"TimPerry" <timperry@[EMAIL PROTECTED]
> wrote in message
news:AJqdnbZ1GJr3oMbeRVn-pA@[EMAIL PROTECTED]
> >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 important 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
>
pardon my typo: speed of soound is 88 mS / 100 FT
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