I suggest you look into Magneplanars which I specifically mentioned. They are known for having relatively benign load characteristics.
Whether they have "
relatively benign load characteristics" or not, it still doesn't equate to a "fairly constant Ohm load". As I said, there is no such thing as a full range speaker system that has a "fairly constant Ohm load". Only a speaker that's dedicated to a narrow frequency range can have a "fairly constant Ohm load", unless you play a test tone rather than music; then any speaker will have a dead constant ohm load.
This is not the car audio world!
I never said that it was. I was pointing out a funny (i.e., ironic) contrast. On the one hand you have some elaborate and expensive home audio receivers which are often not rated stable at 4 ohms, and on the other hand you can buy an el cheapo "Road Gear" car audio amp from Wal-Mart that's stable at 2 ohms.
Given that I wasn't mistaken in the first place, I can hardly be mistaken "again".
There are very few amplifiers intended for home use that actually double down. Most if not all of those amplifiers have a published 4 Ohm power rating.
I said that most
car audio amplifiers are unrestricted (at least they used to be; I don't know about the current state of them).
This is not the car audio world.
Yes, you already pointed out this obvious and uncontested fact. See my response to it above.
Very few home and/or studio speakers have impedance curves that dip down to one or two Ohms. The ones that I specifically mentioned do and have a reputation for being difficult to drive amp busters
It doesn't matter what the individual pairs of off-the-shelf speakers out there have for a nominal impedance rating; you can can get whatever nominal impedance you want from your speaker system, either by building your own cabinets and choosing the drivers, or by using off-the-shelf speaker systems in various combinations. For example, if you have an amplifier that's stable at 1 ohm, you could could wire up 8 pairs of off-the-shelf 8 ohm speakers in parallel and you have your 1 ohm load. Or you could build a pair of cabinets, each containing eight 8 ohm drivers wired inside the cabinet in parallel and you have your 1 ohm load.
By the way, with regard to your following statement:
"They pretty much put Krell on the map because nothing else could drive them"
What does this "Krell" amplifier cost? I ask because I suspect you could get a 1-ohm-stable car audio amplifier plus a suitable 12 VDC power supply (e.g. 100+ amps, good for 1200+ watts) to run it for less money. You see, car audio isn't irrelevant to home audio. A $200 or $300 power supply can run a pretty healthy car audio amplifier from a wall outlet.
And with regard to your following statement:
"Yes, I've heard them at length and yes, they sound a lot better when strapped for 1 Ohm."
The impedance of the speakers doesn't affect their sound in and of itself, it only affects the current through the amplifier. Given the same amplifier, and assuming said amplifier isn't restricted to output the same amount of power at a lower impedance (like some JBL car audio amplifiers are) they are going to be getting a lot more power at 1 ohm than at 4 ohms, which would account for the difference you heard. However, amplifiers tend to increase distortion levels as the impedance of their load drops, so there is a downside to it. If I had a pair of speakers that could be configured for 1 ohm or 4 ohms (just as any pair of 2-ohm DVCs can be), and I wanted to feed them say 100 watts each, I'd rather wire them for 4 ohms and do it from a 100W x 2 @ 4 ohms amplifier than wire them for 1 ohm and do it from a 100W x 2 @ 1 ohm amplifier.
That's not entirely true. With many amplifiers made for home use an extremely low impedance load will cause them to go into protection mode at almost any volume. This is even more prevalent with the average receiver. There are several posters here who have Infinity speakers with Watkins woofers that have experienced amplifier shut down at moderate volumes. Those same amplifiers simply won't work with Apogee Scintilla's strapped for 1 Ohm operation.
If an average receiver rated stable for 8 ohm loads goes into protection mode driving a pair of 4 ohm speakers with ordinary music at moderate volume, it is either defective and in need of repair, or its 8 ohm rating was optimistic in the first place. For example, driving a 4 ohm load at half volume is electrically identical to driving an 8 ohm load at full volume. So any amplifier that can't handle a 4 ohm load at half volume can't handle an 8 ohm load at full volume either.
As far as a 1 ohm load goes, of course you shouldn't try that with an amplifier that's only rated stable to 8 ohms, but you could generally get away with it with an amplifier that is
honestly rated stable to 2 ohms (like nearly all car audio amplifiers are). I wouldn't hesitate to hook those "Apogee Scintilla's strapped for 1 Ohm operation" up to my 1990s-manufactured Rockford Fosgate Power 1000a2, for example.
And getting back to the point, the OP's Pioneer receiver is rated stable to 4 ohms, so it obviously will be fine driving 4 ohm speakers.
