Amp damping factor?

Bifwynne, I did some quick calculations to provide a quantitative perspective on the effects I described above. In comparison to an amp having negligibly small output impedance, the 1 ohm output impedance of the 8 ohm taps on your amp will result in an emphasis of the mid-range frequencies for which the speaker has an impedance approaching 21 ohms, relative to bass frequencies where speaker impedance is around 3 ohms, of about 2db.

Using the 4 ohm taps would reduce the 2db figure to about 1.1db, although it would significantly reduce maximum power capability, as I indicated.

Regards,
-- Al

Al: Thanks very very much. I'll try using the 4 Ohm tap and see what happens. I'll report back in a couple of days to let you know how the 4 Ohm tap worked out. BIF

One point NOT addressed so far is that of phase angle.
When voltage leads or lags current, power to the speaker is compromised.
Tube amps do not like capacitive loads, either.

Sensitivity, while important, may in some cases be trumped by a phase.
A high sensitivity speaker with a huge phase angle will still not be proper for a tube amp. OTOH, a low sensitivity speaker which is a moderate load, can and does sound fine with tubes. Harbeth comes to mind.

To the extent that compatibility can be decided without listening to a given combination, I'd avoid big impedance swings and low impedance coupled with high phase angles at particular frequencies when using tube amps.

OK guys, here's the verdict. But first, let me wax a little philosophical. As a lawyer, but not an electronics techie, I am reminded of the axiom that some legal discussions are "multi-dexterous." In other words, on the one hand -- this, but on the other hand -- that, but then again, on another hand -- something else. When you add up the hands, you can have three or more hands -- a clear physical impossibility.

Ok, here's the bottom-line verdict, I spoke with Paradigm about the wisdom of trying the 4 Ohm taps on my ARC VS 115 tube amp. The tech said using the 4 Ohm taps "might" improve the sound, but then again, maybe not.

Well, I tried the 4 Ohm taps. I did not detect any sound improvement -- if anything sonic degredation. I tried the 8 Ohm taps again, and to my untrained ears, the sound improved. Well that's it. Fascinating technical discussion. I wish I knew more about electronics, but I don't. But I do know what sounds good, at least to my untrained ears.

I'll stick to the 8 Ohm taps, but continue to read on to learn more. In summary, I love the sound of my ARC VS 115 amp and Paradigm S8 v2 speakers, using the 8 Ohm taps. Maybe I shouldn't, but ignorance can be bliss. Thanks for the posts. BIF

In summary, I love the sound of my ARC VS 115 amp and Paradigm S8 v2 speakers, using the 8 Ohm taps. Maybe I shouldn't, but ignorance can be bliss.

BIF, thanks for the update. I don't think there is any reason that you "shouldn't" prefer the configuration which sounds best to you. The impedance curve of your speakers seemed to suggest that trying the 4 ohm taps would be a worthwhile experiment, but clearly there are an enormous number of other variables in the system, the room, and your own listening preferences that can overshadow what MIGHT be best in terms of that single variable.

Best regards,
-- Al