SET 45 Amp Driving Dynamic Speakers

The vast majority of horn-based systems, particularly modern systems, are not my personal ideal.  Many are excessively colored (nasal or shrill or ragged sounding) for my taste.  Among those that I like, would be the Avantguarde systems and Edgarhorn systems.  It has been a while since I heard and Odeon, and I thought it was okay back then.

But, certain older systems and new systems with certain vintage drivers sound very good to me.  I like old Western Electric compression midrange drivers and the various Japanese clones of these drivers.  These systems cannot be mass produced, so they really don't represent commercial alternatives to speakers like the AN-E.  

Yes, those vintage drivers and their Japanese clones are pricey. I haven't had the pleasure of hearing either.
I heard the Odeon in the same system as the Nenuphar. Neither was drivable by my 45.  When driven by a more powerful amp, I preferred the Odeon.  It sounded closer to my AN-Es but with more grunt, shove, and dynamics.  The Nenuphar presents a light, quick, and airy sound in comparison.  

I'm reading this, almost midnight west coast time, doing all kinds of experimenting with my amps and speakers and iPhone spl meter.  I have  new Thomas Mayer 45/2a3 and a Slagle passive pre. I don't listen loud average 75-80.  My speakers are in the 99 db sensitive range. Like other I'm happy with my 45 tube and what it does for me, I think.  I've listen to a few rock and roll songs over and over. The 45 and peaked out at 87. it was more that I was comfortable with... and according to @atmasphere  its because of distortion and not because its too loud? neither the passive pre dial or my  digital volume on Roon was to the max. I then put the 2a3 in to see if the sound was more dynamic because i was not clipping or now there is less distortion? Listened to the same song. Probably annoying the neighbors now.... and i peaked out at 89.5. it felt louder but i surely it can't be getting distortion, I'm just having a hard time understanding.  Its just math right? watts, listening level, dynamic range.
 

With my Thomas Mayer 45/2a3 I always listen at peaks of 90db and that's only because I live in a condo -- I'd like to push it higher most of the time.  On most songs I could push it to mid-90s without feeling uncomfortable.  My speakers are probably about 95db efficient.  Perhaps this says more about how comfortable each of us is with certain types of distortion than it does about equipment.  

@guf 

Let me try and help there.
One one hand different people are comfortable with different levels of SPL. My wife likes the music much lower than me in our same room, same system with same distortion.
Then there is how each of us reacts to distortion, I'm guessing.
The kind of music you use also has an impact. Recent pop/rock tends to be  compressed so smaller dynamic range in the record. Older records and some current don't use compressors so the dynamic range is much higher. Higher dynamic range means louder passages are more demanding on power delivery from the amp and therefore likelier to distort. Atmasphere has stated repeatedly SETs should be used conservatively to keep distortion very low, under 50% and preferably under 20% of rated power.

Let's take a shot at the math: the 45 is rated for 1W, so on your 99dB/W at 1m speakers they would deliver 99dB at rated power at 1 meter. At rated power distortion is high, per Atmasphere. At 20% it would be 0.2W, so your speakers would deliver 92dB SPL at 1m, per speaker. Add the second speaker (and some losses) and let's add 4.5dB at 1 meter. If you listen at 8' away (2.4m), SPL would drop to 88.9dB SPL at the listening position. Add room gain...say 4.5dB and you are at 93.4dB SP at the listening position.

What were your settings on the SPL meter? C weighting?
Then there is also the speaker rating...99dB depends on how the manufacturer measures and defines this. Oh well...everything seems to be "it depends"...

You mentioned above 87dB with the 45 it became uncomfortable. If that was with current pop/rock music maybe your speakers aren't really 99dB efficient? Or the phone app isn't calibrated. Or a number of variables out there...

Like other I'm happy with my 45 tube and what it does for me, I think.

This is the key part. Don't think you are happy. Be happy and enjoy your system!! Understanding all of the above helps in just that: understanding. The enjoyment shouldn't be affected by our understanding, in my view.

cheers!