Autoformer vs Speaker impedance Curve

Thanks Al.  Guess that explains the bloated bass when I run 802D3s on my tube amp. 

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

No- it doesn't. If the amp is able to act as a voltage source, then it can make enough energy to be flat on the 4 ohm load of your woofer array. Since you say the bass is bloated, its doing that, so the bass bloat is something else. One possibility is that like at amps, yours is making more distortion into 4 ohms. The extra distortion could easily be perceived as bass bloat, since the 2nd harmonic is likely predominant. 

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!

Thanks atmasphere. Maybe bloated isn’t the correct word. The bass is markedly more pronounced from my tube amp (60 Watt push pull, KT88, “some” local negative feedback) than my SS CA-2300. It’s also seems “looser” or less defined.

Nonetheless, it seems reasonable to my novice brain that if an increase in speaker impedance increases the sound level “heard”,  that the bass should sound louder where the impedance spikes. No?

73max OP
bloated bass when I run 802D3s on my tube amp
60 Watt push pull, KT88, “some” local negative feedback

Without global feedback to keep the output impedance low, you probably have quite high output impedance giving you very mediocre damping factor, and no control over the bass hence your term "bloated" compared to the control the Classe has over the bass.

You could always bi-amp with the tubes on the mids/highs and the Classe on the bass, but you’ll need a passive volume control on the input of louder of the two amps to reduce and set it so it’s the same gain as the other amp.

Then use your master volume control on the main pre or dac to vary the whole (both amps) volume.

Cheers George

The bass is markedly more pronounced from my tube amp (60 Watt push pull, KT88, “some” local negative feedback) than my SS CA-2300. It’s also seems “looser” or less defined.

Nonetheless, it seems reasonable to my novice brain that if an increase in speaker impedance increases the sound level “heard”,  that the bass should sound louder where the impedance spikes. No?

If the tube amp is able to act as a voltage source, then it should not make any more bass than the solid state amp. In your speaker, there are two bass impedance peaks, which represent the box resonance with the port. If the amp is behaving as a voltage source, it will make less power, not more, into these peaks. Otherwise the speaker is a fairly benign load for a tube amp- our amps would do fairly well on that speaker (seems to me we have customers with them too).

Solid state amps often have what is called 'tight' bass, but I've yet to encounter tight bass at any show I've attended. IMO/IME tight bass is a symptom of an over-damped speaker. Here is an older article, written by the head engineer at Electro-Voice back when the industry was trying to sort out the voltage rules (EV and Mac lead the charge on that one):

http://www.dissident-audio.com/Loudspeakers/CriticalLSDamping.pdf

As you can see from the article, not all speakers need high damping factors and there are some that need really low damping factors. That is still true today and is why equipment matching is still an on-going conversation!