Speaker Efficiency

Oh it will work. Almost any pairing will “work” and make sound.    It might even work well enough for some  in some cases.  But the pairing will never bring out the best in either component.  

If the source has large and sudden dynamics, when low powered amp is driving lower sensitivity speakers, and they are lower impedance speakers (a hard combo for any amp) the amp will not have enough reserve to supply the juice to the speakers for the dynamics, especially bass which is the most power hungry frequencies.

My Office System: My Little Luxman Tube Integrated:10 wpc at 6 ohms

https://www.luxman.com/product/detail.php?id=33

is driving Vintage AR-2ax, 91.5 sensitivity at 8 ohms.

https://stereonomono.blogspot.com/2014/05/acoustic-research-ar-2ax.html

very nice combo, however I need to turn the volume up further than most amps I have owned over the years, and while enjoyable volumes are produced, I would not expect great dynamics out it this combo.

Previously, driving Wharfedale Diamond 225’s, sensitivity 87db at 8 ohms

https://www.stereophile.com/content/wharfedale-diamond-225-loudspeaker

the Luxman Volume had to go even higher.

It also sounded good in this room, but you have to know/acknowledge the limitations.

I bought the AR-2ax for nostalgia for my Garage/Shop system (I had them in college).  they sounded soooo good, I moved them to my office, gave the Wharfedales to my son, and bought a 2nd pair AR-2ax that I am restoring for my Garage/Shop system.

AR gives some power formulas here, page 12, magnify

https://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_brochures/acoustic_research_loudspeak.pdf

When you mentioned 80db at your listening position I’m assuming you mean peak not average, which isn’t all that loud.  The power needed to increase volume is logarithmic, you can still get to relatively loud levels with low power.  Tubes also soft clip so it could be cheating to get to 80 and you might not even notice.  Try hitting 90 or 95 db peaks and you’ll quickly realize why you originally had them paired with the Forte.  I’d also be much more concerned with damaging the speakers then the amp.  Clipping of any type is not good for voice coils.  I’ve paid to replace a few drivers once.  Learned my lesson.  Be really careful with low wattage amps.  They may have sounded great at the time and then you come back the next day and certain songs don’t sound quite right.  Then comes the fear and panic. It’s not pleasant. 

@mikelavigne wrote:

i’m not always the biggest Harley fan with his tendency toward hyperbole.....but in this case he nailes it. a quick read worth your time.

I fully agree - on all mentioned. 

@mapman Wrote:

Oh it will work. Almost any pairing will “work” and make sound. It might even work well enough for some in some cases. But the pairing will never bring out the best in either component.

Exactly!

@marktheshark Wrote:

Typo, the Electa Amator is 4 ohms at 88db

That means the speaker is getting two watts not one watt. I.e. Sensitivity @ one watt @ one meter @ eight Ohms =88 dB SPL @ four Ohms= two watts for 88 dB SPL @ one meter. In other words, your speakers are getting two watts from the amp not one to get 88 dB SPL @ one meter. Also, any amplifier driving lower impedances = higher distortion.😎

@mikelavigne Wrote:

i’m not always the biggest Harley fan with his tendency toward hyperbole.....but in this case he nailes it. a quick read worth your time.

I agree!

Mike