Sometimes Hard to Drive Speakers are a Gimmick

@erik_squires 

Thanks for the writeup.  I get your point regarding the crossovers...  As paralleling two woofers in a tower speaker with a mid and tweeter is very common, deciding the impedance of those woofers along with the crossover design will define the low ohm situation that will fine tune the sound.  The debate seems to be whether some caps & resistors in the crossover are there just to make the speaker sound different (preferably better) with "low ohm" capable amps to elevate the perceived value of the speaker and/or amp ?  especially, if those parts are really not required to enhance the sound.  As you writeup explains, why not parallel 16 ohm woofers rather than 8 ohm speakers to alleviate the issue ?  As you say, because the loudness of the 8 ohm speakes paralleled might match better the cabinet, mid range speaker & tweeter for a better overall sound....   Nowadays, you hear many DIY speakers pushing for flat frequency response and nice impedance curves.  I guess the real question comes down to -- does this or will this really sound better to everyone in every room with every stereo ? 

I would think that the crossover logic that you are seeing as "illogical" is an attempt to differentiate the speaker from other commodity speakers and make them seem special, especially, with a reviewer comment like " these speakers really come to life with xxx amp".  Exactly as your writeup articulates. 

Note: To speak to your point,  I am running Wilson W/P 8 speakers with two McIntosh MC275 tube amps monoblocked.  These speakers have a couple of low impedance dips in the woofer frequencies, and when moderately loud, they sound better with two McIntosh MC275 tube amps in monoblock mode rather than just one MC275 tube amp in stereo mode.

As paralleling two woofers in a tower speaker with a mid and tweeter is very common, deciding the impedance of those woofers along with the crossover design will define the low ohm situation that will fine tune the sound.

If you mean, you’ll end up with a lower impedance than with just one, yes, absolutely, and this trade-off is well known, and expected, often resulting in 3-ish impedance in the mid bass.   I don’t consider this malicious so much as a trade-off.   Want lots of bass in a small footprint? This is one way to do it.  I do this myself with my bass cabinets.  Not what I’d call a designer out on. 

  The debate seems to be whether some caps & resistors in the crossover are there just to make the speaker sound different (preferably better) with "low ohm" capable amps to elevate the perceived value of the speaker and/or amp ? 

I don’t actually have a problem with well-designed impedance flattening circuits used to eliminate drover resonance peaks.  Yes, they take current but they should bring the overall impedance and dissipation down to no worse than the rest of the speaker.   Such a circuit that results in practically 1 Ohm loads, or worse, for no particular gain is not IMHO a well designed circuit.  Is it malicious, or meant to show off what a high power amp can do?  I’d have to put the designer under oath. 

The benign version of this circuit by the way is rarely used as the wattage dissipated and parts costs can be high. 

The Focal circuit I show you was NOT a case where impedance was flattened with clear benefit to anyone.  Half of it should be removed, and the rest I showed could be rethought yielding much better bass impedance. 

Another very typical impedance lowering circuit is a Zobel, which is used to help a filter circuit behave as intended.  I wrote about this here.  Again, perfectly acceptable space heater.  

@OP - With all due respect, there is a lot of dubious logic in your blog post:

"Many audiophiles unfortunately believe that a speaker that shows the difference between upstream components is more musical or easy to listen to.  They are not.  They just show differences better, but these buyers will prefer the speaker that is harder to drive, and then buy a bigger amplifier."

Re above - first there is a false premises argument. The first sentence is merely an unsupported conjecture. Then there is a syllogistic fallacy viz the alleged preference of audiophiles stated in the first premise leads them to prefer speakers that are harder to drive and consequently buy bigger amplifiers.

Sorry if it appears harsh but your argument is just nonsense.

I read your blog post, and from it I glean that you think some speakers have unnecessarily low impedance. Fair enough, though  I would imagine that the professional designers of the speakers might disagree with you. But as for the rest...

It's up to the engineer to watch the impedance curve of their design. Something designed for a big room will use more energy. But it can still have a reasonable impedance curve. Low watt amps make them sound indolent.