Minimum recommended amplification requirements and amplifier matching

You mentioned in your 12:16pm post "...all other things being equal". Am I correct that you are also speaking of the *sound pressure level*? I ask because if so, again it would seem to me that higher speakers impedance (say 16 ohm instead of 8) would mean that one would need to raise the volume/power to achieve the same SPL, and hence in so doing could increase distortion if the amp is not operating in its "comfort zone".

The 'all other things being equal' is meant to suggest that if you could magically have the same exact speakers, differing only in impedance.

16 ohm speakers do not need more power. Impedance and efficiency are two different issues; a watt into 4 ohms is the same sound pressure as a watt into 16 ohms 'all other things being equal'.

If you are used to the sensitivity spec rather than efficiency, then the 16 ohms speakers might seem harder to drive. This is because the sensitivity spec is based on voltage (2.83 volts) rather than power (1 watt). Into 8 ohms the two are the same; into 4 ohms the power is 2 watts if the voltage is the same, and into 16 ohms the power is 1/2 watt if the voltage is the same.  This can make the higher impedance speaker appear harder to drive, but if we are talking about tube amps, they are no different; in fact quite often a tube amp will make more power into 16 ohms rather than less.

In other words, it was/is my understanding that what you’ve stated elsewhere is that if an amps volume is *to low*, that also creates unwanted and excessive (relative to its least possible) distortion. If that is true, then it seems conceivable that a 16 ohm load could cause an amplifiers volume control to be *to low* and create more distortion than it otherwise would if operated into a lower impedance.

The volume (power) level and the impedance of the speaker are different.

For a given impedance regardless of the power, if the impedance is raised the distortion will be lower.

So ideally the speaker would be of the efficiency and impedance that you can take advantage of both.

I like to run tube amps, and while 30 watts or so will make tunes on a speaker of 90 db, I think you will need more power. If it were my room, there would be no doubt. My speakers are 98 db and 16 ohms, and I really think 30 watts is about the minimum on them!

If you really want to work with tubes or even if you want your solid state to sound better, you're always better off not making the amp do something hard, like drive a difficult load. The amp will make less distortion!

To this end generally speaking, an 8 ohm speaker will sound better that 4 ohms and a 16 ohm speaker better than that, all other things being equal. This is simply because no matter the amp, it will make less distortion into higher impedances, and that is audible because the amp will sound smoother and more detailed.

So the takeaway here is if you like the tube amp- get a speaker that is more efficient/easier to drive.