And so it came to pass, on 03-08-96 22:03,
   that Bonnie Goodwin spake unto Drew Hohmann:
DH>> It's widely known that running amplifiers below certain load levels
DH>> (usually 4 ohms), the amplifier has less and less control over the
DH>> speaker movement, causing distortion.  This is mostly seen in
DH>> groups of subs wired in parallel, down to an ohm or so.
 BG> I don't believe that is actually true, but often it results in
 BG> distortion, since the amp is working much harder at a lower
 BG> impedance, often exceeding the capabilities of the amp, which was
 BG> why you made the observation above. Actually, damping factor
 BG> (control over the speaker in essense) increases the lower the
 BG> impedance. This is a good thing for subs, as the amp is able to
 BG> dump more power to the speakers and have better control. The
 BG> difficulty is that most amps aren't designed to work lower than
 BG> about 4 ohms, and below two ohms, it starts to look more and more
 BG> like a direct short to the amp. 
The key word above is "design".  Some amps are designed to handle load 
impedances of two ohms, and do so quite well.  Others aren't.  And of course, 
Drew didn't specify any particular type amp amps -- car audio amps are 
typically designed for and rated at four ohms, and a few will handle 
impedances as low as one ohm (one or two top-end units will even do .5 ohm 
safely).
Of course, all this really only applies to BTL (balanced transformerless) 
output amps -- old tube amps *had* to have their load impedances matched to 
the impedance of their output transformer(s) for proper operation.
 BG> I don't like to see amps run under 2 ohms. The reason is that most
 BG> amps are just not stable enough to handle it, the reason why
 BG> electrostatic speakers are so hard to work with most of the time.
That's "most". There are some noteable exceptions -- one impressive test I 
saw in Audio magazine years ago was the use of a Mark Levinson Model 27... as 
an arc welder.  In fact, two of these mono-block babies were bridged 
together, fed a 1kHz squarewave, and the outputs used to arc-weld steel.  
Something like that wouldn't even notice the presence of an electrostatic 
speaker :-)
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Q: Why don't blind people skydive?
A: It scares the heck outta their dogs!
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