First, as a point of information, keep in mind that since 2.83 volts into 4 ohms corresponds to 2 watts, the speakers will just put out 88 db for an input of 1 watt, at 1 meter. That is particularly significant in the case of a tube amp such as the MC275, since tube amps generally cannot supply much more power into 4 ohms than into 8 ohms. (For 8 ohm speakers this is not an issue, because 2.83 volts into 8 ohms corresponds to 1 watt).
It can be calculated that 75 watts into the two speakers will result in an SPL of around 100 db at a distance of about 10 feet, neglecting room reflections and thermal compression that may occur in the speakers at high volumes. That is good enough for most listeners with most recordings.
However, if you listen to recordings having particularly wide dynamic range (the DIFFERENCE in volume between the softest and the loudest notes), such as some well engineered, minimally compressed classical symphonic recordings, you might find the amp running out of steam on occasional dynamic peaks. If your listening is mainly to recordings that are highly compressed and/or have little dynamic range, such as most rock recordings, and you don't listen at unusually high volume levels or at an unusually great distance, you won't have a problem.
Perhaps a more important concern, though, is what the amplifier will sound like when driving the speakers. If the speakers are the same version of the Cremona that John Atkinson measured here, or if they are a different version having similar impedance characteristics, I would have some concern that their impedance characteristics in some parts of the bass region might be a bit difficult for this amp to deal with gracefully. Note that the impedance magnitude is only around 3 ohms from 80 to 200 Hz (where a lot of power is often required), and as JA notes there is a very challenging phase angle just below that region. And, not surprisingly given those characteristics, I see that JA mentions that the Cremonas "seemed more sensitive than normal to amplifier choice."
Hopefully someone who has tried this particular combination will comment further. Although, again, the dynamic range of the kinds of recordings that are listened to by the particular individual, and the listening distance, are important variables.
Regards,
-- Al
It can be calculated that 75 watts into the two speakers will result in an SPL of around 100 db at a distance of about 10 feet, neglecting room reflections and thermal compression that may occur in the speakers at high volumes. That is good enough for most listeners with most recordings.
However, if you listen to recordings having particularly wide dynamic range (the DIFFERENCE in volume between the softest and the loudest notes), such as some well engineered, minimally compressed classical symphonic recordings, you might find the amp running out of steam on occasional dynamic peaks. If your listening is mainly to recordings that are highly compressed and/or have little dynamic range, such as most rock recordings, and you don't listen at unusually high volume levels or at an unusually great distance, you won't have a problem.
Perhaps a more important concern, though, is what the amplifier will sound like when driving the speakers. If the speakers are the same version of the Cremona that John Atkinson measured here, or if they are a different version having similar impedance characteristics, I would have some concern that their impedance characteristics in some parts of the bass region might be a bit difficult for this amp to deal with gracefully. Note that the impedance magnitude is only around 3 ohms from 80 to 200 Hz (where a lot of power is often required), and as JA notes there is a very challenging phase angle just below that region. And, not surprisingly given those characteristics, I see that JA mentions that the Cremonas "seemed more sensitive than normal to amplifier choice."
Hopefully someone who has tried this particular combination will comment further. Although, again, the dynamic range of the kinds of recordings that are listened to by the particular individual, and the listening distance, are important variables.
Regards,
-- Al