Sometimes Hard to Drive Speakers are a Gimmick

@hjdca 

You are absolutely right that dual woofer designs end up wiring the speakers in parallel, so hard to get any better than 4 Ohms, and I kind of talked about that a little. 

Still, plenty of dual woofer designs which have better impedance and don’t have a missing resonance hump. 

My own SNR-1 uses 4 Ohm woofer instead of 8 specifically to get more output and make it a closer match to the tweeter.  That’s totally legit.  Making your crossover harder to drive just to make it harder to drive is not OK. 

interesting observation but in my 40years of high end audio experience totally irrelevant today

WHY?

today high powered amplifiers which can put power into low impedances are everywhere

So most loudspeaker designers simply don't care it is not a consideration

and most high end loudspeakers will be used with the appropriate matching electronics

today a high powered powerful integrated can be purchased for1500

a Nuprime ida9 can put out400W (8 Ohms), 500W (4 Ohms) so that means under 4 ohms the amplifier can still be putting out power 

as long as you have adequate cooling most amplifiers will have no problem and even in the case of a low impedance dip it still depends on the frequency content, amount, and duration, of that signal

take away not the same issue with most modern high quality amplifiers.

Dave and Troy

audio intellect NJ

@hjdca Some speakers are harder to drive than others, my post was when designers add parts to a crossover to make them even harder to drive than they would be otherwise. 

I think designers are unconcerned because, as Dave and Troy said above, electronics capable of driving such speakers are common.  So designers simply add more and more networks to their crossover to "correct" for various things, like a frequency response bump or dip or ripple, or to correct phase, correct for floor bounce, etc. because they can do it never mind that such added complexity might take away from the sound quality or make the speaker harder to drive.  I once saw a picture of the crossover for a two-way speaker that had more than a dozen capacitors and something like eight inductors.

I tend to like low powered tube amps more than any other kind of amplification, so efficient, easy to drive matter a lot to me.  But, people like me are in the minority.  Most people want high powered amps that can drive punishing loads.

So designers simply add more and more networks to their crossover to "correct" for various things, like a frequency response bump or dip or ripple, or to correct phase, correct for floor bounce, etc. because they can do it never mind that such added complexity might take away from the sound quality or make the speaker harder to drive.  I once saw a picture of the crossover for a two-way speaker that had more than a dozen capacitors and something like eight inductors.

You are conflating a complicated network for one deliberately altered to make it hard to drive.  In the case of the Revel, we have actual anecdotal evidence of it being made hard to drive specifically to sell bigger amps.  

Suggest you review the section on the Focal low pass filter.