SET 45 Amp Driving Dynamic Speakers

Great comments,
Could not agree more. Happy listening, best, Rob

Indeed, high efficiency and high impedance speakers are common factors when you read/hear someone is happy with a SET amp. Another factor is the SET should be driven "well below" its rated power, which is of course undefined how low is low enough.

I'm in the process of building an active system with SETs for treble and midrange and class-D for midbass and subwoofers. It's said power required below and above 350Hz is about the same, so by crossing around there (or higher) you relieve the SET from carrying half the load. If you further divide the upper range into two, then each amp will carry 1/4th of the load.

I have my eyes on Yamamoto's A-08S (45 SET), and while the speaker driver options aren't super wide, there seems to be enough. I guess demand pulls for drivers where high efficiency and impedance aren't as big a deal, the manufacturers follow suit. It is being a fun journey!

The Yamamoto A-08S is on my list, if I come into some unexpected cash. I'd run it into my ANs (92 db?) full range, just like I'm doing now. I'm sure it will have enough "slam" for when I play The Killers. 90 db is LOUD!

Excellent, informative posts from my fuse-loving friends above.  ;-)  I have two Dennis Had amps, an SET and and SEP amp, one based on EL84 and the other on nearly any power tube you can get into the sockets, from EL34 to KT150's.  16 wpc and 6 wpc, respectively.  The smaller amp is sublime mated with the Spatial Audio Holograms and the bigger one drives my Zensor 3 speakers in the bedroom, both with all the power I need.  They both have a warm euphonic sound.  Rolling tubes is joy with these amps and some of the new tubes are as good as the pricey NOS tubes I have heard, particularly the Gold Lions.   

A type 45 can make about a 1 watt or slightly less running single ended.

To really appreciate what they can do (which is to say, they usually sound better than a 2A3 or 300b amplifier) you actually do need some efficiency and the only way to get the efficiency you need is with a horn system unless you are in a really small room, perhaps a closet.

If you drive the amp too hard, the odd-ordered harmonics that the ear uses to gauge sound pressure will appear. This causes the amplifier to sound 'dynamic'. In the initial opening post, we can see that this is happening. Its important to understand that this 'dynamic' quality is really the result of distortion appearing on the transients where most of the power requirements exist. Its a physiological interaction with how we perceive sound.

The problem is, once you know this, you can perceive it as distortion, not just 'dynamics' (in about 90% of audiophile conversations, the word 'dynamics' can be safely substituted with the word 'distortion' without changing the meaning of the conversation). So if you have read this far, I may have wrecked it for you.

You can prove this easily enough by obtaining a sound pressure level meter. They are available as apps for smartphones. You will see that its really not playing that loud- it just sounds like it due to distortion.