-=> On 17 Dec 96  06:46 you wrote to me <=-
 DD>  One advantage of using an active cross over with the ribbons is
 DD> a 3db  gain in sensitivity to 90db because of shedding the
 DD> resistive and  reactive load of the passive networks.  The
        That certainly sounds like it would help.  Although using two
separate amps would be an advantage too.  I was wondering if perhaps I
should use two TFM-55x amps instead of TFM-35x just to be sure and
have plenty of headroom.  Even with the woofers disconnected,
something like the 1812 Overature causes a momentary needle jump on
the 8 ohm centered power meters to jump all the way to the 250 watt
mark, if not beyond, during canon bursts and this is at typical
listening levels that don't often go beyond 30 watts with just the
ribbons.  However, this is an extreme example and a 3dB gain in
sensitivity would be more than the equivalent of buying the larger amp
models which is, of course, significantly more expensive than the
mid-priced TFM-35x.  OTOH, adding in the price of two active
crossovers, there wouldn't be all that much difference, but I suppose
active drive has some other added benefits as well.
 DD> resisters, caps, and inductors  ahead of the ribbons.  The
 DD> original 48" & 60" AOL's used a xover at  200hz, unlike the 150hz
 DD> for the AOLIII.  It is said that the higher  point better avoids
 DD> the 160hz resonant frequency of the driver and a  180hz resonance
 DD> based on standing waves related to the ribbon length.  I think
 DD> however, that the Genesis speakers have a 100hz lower end  using
 DD> both lengths. 
        The lower resonance points must be fairly mild, because I
don't audibly detect anything wrong in that frequency range, but
perhaps my test CD is too limited.  Still, musically I don't notice
anything either, whereas I do notice bass guitar and some percussion
instruments (notably the snare drum) gets softer in the region of the
100Hz-150Hz notch.  But then, I have the subwoofer turned up a bit
more than "flat" so this probably makes the problem worse in some
respects, although it would increase the response in that region a
little as well.
        I also wonder if the resonant point for the 48" ribbon is the
same as the 60" ribbon.  I don't think it would be, but I'm not sure
if it's lower or higher.
 DD>  The Clearview active xover comes in different versions depending
 DD> on  what Carver ribbon model it is to replace.   If I recall
 DD> correctly,  there is a version for your AOLIII'S.   Because these
 DD> are practically  hand made, the builder would likely be amenable
 DD> to setting the xover  point where one wants.  It means replacing
        Who exactly do I contact?  Do I call Carver and ask about it
or does this guy have his own business or personal number for
inquiries on the crossover?  I assume it only includes one high-pass
and one low-pass crossover (as normally there'd only be two drivers),
so I guess I'll need an additional crossover to keep the bottom octave
out of the 10" woofers.  I assume the brand wouldn't matter for this
task.  Actually, it's something the sub should have had built into it
(it does have one, but for some STUPID reason, it only works with the
high level inputs, which I don't want to use).
 DD> some resisters with  different values.  He is an executive at
 DD> Carver doing this on the  side.  I don't know why your sub is
 DD> crossed so low or why with such a  steep slope, perhaps it is a
 DD> 4th or 6th order bandpass where the  lowpass band also avoids
 DD> some higher frequency artifacts of such  designs.  Perhaps the
        The low-pass crossover on the subwoofer is adjustable between
50Hz-100Hz.  Unfortunately, this is not quite high enough to match the
ribbons at 150Hz regardless and the high 36dB/octave crossover (which
admittedly does a great job of keeping directionality to a minimum
even with just the sub on), doesn't give much lee-way.  I'd also just
assume keep the sub's work to a minimum for maximum control.  With a
15" woofer, it's not the fastest sub on earth to begin with, although
sonically it blends better than I would have imagined, given all the
clout about trouble with hybrid designs.  Speed in the bass octaves
doesn't seems as important as at higher frequencies, at least when
you're talking about ribbon speed.
 DD> external xover of your choice. Using an active xover with  an
 DD> additional amp also means that the Carver 10"'s could be used 
        I'm assuming the 10" Carver woofers wouldn't have any trouble
being set at a higher crossover point than was intended by the AL-III
design?
 DD>   I find no problems using a sub with the 200hz xover, despite
 DD> what   one commonly reads about directionallity.  It is a VMPS
 DD> with a 12"   and 15" in one box which is placed between the
 DD> ribbon panels.  I   have not yet been able to notice any
        Placing the sub in the center as opposed to the corners of the
room probably minimizes what directional effects there are.
Unfortunately, I have a television in that position.  If I just play
the sub by itself I can hear a little directionality if I set the
low-pass at 90Hz or greater, but with actual music, the only effects I
hear are the closest walls resonating at a few frequencies.  Even deep
bass effects can image on the opposite side of the room.  The
directional information, such as in the attacks seems to be much
higher and well into the ribbon frequencies.  I think asking my sub
to do 200Hz would be pushing it, however.  I'm sure the 10" woofers
are much better qualified for that region in terms of speed and
accuracy.  It would also strain the sub's amp more and bass already
takes up more power than most regions.  Not to mention I'd have to
take the sub apart and bypass its internal crossover to do it.
        Thanks for the information, though.  I'll probably start with
an active crossover to take the bass out of the 10" woofers to start
and consider full active drive a little later, as I would also need to
buy a 2nd amp and that's no small purchase.  I'm starting to wonder if
I'll ever get around to buying an amp for my BP-2 surround speakers,
which have been sitting in a corner for almost three years now.
Basically, I've been trying to decide whether to by a larger amp for
the main speakers and use the TFM-35x for the surrounds or buy a
smaller 100 watt amp for the surround speakers, as they require far
less power than the main speakers (the most I've ever seen them use
when I did have them hooked up before I got the AL-IIIs was 65 watt
bursts on the TFM-35x's power meters).  Of course, going full active
drive will mean I'll need at least two more amps and probably a 3rd
amp for a center channel at some point.  Sometimes I wonder if I've
gotten in over my head.  I could have bought a cheap surround package
a long time ago, but somehow I don't think I'd be happy with it. :)
 * AmyBW v2.14 *
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