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A change in efficiency to the final sound

I have a p/p tube amp running a pair of 6Ca7's for about 30 watts per channel .
I have read here that p/p tube amps sound their best when they have to work a bit harder , as opposed to a SET amp that sounds best near idle .
My present speakers are claimed to be 92 db. eff.
If this amp is driving a pair of speakers rated at 85 db. efficiency , should it sound a bit better due to working a little harder or closer to its optimum level ?
Conversely , would the same amp sound a bit worse driving a more efficient speaker of 99 db. due to it working less hard or further away from its optimum level ?


Thank you

saki70

Showing 2 responses by kalali

kalali's avatar
kalali
1,977 posts
 
"If I use this 30 watt p/p tube amp with two different speakers , one with 99db. efficiency and one with 86db. efficiency and all other characteristics being equal , would the amp have a different sound with each ? If so , how ?"

If the listed dB specifications are at 1watt/1meter, then the 99dB speaker will sound louder than the 85dB rated speaker at the same listening distance when fed the same power. This applies to any amplifier regardless of its power rating. 
kalali's avatar
kalali
1,977 posts
 
"...I forgot , in the post that you responded to , to add that the volume levels would be adjusted to be the same for both speaker tests .

Does that change your thinking ?"

What I stated was how the efficiency values are interpreted. If you compensate for the efficiency by increasing the volume, then you're basically asking the amplifier to work "harder" which in case of most tube amplifiers, particularly low powered SET designs, means more distortion. Aside from the speaker efficiency, another important criteria is the speaker's impedance and how it varies as a function of the frequency. Typically, the higher the impedance the less demand from the partnering amplifier which also translates to less distortion. 
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