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Rack Em' Up
Dear Old Soundman,
I love reading your articles. I love how you are able to mix what
seems to be endless audio knowledge with a severe dislike for all
of us upcoming, know-it-all sound fanatics. My associates and I
have a question that we have asked many people about, and nobody
seems to have a definite and logical answer.
We are prepared to be bashed, as long as we can have resolution
to this problem:
When providing sound reinforcement for large events in which more
than one mains amplifier rack and one sub amplifier rack are needed,
what is the correct way to distribute the audio signals to multiple
amp racks?
Our production company currently has all of the amp racks equiped
with paralleled multipin I/O panels. When using say three mains
amp racks and three sub amp racks, we simply daisy-chain the multipin
cable in and out of all the racks, which are fed from our loudspeaker
processor. Isn't it wrong to do because of the impedance drop which
happens when many lines of audio are pulling off of the same feed?
Are you supposed to use an active line distribution amplifier to
split the signals to all the amp racks? We can't figure out the
best method, and none of the "big boy" sound companies
make it obvious as to how they do it. Please give us a slap on the
wrists for being so stupid, and point us in the right direction.
Thank you very much for your valuable time.
-Owen from NJ.
AH, OWEN, OWEN, OWEN.
YOU ARE TOO ROUGH ON YOURSELF AND YOUR BUDDIES! THE IMPEDANCE DROP
YOU REFER TO (OR TO BE MORE PRECISE, ARE FANTASIZING ABOUT) IS NEGLIGIBLE
IN THE CASE OF SIGNAL CABLES. THEY ARE DRIVING TOWARDS SPRIGHTLY
AC-POWERED DEVICES THAT ARE TAKING A MINISCULE CUE FROM THE INFORMATION
ARRIVING AT THEIR INPUTS.
YOU AREN’T CHAINING SPEAKERS TOGETHER HERE, SOUNDMAN! SIGNAL,
HERE, VERY LITTLE CURRENT, RIGHT, OWEN? SPEAKER CABLES OVER THERE,
WITH LOTS OF CURRENT DRIVING DOWN THE HOSE AT A DEAD-ASS LUMP OF
METAL’N’PAPER ABSORBING THE CURRENT AND LABORIOUSLY TRANSFORMING
IT INTO WHATEVER KIND OF MUSIC YOUR MARKET FORCES YOU TO AMPLIFY
AND POPULARIZE. THAT’S WHERE YOUR IMPEDANCE CONCERNS ARE, NOT
AT THE RACKS, UNLESS YOU HAVE THIRTY OF THEM ON EACH SIDE OF THE
STAGE.
DID YOU SPEND TOO MUCH TIME AS AN IMPRESSIONABLE YOUNG SOUNDMAN
AROUND A BUNCH OF CRETINS TRYING TO FIGURE OUT HOW MANY MARSHALL
STACKS AND SVT CABS THEY CAN RUN OFF A JCM OR AMPEG HEAD, AFTER
DRINKING A BUNCH OF BONG WATER?
I MEAN, HOW FAR APART ARE THESE RACKS YOU ARE USING, OWEN? A FOOT?
LESS? FIFTY FEET ACROSS A STAGE? WHO CARES? LIVE A LITTLE! RELAX,
DON’T DO IT, WHEN YOU WANT TO GO TO IT! PUT ON A REAGAN MASK
AND WRESTLE WITH A FRIEND IN A VIDEO! THE PURPOSE OF ACTIVE LINE
DRIVERS IS WHEN YOU ARE GOING TO SEND CRUCIAL SIGNAL 300 OR 400
FEET FROM A STAGE TO A TRUCK PARKED OUTSIDE, OR FROM A FESTIVAL
STAGE TO A DELAY STACK OUT ON THE HORIZON.
YOU’RE OK, PAL! BECAUSE YOU CARE! EVEN IF YOU ARE DELUDED!
CAN I HAVE SOME OF WHATEVER IT IS YOU GUYS ARE ON?
LUV
- THE OLD SOUNDMAN
