Sound System For A Large Auditorium

Sounds like you are in a pickle.

What you want is free advice on sound reenforcement. However, most people with the level of knowledge tend to sell it rather than give it out freely. It like a bricklayer asking his competitor for free advice on doing a job.

You may end up paying for a consultant to do this job.

However, you might try asking this question at DIY Audio Forum. There are a lot of professional people on that forum and maybe one or two might be willing to help.

The forums are bot specifically for sound reinforcement, but many members are professional audio people and have a long list of credentials.

The query does not relates to sound re-enforcement.

Since no hard and fast rules or formulas apply it is a simple matter of sharing experience.

Dear 'Anonymous Hero' thank you for responding, I appreciate your effort.

There is also modeling software for doing what you want (if I understand your request), but like anything good, it is going to be expensive and the degree of what you get out of it results-wise depends on how skillful the operator is.

I am not sure what you meant by "no hard and fast rules or formulas apply" or exactly what you were referring to.

If the sound system feeds to multiple speakers at substantial distances apart, it seems that any single listener could receive delayed sound from more distant (but therefore quieter) speakers, sort of an echo effect.

The first arrangement that comes to mind is say 6 speakers in a circular array at the center of the room. (The quantity would depend on how wide the dispersion angle is.) This can only be considered a starting idea.

"If the sound system feeds to multiple speakers at substantial distances apart"

There is a limit to maintain separation among speakers, when the speakers are placed at a substantial distance apart this is what causes the listener to distinguish more than one sound source,

Headphones.

Headphones are there for someone who would like to listen to the language interpretation in a secondary language. It is an auditorium and speakers are mandatory.

If in doubt hit them harder

Yeah - that always works;

I am in no doubt that the project will be successfully accomplished but as for your proposal of hitting harder, am doubtful that my employers would consider it worthwhile. 'ky' please be merciful on my job.

Sorry for following my instincts

Dear Guest; I am delighted with your participation.

You have provided very valuable advise but kindly permit me to discus the matters in the right perspective;

DSP and directional response microphones are very effective against reflected sounds but fall short of expectations if the loudspeaker(s) happens to fall in direct line of sight of the microphone and in such an event as a minimum howls or whistles dominate the speech.

As for the auditorium not only the main stage is projecting inside the hall but there is a double decker seating arrangement at the opposite end so an array of suspended speaker columns from the celling would not effectively cover the audience in two tier formation and placement of loudspeaker columns at the walls would be necessary.

I agree that absorbents like curtains are very effective to control reverberations. In the auditorium the architect has agreed to provide plaster of paris tiles for wall cladding as well as for the dome celling with beam effect for dispersion. Plaster of paris has high absorption coefficient and my assessment with Sabine formula is that things would be fairly normal.

If sound waves deflecting baffles are provided on the sides of some speaker columns the microphones will not get the undesirable sourcing direct from the speaker columns but the Architect is not conducive to the idea on account of aesthetics, architectural disfigurement etc.

The norms at this forum are that for expression of thanks Good Answer score vote is cast and I am rightfully expressing my thanks to you - GA

I personally think you are expecting too much out of this forum and providing too little in the way of critical information.

All of us love a challenge and as you see you are getting a lot of well meaning responses, but:

1. We are not acoustic engineers with professional sound stage crafts.

2. Designing a system like you have eluded to takes a lot of specific information that is missing from your posts.

I think it would be useful for you to do two things:

1. Consider taking your questions to a pro sound forum. Here is one example, but there are probably many, many more out there.

Not that we are not interested (we are), but you probably will get more useful information from people in the field.

2. Define your problem space with much more detail. It is meaningless to give a 100,000 foot view and expect to get answers that are on target. Frankly, I just don't know what exactly you want to know.

As for the previous post's recommendation for the use of DSP and microphones, I think that advice is probably correct. Again, we don't know your specific questions, but even mediocre equipment like Behringer specifically makes devices to cut feedback. I have one called the Shark that uses what Behringer calls Feedback Destroyer and there are much more sophisticated gear out there designed to address these issues.

Typically, loudspeakers are place ahead of the microphones on stage and suspended from the ceiling in arrays. Every professional auditorium and concert hall I have seen has arranged them as such.

Broadcasting even sound throughout a venue usually is done with line arrays. JBL (for example) makes them and so do others. You just build a stack to the desired width and height and point each individual member as required. Multiple stacks are placed or suspended as needed to provide uniform sound. Here is an example:

I really don't know your skill level in this domain, but there should be plenty of help out there that can guide you if you find the right forum and provide all the relevant information. Then follow their advice.

Good luck!

I have not been expecting too much out of this forum, all I wished for is a few practical useful tips relevant to acoustics related to any large auditorium - not necessarily an expert advise from another Designer.

Just for example when an auditorium is spacious there is a possibility that a large section of audience cannot pick up what actually is being conveyed to their ears due to standing sound waves phenomenon.

Standing sound waves are out of reach and domain of any of the "Cut Feedback" devices and appropriate alternate correction measures are necessary.

On my part I am carrying out vector modelling besides mathematical assessments using empirical relations however there is always a possibility that despite all efforts some grey areas would be there.

It would be inordinate to expect the respondents at any forum to indulge in designing - I readily agree to that.

This is yet another area that I'm not an expert in.

What I do know, is that there are sound guys out there that have a sixth sense when it comes to this stuff.

I doubt the answer will come from any forum, he needs to get one of those people on site. It will cost far less than not getting it right and paying for a redo.

You might also consider joining ALMA International

As a former member, I know that these guys are at the cutting edge of technology.

I agree with AH's comments, too.

Ask the people who built the NIA National Indoor Arena In Birmingham

various links fro google

http://www.google.co.uk/search?q=birmingham+nia+accoustics&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=3VsOTe6ADaaShAeggYW3Dg

open this link and subscribe to the link at the bottom

http://www.google.co.uk/search?hl=en&newwindow=1&safe=off&rls=com.microsoft%3Aen-gb%3AIE-SearchBox&rlz=1I7GGLT_en&tbs=vid%3A1&q=large+indoor++acoustics+design&aq=f&aqi=&aql=&oq=&gs_rfai=

acoustic design forums search on google produced

http://www.google.co.uk/search?q=acoustic+design+forums&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=mF0OTZjpHNCzhAfK3fW2Dg

these may be more fruitful

though if you need to ask about such a thing, Should you be designing something you plainly do not know enough about ?

Acoustic delay lines need to be incorporated in mulpiple speaker system to avoid acoustic cancelation caused by by time differences in front speaker output and rear speaker output and i know that but i am not in acoustic design.

I think I think a 10.2 surround, 0.04 - 0.07 second delay and DBX Driverack would get you off to a good start.