High Sensitivity Speakers that work best with SS

Hi Mapman, high sensitivity speakers are problematic with a lot of solid state amps because they have much higher back EMF, which tends to really mess with the negative feedback that the amp employs.

If the amp has a higher output impedance this is less of a problem. One way to simulate this if you have a solid state amp is to put a resistance in series with the output of the amp (which will also reduce the back EMF that the amp sees) but of course you will loose a fair amount of power across the resistor. This will result in the higher sensitivity speaker (ex.: horn) being less shrill.

However if you are auditioning high sensitivity (I would define that as being 98 db 1 watt/1 meter or more, less than that I regard as moderate and less than 89 db is low) speakers, if you happen to hear what tubes do on them there may be no going back. Good Luck!

Almarg, I suspect that the Daedalus efficiency is less than the 98 db figure stated. Duke of Audiokinesis makes a speaker that he claims is about 95 db, yet it is more efficient. I do agree though that a nice flat impedance curve does allow you to audition the differences between tube and transistor without much editorial from the speaker. In most cases.

However, If you are using Voltage Paradigm design rules, it may well be that the speaker's crossover points will not work properly with all tube amps even though the speaker has a flat impedance curve. From what I've seen/heard of the Daedalus though I don't think that it is any concern in that regard.

Daedalus_audio, it was in Thom-mackis' room that I got to hear and see that. Duke had brought his speakers down the hall and we played them on Thom's M-60s. I pushed the system hard during that audition and found that I could play the system considerably louder, yet the meters on the amps showed that the amps were not working as hard.

Since Duke's speakers were nominally 16 ohms, the meters were more sensitive (should have read higher), yet they were reading lower.

Class A works well with an A class design :)

Larryi, in many cases you are correct, as I am guessing that Nvp also suspects.

Many high power amplifiers have a distortion characteristic that is actually higher at low power levels; depending on the amp the distortion might begin increasing at levels below 2-5 watts.

Due to the dynamic nature of music this 'first watt' is quite audible even on speakers of only moderate efficiency. For this reason to get that 'inner detail' that is often the 'magic' of a good system, it may well not be a great idea to put a high power amplifier on a high efficiency loudspeaker as the distortion might be higher rather than lower. The human hear translates many forms of distortion to tonality (odd orders are brightness and harshness, even orders contribute to warmth and lushness) and due to the ear's masking characteristic, distortion can obscure low level detail.

On higher efficiency speakers the distortion character in an amplifier that seems to be most successful is that where the distortion linearly decreases to unmeasurable as power is decreased. This is the realm of SETs, the Nelson First Watt designs and our own OTLs.

If the amp has this characteristic then it will likely work fine with a high efficiency speaker even if it has high power. Sorry if I am being a bit verbose.

Mapman, I agree, which was part of why I wrote this article:
http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

I used the word 'paradigm' in the article because the industry and designers that are taught a certain way don't always want to look at things that are outside of their box. But if they did, I think it would save a lot of audiophiles enough change to buy a new car...

Is this intrinsic to these specific designs, i.e. it is simple not possible to achieve similar signal-to-noise rations when building powerful amps? Or, is this because in these designs the designers pay special attention to this (unlike most designers of powerful amps)?

With the designs I listed 'intrinsic' is probably the best word. I don't think either the First Watt or an SET can be particularly powerful, but the OTLs can- the biggest so far is 500 watts.