Relate sensitivity/impedance to speaker efficiency

Thanks Al and Atmasphere: I experimented with the 4 Ohm taps. Although I can not offer a technical explanation, I can only say that my speakers sounded terrible across the board when played off the 4 Ohm taps: way less efficient, rolled off treble and muddy bass. By contrast, everything was great on the 8 Ohm taps. As I mentioned above, the speakers are nominally rated at 8 Ohms, so I guess that's the way the manufacturer intended them to be played.

I plan to switch out the 6550C power tubes for the KT 120 tubes in a month or two. There's an outfit that breaks the tubes in for 72 hours and matches the tubes using three criteria. The cost is less than half of what ARC charges. I may try them out. When I do, I'll report back. Hifigeek1 is an ARC buff, so he may be interested. Thanks again.

Hi Al, I was involved in a rather ambitious speaker cable project about 25 years ago, wherein we used a time delay reflectometer to analyze a variety of cable geometries. What we found is that characteristic impedance does indeed play a role (not nearly so important as it does at RF frequencies though) in the performance of the cable.

If the load is highly reactive, then the characteristic impedance can be important if the amplifier is otherwise unstable with the back EMF. Just a side note- obviously I am way OT here.

Nnck, my apologies- you were correct and it was me that was getting confused with all the conjecture. But as it has turned out, the less efficient speaker is on the Voltage Paradigm and the more efficient one is on the Power Paradigm, so now we find that it is true that one is about 4 db more efficient than the other, despite the sensitivity of them being almost the same.

Thanks, Ralph. Yes I recall discussing those experiments with you and others in a thread here about a year or so ago. And it certainly does seem conceivable that characteristic impedance could affect the sonic performance of a speaker cable in some systems, due to the effect you mentioned, as well as because of its correlation with inductance, and perhaps because of its relation to antenna and vswr effects.

As you realize, though, my point was simply that it is not relevant to Bif's question about easing the load on the amplifier, in the manner that going to a higher impedance speaker would ease the load.

I'll add, also, that to the extent that characteristic impedance may have audible consequences in some systems, both the anecdotal indications and some technical considerations would seem to suggest that in general lower is better. The technical considerations being the correlation between low characteristic impedance and low inductance, and possibly (although I am dubious) the impedance match with the speaker at high frequencies.

Best regards,
-- Al

Agreed!