And so it came to pass, on 14-07-96 18:30,
   that Gordon Gilbert spake unto Matt Ion:
 >> TM> Great sound, however, rocks my boat every time.  Competition car
 >> TM> audio, for the most part, is ONLY concerned with loud.  
 >> *Ahem* not quite.  As far as IASCA (International Auto Sound
 >> Challenge Assocition, *the* car-audio competition authority) is
 >> concerned, SPL counts for only a very small part of a competitor's
 >> total score.  Maximum score is given for 140dB SPL, with points
 >> deducted for levels below that... so in essence, going beyond 140dB
 >> is pointless, at least as far as competition is concerned.
 GG>      Not quite?  Do you realize how *loud* 140dB is and you say
 GG> *not quite* !?!? 
Read what I wrote, Spanky.  Tom said, "Competition car audio, for the most 
part, is ONLY concerned with loud," to which I replied "Not quite."  As in, 
there's a lot more to it than that.  Which is exactly what the rest of what 
you quoted of my reply to him says.
 GG> Why 140dB?  Is that the level your ear drums instantly explode at
 GG> or something?  Human hearing is incapable of even realizing dynamic
 GG> levels beyond 120dB (it just becomes distortion after that). 
Maybe YOUR ears.  My ears are not your ears.  Mine might top out at 117dB.  
They might handle 122dB.  You don't know.
 GG> I just can't understand why they would award maximum points for
 GG> 140dB if *loud* wasn't high in their minds. 
As far as IASCA's rating system was concerned, they had to put a cap on the 
SPL somewhere.  People were just dumping more power into their systems to try 
to crank a few more points out on SPL, so they picked a glass ceiling for it. 
 Your system could produce 180dB SPL, but nothing about 140 counts for 
anything.  Rather than just adding one more point for every dB SPL over a 
certain level, they instead picked an upper limit, assigned it a given number 
of points, and deducted them for levels below that.
 >>Most of the points are based on such criteria as installation safety
 >> and quality (running 500W worth of amps on 16-gauge zip cord that
 >> comes out the hood and through the door hinges is an automatic zero
 >> :), sound quality (subjective to individual judges' ears and, to
 >> some degree, tastes), imaging and sound stage, and RTA measurements
 >> (they do pink-noise RTA at around 100dB SPL).  There are even points
 >> for presentation (the car's owner has to give a brief speech on his
 >> system :) and car detailing (a rusted-out '74 Plymouth that you used
 >> for mud-racing immediately before the sound-off is a definite
 >> liability! ;-)
 GG>      These sound more reasonable.  Actually, it's a shame a person
 GG> has to be penalized for having a stereo that can't do 140dB.  
Get a grip, and think about how this scoring system actually works for a 
moment.  
If they started the scoring at, say, 100dB and awarded a point for every dB 
over that, someone whose system does 120dB would get 20 points, someone whose 
system does 140dB would get 40 points, and someone whose system does 155dB 
would get 55 points.  
Since raw SPL can be had by simply adding more power, more sensitive drivers, 
or specific sub-enclosure designs, without concern for sound quality (which 
is the primary focus of all *major* autosound competitions) this is, at some 
point or another, an unfair comparison, in addition to being harzardous to 
the hearing.
So instead, they (hypothetically) assign a MAXIMUM of 40 points for 140dB 
SPL, and deduct one for every dB under that.  The 120dB system then gets 20 
points, same as with the other method, but the 140 and 155dB systems each 
only get 40 points.
The less powerful system doesn't lose anything (ie. is not "penalized"), and 
the guy with the system on steroids has no reason to crush his own head with 
bass.
IKEA ... Swedish for "particle board."
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