Question on speaker sensitivity / power.

I was looking at some Opera Callis bookshelf speakers and noticed that they are rated for 50 watts max and have a sensitivity of 86db. I would think speakers with that low of a sensitivity would actually perform best with a more powerful amp. Am I off base on the power/sensitivity issue?
In general, yes you are correct. Rather than get into all the science behind this, you will also need to factor in how big is the room that you will be setting up your system in, how loud do you like to listen to your music, and what type of music do you like to listen to. Also, you want an amp with more reserve power than a speaker's max. If you drive your amp to near clipping/ clipping, you will fry your speakers as the power is "dirty" power.

I have Opera Plateas that I use with a Prima Luna Prologue 5 (tube based, 36 wpc). Even though the room is pretty big by NYC apartment standards (15 X 23 X 9), I listen at low levels, so the amp choice works out ok. If I were listening to orchestral music at loud levels and wanted to hear all the details, I would most likely need a more powerful amp.

FWIW, the Opera Callas are rated from 50 to 100 watts. So, you have many choices available to you in an amp.


Actually the max power rating(w/o clipping) for the Callas is 250W(RMS). That's IF this is the Callas you are referring to(there are others): ( If you were shopping for SS amps to go with them, most would probably double their 8 ohm output into the Callas' 4 ohm nominal impedance. With tubed amps(if using output transformers) the output will be less into a 4 ohm load than into 8. Everything Rich says about room size/music genre applies. As long as you're not trying to listen to philharmonics at concert levels, 50 to 100 watts should suffice.
very general rule of thumb...under 90db go ss and over go tubes but you must also consider speakers impedance....under 8 ohms go ss and 8 ohms nominal or higher is tube land....don't get hung up on mfg. power rating for's almost meaningless
The 50W max rating means the drivers can't handle a ton more power than that. However, the amount of time spent at that power level plays a large role in determining potential damage - and yet the specs say nothing of this. Is it 50W continuous or 50W for 1ms? or 5ms? with music? with sine waves??

So the bottom line is the specs as given don't mean much of anything. You can get an amp around 100W and be just fine. Enjoy!

1 watt = 86db
2 watts = 89db
4 watts = 92db
8 watts = 95db
16 watts = 98db and so on.
You have to double wattage to gain 3db.
You have to go up about 10db to hear a doubling of volume.
THX is 110db, Ultra THX is 112db.

Yes, I'd suggest at least 100 watts on those speakers. 200 won't hurt?
Dear Chrizmontes: You are right on the power/sensitivity issue.

There is not much to write of what already posted Rich and Rodman999999 other than take in count that the speaker impedance goes as low like 3.2 Ohms that it is not a very friendly to a tube amp. Anyway try to match it with an amp with very low output impedance: say less than 0.3-0.4 Ohms.

Regards and enjoy the music.