>Hi Gang,
>Just wondering how often you go through the process of equalising/tuning
the
>Auditorium Sound System of a fixed sound installation such as a community
>theatre, and what steps you take.
this is an easy sounding question to ask but difficult to answer in a
comprehensive manner as each theater is as different and unique an a
fingerprint.
the short answer is: as often as it is deemed necessary based on the
availability of competent technicians and accurate test/measurement
equipment and sufficient budget. this may be before each major event or
in
a fixed schedule but in my experience most commonly is never including the
day the PA was installed. let me elaborate here; im talking about a
thorough
EQ of the system using calibrated accurate equipment.
unless the EQs are locked down this is a complete waste of time effort and
$
as surely as god made little green apples someone will readjust it to
their
"golden" ear.
as properly done this process is exhaustive and time consuming and once
done
some little old lady with a hearing aid will complain that she cant hear.
unfortunately, in community theatre, the sound system budget usually comes
in behind getting a new popcorn machine.
so what can you do to best prepare for the next show? make up a test CD or
buy an off the shelf one. programs such as cool edit pro / adobe audition
can easily make pink noise, single tones, sweep tones.
first you find a time when you have the house all to yourself. it amazing
how people (directors, performers et all) want perfection but are not
willing to allow any inconvenience to themselves to achieve it.
lets assume we have a stereo triamped system. with the system on turn off
all amps save the lows. play pink noise as it gives a nice steady signal.
drop down left or right channel with your ears halfway between the
speakers
(about equidistant) the volume should add. if as you raise one side and
the
volume seems to decrease one speaker/ amp/ or something in that channel is
wired backwards (out of phase / polarity, whatever)
repeat with only mids then only highs.
fix miswired/blown speakers or components and repeat.
if you have delay speakers play some music and walk forward and back
under
them. the sound should be even and clear as you enter the delay zone. if
you
hear the delay speakers "first" followed by a slight echo from the mains
the
delay is off or incorrectly adjusted. most newer delays have readouts the
display feet or meters saving you the effort of remembering that its 66 mS
/
100 ft. some feel that is an advantage to a slightly longer delay so that
the mains are heard first this is OK as long as it doesn't create a
"flange
effect" at the boundary where the audio from the delay speakers
approximately equals the audio from the mains. its im****tant that both the
time and phase of the delay match the mains.
you could make a test jig to adjust this using 2 directional mics and a
an
oscilloscope. run a tone through the system and adjust the delay until the
display in in phase. most commonly its just done by ear and measuring the
distances.
im sure there will be some who take exception to parts of the above as
indeed general advice may not be applicable to all situations.
i suppose i could have shortened this to:
step one: hire a qualified consultant
step two: pay him
step three: act on his recommendations
best of luck and break a leg or something :)
Tim
>E.g. do you tend to do it at least once a year, or as major equipment
>changes?
>What steps do you take, and what equipment do you use.. i.e software
based
>RTA & measurement mic, in what areas of the room.. etc. etc.
>Cheers,
>Ric
> Good question, I have been curious about that myself.
>
> One suggestion that I have is to cover the chair with cloth to simulate
> the absorption of sound by people.
creating the characteristics of a full house verses an empty house will be
pretty labor intensive. the larger the venue the more labor and materials
will be required. even then it wont create the noise floor of people
breathing, coughing, sneezing, and chatting.
a roll of insulations or acoustical batting every second or third seat
might be an adequate simulation but i have not seen an occasion where this
amount effort was necessary. usually you just boost the upper mids/highs a
bit for a full house.
>
> But I am not an expert in PA systems. I would be very interested to
> hear the response of a PA expert.
>
> RAUL
>
Raul, im not claming to be an 'expert'. i just have some experiance and a
few opinions that im willing to divulge :)
Tim
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