Tube amps and speaker ohms

In your opinion , do push pull amps work better with 8 ohms or 4 ohms. .I am under the impression the lower the ohms, the more power is demanded from the amp....Another question, are there low powered SET amps ,and high power SET amps?
I'm looking at a 40 watt 845 tube amp for my 8 ohm, 89 db speaker.. just cked the Thor has a 86 db W18 midwoofers(2 per cabinet) and a 88 db tweeter. Will an 845 amp rated 40 watts be able to drive the 86/88 db speaker? With authority, bass, mids, highs, in dynamic sound stage? Synergy? Or poor match?
Dear bartokfan: +++++ " This is the way loudspeakers behave. Loudspeakers are not constant power devices. Loudspeakers must have a constant drive voltage to provide a constant acoustic output with changing frequency. As demonstrated by the simple mathematical relationships shown above, the only way to achieve constant voltage drive with a changing load impedance is by having very low amplifier impedance. " +++++

This is what you can read on the link you posted, as you can " see " this subject is critical.

Now, the tube amplifier technology has many trouble to handle in the right way all those speaker needs, so ( if you want to go with this technology ) you have to make big trade-offs with it.
Of course that you could choose for SS technology that could mate in a better way your speakers needs and your music sound reproduction priorities.

Regards and enjoy the music.
Raul you hit on a essential issue in tube amp output. The impedance factor of the speakers, how difficult is it to keep the motor of the speakers moving in a musical line as the fq's change or amount of fq's are thrown at the amp. Which big orch does. Here the quality of transformers and other internal parts is critical. Thats why i leave it up to the amp manufactore to provide me with the best possible dynamics to run the demanding speaker as are the Seas Excel. I think I have the correct amp. I am waiting on components to arrive. many folks here boo hoo the Seas Excel with no foundation of their criticisms. They seem to be disgusted with my cheering the Seas labs creation, The Excel. Funny that these complainers have nothing to say good about their favorite driver. (not speaker, DRIVERs). Most don;'t have a clue what driver is in their speakers. Most drivers are bought on the open market. Seas actually makes their drivers IN THEIR OWN LAB> Which speaker manufacturer does that???
+++ the only way to achieve constant voltage drive with a changing load impedance is by having very low amplifier impedance+++

This statement is not totally accurate.

Constant voltage can be achieved when the amplifier has a relatively low output impedance compared to the speaker impedance AND when the speaker has a benign impedance curve across the frequency range.

In the same manner that some carts require very careful matching with a specific tonearm to perform their best, vacuum tube amplifiers require the same careful attention in matching them to the appropriate speakers.

But then I am not telling you something you do not know already Raul? ;-)

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