soundhound - Are you thinking primarily of home theater receivers here as compared to older amps, integrated amps, and receivers? I'd certainly agree when it comes to the typical receiver power amp section, as the "4 ohm" or "6 ohm" switches you mention attest to. On the other hand, I've been under the impression that separate power amps from companies like Outlaw, ATI, Rotel, Anthem, etc. are built robustly enough to handle lower impedance loads without issue.

the great GONK questions the great SOUNDHOUND this should be enough for us all to sit back and LEARN!

not being sarcastic i really appreciate BOTH of your experience above and beyond!

look forward to ALL feedback!

btw, just killed my monitor asw-210 amp....HEARTBREAKER!

I was referring to seperate power amps and receivers. Any amplifier that has the "4 ohm" switch is not robust enough to drive that impedance without the reduction in rail voltages that the switch provides, whether seperate or receiver. This is done for cost reasons mostly, as it would be impractical and costly to make a multi-channel power amplifier with the transistor complement, heavy heatsinking, and large power supply of the more robust stereo amps of 20 years ago. Many of those could drive 2 ohms without complaint.

Home theater amps that have the switch can sometimes drive a 4 ohm load, but the switch limits the power output to levels that won't overload the amp.

what does that switch do, throw a 4 ohm load in series with the output to "stabilize" the ouput?

No. It typically reduces the power supply voltages that feed the output stages of the amp by use of a power transformer with two secondary windings. It essentially transforms the amplifier into a lesser powered one. An "ideal" amplifier that is capable of outputting 200 watts into 8 ohms will output 400 watts into 4 ohms. Many older stereo amps came close to that ideal. The Altec solid state professional amps that I have will do that easily, and they will do almost 800 watts into 2 ohms.

I'm not singling out any particular manufacturer of home theater amps - almost all of them make use of this switch.

Could part of the issue be manufacturers trying to push more out of the 8 ohm value than they used to? Say they made an amp like the example, but instead tried to get up to 250 or 300 watts @ 8 ohms instead of 200. Then they're still kind of limited to the 400 or barely over at 4 ohms.

painttoad, you probably already see this, but it would be better to use the amp's value at the 4 ohm load instead of just doubling the 8 ohm value for the reasons we are discussing now.

i may be going off on a different subject kinda,

i deal more with car than home so i never actually go by the power rating so to speak,speakers are continuously(did i spell that right curegeorg?haha!) variable, i understand that so the wattage at the impedance never comes in at a constant level.(as i believe)but...

i have b&w 601's,passive biamped.if this is an 8 ohm(nom) speaker does that mean each section will be 16 ohms,am i driving my amp half power(load)?
60wpc x 6(at 8 ohms) even though i still push full bandwidth all the way to the speaker x-over, have i reduced the load at all? it sounds better,has better dynamics,doesn't get as hot as it used to.
i thought i knew about audio but i surely never meant to confuse myself(others of course) but never me!

It's still an 8 ohm speaker.

No - due to cost and heat constraints, the power ability must be reduced into 4-6 ohms. Additionally, some manufacturers now are not as honest about their ratings as they once were when most everybody held to rigid FTC rules on stating power output.

Ditto.

Car, home, boat, they're all variable, but just ust the nominal value listed. It's close enough for practical purposes and just easier that way. I believe the amp itself can respond to different frequencies with different power amounts. There isn't much constant, but we can do well enough despite that.