Conference room PA system - N00b needs advice

[Enzo]

6BG6 - come on, relax.

If I read the original poster correctly, this is a utility ballroom in a hotel, not a concert venue. This is the sort of room that is configured for a sales meeting one day, and a family reunion the next. The stages are risers set up for the particular needs of the day, so he has been asked to provide for them in two places.

The whole point of a ceiling speaker array is that one or two speakers will be over any listener. This is not the same as a main speaker system at the end of the hall serving the entire audience. SO for a lecture room, delay lines and multiple amps is way overkill.

[Original Burnedfingers]

SO for a lecture room, delay lines and multiple amps is way overkill.


Spoken by a person with absolutely no experience what so ever.

If its worth doing its worth doing correctly. Your looking at a room with dims of 36ft wide X 78 ft long.

[Enzo]

Sir, please feel free to disagree with anything I say. However it is not necessary to try to make disagreements personal, nor is it prudent to assume my 40+ years in the business constitute "no experience whatsoever."

[Original Burnedfingers]

Enzo

Just wondering if that 40 yrs is in the commercial sound field designing and installing equipment or is it in your sound repair shop?

There is a difference and from my experience every little audio shop out there thinks they are the experts in sound design and installation. Sorry but if I had a dollar for every mistake I have repaired or corrected I wouldn't have to work. What I stated is the best in design for the uses of that room. The ability to switch to different parts of the room and have the system be correct. Any idiot can and usually does install a blanket system in this case and expects it to work flawlessly and I'm sorry to inform you of this but they don't. I surely do understand that the rooms, ballrooms, banquet, meeting, or what ever the heck you want to call them have needs and these needs have to be satisfied so that the end result will be flawless. I cannot do a system that will result in ones ability not to be able to understand what the speaker is saying. I have done probably thousands of these systems and generally cost is not a consideration but usefulness of the system and the systems ability to provide to the people that come in for their conventions and such is. My experience is the completely flawless systems are the ones that are booked and the others of questionable design sit unused 50-60% of the time. .

[simon7000]

OK,

So the basics. The reverb time of the room is a maximum of around 2.65 seconds at 500 Hz. It drops to .77 seconds at 4K. 250 - 2.42, 1K - 1.42, 2K - .87.

This is going to be a "Tubby" room. Equalization will not fix that. People and furniture will. However those are variables and not the same for every use. So draperies on the walls are the best choice.

Next is SPL for the intended use. Loud multipurpose rooms would be 95 db. You can get away with as low as 85. These are average levels so add about 15 db minimum for peak levels. That is a minimum of 100 db. The loss from the loudspeaker at 4m high to ear level between two loudspeakers would be 15 db. so you require 115 db out of each loudspeaker. A ceiling speaker might do about 92 db per watt, so you need 23 db of power per loudspeaker. That is 200 watts per loudspeaker.

Now look at coverage of ten loudspeakers. A decent real coverage angle at HF is +/- 45 degrees so each loudspeaker will cover an area of 25 sq M if everyone places their ears on the floor. Using a more reasonable height of 1.25 M (seated ears) would give a coverage of 12 sq M per loudspeaker. The room area is 264 sq M so 22 loudspeakers would be required to cover. Of course now you can get away with 100 watts per loudspeaker.

Now you can use two delay lines to feed an amplifier matrix feeding the loudspeakers. That way you can put the signal into one delay for the left wall and the other delay for the front.

So in reality. Be sure there are always curtains in the room. Use the maximum transformer tap on the loudspeakers in the room. Play music and walk around turn down the HF until it sounds uniform all over. Put is about 3 db of cut from 200 to 800 Hz.

[mickeymoose]

Simon:

How did you arrive at those RT60 times? Measurement or guess? E

[simon7000]

Originally Posted by mickeymoose

Simon:

How did you arrive at those RT60 times? Measurement or guess? E

From post #1 dimensions and surface materials. The equations are well known.

You can even find free calculators on the web!

[pinkmouse]

Originally Posted by 6BG6GA

As you know you cannot get away with hooking a computer straight to a direct box because 90 times out of 100 you will end up with hum.

I'm with Pano, never had an issue with a decent DI box and PC causing hum. And I'm not just agreeing because he's a mod too, but based on lots of practical experience.

[Enzo]

6BG6, I am not going to get into a p***ing contest with you. I'm no kid in a basement.

The hotel has asked their employee to design a system for them, that doesn;t sound like cost is no object to me. That sounds like "we want it cheap."

MY experience is in live sound, as well as many years designing and installing sound systems in restaurants and bars, yes most based upon 70.7v distribution and ceiling speakers. Not to mention 8 years in broadcasting.


I see this utility room project as for spoken word or background music. Any bands or wedding DJs will be bringing their own sound systems, certainly they're not going to rely on his ceiling speaker array.

Since there will be no main speaker stack at the stage in his setup, when you add delay to some speakers, what will you delay them with respect to? Each audience member will be listening to the speaker over his head.

[Pano]

Originally Posted by 6BG6GA

From a moderator like yourself I expected more than a sarcastic reply and attitude. I'm not a Hawkeye fan nor do I consider this to be Hawkeye land and maybe we do things better here. In N.C. I only have a football stadium that I've worked on so I cannot comment as to the back woods equipment used in the hill country. I can tell you this much...the system under consideration is an abortion in the making. You guys go ahead and have at it.

Whoa, dude. Chill out! I thought they had a sense of humor in Iowa. Nothing I posted was meant to offend, quite the contrary. I apologize if that wasn't clear. In no way was I trying to disparage your work or knowledge. Sorry you read that into it. It was all meant in good humor and good fun.

BTW, if you don't see a cop hat, then it is not a moderator posting. Just a post from another forum member. That is true for all moderators.

If you don't wish to help the OP, that's understandable, it's what you get paid for, no need to give it away. There are others here who can help.