Double down, good or bad?

Kirkus, it seems you got my point in your last paragraph. We could easily build an OTL with an output impedance of 0.1 ohms with enough feedback, but it would never sound right, and the lower output impedance would say nothing about what loads it could effectively drive.

The other aspect of the conflict of the Voltage and Power paradigms that is important here is equipment matching- any time you mix the two, you get tonal anomalies: a transistor amp driving horns for example will be shrill, a tube amp driving a set of B&W 802s will have insufficient bass.

In the case of the horns, the drivers are very reactive and the back EMF wreacks havoc in the feedback loop of the traditional transistor amp, making the presentation shrill, in the case of the B&W, the woofers are in parallel (4 ohms) and are 3 db less efficient than the 8 ohm midrange and tweeter; if a transistor amp is used it will have double the power into the 4 ohm portion of the impedance curve, thus driving the woofers with the 3 db extra needed for them to operate with the midrange and tweeter. The speaker cannot be driven properly by any amp that does not double power as impedance is halved.

There are many other examples!

Awesome and informative post, Kirk! Thanks.

Best regards,
-- Al

In the case of the B&W, the woofers are in parallel (4 ohms) and are 3 db less efficient than the 8 ohm midrange and tweeter; if a transistor amp is used it will have double the power into the 4 ohm portion of the impedance curve, thus driving the woofers with the 3 db extra needed for them to operate with the midrange and tweeter. The speaker cannot be driven properly by any amp that does not double power as impedance is halved.

Ralph, re "the speaker cannot be driven properly by any amp that does not double power as impedance is halved," you may recall that we discussed a similar point in another thread a couple of months ago. Wouldn't it be more correct to say that to be able to drive this impedance characteristic properly the amp has to have a low output impedance (relative to 4 ohms), and power capability into 4 ohms that is adequate to support the required volume? In other words, a solid state amp rated at say 200W into 8 ohms, but only 300W into 4 ohms, will do just as well with this speaker (IF all else is equal, and if the output impedance and 4 ohm output power criteria are met) as a solid state amp rated at 200W into 8 ohms and 400W into 4 ohms.

Regards,
-- Al

Kirkus, how do the current dumping type amps like the Threshold Stasis designs fit into your thinking?

Al, in the case of the B&W 802 you need to have 3 db more power into the 4 ohm woofer load as you do into the mids and highs because the woofers are 3 db less efficient. I am ignoring the effects of feedback here and doubtless there are amps that don't quite double power that can do OK on this speaker. I point it out though, because your typical tube amp is not going to work right on this speaker- it literally is designed with the constant voltage model -the Voltage Paradigm- in mind.