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Single Ended Triodes (SETs), the ultimate tube lovers dream.

Re: SET / speaker calibration

Paul,
Here is some measured data for the Circe from an old Stereophile review. The link included plots of impedance and phase vs freq. Here is a quote:
The big Alón's sensitivity was to specification at an estimated 87dB(B)/2.83V/m. Its impedance plot of magnitude and phase against frequency (fig.1) dropped below 6 ohms only in the upper bass and upper midrange, with a moderate phase angle across most of the band other than in the bass. The Circe will be relatively easy to drive, which presumably explains why listeners have had success using the speaker with SE triode amplifiers. But note the very high impedance peak at 39Hz: 24 ohms. This will exaggerate the midbass with such amplifiers. It also indicates that the quite large sealed bass bin is tuned relatively high in frequency, which will impact ultimate bass extension.

The DRD 300Bs are tapped for 8 ohms right now.

You said:

***If the speaker has a benign impedance - no wild swings, no large phase angles - then running a 6 ohm speaker on the 8 ohm tap will produce the most available power. If the impedance dips much below 6 ohms, you may want to try the 4 ohm tap instead.***

I think that your point is that matching amp output impedance closely with speaker load should result in max power transfer, correct? Where I am still unclear is how this relates to DF = speaker load / amplifier output impedance. Considering only DF, it seems that either minimizing amp output impedance, or increasing speaker load should help bass control.

I am assuming that both power transfer and bass control are separate issues that are optimized differently, but must still be considered in total. Where is the balancing point in system design?

bty, I really appreciate you taking time to explain these fundamental issues. Thank you, Paul.



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