Power output of tube amps compared to solid states

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.

Another way to think of damping is that a high damping amp "shorts" the speaker woofer voice coil when the signal is "zero" - this means that the voice coil current is maximized (sees least resistance) in response to the movement of the coil through the magnetic field which creates the strongest possible back emf which opposes the coil movement and acts as a "damper" for as long as it takes the coil to come to rest. The more powerful the magnetic field (magnet size/weight) and the bigger the diameter of the voice coil and lighter the cone weight then the better an amplifier is able to tightly control a woofer. (This is why large 4 inch voice coils that are very short (light weight) and sit in a long powerful magnet gap are so desirable. These are extremely expensive as well with a quality 12 inch woofer costing around $1000 and weighing about 25 lbs or more.

Of course at resonance, the impedance of the voice coil rises and electrical damping is not as powerful and that is where the "acoustic suspension" design becomes critical to how the speaker will sound.

These are extremely expensive as well with a quality 12 inch woofer costing around $1000 and weighing about 25 lbs or more.

I would add that outside of pro applications these kind of woofers are few and far between - buyers will pay for veneer or cabinet work but not for honking great big magnet and voice coil that they cannot even see - of course manufacturers respond accordingly to the customer demand (customer is king).

Without a good expensive woofer the best damping factor in the world is not going to put lipstick on the proverbial pig...