>   For complete technical info and nice photos of DIY systems based 
 > on
 > the Carver ribbons go:
 >      http://rsphysse.anu.edu.au/%7Ebill/sp.html
        I've actually got that one referenced on my own WEB site.  I didn't 
recall information specifically about the Clearview.  I'll have to take 
another look.  Meanwhile, a long day of measurements have revealed a number 
of things about my system.  It turns out that the Definitive Sub I'm using 
does indeed have a high pass filter that works with the low-level 
connections.  A poorly documented manual led to confusion.  There are 
actually TWO high pass filters in the sub, a 50/100Hz adjustable one for 
low-level and a fixed 80Hz one for the high-level.  I'm not sure how I failed 
to notice it work.  I must have not really played with it with the AL-IIIs (I 
had bookshelf speakers hooked up with the sub before I got the AL-IIIs).  I 
also haven't had the woofers hooked up for some time now.  It turns out I've 
never heard my own AL-IIIs run completely full range before.
        So, I hooked them up again for measurements.  It turns out the dip I 
thought was there isn't really there at all.  The lowest part of the dip 
should be at about 125Hz.  I have a test tone at exactly this frequency on a 
test cd.  If I cross my sub at 90Hz and I set it for 20dB above "flat," (this 
is where kick drums sound the most realistic and it's the most satisfying 
overall...flat just doesn't sound right until I crank it at levels that are 
painful over any signficant amount of time), the response at 125Hz is the 
same as at 150Hz where the ribbon begins to cross.  It slopes up from there.
        Surprsingly, turning on the AL-III 10" woofers and crossing the sub 
at 50Hz instead of 90Hz at the same level produces an almost identical 
response curve as having the sub at 90Hz with no woofers on.  I tried many 
combinations, but only these two match up like that...a bizarre coincidence 
since those are the two I used all along (50 with woofer before I ran into 
the clipping issue & 90 without afterwards).  I was rather shocked to say the 
least.
        So, the issue has now become do I buy a 2nd amp (to avoid clipping 
with the woofers on and allow full active drive in the future) and cross at 
50Hz OR cross at 90Hz the way I have been and have the virtual same response? 
 It would seem to come down to whether the 10" woofers provide more detail 
over that same 1.5 octave range (although the sub still would blend over a 
large portion of one octave) than the sub would alone.  I spent hours 
measuring and listening and I'm still not sure.  I think there may have been 
a slight bit more detail in the speed of bass guitar transients, but it's so 
close that I really wish I had a method of A/B comparing to be sure one way 
or the other.  The difference is subtle to say the least.  I think I'd really 
need to spend more time comparing, but at the moment I'm all compared out.  I 
think I'll leave it alone for awhile longer and concentrate on room 
treatments next. :)
        Oh, what was really surprising about it not having a dip like I 
expected was possibly because all measurements indicated to me a 24dB/octave 
low pass slope, not a 36dB/octave one as the manual states.  This then 
calculates out much closer to the measured response in relation to the 
overall level I set.  I find it hard to imagine they would botch something 
like that in a manual, so I'm at a loss to explain it.  It actually helps in 
this situation, but I wasn't expecting it.
        One bad thing I did find out was that in either setup there is a room 
dip at 50Hz of about 7-10dB (I close miked the sub to make sure it wasn't the 
sub and it had 2dB more energy there than at 40Hz, which is what measures the 
most at the listening position.  In fact, except for the 20Hz tone, the whole 
sub measured relatively flat (within 2dB) from 30Hz-100Hz with close miked 
measurements.  The room response at the optimum settings mentioned above were 
relatively flat until the gradual slope down to flat at 150Hz except for that 
50Hz dip.  There's also a 6dB rise at 400Hz in the room.  I'm thinking a 
parametric equalizer might do the trick to correct for the room problems.  
I'm also thinking of putting Sonex on the front wall to diffuse and absorb 
the rear wave a bit since the room response isn't even due to no wall on the 
right side of the room, which I have to correct with a balance control, which 
isn't entirely effective due to uneven frequency reflections.  I especially 
need to dampen the area behind the left speaker (1st reflection) and the left 
wall where the 2nd reflection occurs back towards the listening area.
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