How to determine which PA to install in an existing auditorium

[chickenfingers]

Hi

What is the procedure to follow to decide upon the best PA system
(only which loudspeakers and their positioning) for an existing
auditorium. Unfortunately I can´t change anything related to the room
´s architecture/structure.

I was thinking of a carrying out a computer simulation (taking into
account the shape and size of the room) with different loudspeaker
models and brands to determine their most appropriate location and
whether or not I needed delayed units to cover to auditorium
uniformly. Later I will measure the freq response across the
auditorium using pink noise (by the way it is 8m wide by 18m long and
around 3m high,
sounds like a perfect shoebox but its got some annormalities here and
there) to find out the acoustics I´m dealing with (although in my
perception the room sounds pretty alright) and accomodate them in my
design. This is a brief procedure of what Im planning to do.

I am aware of other procedures such as RASTI where I shoud take into
account the Rev times and Signal to Noise ratios, but as far as I
understand this are useful at the design stage of the auditorium,
besides at this moment the auditorium´s budget only allows for a PA
upgrade (no acoustic upgrade).

By the way is a multi-purpose auditorium (acoustic/classical orchestra concerts as well as conferences/speeches).

I could be overdoing it since the end result will only be buying a new set of speakers and locating them adequately within the room. However I´m interested on your approach towards this type of work since the auditorium´s budget may allow for further changes next year and also for to gain further knowledge on this matter.

I will appreciate any feedback on this, including which software you
prefer, what Loudspeaker brands, positioning (central cluster??),
should I aim for a different method?, anything...


Thanks a lot for taking time off to read this!!!


Sergio

 

[TLS Guy]

Hi

What is the procedure to follow to decide upon the best PA system
(only which loudspeakers and their positioning) for an existing
auditorium. Unfortunately I can´t change anything related to the room
´s architecture/structure.

I was thinking of a carrying out a computer simulation (taking into
account the shape and size of the room) with different loudspeaker
models and brands to determine their most appropriate location and
whether or not I needed delayed units to cover to auditorium
uniformly. Later I will measure the freq response across the
auditorium using pink noise (by the way it is 8m wide by 18m long and
around 3m high,
sounds like a perfect shoebox but its got some annormalities here and
there) to find out the acoustics I´m dealing with (although in my
perception the room sounds pretty alright) and accomodate them in my
design. This is a brief procedure of what Im planning to do.

I am aware of other procedures such as RASTI where I shoud take into
account the Rev times and Signal to Noise ratios, but as far as I
understand this are useful at the design stage of the auditorium,
besides at this moment the auditorium´s budget only allows for a PA
upgrade (no acoustic upgrade).

By the way is a multi-purpose auditorium (acoustic/classical orchestra concerts as well as conferences/speeches).

I could be overdoing it since the end result will only be buying a new set of speakers and locating them adequately within the room. However I´m interested on your approach towards this type of work since the auditorium´s budget may allow for further changes next year and also for to gain further knowledge on this matter.

I will appreciate any feedback on this, including which software you
prefer, what Loudspeaker brands, positioning (central cluster??),
should I aim for a different method?, anything...


Thanks a lot for taking time off to read this!!!


Sergio

This question is impossible to an answer except in generalities.

Much more information is required as to size and layout of the room. I understand that his room is to be used for both speech and music reinforcement.

The size and layout of the room are crucial.

There are several key points to professional sound reinforcement.

Efficiency and high sensitivity of the speakers is crucial. This requires the use of active electronic crossovers and bi and even triamping. Passive crossovers are a problem in domestic speakers, in professional PA systems they are a disaster.

The requirement for high efficiency usually calls for horn loaded speakers. However horn mid and HF units seldom have he best fidelity. I have obtained the best results with highly efficient low Qt drivers in large back loaded horns, with linear arrays for mid and HF. This is however is very expensive, and usually requires a custom design and build.

A very linear frequency response and intelligent use of room Eq, really helps forward gain of the system (minimizing feedback).

Very good microphones as well as good speakers are also required for good clarity and optimizing forward gain.

There are now sophisticated digital systems that greatly aid in increasing forward gain.

For live sounds, using mixers with superior headroom on each input channel is a must. It has always astonished me how so many mixers are wanting in this regard.

If the room is used for live music, acoustic treatments that deaden the room in any way have to be approached with extreme caution.

Those are at least some of the basics.

 

[Donna Negus]

what is a pa is that personal assistant

 

[TLS Guy]

what is a pa is that personal assistant

Welcome to the forums. However please do a little research before posting. If you are trying to be funny, this sort of post will get tiresome. This is your second one. PA, stands for public address, and that is not on a Federal mail route either.

 

[Savant]

Sergio,

This might be a bigger undertaking than you're anticipating. Large room acoustics / sound system design is not usually something that's addressed well in a forum such as this. If you are not a professional acoustician / acoustical consultant, you should consider hiring one. The best resource for this is www.ncac.com, which has a directory you can search.

If you feel up to the challenge, you can try out various software programs. The most popular is EASE, but CATT-Acoustic (just as good as EASE) and ULYSSES (more low-budget) are others. EASE comes with a loudspeaker database. CATT might also, but I know less about it. None of these programs are what I would call "intuitive." Intensive training is usually required to understand how to use them. (And even more experience is required to understand how to use them well.) (Not to mention a background - degree or equivalent training / experience - in acoustics and sound system design. I.e., neither the software nor the actual task of desigining a sound system are for novices.)

As for loudspeakers, there are many brands that can work for large venues. If you do not know of any, it's indicative that your money might be better spent on a consultant. It would be better to hire a pro, as opposed to spending money on a (not inexpensive) software package that will take many, many hours to understand and use effectively.

HTH.

 

[MidnightSensi]

Contact Bag End Loudspeakers: 847.382.4550

www.bagend.com

 

[chickenfingers]

Savant and TLS Guy.

Thanks a lot for your replies.
I graduated from a BSc Audio Tech course and then worked for 2 years in noise control. I´d say I definitely feel up to the task of doing the job. My issue here is that...well, I´ve never done this type of work, except during my Spatial Audio lectures. But here the tests we were taught and told about were RASTI and STI and had more to do with SNR and Direct Sound to Rev Sound Ratio, all too theoretical and in my opinion far more oriented towards other purposes such as train stations, shopping centres or venues were speech intelligibility is most important.
Loudpseaker sensitivity, arrays, directivity and all that was also covered.

Mainly I wanted to know how to approach sound system design in a general manner, and both your inputs have definitely helped out!

As for loudspeaker brands... luckyly I´m associated with an expert on that topic.

Cheers guys

 

[jamie2112]

Well I can say for sure that the room is too small for a line array. There are some really nice speakers out there that sound great stacked. D&B has a great little system that stomps. The new Adamson install speakers are getting rave reviews as well.....

 

[Savant]

Sergio,

Well, before you get into any of the programs - I cannot stress enough how user-unfriendly they can be for novices - some suggestions:

Training from Syn-Aud-Con. At the very least, it's a good organization to join. (And has probably the most appropriate forum - for members only - to answer your questions. The annual membership fee is very reasonable.)

Get some good books, like:
Sound System Engineering
Handbook for Sound Engineers (With a great chapter on acoustical treatments written by yours truly. )
Sound Reinforcement Handbook

You can also get help from local loudspeaker manufacturer's reps sometimes...but just keep in mind that they will only be looking at one make of loudspeaker. If you want a good sampling of manufacturers to try, pick up a copy of LiveSound! magazine and flip through the ads.

HTH.

 

[Savant]

Also...

As far as design parameters go, you will be looking at many of the metrics you mentioned, regardless of the use of the space (shopping center or auditorium - the physics are all the same ). Speech intelligibility is important, as well as (probably) musical clarity, S/N (and D/R) ratio, overall sound level (no "hot" or "dead" spots), and even RT60 for a very general idea of what you're going to be dealing with in the room. Loudspeaker performance (sensitivity, directivity, etc.) will play into all these metrics. Your design targets will depend on how the space is being used. The needs of a "traditional" house of worship will be different from those of a "black box" theater, for example. The needs of "classical" music differ from those of "popular" music. And so on.

Best of luck.