Power output of tube amps compared to solid states

This particular paper is interesting, but very dated . . . and no disrespect to the author or his work in context of the time. But it's important to understand that this was published some fifteen years before that of Thiele and Small, and the T/S equations predict exactly every aspect of the driver/source-impedance interactions that he gives these approximate, experimental methods for optimizing.

It also bears mention that at this time, typical loudspeakers were designed with a very small back-enclosure and a horn (using Webster's equations), or a very large infinite-baffle . . . reflex designs were extremely rudimentary and typically more like an infinite-baffle as far as the system Q is concerned. Let's also not forget that liberal application of tone controls was also not frowned upon like it is today . . . a great way to compensate for all kinds of unanalyzed factors relating to speaker design.

THaks Shadorne, that explasins what Bobby was talking about, with which he then says, which is why it works so well with tube amps, Atma-sphere among the best with my speakers.

THaks Shadorne, that explasins what Bobby was talking about, with which he then says, which is why it works so well with tube amps

Indeed, a critically damped acoustic suspension speaker does not need an amplifier with high damping factor as much as your regular underdamped boomy type designs that will get positively sloppy without amplifier control.

Shadorne, a long time ago I remember reading(though for the life of me, I can't remember where or when), that one shouldn't use a DC coupled amp with ported speakers. I am under the impression that DC coupled amps are noted for their tight bass response. Not that I doubt you, but, if all that is correct (and it very well might not be), it would seem to disagree with your last post. My, how this thread has taken off on another path!

Hi Unsound . . . it's not so much a matter of whether or not an amplifier is "DC coupled" so much as what its output impedance is -- Atmasphere manufactures "DC coupled" amplifiers with highish-to-very-high output impedances. I would summarize his position on this (sorry Atmasphere if I'm imprecise) as that speaker manufacturers have a responsibility to keep their impedance curves fairly smooth, and/or that the end user needs to be aware of what speakers produce good results with his amplifiers when making purchasing decision.

My point in the previous post is that with the mathematical tools available to the modern speaker designer, one need not use that very crude experimental methods outlined in the paper Atmasphere linked to . . . it's been possible for some time to accurately predict the loudspeaker "damping" behavior for any given amplifier output impedance. And of course different loudspeaker designers have different goals for this criteria.

BTW, there are very few amplifiers that could truly be called "DC coupled", and very few of these actually have a closed-loop frequency response that extends to DC (which IMO isn't necessarily a good idea anyway). Most conventional "DC coupled" amplifiers may indeed have the output stage DC-coupled to the positive side of the loudspeaker, but on the negative side, the speaker current is actually returned through the main filter capacitors . . . meaning that with the exception of any residual DC-offset current (or if the amplifier has a fault), they are effectively capacitively-coupled amplifiers, with the main filter caps inside the feedback loop.