speakers particularly for his lower-powered OTL (output transformer-less) amps, which unlike solid state amps actually make MORE power into a 16-ohm load. If you haven’t already, I suggest taking a look at his amps. (Disclaimer: I’m a dealer for Ralph, and have been making speakers with his amps specifically in mind for 14 years.) Duke |
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. |
Your Dynaco ST-70 is a tube amp. While SS amps reduce output, as speaker system impedance rises, the typical tubed amp does not(given a correct impedance match/output connection). You might find this article enlightening. Especially, the comments immediately below graph 7, regarding output and distortion figures, into various loads. https://www.stereophile.com/content/dynaco-stereo-70-ii-power-amplifier-measurements Use your 16 Ohm tap, for best results. |
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. |
