Autoformer vs Speaker impedance Curve

73max OP 
Guess that explains the bloated bass when I run 802D3s on my tube amp.

From Stereophile:

" 802 D3's 8, because the bass was entirely devoid of bloat or emphasis or resonance. Despite this, there was no lack of authority when that was called for, and the speaker's reproduction of deep bass was formidable."

This was achieved with Parasound Halo solid state, and Theta Dreadnought, also solid state. 
The big MacIntosh 303 with output transformer was kindly referred as being leaning towards the power, which to me "kindly" says "bloat" (remember MacIntosh are huge advertisers in Stereophile.)   

 
Also this is said about the design of the 802's bass alignment.

"the 802 D3's low-frequency alignment is free from underdamped boom."

  And this is the load the 802's present to the amp. especially in the bass

The magnitude drops to 3 ohms between 100 and 130Hz, and again between 670 and 770Hz.
There is also a combination of 4 ohms and –64° at 69Hz, implying that this speaker does require an amplifier that is not upset by a low effective impedance.

This last paragraph will represent a EPDR load close to 2ohms to the amp.

As I said before with what you have without resorting to buying anything else, go with the bi-amping, your Classe on the bottom for control of the the bass and whatever the the tube amp you have on the mids/highs.

Cheers George
 
  

This is an interesting article.   http://www.dissident-audio.com/Loudspeakers/CriticalLSDamping.pdf

I like what he is doing in figures 2 and 5. However this is just about the woofer. There is no consideration to speakers that have a wide impedance variation over their range. In 1954 speakers had simpler crossovers without the frequency response modifying parts we see today. With at woofer and a tweeter all you need is a capacitor for the tweeter and wind enough inductance in the voice coil so its impedance rises markedly with frequency. 

Once again I encourage people to take off their damping blinders and look at what is going on in the interaction between impedance of the speaker vs the amplifier.

atmasphere. 

  It could also be the power cord, as a cord that limited the amplifier's ability to replenish its power supplies might come off with more distortion as well. This effect is quite measurable- I've seen power cords
rob a tube amp of nearly 30% of its total power!

I would like to know how to measure that. 30% is hard to imagine. I test amplifiers all the time with ordinary power cords and have never seen this. This reminds me too much of Bruce Brission's white paper which was a total embarassment to his distributor who promptly dropped his line.

I would like to know how to measure that. 30% is hard to imagine.

+1

Back in 2010 I asked Ralph about that statement in this thread.  Here are excerpts from our discussion:

Atmasphere: Power cords: a 2V drop across a power cord can rob a tube amplifier of as much as 40% of its output power! Cripes! You're trying to say you can't hear that?? [That comment was addressed to someone else].  So this is very measurable and audible as well. On lesser transistor amps, a power cord will be less audible as the drop across the cable is reduced, but a class A transistor amp will easily bring out cable weaknesses.

Almarg: Ralph, could you provide a technical explanation of why that would be so? I don't doubt your statement, but I'm interested in understanding why that would occur.... Re your other points, all of which strike me as excellent, I think that it should be stated that none of those points NECESSARILY mean, to cite an example, that a $2,000 power cord will outperform a $200 power cord in any given system.

Atmasphere: Al, the reason a power cord can have this effect is simple. If there is a 2 volt drop in a power cord, the filaments of the tubes will run cooler and the B+ will be reduced. Since this is a voltage, the result is we get less voltage output out of the amp. Less voltage=less power. Depending on the amp this can be pretty profound. and I have seen it with my own eyes. I do agree though that that does not justify a $2000 power cord, but it **does** justify one that has decent connectors and conductors that will not heat up at all. That has to cost something, probably not $2000 though. One thing about audio is that if there is a phenomena, there is also snake oil for it.

Almarg: Thanks, Ralph. That would also seem to say that the value of the ac line voltage at each listener's location can be a very significant variable in the performance of a tube amp (assuming it does not have regulated filament and B+ supplies). Which in turn emphasizes how easy it can sometimes be for extraneous variables to lead to incorrect sonic assessments.

Atmasphere: No doubt! But it extends to anything that can draw significant power- and bigger transistor amps can! Imagine the peaks just... not... making it.

This taught us a lesson... when we set up an amplifier for test, we test the AC line voltage from the IEC connector. The meter on the variac (a bit of test instrumentation) cannot be trusted. 

A 2 volt drop in a power cord of typical length seems like a lot, of course.  But if the amp draws say 5 amperes a resistance of 0.4 ohms, including the resistance of the connectors and the contacts as well as the combined resistance of the hot and neutral conductors, would do it.  I'd imagine that could happen in some situations.

Regards,
-- Al