Hi Cameron!
BG>> I used 130dB, because that was the level of  clipping at the sound
console
CH> And in most cases, I'd also suspect that knowing a church usage, it
CH> would get plenty loud and not clip so damage to speakers is minimal
CH> before someone hits a fader to tone it down to kill any feedback.
:-)
Right.. Also I installed a  peak limiter that was set below that
clipping point so that it would be idiot proof.
 BG>> designed, which is about 20 dB above the loudest that sound system
 BG>> would ever be run on an average, giving sufficient headroom before
 BG>> clipping.
CH> It's amazing how easy it is to destroy speakers with underpowered
CH> amplification. :-)
Very true. When drivers are hit with a amplifier that is clipping, that
clipping causes the peaks to square off, creating massive increases in
the high frequency energy, and is often the cause of popping tweeters,
and in the bass side of a biamped system, the woofers can't dissipate
the energy as sound.
CH> I wondered where you shelved the low end to protect against subsonic
CH> mic handling effects.
Two ways. The first was that the response of the bass bins fell off
sharply before that frequency, as it was designed and wired for an
optional sub woofer system (for the electronic "pipe" organ) and the 1/3
octave had a low cut off trim (UREI forgot the model number). The bass
was so potent, that it was decided not to add the subs.
The interesting thing about this installation is that we had the full
cooperation of the sound system committee at this church, and I had
carte blanche in the design and equipment selection, which in the sound
contracting biz is difficult to find a job like this, working directly
with the architect, the acoustical engineer, and the church with full
confidence. One of the most satisfying projects I've ever done, with a
couple of interesting twists to the design.
The room was a "in the round" making about 2/3rds of a pie, with the
stage in the center. While I'm normally a time aligned drivers freak,
the layout wasn't suited for a single central cluster like I would have
liked to use.I did place the bass bins together for coupling where a
central cluster should have gone, and used a split cluster on the high
frequency horns which were the large sized JBL constant directivity
20*40 horns, 4 per side, with the two clusters meeting right at the
center isle. Move to the seats on one side, and the sound moved to that
cluster, move to the other side seats and the sound shifted to the other
cluster. Visually, in the front seats, the sound didn't quite match the
visual location exactly, but this was minimized in the rest of the
house. The balcony was fed with ceiling 8" speakers time delayed to
allow the house system to be heard first, then adding to the sound,
making all the sound seem to come from the stage. The displacement f the
highs vs. the lows was slightly noticable to me, but noone else noticed
the difference.
This configuration was used to have precise control over the sound so
that the direct sound only hit the seating areas, with very little
hitting walls and other surfaces to excite the reverb field, which
turned out to be a little deader than was originally projected, giving a
very high direct to reverb ratio and high intelligability. After all,
getting across the word of God is what church sound is all about
(besides the show biz aspects).
Quite often, sound systems are designed by one person, the consultant,
who specifies the gear to be used, a sound contractor wins the bid, who
then tries to figure out how the hell to give the specified sound system
for that rediculously low bid, what corners can be cut to get there, and
who has to make what that consultant design work perfectly, no matter
how badly that consultant blew the design, and that happens more often
than not it seems. Or like what happened once when the architect moved
the speaker cluster behind the microphones on a church I designed with
out consulting me, and we won the bid to install it. Talk about a major
hassle during that installation. We had to substitute hypercardiod mics
to get anywhere near sufficient gain.. Just try to get an architect to
take blame for anything!
I could go on and on about some of the weird designs and problems I've
had to deal with over the years in
installed sound.
Yak soon!
 Bonnie *:>
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